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How to properly size a serial bulb for protection when troubleshooting a circuit? (discuss.tchncs.de)

submitted 1 year ago by [email protected] to c/[email protected]

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Hello. I'm a hobbist on electronics repairs, and I did some repairs on stuff powered from the wall socket before, using a serial bulb to protect the circuit in case there's a short. Now I want to troubleshoot a board that works at 3V and very low current (like no more than 100mA). So, how can I properly size the bulb I need for this circuit before powering it? Or is there a better way to protect the circuit than a serial bulb? Thanks in advance.

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[–] mattaw 1 points 1 year ago* (last edited 1 year ago)

Figure 22 has a really cheap voltage and current controlled bench supply using two lm317s from an existing DC supply like a laptop charger etc:

https://www.onsemi.com/pdf/datasheet/lm317-d.pdf

Pre built ones with heatsinks may be available really cheap on eBay too.

If you need a lot of DC power there are some kits on eBay etc. that can convert a PC PSU to a bench supply.