ESP8266 Community Forum

- Mon May 11, 2020 12:04 pm #87040 I have a setup with a 3 wires in a buried cable going to a watering valve.
I have a esp8266 with relay to switch this from a 24v ac bell transformer, the esp8266 uses a separate 5vdc supply
I'd like to power a sensor at the same point as the valve that needs 5vdc, but only have the 3 cables, will be a pain to rebury.

Is it OK to make one of the 24v ac the dc 'ground' by connecting it to the 5vdc ground, so the cable has common ground, 24v ac and 5v dc cables?

from a theoritical pov it seems OK as the outputs from the transformer and the 5v supply are all floating, but I am not a squiggly volts expert...

- Wed Sep 09, 2020 10:48 pm #88734 You could but I would not recommend it, all kinds of funny things may happen. Why not simply put or build a small 5V power supply that will operate from the 24VDC. A simple 1 diode single diode rectifier circuit with a capacitor driving a small SEPIC converter would do what you want and compensate for the voltage drop on the 24V AC feed. If you use a full wave rectifier expect about 40 volts DC output. I think this will solve your problem for less then $15.00. Just to be fair I am assuming the 24V powers the valve and you are expanding the control or the third wire controlled a relay or something else.