[SML] Dummy load resistor?

billn at peak.org billn at peak.org
Thu May 3 17:03:37 UTC 2018


> Thoughts?  What size resistor would be necessary to fake a few watts?

I have just wrapped a small incandescent in aluminum foil. I don't know if it
would work for an extended period without getting too hot.

You can always parallel some lower wattage resistors to get a higher wattage.
That would also lower the assembly resistance, which would be a good thing for
soaking up the idle current.

I think Radio Shack has some low value 5 watt resistors available.

To figure out the minimum resistance you will need, use the formula:
Wattage = Voltage^2/R.  Rearranging gives you R = Voltage^2/Wattage

So if you want 10 watts of dissipation in the resistor(s) without overheating
and have 120 volt dimmers:

R = 120x120/10 = 1440 ohms. You could get that value by placing two roughly
2880 ohm 5 watt resistors in parallel.

Four 2880 ohm 5 watt resistors in parallel would give you 20 watts capability
and a 720 ohm resistance.

That would give a dissipation of 120x120/720 = 20 watts.

Bill








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