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this post was submitted on 18 Jun 2023
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Ah. It's not going to be possible to size it because the bulb is then acting as a resistor essentially. Unless you know what the equivalent resistance of the circuit you're testing is, and it draws a fixed current, you aren't going to be able to cap the current; Adding a resistor (or bulb) is just going to drop the input voltage and you will probably end up having other issues
Ah got it. Then a bench power supply is the way to go. Thanks again!
And the bulb is a strange resistor, it has a really high current when starting up cold. This can fry everything behind it.
It has the high current because it's cold, it only needs a short time to heat up and light up and the majority of circuits can handle very short overcurrent really well because the connections need to heat up before they break. Using a lightbulb for current limiting works pretty well.