@@hxhdfjifzirstc894 you want to turn on ac only if someone standing near ac ? You can go for PIR sensor as it have ideal for this type of work, you may have seen automatic lights in corridors, same way you can operate AC too.
Hi Great Scott, just a little translating advice: in your “pro and contrast” dialog, it should be “pro and con” pro = yes (affirmative) / con = no (negative) I am not certain what language this stems from, my guess is either Latin, or Greek.
@@greatscottlab thank you for the video I've been trying to find a good circuit for the job and you found it for me thank you for all the great videos keep it up
I think there is a trend to over-complicate simple devices. you did point out where latch circuits are an advantage, but there hundreds of examples where manufacturers are using a 10 component board to do the same job as a simple device. This is why you cannot repair your own tech any more it always seems to have to go back to the factory to be fixed. For example Apple phones and John Deer tractors. And now the manufacturers of cars that want you to push a button rather than open a door or not have to put a key in the ignition are failing to deliver their cars because of a micro chip shortage. I do hope the current "right to repair" movement is successful and we can stop this madness of having to pay a fortune at the garage to get the cars interior light repaired.
I agree that over-complication is an issue. I bought a used drip coffee maker (barely used, just out of its 1-year warranty) that had a latch circuit to turn it on and off. The heating elements were 230V AC and the latch circuit was 12V DC. After a few months the machine wouldn't turn on anymore. Turns out the latch circuit died, everything else was fine. So I replaced the whole latch circuit with a 230V AC 10A mechanical toggle swith with a built-in LED, which cost me 1.50€. It's been 2 years and the machine is working without an issue. These companies are sacrificing reliability and screwing over the environment for a few pennies.
this seems like an irrelevant complaint. if you're opening up a circuit to (de)solder it, that's already inaccessible to most. and whether a mechanical switch or latch is used, the complexity of repair is about the same at that point. plus you can replace it with a switch if you really want and if the application makes sense for it. "right to repair" doesn't seem to apply here
@@LC-hd5dc The point is: The smallest Replaceable Unit (SRU) used to be something like a switch or relay or some other discreet component costing about £1. Now everything is part of a complex circuit on a Printed Circuit Board (PCB) costing about £100 to replace. Sometimes you cant even replace the PCB and you have to buy the whole unit that the PCB is part of. Soon, you wont even be able to have your car/TV/fridge/washing machine repaired at all, they will all be repair-by-replacement. Then, maybe you'll look back and think, when did this all start? And you will remember, oh yes; it all began 30 years ago when they decided to replace a mechanical switch with a complex switching circuit.
I both agree with you on this, and think it's a bit out of place here. There's been countless examples of stuff being complicated for no other reason than someone either in management deciding it has to be "special" somehow and it gives no real benefit, or just engineers and designers that are lacking time to stop and think about everything from the start. As a parallel talk I'm fully on it, being a product development engineer now it was literally the topic of our last meet up at the company (the boss saying "guys, sometimes we just need to... Stop, breathe, look at what the heck we're doing, and think: WHY is it like this? Can't it be made easier?"), and I agree right to repair just has to happen and disposable devices have to stop. People gotta stop feeding this insanity. But I'll also say that I don't think the complaint relates to the video. There's several situations you'll want a circuit like that in place of a mechanical system. As an example, anything remote controlled. You'll not want that the only way to get that remote controlled device on and off is the mechanical button all the way at the device, neither you'll want to waste power unnecessarily with who knows, a mechanical actuator to that switch. A latch circuit solves the problem no doubt the simplest way. This circuit being or not an unnecessary complication is always a matter of situation. It may very well be simpler than a mechanical switch even, remember a mechanical switch has to deal with contact bouncing and protecting the contacts against corrosion and arching.
Yes! I like older cars where the boot for example is held down with a simple, good old fashioned, mechanical handle. Nowadays, it's some nonsense electronic latch. Just another thing to go wrong.
For battery operated devices that are used infrequently, I really prefer a mechanical switch where there is ZERO drain (other than the compulsory modelled resistance in the battery). Otherwise when you need said devices, you find dead batteries at best or corroded terminals usually.
mechanical switches and relays are important in many applications due to considerations surrounding failure modes. in safety and life critical applications the failure mode is critical.
Can someone explain why? I am building a soft latching circuit myself, based on PMOS, and the leakage current when off is low enough that it would take hundreds of years to drain the battery (yes I know it would die naturally well before that). the resistance of the mosfet is also very low when on. something like 50 milli-Ω...how does that drain/corrode a battery? 😕
Using dedicated ic is kinda cheating, and I feel like transistor latch has some kind of problem where if u held down the button too short or too long a duration, undesired result can happen because of the capacitor And the ic also uses 2 button, a t flip flop will be needed for 1 button latch, and here is where the challenge comes, it will just oscillate if the button is pushed because it is missing clock signal, a master slave configuration is needed this video did not cover that. A latch is essentially a digital flipflop, I challenged myself to build a 1 button latch when I was new to learning flip flop, surprisingly, when I searched, everything I found was transistor latch, I had no resources to learn from and didn't know where to start, I had to figure it out myself. And this video didn't bring anything new to the table, just the same transistor latch as every other video, in a place where latch videos are mostly transistors and digital ones are so rare to find, in most cases they just slap a flip flop on a slide and start teaching theory, where in real world a latch is more than 2 nor gates so it didnt really work in practice, it was more like a digital logic class than a latch video...... Utterly disappointed......
You're right about long & short switch presses possibly causing problems in some designs, though short presses at least usually aren't a problem. As for the circuit itself, it doesn't mention that the "out" terminal needs to always have a current (though small) to ground in order for it to reliably work- otherwise it'll occasionally switch itself to a "default" state (which depends on the "polarity" of the transistors you're using) instead. Not usually a big deal, but something to be aware of. This circuit _is,_ incidentally, a flip-flop, though certainly an optimized one. In particular, the capacitor gets charged to a state such that when that central switch is flipped, it will force the circuit into the _opposite_ state from what it was in before- it doesn't malfunction by oscillating when the press is too short, but instead too long, or even malfunctions by not flipping state if the switch is pressed a second time too soon after it was last pressed. As for the normal T flipflop, the normal situation is to connect the switch to both a capacitor _and_ the clock input of the flipflop _and_ a resistor that shorts the capacitor- the capacitor will be almost instantly charged when the switch is pressed, and will stabilize the signal into the flipflop's clock input long enough for the switch to reach it's fully depressed position, where the switch _is supposed to_ tie the capacitor and clock input directly to power (or ground, for inverted-input inputs). The resistor & capacitor will control the "debounce period" that follows an interruption of the switch connection, but for the small push-switches here can reasonably be a second or less without problems. The data input, of course, needs to be tied to the flipflop's inversion output.
I felt it pretty bad when the NOR based latch was discussed - I've had nothing but trouble when making a transistorized version, it needs equal loading on it's outputs... The NAND version is topologically the same and is very stable, even better you can make them with just 4 transistors o_O And this reminds me of a curious circuit I remember seeing somebody posting on reddit a year ago, there are differences but it'll likely still have a problem with input voltage changes causing malfunction - definitely a no-go for anything battery operated... Though in my take on latching power-switches, I used that effect to not only detect when the battery was low - but also protected against short-circuits! Edit: I just saw the thumbnail to ElectroNoobs' video, and that circuit looks awfully similar to this one... Also worthy of note, GS got 4x views on his rehash of Clive's Joule Thief video - and they say something's not worth doing when it's already been done!
You are showing your gross ignorance based on a single video. Yes, this particular simplified circuit has timing issues (see my other comment for full explanation) but that doesn't mean all latching circuits built with discrete components suffer this issue. Also, IC latches are not just of the R-S type and DO NOT REQUIRE separate input triggers for toggling. You don't know enough to be criticizing.
@@DiffEQ Dude, don't just walk in and drop ad-hominems - saying "your'e stupid, stop talking" is not going to change minds; if you want to show an error, point out what went wrong and how to fix it, don't just hit at it blindly and spew insults like that... Nothing is worse than an ignorant man accusing someone of being ignorant! Also, don't just go 'refer to my previous comment' like that. Nobody will find it, and that's a fact... Either repeat what you said, or put a hard link to your comment - don't just go "x marks the spot" and expect people to go find it... Now it might seem like this guy doesn't know enough to criticize the theory / lesson here; he's absolutely qualified to judge a *video* about the basics - a video which fails to cover the basics in a complete fashion, only skims through the cool and important bits. No variations, no run-down of the caveats - I found this format in the SEPIC converter video, where that design was all hyped up - without discussing the huge drop in output efficiency, or the alternative (a flyback converter) which would achieve the same goal, and add the benefit of electrical isoation... At least, that's what I think is being discussed here; this thread is pretty old... Anyway, thanks for coming to my TED talk - that is all for now
Don't forget you can buy latching push buttons, which when pressed and released close a pair of contacts and they remain closed until the button is pressed again. So there are times when a latching push button is a good option and you don't need to build a load of electronics.
Unless momentary, ALL switches are latching switches. WTF are you babbling about? The TYPE of button is not the topic here... it could be push, toggle, slide, etc. UGH How did you miss the context of this discussion so completely?????
For a headphone I am designing I would like to use a nice looking button, but the circuit requires a switch or a latching button. The latching button is too tall meaning I would have to increase the case of the headphone. A circuit like this could solve my issue. I only wish a circuit of some kind existed so I wouldnt have to solder as much.
Mechanical switches are certainly not obsolete. They are simpler and cheaper for nearly all maker-type projects. Nice information to know if I ever build a project that requires it. I probably have 200 switches of a dozen or more styles and there will probably be many left when I am gone. Why change the way I do things now?
Great Circuit for high current. FYI the Momentary button 1-2 is floating when off. I made this for a project and it would randomly turn on. Use a 100k ohm or more resistor to Tie the 1-2 of the switch to GND and no more problem
Been learning electronic as a hobby and this channel is such a gem, the pace and diagram explanations are on point. Thank for making high quality content.
Honorable mention to the humble (two coil) bistabile relay which is also set reset, and very useful in applications where a pseudo-latched run off the mill relay might draw to much power over time.
This is obviously a really interesting and problem specific solution to mechanical switches with potential benefits, but all I see when I look at a latch circuit is extra points of failure.
Mechanical switches (relays, contactors, even buttons and switches meant for small loads or logic signals) have to be the number one cause of electrical failure in industry.
@@kuni45 But the vast majority of mechanical switches fail to a safe state. Mechanical switches also maintain fidelity for small signal AC information that would otherwise be distorted or completely destroyed by the gate logic transistors and they are immune to voltage polarity. Mechanical switches are far from obsolete.
Because you think complexity means unnecessary. Adding a square-root button to a calculator also adds an extra point of failure. Funny how calculators work for decades with all the "added points of failure." SMH
I've made a nice PCB that toggles a switch output on button single press, double-press, long press, etc., with debouncing. And it has an I2C and serial interface. It's very neat.
In equipment reviews often a mechanical on/off switch is seen as a good thing. I agree. I would never use a latch circuit in anything I build as it is just a complicated and expensive solution to something that is not a problem. An electronic light switch that was widely used and prone to remote activation would be a hugely entertaining discovery. In a winters evening you could take a dog for a walk and switch peoples lights off in a block of flats and listen to the residents blundering around in the dark to turn them back on. Then in summer walk the same dog at three in the morning and turn them all back on. Even bad design can be fun in a prankster kind of way.
I use a power latch circuit for my bicycle automatic shifter. The cadence reed switch latches it on (also an input) and the Arduino switches it off if 0 speed for 30 seconds. Works great and no power draw when off.
Funny enough, when I fix up 80's Saab radios, the one model that has a latch circuit is the one that often won't power on until the circuit is recapped or power button repaired. The mechanical volume dial switch models just about always power up
Use a NAND latch for better performance, it doesn't need equal loading on the outputs to prevent it from 'sticking' to one state should it have a lower impedance. Also, unless you used capacitive touch or some sensor - you needed a mechanical switch to make the button! And then another in the form of a relay...
Please don’t use this kind of switches or latches for mains voltage purposes. See the comments below (Joop and others). Mains switches shall comply requirements for thermal resistance, fire resistance, clearance distances (as per over voltage category II), failure mode requirements, between others. Component standards and product standards are mandatory in mains related, not an option.
The problem of electronic switches like shown in the video is that it has no "memory" to remember its state. When there is a power problem/dip for a short period of time, it turns the device off and it will stay off until you press the button again. Not very suitable for devices that needs to stay on.
Have a think about using TRIACs & SCRs as your switching elements. There is a latching function built in for DC & a very simple capacitor shunt bypass allows the SCR or TRIAC to switch off. These are often overlooked devices with impressive ratings for literally pennies...
And by "sometimes" you mean to say that PLSM is NOT unique to mechanical switches/latches. So, what was the point of your qualified statement? I have over a dozen devices in my home, including a PC, that has programmable return-from-power-loss state with NO MECHANICAL latches.
Every switch, every tool, and most (maybe not every) programming features have their own purpose and application. There is never a one size fits all situation, and it is about determining which one is best for the situation.
I used a latching relay to drive a fog light relay in my SUV so I could use an OEM push button. The latching relay gets power from the tail light circuit so the fog lights can only come on when the tail lights are on. When the tail lights turn off, the latching relay loses power, and the fog lights automatically turn off. They won’t turn back on again unless the OEM button is pressed.
I wanted a circuit to pop up my headlights. There was a one year only button that can keep them up with the lights off. Completely different wiring and controller... or an annoying blank off plate. I had to consider, flash to pass overide to make sure the buckets go up for that, no matter the state. Fog lights require park lights like your circuit, also should switch off with high beams since fogs and high beams are considered as 6 lights, whereas regular headlights and fog lights are considered 4, the legal limit. Automotive lights are more complicated than they look on the surface.
Funny - this is timely as I fight the failing latch-type power switch on the back of my Keurig and wonder why they didn't use a toggle. At least I know why now. :-)
Thanks, interesting video. I use a latch circuit in a ESP8266 doorbell using a P and N channel MOSFET, very small IC's exist that have both included, like the Si4599
I can't find the part you're describing. Any chance you could post a link or some more info? Something like that is exactly what I need cluttering my parts bin waiting for a future project.
@@wjn777 perfect, thank you! I managed to find the part but unfortunately I can't find any in stock. I'll have to find similar parts but this gave me a great start, thanks again!
Without me even watching the rest of this video, I do have to agree that latch circuits have their place. However in the automotive industry they are widely over used and result in overengineered circuits that provide no extra benefit from their counterparts 20 years ago. On top of that with vehicle thefts on the rise, having something mechanical like an ignition cylinder is more important than ever. I know nothing I say here will have any impact. And I am not against latch circuits, or any electronic controls that go beyond a simple relay circuit. They have their place most definitely. I am just upset that the core of automotive design doesn't need over complicated circuits. It doesn't improve fuel efficiency. It doesn't lead to greater power gains. Worst of all it leads to vehicles being scrapped way before their time due to increased repair costs. Today Toyota considers the lifespan of a vehicle at 3 years. What happened to vehicles lasting 30+ years? Wouldn't that have a larger positive environmental impact? Of course companies will lose money based on their business models. Even EV vehicles are over the top with their engineering. This is proven with many small companies providing EV swaps into classic cars. The only complex electronics are the battery, electric motor, and the computer that drives all that. No different than fuel injection vehicles since the late 80s to early 2000s. After that it just became a nightmare of over engineering. Emissions were never improved. Perhaps some power gains but believe it or not those power gains come with enhanced emissions. The old school dyno emissions machines proved that until they were replaced with OBD2 emission tests, outside diesels. Sorry for the blah blah. I'm just trying to say there are so many ways a simple on/off switch, with relays if necessary, is probably the most viable and most easily repairable circuit that I know of. Just to throw out an example, I would love to know the person that created the footwell module in some later BMWs. I mean, just why? Its software is prone to corruption from most high end scanners. Results in a very expensive repair from the dealer and actually has created a whole market for diy equpiment and specialists. And there is no work around unless you really rewire the harness and will still be left with a module unhappy shouting codes at you. And what does it control? Stuff like power windows and crap. I swear if someone explains to me how that is more efficient than just having either postive or ground control with relays and fuses over your power windows, power locks, and other silly stuff in your door, please, I'm all ears.
How the hell is a mechanical ignition cylinder supposed to provide security here? They're piss-easy to pick and you don't even have to do that, you can just connect the wires and off you go. But you can't do that nowadays, because when the key with a proper code isn't present, the ECM is disabled, and you ain't going nowhere. That's an electronic system that is an (almost) impenetrable barrier to theft, the mechanical bit is worth nothing. That's why cars have fobs instead of keys nowadays. The electronic circuits in cars help save expensive raw materials like copper, and they save weight. For taillights you need a wire for position lights, one for brake lights, two for the indicators, one for reversing light and one for fog taillight. All of them must be thick enough to carry the current required without heating up or creating losses. All the switches - relays, brake switch, light switch and so on - must be beefy enough to make and break the connection, and they must be sturdy enough to do that over thousands of cycles. With an electronic system, theoretically, you just need a power supply wire and a bus wire, and send signals (CAN bus, say), to the rear lamp clusters and they use a couple of Mosfets to switch the lamp required on. That's a lot of copper, lots of weight, lots of mechanical switches, and, above all, lots of money saved, and unless you design the electronics stupidly, it will never fail.
@@horrovac Mechanical cylinder provides a mechanical steering column lock, which takes more skill and time to break, depending on the design. Picking a lock with a laser cut design is not easy. Most likely you'd have to smash the column open. Not saying its impossible but louder and more time consuming than just programming a fob the way current car thefts are being done. Not to mention the key with a mechanical lock also usually has programming that needs to be detected. So now you have much more protection than a simple electronic system where once you get the fob programmed, it takes car of the steering column lock since its electronic, push start means no cylinder needs to be destroyed, and away you go. That electronic barrier you speak of is actually quite easy to get through. There are numerous scanners you can pick up that do key programming. If you have access to dealership info and equipment its even easier. A lot of illegal type of equipment that works flawlessly is available for purchase. These are all the reasons car thefts are happening in such numbers today. Now with the wiring, I'm not sure how you think the computer instead of a relay and switch is getting the power to the lights? The computer is just bypassing what the relays used to do. You still need to run wiring regardless. And the wiring needs to be thick enough for whatever the load requires. Most manufacturers switched to aluminum wires awhile ago anyways. A lot of wiring now is too thin actually causing issues and needing repairs which require thicker copper wiring to be spliced in if you want the repair to last. And if you want a completely computerized relay system, the board and components must be hefty enough to take the load. Look at the infamous Chrysler/Dodge integrated power module. Piece of a junk. I rewire these for people regularly leading to the thing looking like a christmas tree. It fails. Often. And instead of just replacing one silly relay, the proper dealer approved repair is to replace the damn thing which is 1000 bucks plus. So you are actually losing money since the average joe doesn't know how to repair the computerized controllers, and the specialists that do charge quite a bit. Even then there is no guarantee of a repair. Depends on the damage. But having just a basic body control module and engine control module with relays as support is the best most cost effective way that allows for quick inexpensive repairs since every system is isolated. In the event a relay box is burned, you can still either buy a box which is cheaper than power modules, or just rewire the thing. I mean seriously, where is the extra weight? Have you held the stupid BMW footwell module in your hand and held an interior Ford relay/fuse box in the other? Tell me which is heavier and which has the thicker wiring harness?
@@Membreins AFAIK the thieves just break the steering column lock by turning the steering wheel with a lot of force. But I'm not a car thief, so I won't claim any knowledge on that. The electronic barrier I'm talking about is not the car remote lock. Those can be defeated by replay attacks in some cases (but not if designed properly). The code I'm talking about is on the key itself and is not transmitted via radio. You can't scan that. Programming a new key on-the-spot is *way* above the paygrade of a typical thief. At least here in central Europe, car theft is a non-issue. Apparently there is significant car theft in the UK, but those are break-in thefts - that is, they break into the front door of your house and get the key, or fish the key out through the letterbox. Having one power bus wire instead of many different ones is more economical, whatever the material used. The example with the light clusters is just that - an example that should be easy to comprehend. But in modern cars there is waay more stuff than that, and the wire harnesses are already getting out of hand. Electronics is dirt cheap, way cheaper than mechanical switches or relays or copper, and much more reliable. So instead of wiring every bit of electronics front to back and top to bottom, having a common power bus and a signal bus that transmits commands or feedback is just common sense. I know that it's not the case yet, but you could really supply the whole car with just a couple of wires. Sure, you could build a car that the "average Joe" could repair - but then everyone, including Joe, would just throw it away when it's broke and buy a new car. People are not interested in doing that. They either get it fixed or exchange it. What they are interested in are gadgets - sensors every which way, cameras, motorised everything, heated this and that, soft-touch controls instead of ker-chunk switches, or touchscreens and automatic controls, and chimes instead of clicking of relays. So yeah, you could build an all-mechanical switch and wiring car, but good luck selling it to anyone. You're talking about something that offers nothing to almost every car buyer, and just a fringe benefit for a couple of weirdos like you. There is nothing unreliable about electronics. It can last forever and usually does, when designed correctly. Have a look at the ECUs which almost never fail, or the fly-by-wire systems in modern aircraft. I'd much prefer solid state electronics instead of contactors and relays and switches. I had a lot of those go wrong on me. Sure, you can also screw it up, and manufacturers like Mercedes and BMW are likely offenders when it comes to electronics overengineering and failures, but solid state electronics is a huge boon.
@@horrovac You're wrong about steering locks but you are right about the fact that the moronic consumer is driving auto manufacturers towards marketing gadgets to people and delivering a low-quality car attached. But you're wrong, at least in North America, there are still people with knowledge and skill to maintain a vehicle, build a house, make a gun. That's why there is a strong market for older (pre-2008-ish) vehicles here. I am a mechanic, solid-state ECU's of all types. brands and functions fail all the time. The problem is for consumers, replacing a $1200 body control module so you can open your trunk, is not worth the savings using less copper reduced the vehicle's sales price. Only the manufacturer benefits. Don't call people weirdo, weirdo
@@horrovac Modern keyless entry and start vehicles are susceptible to relay (range extension) attacks. Was not a problem before because keys would not transmit anything without pressing a button. Engine immobiliser transponders were very short ranged, only a couple of cm, which made it highly unlikely that you could walk up to someone and read the key from their pocket. To allow button starts without having to take your key out of the pocket the range had to be extended, thus making it vulnerable. A man with a briefcase walks past you in a supermarket, another man with a similar briefcase is near you car, and they can easily steal it. Manufacturers are introducing motion sensors into keys to prevent them being read while sitting on a table, but that is just a band aid to the problem.
Replacing 1 simple component by multiple other components may result in: more expensive, more complicated, more points of failure, more space requirements and more assembly costs. There better be enough benefits to make this idea valuable.
Have to say, for like my Bench Power Supply, Oscilloscope, and Frequency Generator they all had to have physical latching buttons or rocker switches, removing the slightest possibility of a logical malfunction of a momentary latching _circuit_.
This is an argument from ignorance as you IGNORE the fact that the entire device is billions of transistors working ALL THE TIME. And you're worried about the power-on circuit failure, only??????
Could still pop in a mechanical switch as the input to a set-reset latch. I understand some vintage computers did that for critical signals, so the switch bounce wouldn't fire things by mistake.
10:08 You are exceeding the input common mode voltage (max of VCC - 1.7V) for the LM358 opamp using this high-side current sense. This can lead to some odd circuit behavior in your difference amp.
@@greatscottlab "So far it has worked just fine"; one of the most dangerous statements I hear with regard to circuit operation. Yes, it works in this configuration, but you are reying on the stress margins the designer/manufacturer put into this LM358. Another brand of LM358 may not have the same margins, and could fail if used in the same manner. For long term, i.e. product level, reliability components must be operated within datasheet parameters, often with some additonal margin to boot. You're showing how a circuit can work, but not highlighting risks that may be exposed by this configuration. This can be the difference between "hacking" electronic circuts and designing them.
I've tried to make a single-button latching power switch several times, and I find it quite difficult to get right. Never even thought of just getting an SR-latch IC, though...
Thanks for this great Video. One thing you missed is the useful and for safety often used restart protection of this circuit. For example a safe angle grinder or drilling maschine don't start by itself after replug the power cable even when the power button wasn't shut off
A "555" latch will be much simpler to implement and also less complex and also a little cheaper. But for understanding the concept this is a great circuit. Thank you
What if you build a DC motor speed controller, that changes the speed by how close your hand is (closer the hand gets, the faster the motor spins). Achieving with a discrete transistor amplifier and an opamp, it would work. So what do you think? Is this interesting enough?
i was looking for weeks for this machine and YOU did it? xDD nice! Edit: Hey I noticed u got a loaded cap shorted to the ground through BE of Q2 everytime you push the switch, I'd add a small Q2 E resistor just in case.. But otherwise great design!
This is not truly a latching circuit because it requires timing on the button press. If the initial press of the button from the quiescent state (off) is too long, the output is only going to be ON for a brief period of time. After that, Q3 will have sufficiently discharged C1 and the base of Q2 goes low... and stays low. A true latching circuit would require two manual triggers to cycle the output.
Why are mechanical switches obsolete? They do not require power to work and generally do not breakdown if the are rated correctly. They are also a one piece solution. Unlike the circuit described. Therefore the mechanical switch is least prone to failure due to age and requires no power to operate.
"obsolete" ? what about the satisfying clicking sound ? or the joy of trying to balance the on/off right in the middle. and an array of on off switches allows for an artful/pathetic switching act performance (even if there isn't any device connected at all). it's just not the same. :-D
There is much less chance of magic blue smoke with a switch. Look at new ship controls. You loose ship controls because of some electronics failure. Now you are just along the ride as the ship rams the dock or other ship.
A long time ago I criticized your channel. I was so stupid. This is one of the BEST electronics channels online now. Your simple explanations are so useful and concise. You really improved the production value as well. Anyway, thank you for such excellent content. Cheers! W0XO Jonathan
Dunning-Kruger effect. Most people, however, never learn enough to realize how little they knew when they were so very confident of their own abilities. Good on you!
I'm curious to know what the criticism was back then? I'm a new electronics student, and I believe in learning from all types of questions! It would be interesting to hear your perspective, knowing now that it has changed. No pressure though, take care!
Mechanical switches are so nice and simple and rely on nothing but a physical connection . I work in automation and I see anything else fail on any given day . Plc’s get stuck on on out puts inputs break .. but a mechanical switch lasts almost forever
For mains voltage applications an important failure mode of electronic switches (latch or not) is Failing On, which is often undesirable or even dangerous. This is a failure mode that is very rare in mechanical switches. Failing On can be caused by component failure or by high voltage pulses on the mains voltage. These pulses can be caused by (inductive) switching actions or can be induced by lightning, even without a direct strike. Therefore I prefer to have at least an (additional) mechanical means of switching.
At the industrial level, having mechanical switches and buttons are far more useful than electronic latches, because they ensure a clear break in the line.
What a waste of electricity. A mechanical switch consumes no power. And if I want to disconnect Mains, I want a mechanical switch. I hate non-mechanical switches. Spend the money and buy a real switch that turns things really... off... the life you save may be your own.
Great video @GreatScott! Interesting thing to note is how much current does it use when on standby as I needed to use this latch circuit on coin cell. Since coin cells dont have alot of power, it would be helpful to have a latching circuit to turn off after use or when a specific event occurs.
I teach mechatronics, the latch circuit using a relay is one of the things we teach our students, it is absolutly essential for safety in an industrial setting, love the video! keep em coming scott!
Right. Most common project in my house is adding a true power switch to all my devices that came with a darn long-press to turn on. They drive me insane. Especially on something important in emergencies like a flashlight. I'd rather destroy the looks & case and be able to turn something on & off when I need it than fiddle with long-press.
For future reference, if looking for wall-voltage electrically controlled relays, look at HVAC contractor stores. Every AC powered air conditioner or heat pump uses such a relay, and since they sometimes die there's a need to be able to quickly & easily replace them, thus they're sold in such stores in areas where such appliances are common. In the US, the relays are commonly refered to a "contactors".
While latch circuits are great and have their purpose, I think it is often times unnecessarily over complicates a system. And that is something that is a recurring issue in engineering. We want to over complicate and over engineer a system when a device already exists that is far cheaper and far more reliable. Remember, the more components, the more room for error to occur. As such, we are shooting ourselves massively in the foot for ZERO gain.
A high quality mechanical switch can last longer than a can capacitor and outlast a latch circuit for controlling a large, high voltage, or inductive load.
I have a 1970’s car which I drive erratically in a sand mine. I’ve removed the original wiring loom (as well as doors and panels) and fitted the essential wiring to the ignition, battery, starter motor and Earth. The sand mine has very fine sand which is very Alkaline, so by having a simple mechanical switch I feel it is more robust and easy to diagnose if at fault. Is my assumption correct?
Using electronics for the sake of the technology is a poor practice that is increasingly seen in modern devices. It increases cost and in a lot of cases decreases reliability.. Things like car doors that used to use a perfectly functional mechanical catch and in a lot of new vehicles has been swapped with an electronic push button circuit. Very cool, but the old mechanical part is very reliable and most importantly, continues to work if the vehicle is in an accident and loses power.. In vehicles with electronic door latches, they have to put in a clunky emergency pull which is actually *less* safe because it's not the regular way to get out of the car and it's usually hidden away so it's not so obvious in the name of "design" and fashion, and humans panicing in an emergency tend to forget about things like hidden emergency latches unless like NASA astronauts, they drill and practice emergency procedures over and over.. There are definitely applications for electronics where they can be more reliable and cost effective, but we should be very carefully considering whether electronics are really "better"..
oh, there are so many instances where bad design is used for the sake of looks or high-tech feel. One simple example is hiding screws under glued-on feet, labels and such. It's both funny and sad how we went from "it's solid state, it's eternal" to "it's solid state, drains batteries, glitches, breaks faster, and is very difficult to repair".
Good point. The problem is that when the new over complicated solution becomes the "norm" it may become cheaper to mass produce than the previously cheaper simple solution which, now being more expensive, gets discared.
imagine a stove plate with touchscreen that uses such latch circuit to turn it on and off , imagine they use relay's instead of solid state switches ... and then imagine one relay gets fused in the on position and now you got no way of turning the darn thing off... yeah that is actually a true scenario that a friend of mine experienced a few weeks ago, he had to cut the power to his whole kitchen for a while , dunno who made/designed that stove plate but they should be sued for using crap quality relay's to deal with 20-30A at 220V
More sensitive to small changes e.g. trip wire alarm/burglar system in the form of a laser curtain needs to be very sensitive and may need a hundred different trigger points
when mechanical switch systems got malfunctions/broke. you only spend pennies to replace 1 items, simple trouble shooting since it less components thus less time waste. If Digital/micro electronics got malfunctions/broke. You'll spend the same pennies with more items to replaces and more time spend to troubleshoot it if no visible damages are seen. I've meet lot's of new Uni graduates that promotes all digital or micro electronics to replace the decades old rugged mechanical switches just to be scrapped after the Company spend Ten of Thousands of Dollars to Install it and another Thousands of Dollars spend to hires the "experts" to trouble shoots why the signal lamps on some of CNC machines goes off and some malfunctions to the start stop commands on the HMI, not also mentioning the money the Company lost to the downtime because the Programmer have to contact his HQ for the Administrative password set up by the previous Engineer..on Sunday. The flaw of young peoples that watched some Non-Industrial standard Engineering RUclips Videos thinking "Why No One Do this thing" when get their first Professional Job on the Engineering sectors.
Pretty normal in Denmark too. We also have houses from 1980's with latching relays and 8VAC low-voltage input switches , homerun to electrical panel. I made nice DIY project automating all the 16 mechanical relays with ESP8266/ESPHome/HomeAssistant relatively easy :)
Hey Scott I hve been watching u for many days but u have written everything in your notebook next video plzz show us about ur electronics book Or send pdf please 📕
You cant beat a simple mechanical switch for anything battery powered. A latch switch will always require power and that will be a drain on the battery which will ultimately go flat. A proper switch disconnects the battery completely and this means the battery will last as long as its able to hold charge, which in some cases is years. Apart from that it takes up so much less space. Its a no brainer, use a mechanical switch whenever possible.
So, in theory, this would be capable of running a DC motor, then reversing the polarity to make it run backwards. That was a question but I did not word it like one lol
This sounds good for low-power applications, but I wouldn't trust it for the lighting in my corridor. Also I would have to have a place to put it, when a commercial latch like that mechanical one would fit neatly in my fuse box.
Honestly, depends on building size and area of operation. A latch circuit would be useful if you are trying to use it alongside a occupational sensor and want to reduce energy consumption. That being said, a hard switch should still be in the room to override the latch switch.
I won’t mention it again, but I have a challenge for Great Scott! Build a video monitor camera system that sits under the workbench and tracks dropped items, with a laser pointer to show you where the tiny screw, resistor, or whatever you dropped actually ended up! The savings in man/hours looking for the tiny item alone might save millions of hours! I have been known to drop the same item up to three times, and spend a half hour trying to find it. Amazing how far they can bounce and where they can end up. Would be so cool to have it mounted under the workbench, and a laser pointer shows where it went (or as far as last point in space seen, in case it went out of sight.
I have a personal rule that if I don't find the dropped item within 10 seconds, it is lost to the abyss. Life is too short to be on my hands and knees looking for a 10 cent component. It also focuses my attention when handling expensive and/or limited supply components.
@@msmith2961 it’s a good philosophy. I find though often the tiny little item I dropped is the last one, or the only one. It’s either find it, or spend an hour finding a replacement, ordering it, and waiting for it.
While I do use mosfets or IGBT's for circuit switching, they do have an inherent issue. The BIG reason mechanical switches are NOT obsolete is the electrical isolation. Exactly what was seen in your breaker! You have a solenoid coil that latches and delatches a mechanism that holds the contacts closed, BUT more importantly, they are electrically isolated from each other. Build an isolated solid state switch that can handle 40 amps at least. Then maybe, mechanical switches are obsolete!
Hi, my 8 year old wants to know the max input voltage for your circuit- does it go all the way up to 120? Can we use 3? And how do we calculate this for next time? Thanks!
Another place the latch circuit would be handy is for machinery in the event of a power outage. If the power goes out, I don’t want my table saw to restart automatically when the power comes back up. It would be nice to replace the mechanical switch with a latching circuit. More expensive saws have a magnetic switch that automatically shut off when the power dies.
No! Mechanical switches don't use any energy when they are off. Iits a shame we have to use power strips to turn off our electronics. Bring back the TV that the switch actually turns off the TV. Routers and cable boxes the same. We want to save energy? We must use appliances that don't use one drop of energy when they are off. I won't run any neutrals on my switching circuits in my home. The hot is the only conductor that needs a switch. The neutral it were it belongs at the light box or at the outlet box. I'm old school and plan on staying that way. I have all the new electronics but when I want them off they are off completely. 73
Hola, dando vueltas en yt apareció éste video que me resulta muy útil ya que quiero hacerle unas mejoras a mi auto y puedo aplicar este proyecto para los faros auxiliares. Pero hace ya más de dos semanas busco un circuito que no tenga programacion alguna(no PIC, no Arduino, no 555), que funcione con transistores y un solo boton que al pulsarlo genere unicamente dos o tres destellos. La duracion de los destellos es poco relevante, con que duren .3 segundos ya es más que útil. Si tenes algun video con algo asi estaría muy agradecido. Saludos desde Buenos Aires!!!
Thanks for this video Scott. The single-button latching circuit seems exactly what I've been looking for for a little battery box I'm currently throwing together. Quick question, though: What is the time constant for discharging the capacitor when turning the circuit on? I.e. how fast do I have to let go of the button to avoid immediately turning the circuit off again? ;-)
The first 1,000 people to use the link will get a 1 month free trial of Skillshare: skl.sh/greatscott07221
1:35 i hate this new bgm while placing those LEDs.....
Older one was awesome to hear 🤠🤠
Can you make a momentary wireless AC footswitch project? Normally open.
@@hxhdfjifzirstc894 you want to turn on ac only if someone standing near ac ? You can go for PIR sensor as it have ideal for this type of work, you may have seen automatic lights in corridors, same way you can operate AC too.
Spending 10% of your video on an advert wasn't enough?
Hi Great Scott, just a little translating advice:
in your “pro and contrast” dialog, it should be “pro and con”
pro = yes (affirmative) / con = no (negative)
I am not certain what language this stems from, my guess is either Latin, or Greek.
In most situations I still feel better when I hear and feel the "clack" of a mechanical switch
Well, that is definitely a selling point for mechanical toggle switches.
@@greatscottlab you can still include haptic feedback to the latch, so... it is something that can be a big plus
When I read "clack" I expected you to talk about relays...
And no battery drain when off.
@@greatscottlab thank you for the video I've been trying to find a good circuit for the job and you found it for me thank you for all the great videos keep it up
I think there is a trend to over-complicate simple devices. you did point out where latch circuits are an advantage, but there hundreds of examples where manufacturers are using a 10 component board to do the same job as a simple device. This is why you cannot repair your own tech any more it always seems to have to go back to the factory to be fixed. For example Apple phones and John Deer tractors. And now the manufacturers of cars that want you to push a button rather than open a door or not have to put a key in the ignition are failing to deliver their cars because of a micro chip shortage. I do hope the current "right to repair" movement is successful and we can stop this madness of having to pay a fortune at the garage to get the cars interior light repaired.
I agree that over-complication is an issue. I bought a used drip coffee maker (barely used, just out of its 1-year warranty) that had a latch circuit to turn it on and off. The heating elements were 230V AC and the latch circuit was 12V DC. After a few months the machine wouldn't turn on anymore. Turns out the latch circuit died, everything else was fine. So I replaced the whole latch circuit with a 230V AC 10A mechanical toggle swith with a built-in LED, which cost me 1.50€. It's been 2 years and the machine is working without an issue. These companies are sacrificing reliability and screwing over the environment for a few pennies.
this seems like an irrelevant complaint. if you're opening up a circuit to (de)solder it, that's already inaccessible to most. and whether a mechanical switch or latch is used, the complexity of repair is about the same at that point. plus you can replace it with a switch if you really want and if the application makes sense for it. "right to repair" doesn't seem to apply here
@@LC-hd5dc The point is: The smallest Replaceable Unit (SRU) used to be something like a switch or relay or some other discreet component costing about £1. Now everything is part of a complex circuit on a Printed Circuit Board (PCB) costing about £100 to replace. Sometimes you cant even replace the PCB and you have to buy the whole unit that the PCB is part of. Soon, you wont even be able to have your car/TV/fridge/washing machine repaired at all, they will all be repair-by-replacement. Then, maybe you'll look back and think, when did this all start? And you will remember, oh yes; it all began 30 years ago when they decided to replace a mechanical switch with a complex switching circuit.
I both agree with you on this, and think it's a bit out of place here. There's been countless examples of stuff being complicated for no other reason than someone either in management deciding it has to be "special" somehow and it gives no real benefit, or just engineers and designers that are lacking time to stop and think about everything from the start.
As a parallel talk I'm fully on it, being a product development engineer now it was literally the topic of our last meet up at the company (the boss saying "guys, sometimes we just need to... Stop, breathe, look at what the heck we're doing, and think: WHY is it like this? Can't it be made easier?"), and I agree right to repair just has to happen and disposable devices have to stop. People gotta stop feeding this insanity.
But I'll also say that I don't think the complaint relates to the video. There's several situations you'll want a circuit like that in place of a mechanical system. As an example, anything remote controlled. You'll not want that the only way to get that remote controlled device on and off is the mechanical button all the way at the device, neither you'll want to waste power unnecessarily with who knows, a mechanical actuator to that switch. A latch circuit solves the problem no doubt the simplest way.
This circuit being or not an unnecessary complication is always a matter of situation. It may very well be simpler than a mechanical switch even, remember a mechanical switch has to deal with contact bouncing and protecting the contacts against corrosion and arching.
Yes! I like older cars where the boot for example is held down with a simple, good old fashioned, mechanical handle. Nowadays, it's some nonsense electronic latch. Just another thing to go wrong.
For battery operated devices that are used infrequently, I really prefer a mechanical switch where there is ZERO drain (other than the compulsory modelled resistance in the battery). Otherwise when you need said devices, you find dead batteries at best or corroded terminals usually.
Yes. I have a very expensive flashlight and I have to unscrew the end where the batteries go because otherwise they drain when it's not being used.
Use a mechanical latch switch. They only draw power to change state.
@@FullCircleTravis or a regular mechanical switch...
mechanical switches and relays are important in many applications due to considerations surrounding failure modes. in safety and life critical applications the failure mode is critical.
Can someone explain why? I am building a soft latching circuit myself, based on PMOS, and the leakage current when off is low enough that it would take hundreds of years to drain the battery (yes I know it would die naturally well before that). the resistance of the mosfet is also very low when on. something like 50 milli-Ω...how does that drain/corrode a battery? 😕
Using dedicated ic is kinda cheating, and I feel like transistor latch has some kind of problem where if u held down the button too short or too long a duration, undesired result can happen because of the capacitor
And the ic also uses 2 button, a t flip flop will be needed for 1 button latch, and here is where the challenge comes, it will just oscillate if the button is pushed because it is missing clock signal, a master slave configuration is needed
this video did not cover that. A latch is essentially a digital flipflop, I challenged myself to build a 1 button latch when I was new to learning flip flop, surprisingly, when I searched, everything I found was transistor latch, I had no resources to learn from and didn't know where to start, I had to figure it out myself.
And this video didn't bring anything new to the table, just the same transistor latch as every other video, in a place where latch videos are mostly transistors and digital ones are so rare to find, in most cases they just slap a flip flop on a slide and start teaching theory, where in real world a latch is more than 2 nor gates so it didnt really work in practice, it was more like a digital logic class than a latch video......
Utterly disappointed......
You're right about long & short switch presses possibly causing problems in some designs, though short presses at least usually aren't a problem.
As for the circuit itself, it doesn't mention that the "out" terminal needs to always have a current (though small) to ground in order for it to reliably work- otherwise it'll occasionally switch itself to a "default" state (which depends on the "polarity" of the transistors you're using) instead. Not usually a big deal, but something to be aware of.
This circuit _is,_ incidentally, a flip-flop, though certainly an optimized one. In particular, the capacitor gets charged to a state such that when that central switch is flipped, it will force the circuit into the _opposite_ state from what it was in before- it doesn't malfunction by oscillating when the press is too short, but instead too long, or even malfunctions by not flipping state if the switch is pressed a second time too soon after it was last pressed.
As for the normal T flipflop, the normal situation is to connect the switch to both a capacitor _and_ the clock input of the flipflop _and_ a resistor that shorts the capacitor- the capacitor will be almost instantly charged when the switch is pressed, and will stabilize the signal into the flipflop's clock input long enough for the switch to reach it's fully depressed position, where the switch _is supposed to_ tie the capacitor and clock input directly to power (or ground, for inverted-input inputs). The resistor & capacitor will control the "debounce period" that follows an interruption of the switch connection, but for the small push-switches here can reasonably be a second or less without problems. The data input, of course, needs to be tied to the flipflop's inversion output.
I felt it pretty bad when the NOR based latch was discussed - I've had nothing but trouble when making a transistorized version, it needs equal loading on it's outputs...
The NAND version is topologically the same and is very stable, even better you can make them with just 4 transistors o_O
And this reminds me of a curious circuit I remember seeing somebody posting on reddit a year ago, there are differences but it'll likely still have a problem with input voltage changes causing malfunction - definitely a no-go for anything battery operated... Though in my take on latching power-switches, I used that effect to not only detect when the battery was low - but also protected against short-circuits!
Edit: I just saw the thumbnail to ElectroNoobs' video, and that circuit looks awfully similar to this one...
Also worthy of note, GS got 4x views on his rehash of Clive's Joule Thief video - and they say something's not worth doing when it's already been done!
You are showing your gross ignorance based on a single video. Yes, this particular simplified circuit has timing issues (see my other comment for full explanation) but that doesn't mean all latching circuits built with discrete components suffer this issue. Also, IC latches are not just of the R-S type and DO NOT REQUIRE separate input triggers for toggling. You don't know enough to be criticizing.
@@DiffEQ Dude, don't just walk in and drop ad-hominems - saying "your'e stupid, stop talking" is not going to change minds; if you want to show an error, point out what went wrong and how to fix it, don't just hit at it blindly and spew insults like that...
Nothing is worse than an ignorant man accusing someone of being ignorant!
Also, don't just go 'refer to my previous comment' like that. Nobody will find it, and that's a fact...
Either repeat what you said, or put a hard link to your comment - don't just go "x marks the spot" and expect people to go find it...
Now it might seem like this guy doesn't know enough to criticize the theory / lesson here; he's absolutely qualified to judge a *video* about the basics - a video which fails to cover the basics in a complete fashion, only skims through the cool and important bits. No variations, no run-down of the caveats - I found this format in the SEPIC converter video, where that design was all hyped up - without discussing the huge drop in output efficiency, or the alternative (a flyback converter) which would achieve the same goal, and add the benefit of electrical isoation...
At least, that's what I think is being discussed here; this thread is pretty old...
Anyway, thanks for coming to my TED talk - that is all for now
Don't forget you can buy latching push buttons, which when pressed and released close a pair of contacts and they remain closed until the button is pressed again.
So there are times when a latching push button is a good option and you don't need to build a load of electronics.
these are called bistable buttons, and yeah, in many cases it's enough
Unless momentary, ALL switches are latching switches. WTF are you babbling about? The TYPE of button is not the topic here... it could be push, toggle, slide, etc. UGH How did you miss the context of this discussion so completely?????
For a headphone I am designing I would like to use a nice looking button, but the circuit requires a switch or a latching button. The latching button is too tall meaning I would have to increase the case of the headphone. A circuit like this could solve my issue. I only wish a circuit of some kind existed so I wouldnt have to solder as much.
Mechanical switches are certainly not obsolete. They are simpler and cheaper for nearly all maker-type projects. Nice information to know if I ever build a project that requires it. I probably have 200 switches of a dozen or more styles and there will probably be many left when I am gone. Why change the way I do things now?
Great Circuit for high current. FYI the Momentary button 1-2 is floating when off. I made this for a project and it would randomly turn on. Use a 100k ohm or more resistor to Tie the 1-2 of the switch to GND and no more problem
Been learning electronic as a hobby and this channel is such a gem, the pace and diagram explanations are on point. Thank for making high quality content.
Honorable mention to the humble (two coil) bistabile relay which is also set reset, and very useful in applications where a pseudo-latched run off the mill relay might draw to much power over time.
This is obviously a really interesting and problem specific solution to mechanical switches with potential benefits, but all I see when I look at a latch circuit is extra points of failure.
Depends on the use-case. Switch "bounce" can sometimes be the bigger issue.
Mechanical switches (relays, contactors, even buttons and switches meant for small loads or logic signals) have to be the number one cause of electrical failure in industry.
More than loose wire terminations and failed capacitors?
@@kuni45 But the vast majority of mechanical switches fail to a safe state. Mechanical switches also maintain fidelity for small signal AC information that would otherwise be distorted or completely destroyed by the gate logic transistors and they are immune to voltage polarity. Mechanical switches are far from obsolete.
Because you think complexity means unnecessary. Adding a square-root button to a calculator also adds an extra point of failure. Funny how calculators work for decades with all the "added points of failure." SMH
I've made a nice PCB that toggles a switch output on button single press, double-press, long press, etc., with debouncing. And it has an I2C and serial interface. It's very neat.
Good for you. And where is it?
In equipment reviews often a mechanical on/off switch is seen as a good thing. I agree. I would never use a latch circuit in anything I build as it is just a complicated and expensive solution to something that is not a problem. An electronic light switch that was widely used and prone to remote activation would be a hugely entertaining discovery. In a winters evening you could take a dog for a walk and switch peoples lights off in a block of flats and listen to the residents blundering around in the dark to turn them back on. Then in summer walk the same dog at three in the morning and turn them all back on. Even bad design can be fun in a prankster kind of way.
I use a power latch circuit for my bicycle automatic shifter. The cadence reed switch latches it on (also an input) and the Arduino switches it off if 0 speed for 30 seconds. Works great and no power draw when off.
I love the older this channel gets the more confidence you got with making videos and putting some hood humor in
Funny enough, when I fix up 80's Saab radios, the one model that has a latch circuit is the one that often won't power on until the circuit is recapped or power button repaired. The mechanical volume dial switch models just about always power up
A clicky pen is a good latching machine, whose mechanism can be used to design Motor Contactors.
Use a NAND latch for better performance, it doesn't need equal loading on the outputs to prevent it from 'sticking' to one state should it have a lower impedance.
Also, unless you used capacitive touch or some sensor - you needed a mechanical switch to make the button! And then another in the form of a relay...
Please don’t use this kind of switches or latches for mains voltage purposes. See the comments below (Joop and others). Mains switches shall comply requirements for thermal resistance, fire resistance, clearance distances (as per over voltage category II), failure mode requirements, between others. Component standards and product standards are mandatory in mains related, not an option.
Pretty sure he used a mechanical latch for his lights. AC would fry those transistors he used for the other switch.
Use a relay
The problem of electronic switches like shown in the video is that it has no "memory" to remember its state. When there is a power problem/dip for a short period of time, it turns the device off and it will stay off until you press the button again. Not very suitable for devices that needs to stay on.
Have a think about using TRIACs & SCRs as your switching elements. There is a latching function built in for DC & a very simple capacitor shunt bypass allows the SCR or TRIAC to switch off. These are often overlooked devices with impressive ratings for literally pennies...
5:37 Electro Boom moment
Sometimes a power loss state memory can only be done with a mechanical latch.
And by "sometimes" you mean to say that PLSM is NOT unique to mechanical switches/latches. So, what was the point of your qualified statement? I have over a dozen devices in my home, including a PC, that has programmable return-from-power-loss state with NO MECHANICAL latches.
I love one shot- latches, I make bank on service calls swapping them to a mechanical . Keep them coming.
In a nutshell, every switch has its own applications.
Every switch, every tool, and most (maybe not every) programming features have their own purpose and application. There is never a one size fits all situation, and it is about determining which one is best for the situation.
I used a latching relay to drive a fog light relay in my SUV so I could use an OEM push button. The latching relay gets power from the tail light circuit so the fog lights can only come on when the tail lights are on. When the tail lights turn off, the latching relay loses power, and the fog lights automatically turn off. They won’t turn back on again unless the OEM button is pressed.
I wanted a circuit to pop up my headlights. There was a one year only button that can keep them up with the lights off. Completely different wiring and controller... or an annoying blank off plate. I had to consider, flash to pass overide to make sure the buckets go up for that, no matter the state. Fog lights require park lights like your circuit, also should switch off with high beams since fogs and high beams are considered as 6 lights, whereas regular headlights and fog lights are considered 4, the legal limit. Automotive lights are more complicated than they look on the surface.
Thank you for saving other drivers' eyes!
In my opinion soft power is not power saving friendly. It is a novelty at best. A mechanical switch insures isolation.
Funny - this is timely as I fight the failing latch-type power switch on the back of my Keurig and wonder why they didn't use a toggle. At least I know why now. :-)
Thanks, interesting video. I use a latch circuit in a ESP8266 doorbell using a P and N channel MOSFET, very small IC's exist that have both included, like the Si4599
I can't find the part you're describing. Any chance you could post a link or some more info? Something like that is exactly what I need cluttering my parts bin waiting for a future project.
@@swiz747 I tried posting a link but my comment was deleted. I've corrected the part number, it's Si4599
@@wjn777 perfect, thank you! I managed to find the part but unfortunately I can't find any in stock. I'll have to find similar parts but this gave me a great start, thanks again!
@@swiz747 You can also try IRF7317
Without me even watching the rest of this video, I do have to agree that latch circuits have their place. However in the automotive industry they are widely over used and result in overengineered circuits that provide no extra benefit from their counterparts 20 years ago. On top of that with vehicle thefts on the rise, having something mechanical like an ignition cylinder is more important than ever. I know nothing I say here will have any impact. And I am not against latch circuits, or any electronic controls that go beyond a simple relay circuit. They have their place most definitely. I am just upset that the core of automotive design doesn't need over complicated circuits. It doesn't improve fuel efficiency. It doesn't lead to greater power gains. Worst of all it leads to vehicles being scrapped way before their time due to increased repair costs. Today Toyota considers the lifespan of a vehicle at 3 years. What happened to vehicles lasting 30+ years? Wouldn't that have a larger positive environmental impact? Of course companies will lose money based on their business models. Even EV vehicles are over the top with their engineering. This is proven with many small companies providing EV swaps into classic cars. The only complex electronics are the battery, electric motor, and the computer that drives all that. No different than fuel injection vehicles since the late 80s to early 2000s. After that it just became a nightmare of over engineering. Emissions were never improved. Perhaps some power gains but believe it or not those power gains come with enhanced emissions. The old school dyno emissions machines proved that until they were replaced with OBD2 emission tests, outside diesels. Sorry for the blah blah. I'm just trying to say there are so many ways a simple on/off switch, with relays if necessary, is probably the most viable and most easily repairable circuit that I know of.
Just to throw out an example, I would love to know the person that created the footwell module in some later BMWs. I mean, just why? Its software is prone to corruption from most high end scanners. Results in a very expensive repair from the dealer and actually has created a whole market for diy equpiment and specialists. And there is no work around unless you really rewire the harness and will still be left with a module unhappy shouting codes at you. And what does it control? Stuff like power windows and crap. I swear if someone explains to me how that is more efficient than just having either postive or ground control with relays and fuses over your power windows, power locks, and other silly stuff in your door, please, I'm all ears.
How the hell is a mechanical ignition cylinder supposed to provide security here? They're piss-easy to pick and you don't even have to do that, you can just connect the wires and off you go. But you can't do that nowadays, because when the key with a proper code isn't present, the ECM is disabled, and you ain't going nowhere. That's an electronic system that is an (almost) impenetrable barrier to theft, the mechanical bit is worth nothing. That's why cars have fobs instead of keys nowadays.
The electronic circuits in cars help save expensive raw materials like copper, and they save weight. For taillights you need a wire for position lights, one for brake lights, two for the indicators, one for reversing light and one for fog taillight. All of them must be thick enough to carry the current required without heating up or creating losses. All the switches - relays, brake switch, light switch and so on - must be beefy enough to make and break the connection, and they must be sturdy enough to do that over thousands of cycles. With an electronic system, theoretically, you just need a power supply wire and a bus wire, and send signals (CAN bus, say), to the rear lamp clusters and they use a couple of Mosfets to switch the lamp required on. That's a lot of copper, lots of weight, lots of mechanical switches, and, above all, lots of money saved, and unless you design the electronics stupidly, it will never fail.
@@horrovac Mechanical cylinder provides a mechanical steering column lock, which takes more skill and time to break, depending on the design. Picking a lock with a laser cut design is not easy. Most likely you'd have to smash the column open. Not saying its impossible but louder and more time consuming than just programming a fob the way current car thefts are being done. Not to mention the key with a mechanical lock also usually has programming that needs to be detected. So now you have much more protection than a simple electronic system where once you get the fob programmed, it takes car of the steering column lock since its electronic, push start means no cylinder needs to be destroyed, and away you go.
That electronic barrier you speak of is actually quite easy to get through. There are numerous scanners you can pick up that do key programming. If you have access to dealership info and equipment its even easier. A lot of illegal type of equipment that works flawlessly is available for purchase. These are all the reasons car thefts are happening in such numbers today.
Now with the wiring, I'm not sure how you think the computer instead of a relay and switch is getting the power to the lights? The computer is just bypassing what the relays used to do. You still need to run wiring regardless. And the wiring needs to be thick enough for whatever the load requires. Most manufacturers switched to aluminum wires awhile ago anyways. A lot of wiring now is too thin actually causing issues and needing repairs which require thicker copper wiring to be spliced in if you want the repair to last. And if you want a completely computerized relay system, the board and components must be hefty enough to take the load. Look at the infamous Chrysler/Dodge integrated power module. Piece of a junk. I rewire these for people regularly leading to the thing looking like a christmas tree. It fails. Often. And instead of just replacing one silly relay, the proper dealer approved repair is to replace the damn thing which is 1000 bucks plus.
So you are actually losing money since the average joe doesn't know how to repair the computerized controllers, and the specialists that do charge quite a bit. Even then there is no guarantee of a repair. Depends on the damage. But having just a basic body control module and engine control module with relays as support is the best most cost effective way that allows for quick inexpensive repairs since every system is isolated. In the event a relay box is burned, you can still either buy a box which is cheaper than power modules, or just rewire the thing. I mean seriously, where is the extra weight? Have you held the stupid BMW footwell module in your hand and held an interior Ford relay/fuse box in the other? Tell me which is heavier and which has the thicker wiring harness?
@@Membreins AFAIK the thieves just break the steering column lock by turning the steering wheel with a lot of force. But I'm not a car thief, so I won't claim any knowledge on that.
The electronic barrier I'm talking about is not the car remote lock. Those can be defeated by replay attacks in some cases (but not if designed properly). The code I'm talking about is on the key itself and is not transmitted via radio. You can't scan that. Programming a new key on-the-spot is *way* above the paygrade of a typical thief. At least here in central Europe, car theft is a non-issue. Apparently there is significant car theft in the UK, but those are break-in thefts - that is, they break into the front door of your house and get the key, or fish the key out through the letterbox.
Having one power bus wire instead of many different ones is more economical, whatever the material used. The example with the light clusters is just that - an example that should be easy to comprehend. But in modern cars there is waay more stuff than that, and the wire harnesses are already getting out of hand. Electronics is dirt cheap, way cheaper than mechanical switches or relays or copper, and much more reliable. So instead of wiring every bit of electronics front to back and top to bottom, having a common power bus and a signal bus that transmits commands or feedback is just common sense. I know that it's not the case yet, but you could really supply the whole car with just a couple of wires.
Sure, you could build a car that the "average Joe" could repair - but then everyone, including Joe, would just throw it away when it's broke and buy a new car. People are not interested in doing that. They either get it fixed or exchange it. What they are interested in are gadgets - sensors every which way, cameras, motorised everything, heated this and that, soft-touch controls instead of ker-chunk switches, or touchscreens and automatic controls, and chimes instead of clicking of relays. So yeah, you could build an all-mechanical switch and wiring car, but good luck selling it to anyone. You're talking about something that offers nothing to almost every car buyer, and just a fringe benefit for a couple of weirdos like you.
There is nothing unreliable about electronics. It can last forever and usually does, when designed correctly. Have a look at the ECUs which almost never fail, or the fly-by-wire systems in modern aircraft. I'd much prefer solid state electronics instead of contactors and relays and switches. I had a lot of those go wrong on me. Sure, you can also screw it up, and manufacturers like Mercedes and BMW are likely offenders when it comes to electronics overengineering and failures, but solid state electronics is a huge boon.
@@horrovac You're wrong about steering locks but you are right about the fact that the moronic consumer is driving auto manufacturers towards marketing gadgets to people and delivering a low-quality car attached. But you're wrong, at least in North America, there are still people with knowledge and skill to maintain a vehicle, build a house, make a gun. That's why there is a strong market for older (pre-2008-ish) vehicles here.
I am a mechanic, solid-state ECU's of all types. brands and functions fail all the time. The problem is for consumers, replacing a $1200 body control module so you can open your trunk, is not worth the savings using less copper reduced the vehicle's sales price. Only the manufacturer benefits.
Don't call people weirdo, weirdo
@@horrovac Modern keyless entry and start vehicles are susceptible to relay (range extension) attacks. Was not a problem before because keys would not transmit anything without pressing a button. Engine immobiliser transponders were very short ranged, only a couple of cm, which made it highly unlikely that you could walk up to someone and read the key from their pocket. To allow button starts without having to take your key out of the pocket the range had to be extended, thus making it vulnerable. A man with a briefcase walks past you in a supermarket, another man with a similar briefcase is near you car, and they can easily steal it. Manufacturers are introducing motion sensors into keys to prevent them being read while sitting on a table, but that is just a band aid to the problem.
I find over complicating something that has worked very well for so many years dumb. Mechanical switches will never be obsolete
you are right. but bulky and pricey yes they are, compared to digital stuff. that is why we so rarely see them nowadays.
I agree but sometimes you want a microcontroller to switch itself off and that's where a power latch circuit is very useful.
Replacing 1 simple component by multiple other components may result in: more expensive, more complicated, more points of failure, more space requirements and more assembly costs. There better be enough benefits to make this idea valuable.
Have to say, for like my Bench Power Supply, Oscilloscope, and Frequency Generator they all had to have physical latching buttons or rocker switches, removing the slightest possibility of a logical malfunction of a momentary latching _circuit_.
This is an argument from ignorance as you IGNORE the fact that the entire device is billions of transistors working ALL THE TIME. And you're worried about the power-on circuit failure, only??????
Love your content. Love my mechanical switches. Compact, tactile feedback, certainty.
I mean cool...but adding an absurd amount of unnecessary toggle switches inside your car will make you feel like a fighter pilot 😎
My electric converted ride-on mower's blades are operated by a toggle switch with cover (missile style) over it :)
@@RaglansElectricBaboon Yes. Need to prevent accidental triggers until you're fully ready to initiate a grass-blade massacre!
Could still pop in a mechanical switch as the input to a set-reset latch. I understand some vintage computers did that for critical signals, so the switch bounce wouldn't fire things by mistake.
10:08 You are exceeding the input common mode voltage (max of VCC - 1.7V) for the LM358 opamp using this high-side current sense. This can lead to some odd circuit behavior in your difference amp.
Thanks for the feedback. So far it worked just fine.
@@greatscottlab "So far it has worked just fine"; one of the most dangerous statements I hear with regard to circuit operation. Yes, it works in this configuration, but you are reying on the stress margins the designer/manufacturer put into this LM358. Another brand of LM358 may not have the same margins, and could fail if used in the same manner. For long term, i.e. product level, reliability components must be operated within datasheet parameters, often with some additonal margin to boot. You're showing how a circuit can work, but not highlighting risks that may be exposed by this configuration. This can be the difference between "hacking" electronic circuts and designing them.
@@donbarr9487 Aha!
I've tried to make a single-button latching power switch several times, and I find it quite difficult to get right. Never even thought of just getting an SR-latch IC, though...
5:37 Love the way you pronounce Strong-So-Ko-Lear
Sounds supper awesome !!
German is so hardcore
Thanks for this great Video.
One thing you missed is the useful and for safety often used restart protection of this circuit.
For example a safe angle grinder or drilling maschine don't start by itself after replug the power cable even when the power button wasn't shut off
Great observation 👌
A "555" latch will be much simpler to implement and also less complex and also a little cheaper. But for understanding the concept this is a great circuit. Thank you
Mechanical Switches will never be obsolete. good luck making a 240vAC 32amp electronic switch
Thanks for the circuit/video. I really enjoy them!
You are welcome 🙂
What if you build a DC motor speed controller, that changes the speed by how close your hand is (closer the hand gets, the faster the motor spins). Achieving with a discrete transistor amplifier and an opamp, it would work.
So what do you think? Is this interesting enough?
i was looking for weeks for this machine and YOU did it? xDD nice! Edit: Hey I noticed u got a loaded cap shorted to the ground through BE of Q2 everytime you push the switch, I'd add a small Q2 E resistor just in case.. But otherwise great design!
This is not truly a latching circuit because it requires timing on the button press. If the initial press of the button from the quiescent state (off) is too long, the output is only going to be ON for a brief period of time. After that, Q3 will have sufficiently discharged C1 and the base of Q2 goes low... and stays low. A true latching circuit would require two manual triggers to cycle the output.
man I love this guy
😉
The ergonomics of a mechanical switch are unique. They will not be replaced where they make sense.
Why are mechanical switches obsolete? They do not require power to work and generally do not breakdown if the are rated correctly. They are also a one piece solution. Unlike the circuit described. Therefore the mechanical switch is least prone to failure due to age and requires no power to operate.
"obsolete" ? what about the satisfying clicking sound ? or the joy of trying to balance the on/off right in the middle. and an array of on off switches allows for an artful/pathetic switching act performance (even if there isn't any device connected at all). it's just not the same. :-D
I do love a mechanical toggle switch. But sometimes latch is the way to go ;-) You will see it in upcoming projects ;-)
Great video as always 👍
There is much less chance of magic blue smoke with a switch.
Look at new ship controls. You loose ship controls because of some electronics failure. Now you are just along the ride as the ship rams the dock or other ship.
Or bridge.
A long time ago I criticized your channel. I was so stupid. This is one of the BEST electronics channels online now. Your simple explanations are so useful and concise. You really improved the production value as well. Anyway, thank you for such excellent content. Cheers! W0XO Jonathan
Dunning-Kruger effect. Most people, however, never learn enough to realize how little they knew when they were so very confident of their own abilities. Good on you!
I'm curious to know what the criticism was back then? I'm a new electronics student, and I believe in learning from all types of questions! It would be interesting to hear your perspective, knowing now that it has changed.
No pressure though, take care!
The switches you use are also mechanical. The problem is when the electronics go wrong your load won't switch off or maybe on.
Hey Scott! Wondering if you could do the Seeduino XIAO boards as your next arduino replacement video. Great video as always.
Great Video! 👍
... And long live the *Stromstoßrelais* !
Haha YES!
Mechanical switches are so nice and simple and rely on nothing but a physical connection . I work in automation and I see anything else fail on any given day . Plc’s get stuck on on out puts inputs break .. but a mechanical switch lasts almost forever
Yes, theres also the problem with current draw using electronic switching
For mains voltage applications an important failure mode of electronic switches (latch or not) is Failing On, which is often undesirable or even dangerous.
This is a failure mode that is very rare in mechanical switches.
Failing On can be caused by component failure or by high voltage pulses on the mains voltage.
These pulses can be caused by (inductive) switching actions or can be induced by lightning, even without a direct strike.
Therefore I prefer to have at least an (additional) mechanical means of switching.
At the industrial level, having mechanical switches and buttons are far more useful than electronic latches, because they ensure a clear break in the line.
What a waste of electricity.
A mechanical switch consumes no power.
And if I want to disconnect Mains, I want a mechanical switch.
I hate non-mechanical switches. Spend the money and buy a real switch that turns things really... off... the life you save may be your own.
Great video @GreatScott! Interesting thing to note is how much current does it use when on standby as I needed to use this latch circuit on coin cell. Since coin cells dont have alot of power, it would be helpful to have a latching circuit to turn off after use or when a specific event occurs.
I teach mechatronics, the latch circuit using a relay is one of the things we teach our students, it is absolutly essential for safety in an industrial setting, love the video! keep em coming scott!
Why are electronics and electricity so complex and consumerist ?
These latch circuits have their place, but you should use the right kind of switch for your application.
Why over complicate it?
Right.
Most common project in my house is adding a true power switch to all my devices that came with a darn long-press to turn on. They drive me insane. Especially on something important in emergencies like a flashlight.
I'd rather destroy the looks & case and be able to turn something on & off when I need it than fiddle with long-press.
Great experiment.
i have tried it with 555 timer ic.
The issue is the circuit required always a healthy power supply.
May be you picked a bipolar 555. There are CMOS versions that take a fraction of the current.
For future reference, if looking for wall-voltage electrically controlled relays, look at HVAC contractor stores. Every AC powered air conditioner or heat pump uses such a relay, and since they sometimes die there's a need to be able to quickly & easily replace them, thus they're sold in such stores in areas where such appliances are common. In the US, the relays are commonly refered to a "contactors".
While latch circuits are great and have their purpose, I think it is often times unnecessarily over complicates a system. And that is something that is a recurring issue in engineering. We want to over complicate and over engineer a system when a device already exists that is far cheaper and far more reliable.
Remember, the more components, the more room for error to occur. As such, we are shooting ourselves massively in the foot for ZERO gain.
A high quality mechanical switch can last longer than a can capacitor and outlast a latch circuit for controlling a large, high voltage, or inductive load.
I have a 1970’s car which I drive erratically in a sand mine. I’ve removed the original wiring loom (as well as doors and panels) and fitted the essential wiring to the ignition, battery, starter motor and Earth. The sand mine has very fine sand which is very Alkaline, so by having a simple mechanical switch I feel it is more robust and easy to diagnose if at fault. Is my assumption correct?
Using electronics for the sake of the technology is a poor practice that is increasingly seen in modern devices. It increases cost and in a lot of cases decreases reliability.. Things like car doors that used to use a perfectly functional mechanical catch and in a lot of new vehicles has been swapped with an electronic push button circuit. Very cool, but the old mechanical part is very reliable and most importantly, continues to work if the vehicle is in an accident and loses power.. In vehicles with electronic door latches, they have to put in a clunky emergency pull which is actually *less* safe because it's not the regular way to get out of the car and it's usually hidden away so it's not so obvious in the name of "design" and fashion, and humans panicing in an emergency tend to forget about things like hidden emergency latches unless like NASA astronauts, they drill and practice emergency procedures over and over.. There are definitely applications for electronics where they can be more reliable and cost effective, but we should be very carefully considering whether electronics are really "better"..
oh, there are so many instances where bad design is used for the sake of looks or high-tech feel. One simple example is hiding screws under glued-on feet, labels and such.
It's both funny and sad how we went from "it's solid state, it's eternal" to "it's solid state, drains batteries, glitches, breaks faster, and is very difficult to repair".
Good point. The problem is that when the new over complicated solution becomes the "norm" it may become cheaper to mass produce than the previously cheaper simple solution which, now being more expensive, gets discared.
imagine a stove plate with touchscreen that uses such latch circuit to turn it on and off , imagine they use relay's instead of solid state switches ... and then imagine one relay gets fused in the on position and now you got no way of turning the darn thing off...
yeah that is actually a true scenario that a friend of mine experienced a few weeks ago, he had to cut the power to his whole kitchen for a while , dunno who made/designed that stove plate but they should be sued for using crap quality relay's to deal with 20-30A at 220V
Ты большой молодец :)
I really would like to see you calculating components values in the next video! Tadaaa here is the schematic, doesn't work for me 😅.
wait, why latch circuit is better than mechanical switches again?
Decoupled components?
I’m using a latching circuit for my CNC’s power distribution box.
More sensitive to small changes e.g. trip wire alarm/burglar system in the form of a laser curtain needs to be very sensitive and may need a hundred different trigger points
when mechanical switch systems got malfunctions/broke.
you only spend pennies to replace 1 items, simple trouble shooting since it less components thus less time waste.
If Digital/micro electronics got malfunctions/broke.
You'll spend the same pennies with more items to replaces and more time spend to troubleshoot it if no visible damages are seen.
I've meet lot's of new Uni graduates that promotes all digital or micro electronics to replace the decades old rugged mechanical switches just to be scrapped after the Company spend Ten of Thousands of Dollars to Install it and another Thousands of Dollars spend to hires the "experts" to trouble shoots why the signal lamps on some of CNC machines goes off and some malfunctions to the start stop commands on the HMI, not also mentioning the money the Company lost to the downtime because the Programmer have to contact his HQ for the Administrative password set up by the previous Engineer..on Sunday.
The flaw of young peoples that watched some Non-Industrial standard Engineering RUclips Videos thinking "Why No One Do this thing" when get their first Professional Job on the Engineering sectors.
Wait... I've never seen this before. Your wall switch toggles a device that lives in your breaker box?
Yep. Pretty cool stuff :-)
Why not to go even further with just low voltage inputs all over the house and process them with wago/teco/knx/loxone ;)
Pretty normal in Denmark too. We also have houses from 1980's with latching relays and 8VAC low-voltage input switches , homerun to electrical panel. I made nice DIY project automating all the 16 mechanical relays with ESP8266/ESPHome/HomeAssistant relatively easy :)
I was expecting debounce to get mentioned. Especially when switching digital circuits and microprocessors.
This is inherently debouncing. That's part of the joys of the latch, I believe.
@@michaelschwager786 that was my point, that was not mentioned
Great video as always 👍
I made the latch switch circuit with the transistors at some point but it keeps triggering every time I touch the BJT or the MOSFET.
How to make something simple and easy to build extremely complicated and prone to fail much quicker in comparison...
Excellent video! By the way, what perf board was used at 8:12 ? seems really easy to cut compared to some of the ones I've had before
Hey Scott I hve been watching u for many days but u have written everything in your notebook next video plzz show us about ur electronics book Or send pdf please 📕
You cant beat a simple mechanical switch for anything battery powered. A latch switch will always require power and that will be a drain on the battery which will ultimately go flat. A proper switch disconnects the battery completely and this means the battery will last as long as its able to hold charge, which in some cases is years. Apart from that it takes up so much less space. Its a no brainer, use a mechanical switch whenever possible.
So, in theory, this would be capable of running a DC motor, then reversing the polarity to make it run backwards. That was a question but I did not word it like one lol
you use no power and have a visible indicator of what state its in when using a mechanical switch
This sounds good for low-power applications, but I wouldn't trust it for the lighting in my corridor. Also I would have to have a place to put it, when a commercial latch like that mechanical one would fit neatly in my fuse box.
Honestly, depends on building size and area of operation. A latch circuit would be useful if you are trying to use it alongside a occupational sensor and want to reduce energy consumption. That being said, a hard switch should still be in the room to override the latch switch.
Thanks sir from india
I won’t mention it again, but I have a challenge for Great Scott! Build a video monitor camera system that sits under the workbench and tracks dropped items, with a laser pointer to show you where the tiny screw, resistor, or whatever you dropped actually ended up!
The savings in man/hours looking for the tiny item alone might save millions of hours! I have been known to drop the same item up to three times, and spend a half hour trying to find it. Amazing how far they can bounce and where they can end up.
Would be so cool to have it mounted under the workbench, and a laser pointer shows where it went (or as far as last point in space seen, in case it went out of sight.
I have a personal rule that if I don't find the dropped item within 10 seconds, it is lost to the abyss. Life is too short to be on my hands and knees looking for a 10 cent component. It also focuses my attention when handling expensive and/or limited supply components.
@@msmith2961 it’s a good philosophy. I find though often the tiny little item I dropped is the last one, or the only one. It’s either find it, or spend an hour finding a replacement, ordering it, and waiting for it.
@@shader26 it's guaranteed that it'll be found in the last place you look, so just start there 🙃
@@dubmob151 thanks, but I tried it and it ended up being the first place I would have looked.
@@shader26 😂
Can you do this with an n-channel Mosfet too? I've bought a bunch of those, and I'm not sure if I have any p-channel ones 🤣
Gotta love the German names of relays 😂
While I do use mosfets or IGBT's for circuit switching, they do have an inherent issue. The BIG reason mechanical switches are NOT obsolete is the electrical isolation. Exactly what was seen in your breaker! You have a solenoid coil that latches and delatches a mechanism that holds the contacts closed, BUT more importantly, they are electrically isolated from each other. Build an isolated solid state switch that can handle 40 amps at least. Then maybe, mechanical switches are obsolete!
I prefer a mechanical switch: I see from the outside, if it is switched on or off b) when it is switched off, there is really zero power flow
Replacing a troublesome mechanical switch with a problematic electrolytic cap...
A no win situation
Glad to see you back to basics. Love you Great Scott.
Hi, my 8 year old wants to know the max input voltage for your circuit- does it go all the way up to 120? Can we use 3? And how do we calculate this for next time? Thanks!
Way too much electronics to deal with to replace a simple toggle switch. KISS!
Another place the latch circuit would be handy is for machinery in the event of a power outage. If the power goes out, I don’t want my table saw to restart automatically when the power comes back up.
It would be nice to replace the mechanical switch with a latching circuit. More expensive saws have a magnetic switch that automatically shut off when the power dies.
No! Mechanical switches don't use any energy when they are off. Iits a shame we have to use power strips to turn off our electronics. Bring back the TV that the switch actually turns off the TV. Routers and cable boxes the same. We want to save energy? We must use appliances that don't use one drop of energy when they are off. I won't run any neutrals on my switching circuits in my home. The hot is the only conductor that needs a switch. The neutral it were it belongs at the light box or at the outlet box. I'm old school and plan on staying that way. I have all the new electronics but when I want them off they are off completely. 73
exactly
Hola, dando vueltas en yt apareció éste video que me resulta muy útil ya que quiero hacerle unas mejoras a mi auto y puedo aplicar este proyecto para los faros auxiliares. Pero hace ya más de dos semanas busco un circuito que no tenga programacion alguna(no PIC, no Arduino, no 555), que funcione con transistores y un solo boton que al pulsarlo genere unicamente dos o tres destellos. La duracion de los destellos es poco relevante, con que duren .3 segundos ya es más que útil.
Si tenes algun video con algo asi estaría muy agradecido.
Saludos desde Buenos Aires!!!
09:14 thx ! it works
Simple but powerful idea⚡😃 This will never wear out and last long
True ;-)
Thanks for this video Scott.
The single-button latching circuit seems exactly what I've been looking for for a little battery box I'm currently throwing together.
Quick question, though: What is the time constant for discharging the capacitor when turning the circuit on?
I.e. how fast do I have to let go of the button to avoid immediately turning the circuit off again? ;-)