Building a load lamp setup for circuit testing

[ddewaele]

Hi,

I have a 3 way extension lead that I would like to use to stick it in the wall, put a load lamp (40W oven lamp) in series with it, and then use one of the prongs to insert my circuit under test. (the idea is that the load lamp would prevent the circuit from destroying itself in case of an issue).
(I'm in Europe where we have 230v AC, and I would like to setup a load lamp circuit to protect my circuits under tests.)

If I cut the extension cord cable , and I take the black wire out (hot), cut it and put a load lamp in between, would that be a valid circuit for a load lamp.

My apologies for the drawing, the amateurism reflects my knowledge of basic AC electrical wiring



The goal is to test a circuit that is currently causing some kind of short, and put this setup behind an isolation transformer also.

Some questions :

• Is this the way to do it ?
• I only have a relatively small 40 watt oven lamp ? Would that be ok ? The circuits that I would test with this are mostly switch mode power supplies
• If I would short one of the prongs in the extension lead would the light simply come on and would nothing else happen ? (it is a bit counter-intuitive to short a prong like that in my head, but the way I see it the circuit would just look a standard AC light bulb circuit)
• If the circuit under test is running without issues I would hardly see the bulb go on I imagine ?
• I've seen videos where people put the bulb in series with the black lead, but others that put in series with the neutral / gnd lead. What is the difference ?
• Does adding an isolation transformer change anything ? (the idea would be to put this on an isolation transformer instead of plugging it in the wall socket directly)

[ledtester]

This device is also called a "dim bulb tester".

It's been discussed a lot on these forums. Some recent discussions:

https://www.eevblog.com/forum/projects/dim-bulb-tester-totally-enclosed-with-switchable-cooling-fan/msg3180804/#msg3180804

https://www.eevblog.com/forum/buysellwanted/ebay-dim-bulb-tester/msg3125264/#msg3125264

I only have a relatively small 40 watt oven lamp ? Would that be ok ?

Generally you want to use a bulb that has about the same wattage as the device you are powering. For instance, this page (https://antiqueradio.org/dimbulb.htm) suggests:

Your radio should play normally without fully lighting a bulb that is roughly 1.5 to 2 times the radio's stated wattage.