Help with 24v relay

Hi everyone! I am new to Arduino and attempting to make an automated garden watering system, based on some instructables I've read. I've done basic Arduino with LEDs and successfully set up the RTC on a prototyping board. The next step is the 24V relay to open the valve solenoids and I have been completely unsuccessful getting this to work so far.

For my latest test, I have a very simple program that just sets pin 6~ to HIGH for 10s then low for 10s and I get the builtIn relay LEDs lighting correctly. I have removed the solenoid from the equation and just have the NO relay post looping back to the 24V adapter. When I measure the voltage with my multimeter, I get a constant 25.5V, regardless of whether my 6~ pin is HIGH or LOW. I have tried with the JD-VCC to VCC shunt on and off. I am not using the GND pin that is beside the JD-VCC and VCC pins, but rather using the GND pin that by the IN1 pin (not sure if that is correct).

I have attached a schematic drawing and a picture of the relay and I am using an Arduino UNO WIFI REV2 (ATMEGA4809). Any help or pointers will be greatly appreciate!

Thanks in advance,

The relays you have are 24vdc relays and need 24vdc on their coils to operate. Connected to the Arduino VCC they are getting only 5vdc, so not enough to operate those relays as wired. However, those relays have a way to operate off just 5v if wired differently, using the JD, VCC and GND pins. Study the attached schematic before you do anything and make certain you understand how to connect the 24 v supply so as not to damage your Arduino.

Leave the Arduino connected as is and connect a 24 VDC supply to JD and GND.

That will provide 24vdc to the relay coils, and the Arduino 5v will drive the optocoupler (and LED) to switch the relays.

Good luck and hope it helps.

4 channel relay.pdf (17.1 KB)

Hi Steve,
Thanks for the quick response. So after reading your response, I’m realizing I must have bought the wrong relays. The adapter output is 24vAC and the solenoid is expecting 24VAC. Sounds like a I need a 24VAC relays instead of a 24VDC. Like I said, I’m new to this :slight_smile: .

Thanks again,

The relays are fine if you have a 24vdc supply you can use to drive them, but the solenoids will need 24vac. There would be three supplies to consider in that arrangement: 5VDC (or whatever you are driving the Arduino with), 24VDC to drive the relays on the JD pin (with the Arduino ground and the 24vdc ground common) and 24vac to drive the solenoids.

Other arrangements are possible if you change the relays - you could use 5vdc relays, but don't drive them directly from the Arduino output pins which can source only 40mA - the relays will draw more than that when they operate, and damage to the Arduino's microcontroller pins may occur.

Decide what you want to do and draw it up if you'd like further comments.

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