Great Video Richard, When I made a dim bulb tester, I had to watch several videos on RUclips and and I still wasn't sure exactly how it worked or which wattage bulbs to use. This tutorial has everything a beginner needs to know and clear instructions on how to build it safely. Such an essential piece of equiptment as one RUclipsr put it, " if you don't like shitting your pants". I'm sure this will be very helpful to lots of people starting their journey with electronics.
At 7:00 the neon bulb should always be on (I haven’t watched to the end yet so maybe you correct this). You would need a two pole switch and the 2nd pole would switch the neutral to the neon. Maybe the reason that it turns off is that the light bulbs are limiting the current through the neon. The neon should be wired to the live before the lamps and when open (ie the lamps are in current limiting mode) the neon turns on. Note the neon would indicate current limiting is on which is the opposite to what you have done. Maybe your method works because the output current available when the lamps are used is too low to turn the neon on. I guess if it works then that’s ok.
Been waiting for this one :) I used to do something similar with a 1000W heater which went to two carbon rods in a homemade arc furnace. If you connect the rods straight to the mains, it will trip the breaker when you strike an arc. The heater would limit the current but still pull a good amount through the arc! Thanks for the video, best electronics repair channel on YT!
15:56 - You could trim the edges where they meet of both sockets at the angle you have them, which would allow both lamps to mount on the cover without going over the edge. -JAT
I modded a $30 off-the-shelf 4-bulb light bulb tester from Aliexpress to create a 4-Bulb Current Limiter Tester with 4-independently switched light bulbs, lighted power switch, fuse, Voltage/Current/Power meter, test button, and dual wiring-block plus load socket. All I had to do was to correct/replace some shoddy internal China-quality wiring, change the load-block from being in parallel with the bulb to series, add an external standard AC socket and an (optional) test push button. Assuming you can salvage the socket from an old extension cord, the total cost is not much more than the $30 Aliexpress device and it can be done in under an hour. The beauty of this modding approach is that it all fits in a nice package -- plus 4 bulbs allows you to create an "exponential" series of lamps. I used 25W/40W/60W/100W on 110v. See hackaday.io/project/191175-deluxe-ac-current-limiter for detailed instructions on the hack. Love your channel btw!
This is a nice hack, I will have to come back to this if I make one of these down the track! I'm in Australia, it's getting harder to find bulbs that are not energy efficient ones so might become an issue in the future, probably have to order in from China etc!
Thanks Richard, your version is very good because it has the double throw switch, some have just one so this is a safer design. you also clearly describe how the mains earth fits in. As always you provide safety warnings in a very concise way. One thing that was hard to see is the type of wire as I you don't want to use too thin. Really appreciate your work.
I saw another video were the presenter said that if you don't cut metal tab in between the two screw holes where the wires are attached on the sides of the outlet that it will create a short because the outlet is constructed in parallel and needs to be in series? is that correct? I don't want to damage either the light bulb or my stereo. Thank you
Thank you !!!!! This is a great video !!! I was waiting to see how you make yours compared to the others. You always explain everything very well for the beginners out here. A+++
Just one warning. The neon bulb would absolutely need a series resistor. Otherwise it is a one blow device. Luckily most that you can buy already have one. So it really applies only to the schematic.
I also did a Series lamp with switch using a 4x2” Surface Mount Backbox with a 3 position faceplate: 2x switches (main and bypass) + 1x plug (USA & Brazil 🇧🇷 STDs). As I live in Brazil, such pattern exist in our household standards. I just guess a larger 4x4” could also be applicable for UK standards. 3 points to mention: #1 Your main switch being 2 phase (line & neutral) is a Huge benefit. #2 As you, I also added a FUSE in series with the Live to avoid nastier consequences for any oversight. My suggestion to other users is to not oversee and skip adding one. #3 I also saw the benefit of visual indication, using the Neon lamp gives a clear indication. I may adapt mine with color LEDs (w/ cap/res limiting & diode in anti-parallel) as a useful reminders. Thanks for posting!
@@LearnElectronicsRepair Good point, my bad, sorry… you did include in the final drawing at last couple of minutes. I guess I posted the comment based on the review of other parts of the video and their sketches, but you highlighted the final “deluxe” version with the fuse. I will adjustment post to just emphasize the fuse - this may preserve our interaction and your fair points. Thank you for the reply!
Greetings from Australia. I'm sure you meant ''main switch being 2 pole'. Single phase = one active phase and neutral; Two phase = two active phases and neutral; Three phase = three active phases and neutral.
Thanks. Being myself, I would add test points/sockets across the load and I would coil the neutral wire 5 times and have a cutout to allow a clamp ammeter to reach that coil. Oh, and a fuse blown indicator. I then to over-engineer.
It's my understanding that halogen lamps are not recommended for dim bulb testers. Although both halogen lamps and filament lamps are both incandescent lamps, they have different characteristics. The resistance of filament lamps and halogen lamps both go up as they heat up, but halogen lamps do so at a slower rate. Therefore, a halogen lamp may not provide enough resistance quickly enough to protect the device under test. I had to hunt around to find filament lamps, because they are no longer generally available in Australia. Eventually I found some in a mate's shed. What do you think?
Thanks for the explanation and how to make and use a bulb current limiter. Very useful. Stick on various size of bulb holders and you also have a lamp tester.
We started useing a lamp limiter in the eary 70s in series with the HT line of solid state tv sets before that we had a large neon bulb with one side connected to mains earth and the other end to a test lead to check for a hot chassis Now because i dont like loud bangs i use one for the same reason as you .
Would a 3 position rotary switch or slider be safer? Position 1 would be All Off. Position 2 would be On Limited and Position 3 would be On Unlimited? In that way to get to the potentially dangerous On Unlimited position the operator would need to move through All Off and On Limited positions first? Possibly more visually obvious than relying on neons (although these could be fitted as well if required)?
thanks i was researching it on youtube couple of times and im new in your channel and i trust and learned so much in your tutorials and thats why ive try to ask how thanks so much!
On the subject of variac's, for anybody interested.....Ebay/Vevor has a great new version that actually doubles the input/output voltage from 120v input to 0-250v possible output. Works fantastic, if you want one. I picked one up on special offer for 55 bucks.
A really nice clear video thank you , and excellent that you showed it being used so we know what to expect. I have 2 questions 1 can you use two different size builds , maybe a 60 and a 100 watt or does that decrease resistance? 2 why have the bypass switch? Is it so when testing the tax psu after initial short testing you can remove the bulbs easily.
In the EU, we can turn the plug so that L and N switch places. How does it affect. Does it matter, or do you have to think about where the L is in the outlet? /Thomas
Maybe I am missing something, why would the Neon not light with the bypass switch open ? Surely the 52 or 26 ohm resistance of the light bulb(s) would have no practical effect on the voltage to the Neon lamp. If the Neon was replaced with a pair of Incandescent lamps they would still light at half voltage with the bypass switch off! Only possible explanation I see for it working is the switch being used actually has a second pole for the Neon separate from the power contacts
This behaviour is to be expected from the circuit. I reckon the switch he used actually is a dual pole switch - one for the bulb and one for the switch.....Edit: should have read the whole comment ;)
Finally a video which makes it easy for me to understand how to build this. Can’t thank you enough. Would you be able to advise on the size of bulbs required to work on valve amplifiers with around 450v on plates ? Also another request for an explanation of the isolation transformer and why you need it. Many thanks again
Thanks for illustrating this. I'm starting doing it, adding an isolation transformer before so no ground present on the current limiter. Any particular issue I should be aware of, does it make sense in your current limiter schematic?
That, an isolation transformer, coupled with a Variac, should be the first things on the list of indispensable tools for people wanting to fix stuff, followed by the usual socilloscopes, etc.
The neon lamp requires a current limiter of its own or the current thru the lamp will be unlimited. Some lamps have a built in resister, if not add one.
G, day from Sydney Australia. I was thinking how you were going to illuminate very small currents with (2) incandescent globes 100w 20w then simply "unscrew" the 100w leaving 20w (bridge of curly wire) to glow. If I want V and A meter or banana plugs for multimeter measurements: you said 'on the output'. Is that just before the 240V plug socket: where the appliance will be connected? Moreover what size fuse (10Amp) would you use Is that wire gauge thick enough to resist over heating if one decided to unscrew the 70W and you test a short with only the 20W Thank you🕛💫
Very simple setup. You could have a low wattage globe and a high wattage globe hooked up like you have done it but put a switch on the high wattage circuit so you can have a low and high current setup
Nice idea... I'm going to build one of these very soon. I live in the states, so I'll need a pair of 30W bulbs since our system is 120V. That will give me a limiter capable of 0.25A and 0.5A (or more if I use higher wattage bulbs)... very handy ranges for my use.
hi. i am actually building a 14 volts one with 2 bridge rectifiers in parallel using a single car's head light bulb or 2 so i can dispose of more than 8 different power levels.
Very nice tutorial Rich.. might make an "over engineered " one in the not to distant future 😎. Would love some more info on your variac and isolated power sytem. Looking to make a complete set up for safely using an osciliscope and bench top troubleshooting. Love your channel and that you are uploading info almost daily.
I use this system for many years now. It is part of my workshop gadgets I use during a repair or whilst servicing equipment which has not been used in years. . The only difference is that I connect the unit across the fuse holder with the fuse removed of course. And I use switchs to put the bulbs in or out instead without removing them. But basically same idea. This system saved me loads money in fuse replacement expenses over the years. Well done nice video and enjoyed watching it till the end and keep up the good works.
I was testing a power supply today using the current limit bulb which has worked in the past but this time it didn't it still trips the main breaker instantly. Would that be a short to ground issue, I'm not seeing it when testing the plug with the multimeter I just get OL. There is no bang,flash or smoke and the bulb never comes on.
Great video. Mine is somewhat similar to yours but with crocodile clips as the output and a separate earth terminal if earthing is required. Started as a simple inline light bulb but developed as more functionality was required!
I put a neon bulb in but it alway stays on (regardless of when bypass switch is closed or open) as power can flow through the bulbs and will light neon bulb even with bypass switch open, The only way to tell whether bypass is on or off and working is if bulbs are fully removed and then the neon bulb lights when the bpass switch is closed. no other path exists except through the bypass switch.
This behaviour is to be expected from the circuit. I reckon the switch he used actually is a dual pole switch - one for the bulb and one for the switch.
@@florianhofmann7553 That's the only explanation. But I don't think all illuminated switches work that way. I think some have the neon permanently connected to the neutral terminal, rather than internally switched. Whichever way you look at it, the circuit diagram is wrong. If you want to add a seperate neon, then a double pole single throw (DPST) switch is needed.
Might be a good idea to colour code the switches. Green for mains power on/off, red on/off for mains/bulbs directly connected or not, and orange on/off for both or one bulb connected 😀
Hi, good and nice tool for secure the circuits👍👍. I've got a gift from my neighbor, a variable transformer after that is a isolation transformer installed. A volt and ampermeter too.
Are you sure the variable transformer is also an isolation transformer? Most variable transformers (variacs) are a type of auto-transformer and have no isolation. I have to use a separate isolation transformer with mine.
@@LearnElectronicsRepair Hi🤗, The variable transformer isn't isolated. Because, after that are two 1:1 220V 4 amps (2x1=1🤣) isolated transformer parallel connected. The isolation transformers are from two very old Grundig television ripped🥰. Back in time, the old televisions consumed a lot of power😵💫. Ahhhhh 🥰😍 the good old time with tube television's. Eg Grundig typ CUC😍. The good old qualifikation time .
If you add the on/off switch after the fuse instead of before the output, then the red light on the bypass switch wouldn't light up when the on/off switch is off.
The red light on the bypass switch does illuminate (when it is set to short the lightbulbs) with the output switch set to off. I demonstrated that in the video. I'm not certain what you are referring too - could you elaborate further?
Mine is Isolated from the mains and can give me 0-120V in the gray outlet or 0-240V, 0-360V, 0-480V in the red outlet depending on which transformer tap I use.
i built a r7s halogen lamp 230v 100w in series with a 400w dimmer so i can lower the wattage... (one wire makes a loop outside the box so i can clamp a ampmeter probe if need be) And in parallel of this i have a 6amp breaker to bypass the lamp and still get protection And on power up a yellow led always on in both modes with a 33k resistor and diodes on both legs Its my setup small profile due to the type of bulb outside the box with heatshield and glare reduction thx for explaining also yours
Like your videos a lot but the most funny thing that instantly came to my mind looking a the video title was ... were am I going to find light bulbs 😀😀 the ue has made them illegal ! 😀😀 Also on your circuit the neon light needs a 100KOhms to 150K resistor (1/4W is more then sufficient).
@@LearnElectronicsRepair 😀 I also live in the EU ... I will dig more for those illegal bulbs 😀😀 And I had a setup just like your also back in the 90's ... can not find it tho, so I truly have to make another one.
I noticed the same, probably the plastics will not take much heat before getting "melty". I would guess that the rating is for continuous use, so should be fine, but still it triggers me...
I had an amp hooked up to a 100 watt bulb. And chased my tail for 3 days trying to figure out why the amp output was so low. It would be nice if you could explain how using such a lamp impacts the voltage drop going into the transformer. And then comming out the transformer as well as how much it limits the amps the speaker can pull. For now I will just add a by pass switch like you have.
Love this video Richard. Helps me understand why current limiter is essential for troubleshooting a device. Anyway, i was wondering, could you please make a video on isolation transformer when using a oscilloscope? I found so much on these subject. But couldn’t understand it. Should i use one when troubleshooting an amplifier using oscilloscope or the otherwise? Thanks again. Cheers
These days it is getting harder to purchase incandescent bulbs in uk - being replaced by LED - low power versions - with this in mind any ideas how to work with what is now available?
I use a junction box with an outlet and a light socket, no switches. That way, I know if I am connected to the limiters outlet, I am limiting and don't inadvertently connect directly by forgetting to have a switch in a certain position. If I don't need the limiter anymore I move the device to a normal outlet.
That method is as good as any. I added the bypass switch because the DUT on my bench will always connect to my isolation transformer, not a 'normal' outlet. You are correct though, you have to make sure you put the switch in the correct orientation 😉
These are really effective simple devices . In the event that incandescent bulbs are no longer available could you use PTC Thermistors the way they are sometimes used on transformer primaries as the basis for a similar protection device ? You might need some sort of current detection circuit that triggered an LED once the Thermistor had done it's job . Once I think about the best thing to say is long live the incandescent bulb ! Great video!
Hi! Great video. Please tell me. Can I use the lamp in series after the isolation transformer (230/230) at the same time in the same circuit? Like this: Main power (230) -> isolation transformer -> series lamp -> and socket (outlet) Is this right? ( I want to test audio amplifiers.)
I connected the input socket ground to the output socket ground. So this will ground the device under test even when using the limiter. Having said that, in my case I have an isolation transformer powering the bench so I don't have any ground connected
Hi Richard, I have built one of these very similar to that one. Only issue I have is when the lamp is in the socket the bypass neon is permanently on. How could I change this so its only on when I switch to direct. I know you may not see this as its an old video.
@steliosmakrodimitris9305 no not solved, just have to put up with it. I have labelled the switch so not to make the mistake of having it switched the wrong way.
@steliosmakrodimitris9305 fair point, I might look at that. I have a double pole single throw as my main isolator switch. Might just use a normal double pole for that and use the neon one for the lamp. Thanks for the info my friend. 👍
Your audio amplifiers should have a suitable fuse in their plug. If not look at the manual as it will depend on the wattage and efficiency of the amplifier plus it depends on whether you are driving a load or not. Many amplifiers have internal fuses that protect them rather than relying on the mains fuse.
Brilliant I'm going to make one. Great video. The format you use is excellent. You show the parts and you draw the circuit. I don't always remember everything but at the time it makes perfect sense. Thanks
I'm currently building one of these using a 150W Halogen floodlight globe for testing 500W-1000W ATX PSUs. Based on my initial research, 150W should allow enough current to pass during normal operation without illuminating the globe, but still light up in the event of a short. Maths tells me the 150W globe will provide a 0.625A current limit on my 240V AC input. And with 500-1000W PSUs requesting around a few hundred mA's under minimal load / testing conditions, this should be sufficient. I could be wrong, but so far, my research has suggested this wattage should be optimum for my use case. Anyone else using Halogen globes?
Hi Richard, I'm about to build one of these. I'm a complete beginner so thought it was probably the best place to start! If I understand the lightbulb in this circuit is acting as a PTC thermistor is that right?
I can't understand why the limiter switch neon isn't glowing all the time. It will have an internal ballast resistor of a couple of hundred kOhms probably, so the addition of just 26 Ohms would make no difference. Indeed, you even said that the on/off switch was incorrectly wired so that it's neon was on when the switch was either on or off. Looking at the circuit diagram, this would put it's neon in parrallel with the limit switch neon. So why would one be on, while the other is off?
Luckily, my local hardware store stocks these awesome clear G.E. 300W / 130V incandescent bulbs. I ended up buying a box of 6 a few years ago, just in case they stop carrying them. Sooner or later I'm sure production of them will cease.
Thanks! I’m gonna build one! Question: Is the 'polarity' (neutral and live) of any relevance? The reason I ask is the differences between the power grids between countries. I think that in England there is only one way to put a power plug in a socket, while here in Holland it does not matter if you turn the plug 180 degrees?
I have a 100w bulb preceded by a variac, then isolation transformer. The isolation transformer in my case prevents the variac from tripping the mains in this configuration, which seems to work well. But is it possible that in some instances the limit of the isolation transformer in series with a bulb can reduce current to an smps such that it starts then stops under load because the current input is reduced, not unlike, or similar to the example you gave with the pfc? I have this occurrence with an smps that works without load but when plugged in with all the safety features turns everything on but then restarts. The time it turns on is longer than the kick start period so I am sure it's a current supply issue on load, if that makes sence. I therefore thought perhaps I might try another bulb in parallel to increase power, as in your demonstration.
@@LearnElectronicsRepairI plugged the psu directly into the mains and found that I had indeed cured the problem and that it was the safety features limiting the current. So happy days! But getting a large transformer is rather expensive.
At a local industrial site, an engineering print called for a 3 phase 60 amp breaker on a 250 foot 14 guage cable. I told the head electrician we had a name for that. A fuse link!
I envision a future where incandescent light bulbs might not be available anymore, in that case we could use a resistance from a small oven or similar and work out the desired current limit with other resistors in parallel.
A great video, but I'd prefer the second bulb to be on a a switch, so you don't have a open Live socket. Because, ultimately would drop something into that socket...
Im gonna build me one of these, im a electrician so i have access to all these items, but, since im in Denmark and halogen ect in e27 is illigal to sell now, im gonna go with two G9 60W 230V bulbs, should do the same, and they can sell em :P
Concept of this is good, but personally, I would make this limiter with 3-4 bulbs, and they should be chosen on switch. Bulb 1 = 60W, bulb 4 to have 300W. Then you can select different bulbs via switch. Different bulbs means different limiters, in single device, but you really must have 4 different bulbs.
One word of warning, I was repairing an exposure audiophile amp . On completion the power supply oscillated terribly until I removed the current limit !then all was fine
I would like to point out that two, parallel wired, 70w bulbs is not the same as a single 140w bulb in this circuit. The parallel setup allows twice as much current compared to a single 70w and four times as much as a single 140w. Might be obvious to most.
I asked myself how many watts can pass throught the bulb before it lights up? Or which light bulb do I need for a certain device knowing the power it normally draws. I live in a country with 230V mains. My light bulbs start to glow around 30V. So the device still gets around 200V which should be sufficient for a normal operation. The official voltage is 230V +/-10% and 200V is only slightly below (-13%). I measured 40W, 60W and 100W light bulbs and in all cases the current at 30V is just slightly above 1/3 of the nominal current. That means the device can draw around 1/3 of the nominal power of the light bulb. Hence a 40W, 60W, 100W light bulb allows for 13W, 20W, 33W power into the device. This should not differ significantly in countries with different mains voltage like 115V as these are power ratios.
Best electronics repair channel in the world. Thanks you for teaching.
Great Video Richard,
When I made a dim bulb tester, I had to watch several videos on RUclips and and I still wasn't sure exactly how it worked or which wattage bulbs to use. This tutorial has everything a beginner needs to know and clear instructions on how to build it safely. Such an essential piece of equiptment as one RUclipsr put it, " if you don't like shitting your pants".
I'm sure this will be very helpful to lots of people starting their journey with electronics.
Thank you, it's good to see you liked it 🙂
At 7:00 the neon bulb should always be on (I haven’t watched to the end yet so maybe you correct this). You would need a two pole switch and the 2nd pole would switch the neutral to the neon. Maybe the reason that it turns off is that the light bulbs are limiting the current through the neon.
The neon should be wired to the live before the lamps and when open (ie the lamps are in current limiting mode) the neon turns on. Note the neon would indicate current limiting is on which is the opposite to what you have done.
Maybe your method works because the output current available when the lamps are used is too low to turn the neon on. I guess if it works then that’s ok.
i really love and appreciate the depth that went in to make this video
Been waiting for this one :) I used to do something similar with a 1000W heater which went to two carbon rods in a homemade arc furnace. If you connect the rods straight to the mains, it will trip the breaker when you strike an arc. The heater would limit the current but still pull a good amount through the arc!
Thanks for the video, best electronics repair channel on YT!
Fantastic and thanks for pointing me in this direction, Richard!
15:56 - You could trim the edges where they meet of both sockets at the angle you have them, which would allow both lamps to mount on the cover without going over the edge. -JAT
I modded a $30 off-the-shelf 4-bulb light bulb tester from Aliexpress to create a 4-Bulb Current Limiter Tester with 4-independently switched light bulbs, lighted power switch, fuse, Voltage/Current/Power meter, test button, and dual wiring-block plus load socket. All I had to do was to correct/replace some shoddy internal China-quality wiring, change the load-block from being in parallel with the bulb to series, add an external standard AC socket and an (optional) test push button. Assuming you can salvage the socket from an old extension cord, the total cost is not much more than the $30 Aliexpress device and it can be done in under an hour.
The beauty of this modding approach is that it all fits in a nice package -- plus 4 bulbs allows you to create an "exponential" series of lamps. I used 25W/40W/60W/100W on 110v.
See hackaday.io/project/191175-deluxe-ac-current-limiter for detailed instructions on the hack.
Love your channel btw!
This is a nice hack, I will have to come back to this if I make one of these down the track!
I'm in Australia, it's getting harder to find bulbs that are not energy efficient ones so might become an issue in the future, probably have to order in from China etc!
how would this differ with a 100v supply?
Thanks Richard, your version is very good because it has the double throw switch, some have just one so this is a safer design. you also clearly describe how the mains earth fits in. As always you provide safety warnings in a very concise way. One thing that was hard to see is the type of wire as I you don't want to use too thin. Really appreciate your work.
I saw another video were the presenter said that if you don't cut metal tab in between the two screw holes where the wires are attached on the sides of the outlet that it will create a short because the outlet is constructed in parallel and needs to be in series? is that correct? I don't want to damage either the light bulb or my stereo.
Thank you
Thank you !!!!! This is a great video !!! I was waiting to see how you make yours compared to the others. You always explain everything very well for the beginners out here. A+++
Fantastic video, Richard.
Just one warning. The neon bulb would absolutely need a series resistor. Otherwise it is a one blow device. Luckily most that you can buy already have one. So it really applies only to the schematic.
Thanks Richard. Another piece of kit to add to the collection.
Great tutorial Richard, thanks. It just goes to show you people don't need to spend a lot to have a nice piece of test equipment.
I also did a Series lamp with switch using a 4x2” Surface Mount Backbox with a 3 position faceplate: 2x switches (main and bypass) + 1x plug (USA & Brazil 🇧🇷 STDs). As I live in Brazil, such pattern exist in our household standards. I just guess a larger 4x4” could also be applicable for UK standards. 3 points to mention:
#1 Your main switch being 2 phase (line & neutral) is a Huge benefit.
#2 As you, I also added a FUSE in series with the Live to avoid nastier consequences for any oversight. My suggestion to other users is to not oversee and skip adding one.
#3 I also saw the benefit of visual indication, using the Neon lamp gives a clear indication. I may adapt mine with color LEDs (w/ cap/res limiting & diode in anti-parallel) as a useful reminders.
Thanks for posting!
I don't understand point #2 as I did clearly fit a fuse. What should I add?
@@LearnElectronicsRepair
Good point, my bad, sorry… you did include in the final drawing at last couple of minutes. I guess I posted the comment based on the review of other parts of the video and their sketches, but you highlighted the final “deluxe” version with the fuse.
I will adjustment post to just emphasize the fuse - this may preserve our interaction and your fair points.
Thank you for the reply!
Greetings from Australia. I'm sure you meant ''main switch being 2 pole'. Single phase = one active phase and neutral; Two phase = two active phases and neutral; Three phase = three active phases and neutral.
Thanks. Being myself, I would add test points/sockets across the load and I would coil the neutral wire 5 times and have a cutout to allow a clamp ammeter to reach that coil. Oh, and a fuse blown indicator. I then to over-engineer.
That is exactly what I'm looking for, thank you so much!!
It's my understanding that halogen lamps are not recommended for dim bulb testers. Although both halogen lamps and filament lamps are both incandescent lamps, they have different characteristics. The resistance of filament lamps and halogen lamps both go up as they heat up, but halogen lamps do so at a slower rate. Therefore, a halogen lamp may not provide enough resistance quickly enough to protect the device under test. I had to hunt around to find filament lamps, because they are no longer generally available in Australia. Eventually I found some in a mate's shed. What do you think?
Made myself one Rich. Very handy. Thanks
Thanks for the explanation and how to make and use a bulb current limiter. Very useful. Stick on various size of bulb holders and you also have a lamp tester.
I use 250w 3 ohm heater elements. And in the winter it's a joy to use. Not so much in the summer.
We started useing a lamp limiter in the eary 70s in series with the HT line of solid state tv sets
before that we had a large neon bulb with one side connected to mains earth and the other end to a test lead to check for a hot chassis
Now because i dont like loud bangs i use one for the same reason as you .
Would a 3 position rotary switch or slider be safer? Position 1 would be All Off. Position 2 would be On Limited and Position 3 would be On Unlimited? In that way to get to the potentially dangerous On Unlimited position the operator would need to move through All Off and On Limited positions first? Possibly more visually obvious than relying on neons (although these could be fitted as well if required)?
thanks i was researching it on youtube couple of times and im new in your channel and i trust and learned so much in your tutorials and thats why ive try to ask how thanks so much!
hello, is this the same schematics for 230v european power plug?
On the subject of variac's, for anybody interested.....Ebay/Vevor has a great new version that actually doubles the input/output voltage from 120v input to 0-250v possible output. Works fantastic, if you want one. I picked one up on special offer for 55 bucks.
A really nice clear video thank you , and excellent that you showed it being used so we know what to expect.
I have 2 questions 1 can you use two different size builds , maybe a 60 and a 100 watt or does that decrease resistance?
2 why have the bypass switch? Is it so when testing the tax psu after initial short testing you can remove the bulbs easily.
In the EU, we can turn the plug so that L and N switch places. How does it affect. Does it matter, or do you have to think about where the L is in the outlet?
/Thomas
What size fuse would be suitable for testing audio amplifiers. Thanks.
An excellent tutorial on this great tool, thanks, Richard. Puts my basic plank and bulb to shame ;-)
Maybe I am missing something, why would the Neon not light with the bypass switch open ?
Surely the 52 or 26 ohm resistance of the light bulb(s) would have no practical effect on the voltage to the Neon lamp. If the Neon was replaced with a pair of Incandescent lamps they would still light at half voltage with the bypass switch off! Only possible explanation I see for it working is the switch being used actually has a second pole for the Neon separate from the power contacts
I'm baffled too. 26 Ohms in series with a neon should have no effect.
This behaviour is to be expected from the circuit. I reckon the switch he used actually is a dual pole switch - one for the bulb and one for the switch.....Edit: should have read the whole comment ;)
Finally a video which makes it easy for me to understand how to build this. Can’t thank you enough. Would you be able to advise on the size of bulbs required to work on valve amplifiers with around 450v on plates ?
Also another request for an explanation of the isolation transformer and why you need it.
Many thanks again
depends what the normal running wattage or current of the amp is ...start low, about 25w then increase , such as 40, 60, 100, 150, etc .
Thanks for illustrating this. I'm starting doing it, adding an isolation transformer before so no ground present on the current limiter. Any particular issue I should be aware of, does it make sense in your current limiter schematic?
That, an isolation transformer, coupled with a Variac, should be the first things on the list of indispensable tools for people wanting to fix stuff, followed by the usual socilloscopes, etc.
The neon lamp requires a current limiter of its own or the current thru the lamp will be unlimited. Some lamps have a built in resister, if not add one.
Thanks! Been waiting for this!
G, day from Sydney Australia. I was thinking how you were going to illuminate very small currents with (2) incandescent globes 100w 20w then simply "unscrew" the 100w leaving 20w (bridge of curly wire) to glow.
If I want V and A meter or banana plugs for multimeter measurements: you said 'on the output'. Is that just before the 240V plug socket: where the appliance will be connected?
Moreover what size fuse (10Amp) would you use
Is that wire gauge thick enough to resist over heating if one decided to unscrew the 70W and you test a short with only the 20W
Thank you🕛💫
thank you
Could you not use a choke for a sodium light?
Would a GFCI outlet improve the dim bulb tester circuit? I would be interested to see you explain GFCI outlets.
Very simple setup. You could have a low wattage globe and a high wattage globe hooked up like you have done it but put a switch on the high wattage circuit so you can have a low and high current setup
Yeah of course you can add switches to select the bulbs 🙂
I wonder if we can use small hallogen lamps type G4 same wattage instead incandescent light bulbs for space economy for this project.
Good video, Rich. I would also add a none switched ground / earth wire through the box.
I connected an earth wire from the input mains socket to the output socket and showed that n the video. Did you mean something different?
@Learn Electronics Repair Sorry Rich, I must have missed that part. I sometimes nod off while watching RUclips.
Nice idea... I'm going to build one of these very soon. I live in the states, so I'll need a pair of 30W bulbs since our system is 120V. That will give me a limiter capable of 0.25A and 0.5A (or more if I use higher wattage bulbs)... very handy ranges for my use.
hi. i am actually building a 14 volts one with 2 bridge rectifiers in parallel using a single car's head light bulb or 2 so i can dispose of more than 8 different power levels.
Very nice tutorial Rich.. might make an "over engineered " one in the not to distant future 😎. Would love some more info on your variac and isolated power sytem. Looking to make a complete set up for safely using an osciliscope and bench top troubleshooting. Love your channel and that you are uploading info almost daily.
Thank you. Useful.
Hello Richard, thanks for the video the problem is i can't find normal lamps anymore in shops only LED. Do you have an alternative to lamps?
I use this system for many years now. It is part of my workshop gadgets I use during a repair or whilst servicing equipment which has not been used in years. . The only difference is that I connect the unit across the fuse holder with the fuse removed of course. And I use switchs to put the bulbs in or out instead without removing them. But basically same idea. This system saved me loads money in fuse replacement expenses over the years.
Well done nice video and enjoyed watching it till the end and keep up the good works.
Heya, have the coponants inhouse but still have to bild it
thank you for this tutorial, just a quick question, what amps is the separate fuse
I was testing a power supply today using the current limit bulb which has worked in the past but this time it didn't it still trips the main breaker instantly.
Would that be a short to ground issue, I'm not seeing it when testing the plug with the multimeter I just get OL.
There is no bang,flash or smoke and the bulb never comes on.
Great video. Mine is somewhat similar to yours but with crocodile clips as the output and a separate earth terminal if earthing is required. Started as a simple inline light bulb but developed as more functionality was required!
Sounds like it's lethal with croc clips.
Be careful.
I put a neon bulb in but it alway stays on (regardless of when bypass switch is closed or open) as power can flow through the bulbs and will light neon bulb even with bypass switch open, The only way to tell whether bypass is on or off and working is if bulbs are fully removed and then the neon bulb lights when the bpass switch is closed. no other path exists except through the bypass switch.
This behaviour is to be expected from the circuit. I reckon the switch he used actually is a dual pole switch - one for the bulb and one for the switch.
@@florianhofmann7553 That's the only explanation. But I don't think all illuminated switches work that way. I think some have the neon permanently connected to the neutral terminal, rather than internally switched. Whichever way you look at it, the circuit diagram is wrong. If you want to add a seperate neon, then a double pole single throw (DPST) switch is needed.
You may add one more switch to separate one lamp when not needed instead of taking it off
Might be a good idea to colour code the switches. Green for mains power on/off, red on/off for mains/bulbs directly connected or not, and orange on/off for both or one bulb connected 😀
Hi, good and nice tool for secure the circuits👍👍. I've got a gift from my neighbor, a variable transformer after that is a isolation transformer installed. A volt and ampermeter too.
Are you sure the variable transformer is also an isolation transformer? Most variable transformers (variacs) are a type of auto-transformer and have no isolation. I have to use a separate isolation transformer with mine.
@@LearnElectronicsRepair Hi🤗, The variable transformer isn't isolated. Because, after that are two 1:1 220V 4 amps (2x1=1🤣) isolated transformer parallel connected. The isolation transformers are from two very old Grundig television ripped🥰. Back in time, the old televisions consumed a lot of power😵💫.
Ahhhhh 🥰😍 the good old time with tube television's. Eg Grundig typ CUC😍. The good old qualifikation time .
If you add the on/off switch after the fuse instead of before the output, then the red light on the bypass switch wouldn't light up when the on/off switch is off.
Thats a good suggestion!
The red light on the bypass switch does illuminate (when it is set to short the lightbulbs) with the output switch set to off. I demonstrated that in the video. I'm not certain what you are referring too - could you elaborate further?
Mine is Isolated from the mains and can give me 0-120V in the gray outlet or 0-240V, 0-360V, 0-480V in the red outlet depending on which transformer tap I use.
i built a r7s halogen lamp 230v 100w in series with a 400w dimmer so i can lower the wattage... (one wire makes a loop outside the box so i can clamp a ampmeter probe if need be)
And in parallel of this i have a 6amp breaker to bypass the lamp and still get protection
And on power up a yellow led always on in both modes with a 33k resistor and diodes on both legs
Its my setup small profile due to the type of bulb outside the box with heatshield and glare reduction
thx for explaining also yours
Like your videos a lot but the most funny thing that instantly came to my mind looking a the video title was ... were am I going to find light bulbs 😀😀 the ue has made them illegal ! 😀😀
Also on your circuit the neon light needs a 100KOhms to 150K resistor (1/4W is more then sufficient).
The series resistor is built into the switch
I live in the EU and I can easily buy light bulbs in the local shops - so they obviously are not very illegal 😉
@@LearnElectronicsRepair 😀 I also live in the EU ... I will dig more for those illegal bulbs 😀😀 And I had a setup just like your also back in the 90's ... can not find it tho, so I truly have to make another one.
Hi there. I noticed from the back of the packet, that your lamp sockets are max 40w. Is that not a concern ?
I noticed the same, probably the plastics will not take much heat before getting "melty". I would guess that the rating is for continuous use, so should be fine, but still it triggers me...
For incandescent bulbs, you can search for “incandescent traffic signal bulb”. These work very well.
Very nice build! I've built my own a few weeks ago. Yours is better, but mine's have labels on each button (they don't have lights, though) 😁
I had an amp hooked up to a 100 watt bulb. And chased my tail for 3 days trying to figure out why the amp output was so low.
It would be nice if you could explain how using such a lamp impacts the voltage drop going into the transformer. And then comming out the transformer as well as how much it limits the amps the speaker can pull.
For now I will just add a by pass switch like you have.
Hey neat! Thanks for doing it!
Nice to know. Best😊 🇵🇹
Love this video Richard. Helps me understand why current limiter is essential for troubleshooting a device. Anyway, i was wondering, could you please make a video on isolation transformer when using a oscilloscope? I found so much on these subject. But couldn’t understand it. Should i use one when troubleshooting an amplifier using oscilloscope or the otherwise? Thanks again. Cheers
These days it is getting harder to purchase incandescent bulbs in uk - being replaced by LED - low power versions - with this in mind any ideas how to work with what is now available?
Ok. I'll use a 60w for my atx troubleshooting to limit current
I use a junction box with an outlet and a light socket, no switches. That way, I know if I am connected to the limiters outlet, I am limiting and don't inadvertently connect directly by forgetting to have a switch in a certain position. If I don't need the limiter anymore I move the device to a normal outlet.
That method is as good as any. I added the bypass switch because the DUT on my bench will always connect to my isolation transformer, not a 'normal' outlet. You are correct though, you have to make sure you put the switch in the correct orientation 😉
How big is the project box?
These are really effective simple devices . In the event that incandescent bulbs are no longer available could you use PTC Thermistors the way they are sometimes used on transformer primaries as the basis for a similar protection device ? You might need some sort of current detection circuit that triggered an LED once the Thermistor had done it's job . Once I think about the best thing to say is long live the incandescent bulb ! Great video!
i have been thinking of making an 'active' current limiter
Hi! Great video. Please tell me. Can I use the lamp in series after the isolation transformer (230/230) at the same time in the same circuit? Like this: Main power (230) -> isolation transformer -> series lamp -> and socket (outlet) Is this right? ( I want to test audio amplifiers.)
Not trying to nitpick but isn't the first schematic drawing wrong at 5:35 as the switch only bypasses one light bulb?
What are the dimensions of the box please?
What, if anything, should be done with the earth ground? Should it come into play as some sort of safety measure? Just wondered.
I connected the input socket ground to the output socket ground. So this will ground the device under test even when using the limiter. Having said that, in my case I have an isolation transformer powering the bench so I don't have any ground connected
Hi Richard, I have built one of these very similar to that one. Only issue I have is when the lamp is in the socket the bypass neon is permanently on. How could I change this so its only on when I switch to direct. I know you may not see this as its an old video.
Same issue here!.......Did you solve the problem?
@steliosmakrodimitris9305 no not solved, just have to put up with it. I have labelled the switch so not to make the mistake of having it switched the wrong way.
I did some research.... The best way to overcome this problem is by using a double pole single throw rocker switch with embedded neon lamp!
@steliosmakrodimitris9305 fair point, I might look at that. I have a double pole single throw as my main isolator switch. Might just use a normal double pole for that and use the neon one for the lamp. Thanks for the info my friend. 👍
@@sparky150875 You are welcome mate
The incandescent lamps are like completely out of stock in the local market even on Aliexpress. Is there any other solution for this problem ?
What is the formula to calculate the bulb wattage needed related to the device?
Your audio amplifiers should have a suitable fuse in their plug. If not look at the manual as it will depend on the wattage and efficiency of the amplifier plus it depends on whether you are driving a load or not. Many amplifiers have internal fuses that protect them rather than relying on the mains fuse.
Brilliant I'm going to make one. Great video. The format you use is excellent. You show the parts and you draw the circuit. I don't always remember everything but at the time it makes perfect sense.
Thanks
Cheers, it's good to see you liked it🙂
I'm currently building one of these using a 150W Halogen floodlight globe for testing 500W-1000W ATX PSUs. Based on my initial research, 150W should allow enough current to pass during normal operation without illuminating the globe, but still light up in the event of a short. Maths tells me the 150W globe will provide a 0.625A current limit on my 240V AC input. And with 500-1000W PSUs requesting around a few hundred mA's under minimal load / testing conditions, this should be sufficient. I could be wrong, but so far, my research has suggested this wattage should be optimum for my use case. Anyone else using Halogen globes?
Hi Richard, I'm about to build one of these. I'm a complete beginner so thought it was probably the best place to start! If I understand the lightbulb in this circuit is acting as a PTC thermistor is that right?
Yes
I can't understand why the limiter switch neon isn't glowing all the time. It will have an internal ballast resistor of a couple of hundred kOhms probably, so the addition of just 26 Ohms would make no difference.
Indeed, you even said that the on/off switch was incorrectly wired so that it's neon was on when the switch was either on or off. Looking at the circuit diagram, this would put it's neon in parrallel with the limit switch neon. So why would one be on, while the other is off?
Luckily, my local hardware store stocks these awesome clear G.E. 300W / 130V incandescent bulbs. I ended up buying a box of 6 a few years ago, just in case they stop carrying them. Sooner or later I'm sure production of them will cease.
Thanks! I’m gonna build one!
Question: Is the 'polarity' (neutral and live) of any relevance?
The reason I ask is the differences between the power grids between countries.
I think that in England there is only one way to put a power plug in a socket, while here in Holland it does not matter if you turn the plug 180 degrees?
It will work perfectly well but remember that even if your output socket is polarised then you lose that polarisation by using an unpolarised input.
@@chrishartley1210 Ok, thanks!
I have a 100w bulb preceded by a variac, then isolation transformer. The isolation transformer in my case prevents the variac from tripping the mains in this configuration, which seems to work well. But is it possible that in some instances the limit of the isolation transformer in series with a bulb can reduce current to an smps such that it starts then stops under load because the current input is reduced, not unlike, or similar to the example you gave with the pfc? I have this occurrence with an smps that works without load but when plugged in with all the safety features turns everything on but then restarts. The time it turns on is longer than the kick start period so I am sure it's a current supply issue on load, if that makes sence. I therefore thought perhaps I might try another bulb in parallel to increase power, as in your demonstration.
My isolation transformer and also my variac are both 2000VA so I have not had that particular problem myself
@@LearnElectronicsRepairI plugged the psu directly into the mains and found that I had indeed cured the problem and that it was the safety features limiting the current. So happy days! But getting a large transformer is rather expensive.
What is its advantage over using a simple circuit breaker ?
It wouldnt explode your new component you change.
It's important that people realise that this only works with an incandescent light bulb.
Well... Maybe call it a pico Limiter 😭
At a local industrial site, an engineering print called for a 3 phase 60 amp breaker on a 250 foot 14 guage cable. I told the head electrician we had a name for that. A fuse link!
Yeah, that's why I specifically said in the video this only works with incadescent or halogen bulbs - you can't use an LED bulb.
Halogen bulb as used in downlighters 🤔 assuming 50W variety will do having swapped fir led types. I’ll take some resistance measurements
I envision a future where incandescent light bulbs might not be available anymore, in that case we could use a resistance from a small oven or similar and work out the desired current limit with other resistors in parallel.
A great video, but I'd prefer the second bulb to be on a a switch, so you don't have a open Live socket. Because, ultimately would drop something into that socket...
Im gonna build me one of these, im a electrician so i have access to all these items, but, since im in Denmark and halogen ect in e27 is illigal to sell now, im gonna go with two G9 60W 230V bulbs, should do the same, and they can sell em :P
I noticed the rating of your lamp holders was only 40W. Is that an opps moment?
Surely, if there is a short, this would trip any earth leakage device on a consumer unit before the lamps get a chance to glow.
Concept of this is good, but personally, I would make this limiter with 3-4 bulbs, and they should be chosen on switch. Bulb 1 = 60W, bulb 4 to have 300W. Then you can select different bulbs via switch. Different bulbs means different limiters, in single device, but you really must have 4 different bulbs.
Yeah there are many ways to do this. The range of wattage depends on what you are usually testing. For me the bulbs I selected suit my needs
One word of warning, I was repairing an exposure audiophile amp . On completion the power supply oscillated terribly until I removed the current limit !then all was fine
That may be the same problem I find with switch mode power supplies that have active PFC
You Can Find These Premade Ones on Chinese Markets..Takes bit of Searching thuo..
I would like to point out that two, parallel wired, 70w bulbs is not the same as a single 140w bulb in this circuit. The parallel setup allows twice as much current compared to a single 70w and four times as much as a single 140w. Might be obvious to most.
Just buy a dimmer switch, job done and a fraction of the cost
The neon light will glow no matter the switch position.
I asked myself how many watts can pass throught the bulb before it lights up? Or which light bulb do I need for a certain device knowing the power it normally draws. I live in a country with 230V mains. My light bulbs start to glow around 30V. So the device still gets around 200V which should be sufficient for a normal operation. The official voltage is 230V +/-10% and 200V is only slightly below (-13%). I measured 40W, 60W and 100W light bulbs and in all cases the current at 30V is just slightly above 1/3 of the nominal current. That means the device can draw around 1/3 of the nominal power of the light bulb. Hence a 40W, 60W, 100W light bulb allows for 13W, 20W, 33W power into the device. This should not differ significantly in countries with different mains voltage like 115V as these are power ratios.
The choice of light bulb wattage mostly depends on the type of devices you usually work on
🙏🏻😀🌟❤️👍🏻👍🏻👍🏻