Relay alternative for low power devices?

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EnzoEngr

Joined Nov 7, 2022
5
I have an esp32 to take measurements with an ultrasonic sensor equipped with a separate circuit board. The esp32 mostly sleeps, so to extend the battery life, I want to cut power to the sensor's board while the esp is sleeping. I measured a traditional relay to use about 70ma when it’s on. I also tried a solid state relay (pvn012) to use only 8ma, driving the sensor connected to the board, but it uses about 2.3ma whenever power is applied to the power pin (not the pin that’s connected to the esp's io).

Are there other options to solve this problem? Thanks!
 

sghioto

Joined Dec 31, 2017
3,665
[QUOTE="EnzoEngr, post: 1783912, I also tried a solid state relay (pvn012) to use only 8ma, driving the sensor connected to the board, but it uses about 2.3ma whenever power is applied to the power pin (not the pin that’s connected to the esp's io).

Are there other options to solve this problem? Thanks!
[/QUOTE]
Post the schematic of how you wired all this together please.
 

DickCappels

Joined Aug 21, 2008
9,509
Probably a 2N7000 or 2N2222 or other small transistor but it depends on the particulars. Would you please answer crutschow's questions in post #2 and also tell us what logic levels your ESP-32's output can make? (I would guess 0 and 3.3 volts, but that is only a guess)
 

sghioto

Joined Dec 31, 2017
3,665
I think the PVN012 is an OK choice but seems like the TS must have connected it incorrectly if the part is consuming 2.3ma when not activated. Specs say 5 ma for the LED driver so R1 will depend on the supply voltage for the ESP32.
1670602096599.png
 

bassbindevil

Joined Jan 23, 2014
634
A small power MOSFET? They take basically no current to turn on, just voltage. The low voltage from an ESP32 might be a problem, but it could drive a bipolar transistor that in turn switches the MOSFET.
 
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