Hi, I have bought cat water fountain which has wireless powered water pump. It is not very "Smart" fountain, just plugs into USB and it is ON forever. However it somehow gets the state of the "water empty" from the pump, maybe it measures coil power draw?.. I would like to make this fountain "Smarter" by attaching ESP32 or STM32 and controlling its ON/OFF by motion sensor.
I thought I could attach transistor to one of the coil wires and it should trigger coil ON/OFF if I power transistors Base? I had 2N5551 transistor + 240ohm resistor available so I have attached it and powered Base with 3.3v, but pump does not power on and indicator blinks Blue indicating "water empty". Its the same if I cut one of the coil wires, I get Blue light blinking indicating "water empty". I have attached water and its not empty - so It does not work...
Is it OK, to use transistor for this? Or should I use something else? Why it does not work with transistor? Any help?
Thanks.