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Relay issue - Driving signal input with 5V+ digital wire

Thread starter #1
I bought this relay from amazon:


Im trying to drive it with Adafruits lase breakbeam sensors:


Which shows a 5V+ for the signal wire

I hook it up to the relay with the jumper on HI, and the light turns on but relay doesn't click. I turn the jumper to low and it clicks, but dosen't turn off when beam is broken. I measure the voltage on the signal wire and it measures 5V+ unbroken, and I get open circuit small mA reading.

I have a 10K ohm resistor between power and signal as specified by the datasheet for the sensors.

The relay works with a ground as a signal on jumper low setting, but I feel like its not reading the drop in voltage when jumper is on high setting.

The relay is wired to 24V and the sensors are regulated with a 5V ps. Can someone help?

Ultimately I need to use the relay to drive a ground as a input signal to a controller that only reads a ground. I want to use the relay to read the positive digital signal, and output a ground to the controller.


Active Member
It means the relay in your link is designed for a +12V input to trigger (or at least to power the +12V relay itself), according to the text....
They do make +5V trigger relays, but that is not one of them.


Well-Known Member
Most Helpful Member
the sensors do not provide enough current to drive the relay. you need to use a transistor to drive the relay coil. you need the relay power to be 12vV dc, and the relay coil acts as the collector (for a bipolar transistor) or drain (for a MOSFET) load. the sensor would be connected to the base or gate of the driver transistor. an example of a relay driver transistor is this:
the control signal can be a 5V logic level, or the output of the sensor.

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