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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

Over the top dim bulb tester, improvements

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#41
newbie suggestion
1) a well made inlet with fuse and indicator light to make it compact ? like this
1669125169486.png

2) high wattage series resistor/s at light bulb to make it multiwattage bulb if how bright the bulb glows as an indication is required ?

Ignore if suggestions are silly since we are dealing with mains power voltages and currents.
regards
 
#42
Newby too, but I think a resistor defeats the purpose, adding bulbs in parallel would give you a way to tier the current limit upwards if needed. If your device under test starts to short or go to a lower resistance it's acting like a light switch to turn on the bulb that is in series, making what would be a short or overload, just a harmless turning on of the bulb takes the current instead of the short. My on off will be a magnetic lockout switch, so just a single IEC inlet no fuse or switch there. It will have the fuses on front panel.
 
#43
One other safety feature must be added and that is GFCI. I found a GFCI you can insert into the power supply cord. Ahead of the IEC inlet. 4 ma of leakage and it will trip.

ELEGRP G1215CM G20CMR Patented Auto-Monitoring GFCI Replacement Plug Inline Assembly, Manual Reset 15 Amp Grounded 3 Wires 3-Prongs for Power Tools, Lawn Equipment etc, UL Listed, 1 Pack, Black https://a.co/d/2xkeDm1
 
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#44
Hiten said:
if how bright the bulb glows as an indication
Click to expand...
No. An incandescent (hot filament) lamp is low resistance when cold and higher resistance when hot. If your build is good, the lamp hardly lights at all. If your build is near-short, the lamp will glow near-full-bright, faster than your hand could react, and your house wires are not strained.

Of course the problem is that today the LED lamps are pushing incandescents off the market. I can still buy "pear" incandescents especially in large size (over 150 Watts). We can still buy the small tube Halogen lamps for work-lights (however we may have to find the fixtures in yard sales).
 
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#45
Fortunately, the market for incandescent oven bulbs will be around for a long time though, it is the "A15" sized bulb, medium base, thicker glass, rugged filament, smaller bulb available in 25, 40 or 60 watts. You can't light up a 400 degree oven with an LED bulb, So I'm going to use three 60W A15 bulbs to give it 60, 120 or 180 watt ranges and well/window them into the enclosure because they are just under 2 inches in diameter.

https://www.amazon.com/gp/product/B09Q9SXV9K/ref=ox_sc_act_title_4?smid=ATVPDKIKX0DER&th=1

oven bulbs.jpg
 
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#46
Windcrest77 said:
market for incandescent oven bulbs will be around
Click to expand...
That's what I thought. But my 9 year old oven went dark, and it turns out (after gingerly prying at a glass dome stuck in the ceiling) to take a peanut-size baseless lamp. Recognizing a dead-end when I saw it, I got a 6-pack. Assuming the "equivalents" last half as long as the factory lamps, I'm covered for a couple decades.
JCD50/FR/130V 50 WATT FROST 130 VOLT GY6.35 BASE $1.88
ovenbulb-shopping.png
 
#47
JCD50/FR/130V 50 WATT FROST 130 VOLT GY6.35

mmmm these are nice and small and available in many wattages. Properly considering their extra heat when mounting them in the case, these could work out pretty nice as the dim bulbs due to being so compact. Halogens should behave the same as an incandescent when the DUT shorts out.
 
#49
I drew out what I'd like to build. I only desk-checked it for short circuits in switching, but if anyone spots something wrong or if more safety features could be added, please post. Criticism too.

I chose to not fuse the neutral side as I think that would be a hazard, should a neutral fuse blow first then the hot side fuse wont blow at all, leaving the device with a hot leg that is energized. Someone might touch something thinking the fuse is safely blown when only the neutral fuse is blown, then they touch anything in the room to complete the circuit. Not good.


1669854727067.png
 

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#51
Duh, while sleeping I realized that I made an embarrassing mistake. The lamps need to be added in parallel not in series in order to vary the amount of current absorbing. I will update it today and repost the correction to post #1. #49 schematic is wrong!
 
#57
Hi there,
It's been a couple of years since your last post, hopefully this post finds you well and that you've built out your finalized design. Have you posted any pictures or videos of your completed build anywhere in the forums or elsewhere? If you haven't, I would like to encourage you to do so. As someone who is trying to improve on his rudimentary electronic repair skills, this thread has really helped me think through my own design/build process for an isolated variable AC bulb current limiter. It'd be interesting to see how you laid out the final build and the choices you made, and if you have any thoughts on what features (or layout) are working well/not so well, and what you might improve upon or forego.

I do want to thank you and the other forum members for taking the time to offer up your work and suggestions. It really does make a difference in the lives of people you'll most likely never meet. It matters to me.

Cheers,
James
 
#58

jamesbythebay,​


I have not put it all together in a single enclosure, it's on my long project list 🙂 But I up my use of AC mains safety features since this post. I now use a GFCI power strip, the variac I always ran through an isolation transformer, and I have my old dim bulb in a junction box to absorb shorts. I did find myself frequently needing to connect two bare wires to isolated mains for breadboarding or repairing or experimenting. I would always just use a spring clip or screw barrier terminal, this left those two wires vulnerable to knocking into something or touch. So since this post I have added a handy little thing called a "quick test block" made by RS Pro out of Great Britain. It works great, its basically a knife switch, fuse, neon bulb and spring clips all isolated in plastic. When you open the cover, power is cut and you get access to the spring clips, close it and the power connects. I no longer have to clip mains wires to free spring clips on the bench to attach mains to stripped wire, this little box is really a neat idea. Photo below:

PXL_20241213_210217845.jpg
PXL_20241213_210226872.jpg
 
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