Hi, I have a heating pad with little controller that has failed, so I'm checking if that can be run using straight battery power, 12 V or 24 V.
But I'm wondering, maybe those little controllers only output during one half of the AC
input waveform (at 120 VAC input).
The power would then be 1/2, correct ?
That is because it's essentially only with output for 1/2 the time. Usually, when voltage is halved then so is the current, so that case power is 1/4 of full.
Am I correct assuming that ?
And, do some consumer type products use a triac, for controlling both AC input polarities ?
I measured approx 220 ohms in the pad heater wire, so full output is about 500 mA, and that gives a power of about 60 watts, for the personal heat-pad.
If it's a controller that only outputs 1/2 of the AC cycle, having simpler cheaper circuitry, then that means 30 Watts on the high setting.
Am I estimating correctly, here ?
Thanks.