I use CT (current) sensors on the circuits for both washer and dryer and a small XBee ZigBee device using its ADC pins to transmit the current readings. On the server with an XBee coordinator, I use a moving average window to cover points where the washer or dryer use very little current. It's then pretty easy to detect on/off, and even where the current cycle is. The obligatory Home Assistant integration notifies household members.
Plotting the dryer data, you can see how it works. The heating element turns on for a period, then turns off and the humidity is most likely read at that point. The gap between periods of the heating element on increases, and the heating length of time decreases, until if stops spinning. Cool DIY project.
Plotting the dryer data, you can see how it works. The heating element turns on for a period, then turns off and the humidity is most likely read at that point. The gap between periods of the heating element on increases, and the heating length of time decreases, until if stops spinning. Cool DIY project.