Post #1916147

2026-05-03 12:32 UTC

Those who know electronics a bit more than me: homemade cap discharge tool with a 20k ohm, 5W resistor with a 12AWG cable rated at 600V, sounds reasonable? (I think ifixit is a pretty reliable source: https://www.ifixit.com/Guide/Constructing+a+Capacitor+Discharge+Tool/2177 ) #electronics

Replies (2)

@idiot@mastodonapp.uk 2026-05-03 13:46

@tove@social.tovelago.se that set of parts will be fine to 1mF or so at rectified mains voltage (~300V). The main risk here is from accidentally touching something conducive, so if your old multimeter leads are Cat III (typically have caps on the probe tips to minimise exposed metal) that's probably good. You might put the resistor in a little enclosure with two 4mm sockets to avoid the heat shrink wrapped resistor.

Open ##1916146
@bastelwombat@chaos.social 2026-05-03 16:16

@tove@social.tovelago.se Household electronics: I would expect the main use case to be discharging the input capacitors in switching power supplies, so a max voltage of less than 400V at potentially significant capacities. 400V / 20,000V/A = 0.02A 0.02A * 400V = 8W Even when assuming only 325V, you'll still end up at 5.28W. In practice, the voltage will start to drop immediately, so you’ll quickly fall within the limit of the resistor. But unless size is an issue: Go with 10W, or more kOhms.

Open ##2954759