Controll Relais with low power

Using Arduino Programming Questions
1

Hi guys,
i have a ESP32 and i have a application, where i want to use as little as possible (It should run outdoors with an battery). I bought 4x Relais (like this one Relais).
I use the pins {21, 22,25,32} for controlling the relais.

E.g. with "digitalWrite(22, HIGH);", i controll the first Relais and it works, but if the Relais is idle the Relais "pulls", so it uses more energy than the other way around. I found out, that the relais is switches when i connect the input pin with ground.

Is there a way to controll these relais the other way around?

2

The relays have changeover contacts, so depending on how you wire them, the contacts can be either open or closed when the relay is turned on

3

If the idea here is to save power, you can't. As soon as you need to energize the relay coil, it will draw 80mA. 4 relays energized is 320mA.

SSRs or LATCHING relays or MOSFETS would be very energy efficient to energize, but what's needed depends on your application.

4

Hi,
What is the application?
If it is a garden water control project, you can get water valves(solenoid) that latch ON or OFF and only need an impulse to change their state.

Thanks.. Tom.... :smiley: :+1: :coffee: :australia:

5

Assuming you can't switch between normally open and normally closed in your application (for instance, you may want normally open so if the microprocessor loses power the contacts open and you won't have the controlled equipment running continuously!)

Now you can more than halve the power consumption of the energized relay by controlling it with a PWM signal! You energize the relay with digitalWrite(pin,HIGH) for a fraction of a second and then do an analogWrite(pin,127) to power with a 50% duty cycle. Since the load is inductive, this reduces the power by more than 50%.

6

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