And you need to negate the "race condition" on inital turn on, where the LV trip could trip before the internal voltage rails have charged to their nominal values etc!
Considering the mechanical nature of the tripping mechanism, and the fact that it's up to the circuit breaker next to it to cut the power, I wonder if this device can really avoid cutting the power near the zero crossing.
...... Clive's expertise extends far beyond any electrician I've met. I've said it before, and I'll say it again. I don't care what INTERPOL say, This man is a Gentleman, a Scholar, and a Top Bloke !
thanks clive for getting me back into electronics . ive used a h961-u battery bank pcba , nice , charges on anything , ive discovered that if your battery holder is unknowingly series and not parallel like you thought ... 10 volt on the battery terminals kinda screws the charge regulation.... orederd the correct battery holders this time . thanks for getting back into electronics man , great show im learning alot .
It may also be used to trip mains breakers in the case of if you have a automatic backup generator. That way you don't try to feed the grid and endanger lives. Or break your generator
Most (all?) regional electricity companies will require a dedicated transfer switch to ensure you don't back-feed your generator onto the mains. A transfer switch will stop someone re-closing the mains while the generator is connected to the load which a simple UV on the mains will not.
I've got such a device for my travel trailer, here they're called an EMS or Energy Management System. They also detect things like reversed live and neutral, missing ground, etc and won't connect the load if they detect them or will disconnect on under/over voltage. The number of RV parks and campgrounds with badly wired or badly overloaded service is pretty shocking. While they aren't cheap they are certainly cheaper than replacing an AC unit or God forbid having an electrical fire.
I'd be surprised if they bucked the trend by having _proper_ wiring and load calculation. I did commercial [extra] low voltage for several years in 4 US states, and I can count the number of installations I saw that weren't outright death traps without even taking both shoes off. My favorite was the panel that had _burned through_ the neutral bus bar because some screws were loose. It's always exciting to find the problem before you've even properly started diagnostics. Went to open the first panel cover and saw sparks. Poked it again - more sparks. At this point (a bit late) my brain engaged and the next time I poked was with a meter instead of a finger. The breaker cabinet itself was live at 240V. The sparking came from the front panel being pushed into contact with the aforementioned unanchored neutral bus bar. I'm still not clear on how it actually came about because it was out of scope _and_ outside our license, but we LOTOd the feed to that panel, informed the store manager, and bailed so I could be _deeply concerned not hysterical thank you very much_ somewhere out of sight.
I guessed the overvoltage part correctly - largely because I've use the same Zener technique for years. I was a little way out on the under-voltage as I had a two transistor system in mind, but quite like the elegance of this one.
In the world of haphazardly using microcontrollers for most problems, it's nice to see some analog circuitry for a change. That being said I thought it would be more akin to Clives guess, kudos to whoever came up with that circuit
This tear-down inspired me to create a specialized safety circuit for our observatory. The gearboxes have (from 1971) quite-well-built German "tacho-generators" on them. These generators were used as part of the servo control loop back in the day, and they produce a well-defined output voltage based on their speed. I wanted to re-purpose one to use as an independent "trip" for the brakes and motor power if the detected speed on the axis exceeded certain bounds. I used something similar to what you showed here in your video. The main hazard we're trying to control is the elevation axis "running away" under gravity--that can happen if the control system has disabled the brakes, but is not driving the motor, or there's a break in the drive-train between the motor and the gearbox. This "tacho-trip" circuit will handily provide for a safety-trip in that situation.
Since there is no smoothing on the DC side of the bridge rectifier, the voltage will drop to zero every 8/10ms (120/100Hz). Presumably the capacitor across the Base-Emitter is the only thing preventing the low voltage circuit triggering in this case.
At first I wondered about the colors on the schematic, but I've learned to trust and was rewarded. Clive you are brilliant; your description and graphics very nicely explained something I would have little insight into were I to take it apart. I would be more likely to run off with that coil for the magnet wire to do radio stuff with or make Joule Theives
Really appreciate your videos 😊 I really love the accent and you're in Glasgow!! It's awesome!! My mom is a MacKay from New Glasgow, Nova Scotia, Canada. I have second and third cousins in Scotland. Mom's 92 and reminds me she's still Canadian everytime I contact her. Even though she has been living in the United States for over 65 years. I'm also a Ham Radio hobbyist for over 20 years. US call sign KB1DIG. Did a little contract work with Raython Aerospace and the Department of Defense just after 9/11/2001.. Production Controller for the retrofit of avionics on the KC-135 stratotanker.. Air Force version of the Boeing 707.. Flying gas can.. Played around with UHF VHF antenna design. Halos and collinear design antennas. Some of my stuff is still floating around on Google. I'm retired to the Philippines 4 years now. Have been doing a lot of RUclips videos. Mostly custom built ideas for motorcycle related stuff here in the Philippines. Plus some of the local happenings here. Thank you for your work and best regards for your future from the Philippines 🤠
At work, we have Over/Under voltage RELAYS used in conjunction with PLC control for generator paralleling gear (utility/generator switchgear). We also have options installed in breakers (configurable for things like auto-charging/shunt trip etc.) with over-voltage and under-voltage triggers for the trip units. Typically, at least in our applications, brown-out situations are worse, so under-voltage scenarios are the main worry downstream.
Neat. The UPS I just set up had variable under/overvolt triggering, but I bet it does it with much fancier (read: microcontroller-based) circuits. I really liked the way they basically put caps over every trigger to stop them bouncing and then another over the whole triggering thyristor just to be sure.
OK, I'm 3 minutes 50 seconds in and my guesstimate is going to be: It uses a coil to trigger the trip and the reason it is real low resistance is that coil is in parallel with a near short circuit to allow the breaker to be minimally involved in the system (Not use much power).
Once you explained how it all works it really seems quite elegant. I imagine designing a circuit like this feels similar to writing a really compact and efficient bit of code.... not that I'd know how either of those feel. 😐
Analog circuits are fascinating! Often so simple, yet really hard to design, it takes a lot of time until you can design them rather intuitive like coding is.
20 years ago programing at work I took out 12 a4 sides of code with a complicated loop. Man, I remember that feeling. No one will ever know but it flicked my switch that day
I replaced a standard switch fused spur with an rcd version a while ago. Didn’t pay much attention to the way the old one came off because there were only 2 twin and earth cables, a 1.5 and a 2.5. On re energising it held for a few seconds then the bang it made was impressive. You’ve probably guessed it. The 1.5 was the feed and the 2.5 the load. Excellent videos thanks. It was a timeguard spur from Edmundsons.
It would be interesting to see your calculations. I'm getting slightly different values. Overvoltage: 24k/(470k+24k)=0.0486 12/0.0486=247 V Things not taken into account: 1) Rectifier diode drop. (2*0.7 V, essentially negligible.) 2) SCR trip current/voltage needed. 3) My value is theoretically a peak value, which would put the corresponding RMS value faaar too low. But, the capacitors would also smooth out the voltage, so to some degree the voltage present at zener cathode would be closer to the RMS voltage. Did you perhaps do the same calculation and added 12 V for the diode drop, or assumed trip voltage of the SCR? Undervoltage: 80.1k/(1200k+80.1k)=0.0626 12/0.0626=192 V Not taking into account in this case the E-B voltage drop, as well rectifier voltage drop. My values, taken at face value, would pretty nicely fit with a product for the Chinese market setting the thresholds at 220 V +/- 12-13 % or +/- 27-28 V.
@@Gameboygenius Voltage at center point of OVP divider is roughly zener plus SCR gate = 12.7V. 12.7=X*24/494. X=261 Voltage at center point of UVP divider is roughly zener minus Vce of the PNP = 11.3V. 11.3=X*80/1280. X=181 This assumes gate trip current of SCR is near zero, so it's only an approximation.
Remember that the supply is unsmoothed full wave rectified, and also there's a capacitor across the 24k resistor. This capacitor will average the rectified and voltage divided waveform to around 64% of its peak, or a factor of 0.9 times the rms value. So this will in fact trigger at around 290Vrms if perfectly smoothed, but more realistically a lower voltage allowing for some ripple depending on the capacitor value. The capacitor was unmarked but it would need to be around 1µF to smooth enough to have a 280 Vrms trigger, which I think is the rated value marked on the front of the device.
The device you talked about which trips after applying power (or after removing power, there are both types available), we use one of those at work to trip the main breaker in a small room (lighting is on a separate circuit) to use as an emergency stop for everything in the room, it's a simple additional safety device, you don't think what to turn off, you cut the power if something goes wrong
This would be handy. A voltage spike took out my coffee pot and my Wolfgang Puck pressure cooker. Both of the thermal fuses went. Got new ones from Amazon and they're fixed now.
Wish my rice cooker'd had a thermal fuse. Someone left it plugged in overnight after emptying it. By morning it was cold, so it got washed and put away. Next time we went to use it - nothing. Although one corner of the switch surround was suspiciously melty . . .. Luckily the wires inside were sleeved in fiberglass, so when the hot lead decided to play fuse and burnt itself up it _didn't_ contact the (steel) shell - that would have been rather exciting with wet hands! Also luckily, the wires were connected with standard 1/4" (6.3mm) spades crimped on the ends. 5 minutes later it worked perfectly again.
I demand that that coil be connected across the mains in the case! It would be nice to see the failure mode, is it just going to quietly "fuse" out? Thank you for the video :)
I do like a spectacularly simple circuit. (In terms of components). Mind you my favourite is still a West German stereo valve radio that had very few valves that were used for several different things at the same time because radios were taxed by the number of valves in it.
I think part of the coolness of this design is the failure mode for the two 3 terminal devices. If either shorts the device will trip. The zeners are very lightly loaded so they are very unlikely to fail.
The next, even cheaper, Chinese knock off of this device would contain a capacitive dropper, a diode, a coil, some resistors and a Padauk microcontroller.
I duno, those microcontrollers are expensive, several cents per chip! The local Shenzhen vendor can get you the discrete components for a hundred to the cent, each.
An elegant circuit to be fair. I though wonder how consistent it is from unit to unit. Considering the tolerances of the components. The other units seems quite interesting as well, could be useful to have if one lives in a brown out prone area.
Excellent analysis of a surprisingly clever and robust design. Most fault situations will result in firing the disco solenoid. And not a moderne window comparator in sight. Thanks!
I know this breaker is for over and under voltage protection, but I noticed that you mention the possibility the wires were for tripping the circuit. Over here (USA, I'm sure they have them there too) those are called shunt breakers. My public school system has a vocational school for high schoolers that has various trade classes (metalworking, HVAC, automotive, masonry, etc.) and in every shop, there were several red buttons placed around in different places. When the button was pressed, it would trip the shunt breaker powering the outlets and machines in the shop it was in, in case a kid was about to get their hand chopped off or other dangerous act that needed the electricity off.
A nice simple, elegant circuit... unless it doesn’t trip the circuit breaker! You must try this out and let us know what happens Clive! (I expect the coil will just fuse very quickly).
I found one of those digital ones that you can actually reprogram the over- or under-voltage setpoints. Handily it works on 230 as well as 115! It also has a programmable overcurrent, but it's not really meant to be used as a full-on circuit breaker - even the manufacturer recommends coupling it with isolators and real circuit breakers. It's rated for 63A branch, and is available in 80A branch. Since American branches are usually only about 15-20A, I grabbed the 63A model and will put it behind a 60A breaker.
Clive, that one relay you showed early in the video without the volt meter on it is an overcurrent trip relay. Obviously you would want a breaker or fuse upstream to trip in case of a short.
Excellent video as usual. I like the idea of predicting what might be inside, then open it and see how they really did it. Very interesting and educational.
Have to get the higher current rated one of those - might be very useful where we live "out in the sticks", where "mains" voltage can be somewhat variable! Any chance of an analysis of a mains spike / transient detector / counter? (another delight of a more rural lifestyle . . . . .)
Like you my first thoughts were voltage comparator circuits using op-amps. I reckon that even this circuit could be cut down more at the cost of some reliability in use.
Hey Clive would you consider making a playlist on your channel of all your uploads? I like listening to your videos at night falling asleep, but autoplay starts videos from other unwanted channels after a few of yours. If there was a playlist consisting of all your uploads I could be lulled to sleep by video after video of interesting electronic teardowns.
I did a DIY version with a SSR and a lm339 almost 10 years ago(I was going away for the weekend and the voltage had been fluctuating all week), you know the kind of temporary FOREVER circuits in a perfboard that since it's been working fine will never be disturbed. Some day I'm probably going to put a uC maybe....
Hi Clive. I noticed that the neutral lead is quite short (same length as the live) Are these only designed to trip double pole circuit breakers and RCDs? If you wanted to trip a standard MCB with it, would you have to extend that lead to reach the neutral bar?
Can you test the under voltage functionality please as I can’t see how one would get the required few mA of trigger current through that (emitter) 1.2M resistor. Maybe it doesn’t actually work (he says, sticking his neck out gingerly)
It depends on the inductance. As an open coil without anything on the outside I would think the inductance would be fairly low. I'd blindly guess 2 amps if run on AC.
Ive seen these attached to motor circuit breakers, using the mcpbs switches to turn on/off a conveyor, this trips the mcpb when the conveyor is unplugged, stopping it from auto starting on powerup
Really the circuit which is shown at 15:18 is a very simple one but very clever ingenious circuit. The circuit which is shown at 05:17 is also very clever and it is found in the 555 timer chip to generate the ramp function upper and lower limits where those two comparators set the memory to charge or discharge the RC timing network in the 555 timers. The logic of all engineering is so ingenious and the sequences should be introduced at schools including the logic of the bootstrap circuit and its connotation of someone lifting himself by pulling at his own bootstraps.
It seems the PNP transistor is always reverse-biased between E & B if it is not tripped by under-voltage. What will be the max reverse voltage just before the over-voltage part triggers the SCR ? Does the PNP Tr need a high B-E breakdown voltage ? Thanks.
I assume this won't low-voltage trip on a power interruption due to the time delay? And probably because there wouldn't be enough time to activate the plunger?
@@bigclivedotcom my apologies! For some reason where I'm learning we've been using the symbol for the avalanche diode as zener diode for simplicity. I'm sure this won't be the last time I've confused them
Yes. If it can be achieved simply with discrete components then it's a better option. The best bit about microcontrollers is that they can do so many different things. The worst bit about them is that sometimes they do.
There’s a lot of 12v breakers I’ve seen , most are being used on solar power kits for camper vans , can you check a few out please Clive as one said 200 amp and tripped at 110 amps
Conventional, since it's easier to explain operation when the diodes point in the right direction. The only time I reference electron flow is when dealing with MOSFETs.
Theories are just convenient ways to imagine how the universe works and predict it's behaviour. Use whichever Theory is most useful for any given task. So as Clive said that's mostly but not always conventional.
Reminds me of three phase monitoring relays which are detecting phase order, overvoltage, undervoltage, missing phase and (if you buy correct one, for example HRN-57N) even missing N :)
Are there any main breakers that self trip or switch off if there’s a power outage? For preventing islanding with inverters or a generator. Then you can have the inverter or whatever switch off when it detects voltage on the input side of mains, maybe a variant on the self resetting under over breaker that can work as a single space switch without needing to physically disconnect the inverter which can be connected passively through its own breaker
@@bigclivedotcom this sounds super not legit, but I guess things go different in 🇬🇧, if a relay could be used that would work so well because I could have a controller turn it back on when the prerequisites of power on one side and not on the other are met, or if they are able to take a standard slot and act as a breaker then I could have one for each, or just put them in an enclosure if that was up to code
"I won't touch the leads because it'll interfere with it" Ohhh boy, on a scissor lift a million miles in the air testing fuses for a 3 phase thing on a bus bar box with a fluke clamp meter (using the probes in continuity mode obviously)... All the fuses are fine... Wtf? No, one is gone... The meter is faulty and its reading my body resistance from one hand to the other as continuity. We kept the meter... Fantastic to give to someone to check fuses and to learn this lesson
@@bigclivedotcom when the thiristor shunts the rectifier, doesn't that just complete the circuit, from live through the coil then the shunt to neutral? So using ohms law the 60 ohm coil would draw less current if the mains voltage was very low right? And more if the mains was higher? The 60 ohms of the coil should only draw about 1 amp at 60 volts rms and should draw 10 amps at 600 volts rms. Or am i missing something here?
nice investigation video like always. Is it possible to mod a 6A breaker to a 10A one?? Maybe change some component one the small PCB that trick the coil?? Any idea??
That's like asking if there's some kind of simple mod you can do to make a size 7 shoe fit a size 9 foot. A 10A breaker is more heavy-duty than a 6A breaker. It's not a case of "tricking" it. Put 10A through it and it'll melt. The device in this teardown video *could* be modded to change the thresholds, but that's not what you asked.
Not really. Normal circuit breakers don't have any electronics. When a standard breaker is overloaded the current heats up a bimetallic element which then activates the trip mechanism. You could theoretically change out the bimetallic element with one from an otherwise identical 10A breaker, but I would not trust it at all as a safety device. You'd probably have better luck making a 10A breaker trip earlier by shaving away part of the thermal strip. But again, I would not trust the safety after that.
@@eDoc2020 thx much for the reply, and as You after my initial question, I said wait a min. Usually those breaker got a metalic element, dat does "break" when heated... close to your explanation... to say I saw long ago how those breaker are tricked, and no coil inside them as I remember.... And I think that the breaker that I wanted to mod is those with metalic trick, so guess no go . Thx
so, why dont we get to see it working,? I realise that it is tricky to generate the over voltage but the under voltage can be acomplished with a variac. Im guessing the overvoltage could be done with 2 transformers one 1:1 for the 240v and another to add 30v (plenty of these in old amplifiers) all again on the output of a variac.
What would be good is a heat and smoke module. These are more for industrial where under and over voltage can really fuck up motors. But in domestic, it not really much use. But a module dedicated to cu and smokes makes great domestic sense.
I installed the one with display today. I have 2 panel meters, 2 multimeters, and this breaker. All are showing different voltages at 240v AC. The difference is between 0-6 volt. How can I know which one is more accurate? Is there simple circuit which I can make to get accurate measurement, because I'll know exact component values?
Maybe I'm wrong, but since the relay coil is a purely inductive load controlled by alternating current, most of the power is purely reactive, it would not consume 220²V / 60Ω but much less
These days it has to be a microcontroller. But with discrete components, each has its own strengths. The MOSFET transistor has evolved spectacularly, so it gets special mention.
Clive, we have this heater you can only set for 4 times a day and in winter is utterly useless as it's freezing and we have to manually keep setting it, if I sent you a picture could you talk us through hacking it so we can set it a lot more frequently (for say 15 mins every hour)
@@bigclivedotcom that's cool, I'm OK with some soldering, how would I do it though, regrettably I only had 1 hour a week for maybe 3 months in Electrical class
Whether the auto-restart or permanent off is a better choice depends on the application. You certainly wouldn't want dangerous machinery to automatically restart after a brownout. Imagine someone getting close to said machine, trying to figure out why it stopped working and all of a sudden the power comes back... To be honest I can't think of a good application for an auto-restart after a brown-out from the top of my head...
Hey beardy; there is something called facial cleansing device expanding very fast (apparently it's ultrasonic) in the market and I2m drooling to see its inside for what makes this egg shaped thing so special. Take a guess, no one teardown even a single one in the whole web. yup no schematics too. I just want to know if a regular brush with intense force worth more than those buzzers or not.
@@bigclivedotcom I work in a calibration lab so it's always interesting to see what people are using these days and what's new to us vs what people actually use. The price tags are jaw dropping on some gear.
It’s truly inspired way of using the diode bridge as both a rectifier AND a switching element. Moreover, it functions as a bipolar switch activated by a DC-only driver! I’d love to see what other cool hax that designed has on his pocket notebook!
Also analogous is a 120V 15A power bar made by Furman with their EVS (extreme voltage shutdown), it automatically cuts out and back in depending on whether the voltage is in the proper range. I have no connection with the company, I just like the product.
Something to remember is that for undervoltage detection, it needs to not trip near the AC zero-crossings, hence the cap across the PNP transistor.
That’s a good point
And you need to negate the "race condition" on inital turn on, where the LV trip could trip before the internal voltage rails have charged to their nominal values etc!
Considering the mechanical nature of the tripping mechanism, and the fact that it's up to the circuit breaker next to it to cut the power, I wonder if this device can really avoid cutting the power near the zero crossing.
@@Retep4565 The cap on the gate makes it wait.
@@paulvandergroen9569 I was referring to the mechanical parts.
...... Clive's expertise extends far beyond any electrician I've met.
I've said it before, and I'll say it again. I don't care what INTERPOL say,
This man is a Gentleman, a Scholar, and a Top Bloke !
thanks clive for getting me back into electronics . ive used a h961-u battery bank pcba , nice , charges on anything , ive discovered that if your battery holder is unknowingly series and not parallel like you thought ... 10 volt on the battery terminals kinda screws the charge regulation.... orederd the correct battery holders this time . thanks for getting back into electronics man , great show im learning alot .
It may also be used to trip mains breakers in the case of if you have a automatic backup generator. That way you don't try to feed the grid and endanger lives. Or break your generator
Most (all?) regional electricity companies will require a dedicated transfer switch to ensure you don't back-feed your generator onto the mains. A transfer switch will stop someone re-closing the mains while the generator is connected to the load which a simple UV on the mains will not.
I've got such a device for my travel trailer, here they're called an EMS or Energy Management System. They also detect things like reversed live and neutral, missing ground, etc and won't connect the load if they detect them or will disconnect on under/over voltage. The number of RV parks and campgrounds with badly wired or badly overloaded service is pretty shocking. While they aren't cheap they are certainly cheaper than replacing an AC unit or God forbid having an electrical fire.
I'd be surprised if they bucked the trend by having _proper_ wiring and load calculation.
I did commercial [extra] low voltage for several years in 4 US states, and I can count the number of installations I saw that weren't outright death traps without even taking both shoes off. My favorite was the panel that had _burned through_ the neutral bus bar because some screws were loose.
It's always exciting to find the problem before you've even properly started diagnostics. Went to open the first panel cover and saw sparks. Poked it again - more sparks. At this point (a bit late) my brain engaged and the next time I poked was with a meter instead of a finger.
The breaker cabinet itself was live at 240V. The sparking came from the front panel being pushed into contact with the aforementioned unanchored neutral bus bar. I'm still not clear on how it actually came about because it was out of scope _and_ outside our license, but we LOTOd the feed to that panel, informed the store manager, and bailed so I could be _deeply concerned not hysterical thank you very much_ somewhere out of sight.
I guessed the overvoltage part correctly - largely because I've use the same Zener technique for years. I was a little way out on the under-voltage as I had a two transistor system in mind, but quite like the elegance of this one.
In the world of haphazardly using microcontrollers for most problems, it's nice to see some analog circuitry for a change. That being said I thought it would be more akin to Clives guess, kudos to whoever came up with that circuit
This tear-down inspired me to create a specialized safety circuit for our observatory. The gearboxes have (from 1971) quite-well-built German "tacho-generators" on them. These generators were used as part of the servo control loop back in the day, and they produce a well-defined output voltage based on their speed. I wanted to re-purpose one to use as an independent "trip" for the brakes and motor power if the detected speed on the axis exceeded certain bounds. I used something similar to what you showed here in your video. The main hazard we're trying to control is the elevation axis "running away" under gravity--that can happen if the control system has disabled the brakes, but is not driving the motor, or there's a break in the drive-train between the motor and the gearbox. This "tacho-trip" circuit will handily provide for a safety-trip in that situation.
I wish you were my instructor in school, Clive, as you're genuinely a great teacher and so calming to the ears.
Since there is no smoothing on the DC side of the bridge rectifier, the voltage will drop to zero every 8/10ms (120/100Hz). Presumably the capacitor across the Base-Emitter is the only thing preventing the low voltage circuit triggering in this case.
At first I wondered about the colors on the schematic, but I've learned to trust and was rewarded.
Clive you are brilliant; your description and graphics very nicely explained something I would have little insight into were I to take it apart.
I would be more likely to run off with that coil for the magnet wire to do radio stuff with or make Joule Theives
Really appreciate your videos 😊 I really love the accent and you're in Glasgow!! It's awesome!!
My mom is a MacKay from New Glasgow, Nova Scotia, Canada. I have second and third cousins in Scotland. Mom's 92 and reminds me she's still Canadian everytime I contact her. Even though she has been living in the United States for over 65 years.
I'm also a Ham Radio hobbyist for over 20 years. US call sign KB1DIG. Did a little contract work with Raython Aerospace and the Department of Defense just after 9/11/2001.. Production Controller for the retrofit of avionics on the KC-135 stratotanker.. Air Force version of the Boeing 707.. Flying gas can..
Played around with UHF VHF antenna design. Halos and collinear design antennas. Some of my stuff is still floating around on Google.
I'm retired to the Philippines 4 years now. Have been doing a lot of RUclips videos. Mostly custom built ideas for motorcycle related stuff here in the Philippines. Plus some of the local happenings here.
Thank you for your work and best regards for your future from the Philippines 🤠
At work, we have Over/Under voltage RELAYS used in conjunction with PLC control for generator paralleling gear (utility/generator switchgear). We also have options installed in breakers (configurable for things like auto-charging/shunt trip etc.) with over-voltage and under-voltage triggers for the trip units. Typically, at least in our applications, brown-out situations are worse, so under-voltage scenarios are the main worry downstream.
Neat. The UPS I just set up had variable under/overvolt triggering, but I bet it does it with much fancier (read: microcontroller-based) circuits.
I really liked the way they basically put caps over every trigger to stop them bouncing and then another over the whole triggering thyristor just to be sure.
Prior to opening, Clive accused the Chinese manufacturer of having some semblance of complexity. Upon opening, he needn't have worried.
OK, I'm 3 minutes 50 seconds in and my guesstimate is going to be: It uses a coil to trigger the trip and the reason it is real low resistance is that coil is in parallel with a near short circuit to allow the breaker to be minimally involved in the system (Not use much power).
Once you explained how it all works it really seems quite elegant.
I imagine designing a circuit like this feels similar to writing a really compact and efficient bit of code.... not that I'd know how either of those feel. 😐
Analog circuits are fascinating! Often so simple, yet really hard to design, it takes a lot of time until you can design them rather intuitive like coding is.
20 years ago programing at work I took out 12 a4 sides of code with a complicated loop. Man, I remember that feeling. No one will ever know but it flicked my switch that day
@@SwimBikeRunFastest Unrolling and cleaning up loops is its own reward.
I called those beautifully clean algorithms "computer poems."
I replaced a standard switch fused spur with an rcd version a while ago. Didn’t pay much attention to the way the old one came off because there were only 2 twin and earth cables, a 1.5 and a 2.5. On re energising it held for a few seconds then the bang it made was impressive. You’ve probably guessed it. The 1.5 was the feed and the 2.5 the load. Excellent videos thanks. It was a timeguard spur from Edmundsons.
If my math on the dividers is right, accounting for the 0.7V drop, that's a voltage range of about 180-260Vrms.
It would be interesting to see your calculations. I'm getting slightly different values.
Overvoltage:
24k/(470k+24k)=0.0486
12/0.0486=247 V
Things not taken into account:
1) Rectifier diode drop. (2*0.7 V, essentially negligible.)
2) SCR trip current/voltage needed.
3) My value is theoretically a peak value, which would put the corresponding RMS value faaar too low. But, the capacitors would also smooth out the voltage, so to some degree the voltage present at zener cathode would be closer to the RMS voltage.
Did you perhaps do the same calculation and added 12 V for the diode drop, or assumed trip voltage of the SCR?
Undervoltage:
80.1k/(1200k+80.1k)=0.0626
12/0.0626=192 V
Not taking into account in this case the E-B voltage drop, as well rectifier voltage drop.
My values, taken at face value, would pretty nicely fit with a product for the Chinese market setting the thresholds at 220 V +/- 12-13 % or +/- 27-28 V.
@@Gameboygenius Voltage at center point of OVP divider is roughly zener plus SCR gate = 12.7V. 12.7=X*24/494. X=261
Voltage at center point of UVP divider is roughly zener minus Vce of the PNP = 11.3V. 11.3=X*80/1280. X=181
This assumes gate trip current of SCR is near zero, so it's only an approximation.
Remember that the supply is unsmoothed full wave rectified, and also there's a capacitor across the 24k resistor. This capacitor will average the rectified and voltage divided waveform to around 64% of its peak, or a factor of 0.9 times the rms value. So this will in fact trigger at around 290Vrms if perfectly smoothed, but more realistically a lower voltage allowing for some ripple depending on the capacitor value. The capacitor was unmarked but it would need to be around 1µF to smooth enough to have a 280 Vrms trigger, which I think is the rated value marked on the front of the device.
The device you talked about which trips after applying power (or after removing power, there are both types available), we use one of those at work to trip the main breaker in a small room (lighting is on a separate circuit) to use as an emergency stop for everything in the room, it's a simple additional safety device, you don't think what to turn off, you cut the power if something goes wrong
This would be handy. A voltage spike took out my coffee pot and my Wolfgang Puck pressure cooker. Both of the thermal fuses went. Got new ones from Amazon and they're fixed now.
Wish my rice cooker'd had a thermal fuse.
Someone left it plugged in overnight after emptying it. By morning it was cold, so it got washed and put away. Next time we went to use it - nothing. Although one corner of the switch surround was suspiciously melty . . ..
Luckily the wires inside were sleeved in fiberglass, so when the hot lead decided to play fuse and burnt itself up it _didn't_ contact the (steel) shell - that would have been rather exciting with wet hands! Also luckily, the wires were connected with standard 1/4" (6.3mm) spades crimped on the ends. 5 minutes later it worked perfectly again.
unrelated to the video, but I love how your website is designed. takes me back to my earliest days of exploring the internet.
I demand that that coil be connected across the mains in the case! It would be nice to see the failure mode, is it just going to quietly "fuse" out?
Thank you for the video :)
I do like a spectacularly simple circuit. (In terms of components). Mind you my favourite is still a West German stereo valve radio that had very few valves that were used for several different things at the same time because radios were taxed by the number of valves in it.
I think part of the coolness of this design is the failure mode for the two 3 terminal devices. If either shorts the device will trip. The zeners are very lightly loaded so they are very unlikely to fail.
The next, even cheaper, Chinese knock off of this device would contain a capacitive dropper, a diode, a coil, some resistors and a Padauk microcontroller.
I'm not sure they could get cheaper than this.
Oi! What about the LED to indicate it's ON?
Cheaper chineese one would just be a LED connected to a resistor and nothing else
Having an indicator LED is vital and a (Chinese) standard, 'cause without it we wouldn't know it's (a) Lethal (product)...
I duno, those microcontrollers are expensive, several cents per chip! The local Shenzhen vendor can get you the discrete components for a hundred to the cent, each.
An elegant circuit to be fair.
I though wonder how consistent it is from unit to unit. Considering the tolerances of the components.
The other units seems quite interesting as well, could be useful to have if one lives in a brown out prone area.
Excellent analysis of a surprisingly clever and robust design. Most fault situations will result in firing the disco solenoid. And not a moderne window comparator in sight. Thanks!
I know this breaker is for over and under voltage protection, but I noticed that you mention the possibility the wires were for tripping the circuit. Over here (USA, I'm sure they have them there too) those are called shunt breakers. My public school system has a vocational school for high schoolers that has various trade classes (metalworking, HVAC, automotive, masonry, etc.) and in every shop, there were several red buttons placed around in different places. When the button was pressed, it would trip the shunt breaker powering the outlets and machines in the shop it was in, in case a kid was about to get their hand chopped off or other dangerous act that needed the electricity off.
A nice simple, elegant circuit... unless it doesn’t trip the circuit breaker! You must try this out and let us know what happens Clive! (I expect the coil will just fuse very quickly).
I found one of those digital ones that you can actually reprogram the over- or under-voltage setpoints.
Handily it works on 230 as well as 115!
It also has a programmable overcurrent, but it's not really meant to be used as a full-on circuit breaker - even the manufacturer recommends coupling it with isolators and real circuit breakers.
It's rated for 63A branch, and is available in 80A branch. Since American branches are usually only about 15-20A, I grabbed the 63A model and will put it behind a 60A breaker.
Clive, that one relay you showed early in the video without the volt meter on it is an overcurrent trip relay. Obviously you would want a breaker or fuse upstream to trip in case of a short.
Excellent video as usual. I like the idea of predicting what might be inside, then open it and see how they really did it. Very interesting and educational.
Clive, you didn't get that circuit wrong, you merely invented a better one...
;o|
I have learned SO much watching you tear things to bits. Thanks!
Have to get the higher current rated one of those - might be very useful where we live "out in the sticks", where "mains" voltage can be somewhat variable! Any chance of an analysis of a mains spike / transient detector / counter? (another delight of a more rural lifestyle . . . . .)
Like you my first thoughts were voltage comparator circuits using op-amps. I reckon that even this circuit could be cut down more at the cost of some reliability in use.
Vielen Dank für das sehr gute Video! Ein toller Kanal mit genau der richtigen "Erklärungstiefe".
Hey Clive would you consider making a playlist on your channel of all your uploads? I like listening to your videos at night falling asleep, but autoplay starts videos from other unwanted channels after a few of yours. If there was a playlist consisting of all your uploads I could be lulled to sleep by video after video of interesting electronic teardowns.
Interesting item, excellent teardown and reverse engineering.
Great vlog thanks for sharing.
Best regards from the Black Country.
John.
I did a DIY version with a SSR and a lm339 almost 10 years ago(I was going away for the weekend and the voltage had been fluctuating all week), you know the kind of temporary FOREVER circuits in a perfboard that since it's been working fine will never be disturbed.
Some day I'm probably going to put a uC maybe....
Why do I keep watching these videos I don't understand a word of what this guy is talking about. Yet I keep watching him every time he comes up XD
Hi Clive. I noticed that the neutral lead is quite short (same length as the live) Are these only designed to trip double pole circuit breakers and RCDs? If you wanted to trip a standard MCB with it, would you have to extend that lead to reach the neutral bar?
It connects to the breaker it actuates.
Can you test the under voltage functionality please as I can’t see how one would get the required few mA of trigger current through that (emitter) 1.2M resistor. Maybe it doesn’t actually work (he says, sticking his neck out gingerly)
Yeah I agree. I first thought the cap on the PNP might supply enough of a pulse but the 81K of resistance chokes it return path.
Clive pulls out the power tools again, at least its not explosive this time lol. Love the videos btw, reminds me of my childhood.
Well Clive, videos just got another quality upgrade. Great idea and great vid as usual 😉
The coil runs on AC (50/60 Hz) so the current won't be anywhere near 4 amps. An interesting circuit. Voltage thresholds are temperature dependent.
It depends on the inductance. As an open coil without anything on the outside I would think the inductance would be fairly low. I'd blindly guess 2 amps if run on AC.
220/60=3.6666666666666666667 A
Another issue pf
But it's for about few millisecond
Immensely interesting. Your explanations cannot be faulted.
A very interesting and very simple wiring diagram. Great explanation!
Be great when using a generator powering a house during an outage. Non inverter types rev up and increase output when running out of fuel.
Ive seen these attached to motor circuit breakers, using the mcpbs switches to turn on/off a conveyor, this trips the mcpb when the conveyor is unplugged, stopping it from auto starting on powerup
Zero volt relay/switch.
Really the circuit which is shown at 15:18 is a very simple one but very clever ingenious circuit. The circuit which is shown at 05:17 is also very clever and it is found in the 555 timer chip to generate the ramp function upper and lower limits where those two comparators set the memory to charge or discharge the RC timing network in the 555 timers. The logic of all engineering is so ingenious and the sequences should be introduced at schools including the logic of the bootstrap circuit and its connotation of someone lifting himself by pulling at his own bootstraps.
So they have different models to fit different manufactures breakers or just for Chinesium breakers?
Won't work with Hager or Gyer from what I see.
It'll be deigned for a specific brand.
With that amount of protection, with not so ideal mains, you have to go to the breaker box many times a day :D
didn’t see the livestream - did you test it with a variac to see if/how it worked?
No I didn't.
"COIL" solder point on the upper left corner is confused
It seems the PNP transistor is always reverse-biased between E & B if it is not tripped by under-voltage. What will be the max reverse voltage just before the over-voltage part triggers the SCR ? Does the PNP Tr need a high B-E breakdown voltage ? Thanks.
I assume this won't low-voltage trip on a power interruption due to the time delay? And probably because there wouldn't be enough time to activate the plunger?
It should be fine being turned on and off.
On low voltage detection it seems that the 12V Zener would be forward biased to limit the Gate Voltage. Clever!
This would get tripped so often at my place, haha
At 3:50, isn't that the symbol for a Schottky diode, instead of a Zener diode? Always get them mixed up myself
It's a zener symbol. The schottky diodes curl in.
@@bigclivedotcom my apologies! For some reason where I'm learning we've been using the symbol for the avalanche diode as zener diode for simplicity. I'm sure this won't be the last time I've confused them
Could you do a teardown of a cheap UPS? I recently got one and I've been wanting to know what's inside...
do you think that sometimes, discreet circuits are more elegant than chip/micro stuff is?
Yes. If it can be achieved simply with discrete components then it's a better option. The best bit about microcontrollers is that they can do so many different things. The worst bit about them is that sometimes they do.
There’s a lot of 12v breakers I’ve seen , most are being used on solar power kits for camper vans , can you check a few out please Clive as one said 200 amp and tripped at 110 amps
Clive, do you use conventional current or electron current theory when you analyze circuits?
Conventional, since it's easier to explain operation when the diodes point in the right direction. The only time I reference electron flow is when dealing with MOSFETs.
Theories are just convenient ways to imagine how the universe works and predict it's behaviour. Use whichever Theory is most useful for any given task. So as Clive said that's mostly but not always conventional.
in NA the AFCI breakers have under over V built in. Very annoying when running on a generator, as it trips whenever the generator runs out of fuel.
I didn't know that. Is it part of the UL standard or just present in particular brands?
These are really handy i first came across one on an ebike it worked really well to stop power surges, cheers for the share :-)
Reminds me of three phase monitoring relays which are detecting phase order, overvoltage, undervoltage, missing phase and (if you buy correct one, for example HRN-57N) even missing N :)
Are there any main breakers that self trip or switch off if there’s a power outage? For preventing islanding with inverters or a generator. Then you can have the inverter or whatever switch off when it detects voltage on the input side of mains, maybe a variant on the self resetting under over breaker that can work as a single space switch without needing to physically disconnect the inverter which can be connected passively through its own breaker
Zero volt relay? You set it, but if power fails it turns off and needs reset manually.
@@bigclivedotcom this sounds super not legit, but I guess things go different in 🇬🇧, if a relay could be used that would work so well because I could have a controller turn it back on when the prerequisites of power on one side and not on the other are met, or if they are able to take a standard slot and act as a breaker then I could have one for each, or just put them in an enclosure if that was up to code
You know, seeing the letters of that cathode, it makes me wonder if that was the original inspiration for the headphone company known as AKG.
You mean Samsung? XD
So then what was causing the 5-some-odd mega ohm reading from the leads? Seems from the schematic that it should be less than a mil.
Test voltage of the multimeter not high enough to overcome the forward switch on voltage of the diodes in the bridge rectifier maybe...
"I won't touch the leads because it'll interfere with it"
Ohhh boy, on a scissor lift a million miles in the air testing fuses for a 3 phase thing on a bus bar box with a fluke clamp meter (using the probes in continuity mode obviously)... All the fuses are fine... Wtf?
No, one is gone... The meter is faulty and its reading my body resistance from one hand to the other as continuity.
We kept the meter... Fantastic to give to someone to check fuses and to learn this lesson
I wonder how low of voltage it would still be able to trip. Even down to 60 volts the coil should still draw 1 amp correct?
Current is the same at any voltage. It should theoretically work at 12V. Not suitable for high current DC though.
@@bigclivedotcom when the thiristor shunts the rectifier, doesn't that just complete the circuit, from live through the coil then the shunt to neutral?
So using ohms law the 60 ohm coil would draw less current if the mains voltage was very low right? And more if the mains was higher?
The 60 ohms of the coil should only draw about 1 amp at 60 volts rms and should draw 10 amps at 600 volts rms. Or am i missing something here?
Can you do the video on other two devices? especially the 100amp one?
nice investigation video like always.
Is it possible to mod a 6A breaker to a 10A one?? Maybe change some component one the small PCB that trick the coil?? Any idea??
That's like asking if there's some kind of simple mod you can do to make a size 7 shoe fit a size 9 foot.
A 10A breaker is more heavy-duty than a 6A breaker. It's not a case of "tricking" it. Put 10A through it and it'll melt.
The device in this teardown video *could* be modded to change the thresholds, but that's not what you asked.
Not really. Normal circuit breakers don't have any electronics. When a standard breaker is overloaded the current heats up a bimetallic element which then activates the trip mechanism. You could theoretically change out the bimetallic element with one from an otherwise identical 10A breaker, but I would not trust it at all as a safety device.
You'd probably have better luck making a 10A breaker trip earlier by shaving away part of the thermal strip. But again, I would not trust the safety after that.
@@eDoc2020 thx much for the reply, and as You after my initial question, I said wait a min. Usually those breaker got a metalic element, dat does "break" when heated... close to your explanation... to say I saw long ago how those breaker are tricked, and no coil inside them as I remember....
And I think that the breaker that I wanted to mod is those with metalic trick, so guess no go .
Thx
New breakers are cheap. Just make sure you get the same brand and type. The wiring will also have to be rated for the increased current.
@@bigclivedotcom if he has to ask the question, he shouldn't be doing it.
Same Idea as a Fire Alarm system that turns off the furnace (Kills Gas when Power is Disconnected from panel)
Had to install them at my work.
so, why dont we get to see it working,? I realise that it is tricky to generate the over voltage but the under voltage can be acomplished with a variac. Im guessing the overvoltage could be done with 2 transformers one 1:1 for the 240v and another to add 30v (plenty of these in old amplifiers) all again on the output of a variac.
Variacs are usually configured to deliver a higher maximum output voltage than the input supply. I think you'd probably get an additional 15% or so.
What would be good is a heat and smoke module. These are more for industrial where under and over voltage can really fuck up motors. But in domestic, it not really much use. But a module dedicated to cu and smokes makes great domestic sense.
It always amazes me, how they can build cheap but funcional product :D
Would this be suitable to recognise a PEN fault, I.e. losing netual and earth on a TNC-S system?
I think it would detect that. Plus brown outs.
I installed the one with display today. I have 2 panel meters, 2 multimeters, and this breaker. All are showing different voltages at 240v AC.
The difference is between 0-6 volt.
How can I know which one is more accurate? Is there simple circuit which I can make to get accurate measurement, because I'll know exact component values?
They're always a bit vague. The trip threshold probably won't even relate to the digital display.
BTW one of your better, more relevant videos. A definite upvote!
Maybe I'm wrong, but since the relay coil is a purely inductive load controlled by alternating current, most of the power is purely reactive, it would not consume 220²V / 60Ω but much less
Clive, What's the most important individual component in a circuit you've ever seen?
These days it has to be a microcontroller. But with discrete components, each has its own strengths. The MOSFET transistor has evolved spectacularly, so it gets special mention.
Very interesting 🤔 Thanks for the video Clive. Enjoyed
Congrats on your newly secure workshop.
Clive, we have this heater you can only set for 4 times a day and in winter is utterly useless as it's freezing and we have to manually keep setting it, if I sent you a picture could you talk us through hacking it so we can set it a lot more frequently (for say 15 mins every hour)
Post the brand and model number. One of us will find the schematic online.
@@haywoodyoudome it's an EPH Controls R37-RF A1614A
The only thing I can think of is to bypass the built in control and use an external timer or thermostat.
@Matt Quinn yes that's the one matt
@@bigclivedotcom that's cool, I'm OK with some soldering, how would I do it though, regrettably I only had 1 hour a week for maybe 3 months in Electrical class
Very clever little circuit.
Having the coil always in circuit, attached to the live is kind of weird... wouldn't it make more sense to have it in series with the thyristor?
Nice! Dodgy equipment again - thanx! That's what we need :) Keep it up please
BR Zlatko Jurkovac
What's the point of diode in low voltage part? Transistor would not be conducting in overvoltage condition as far as I understand.
What's the minimum voltage for the under voltage protection to work?
Whether the auto-restart or permanent off is a better choice depends on the application. You certainly wouldn't want dangerous machinery to automatically restart after a brownout. Imagine someone getting close to said machine, trying to figure out why it stopped working and all of a sudden the power comes back... To be honest I can't think of a good application for an auto-restart after a brown-out from the top of my head...
thanks so much for your videos and the work going in to it. really apriciated and worth watching you videos.
Hey beardy; there is something called facial cleansing device expanding very fast (apparently it's ultrasonic) in the market and I2m drooling to see its inside for what makes this egg shaped thing so special.
Take a guess, no one teardown even a single one in the whole web. yup no schematics too.
I just want to know if a regular brush with intense force worth more than those buzzers or not.
btw; ruclips.net/video/tTjL9IKb-GE/видео.html this egg shaped thingies.
By ultrasonic they mean vibrator motor.
Any chance of demoing this on a variac. Both downstream and then upstream of the paired MCB. :).
When he suggested pausing the video I was already lost 😐
But did you watch the whole video? LOL...me too!!
I was hoping, you would test the limits with a variac.
What's the one piece of TMDE kit you'd like to have? And what's one you'd like to upgrade?
Nothing in particular. I have a good selection of meters and scopes.
@@bigclivedotcom I work in a calibration lab so it's always interesting to see what people are using these days and what's new to us vs what people actually use.
The price tags are jaw dropping on some gear.
I would never have guessed the trip coil would be in the input circuit. I wonder how many times it would work before it was fried.
It’s truly inspired way of using the diode bridge as both a rectifier AND a switching element.
Moreover, it functions as a bipolar switch activated by a DC-only driver! I’d love to see what other cool hax that designed has on his pocket notebook!
Also analogous is a 120V 15A power bar made by Furman with their EVS (extreme voltage shutdown), it automatically cuts out and back in depending on whether the voltage is in the proper range. I have no connection with the company, I just like the product.