Relais need to much voltage to switch

Hello,

For our project, we need a DC motor to switch. We've connected a relay and a mosfet to the Arduino board. However the relay didn't switch when its related digital pin was set high.

We discovered that the coil voltage was 8.4 V. The Arduino gives only 5V signals to the relay. After test with stronger signals from a battery the relay did switch.

Is is possible to solve this without buying new relays?

Thanks!

Eli

Yes, just connect the high side of the relay to a supply with enough voltage. :slight_smile:

Is it a logic level MOSFET? Is the MOSFET switching a 12V supply? What voltage is the motor supply when the motor is switched on?

Why not use the mosfet to switch the motor rather than the relay? Is it a case that the motor pulls too much current?

EliVerwimp:
We discovered that the coil voltage was 8.4 V. The Arduino gives only 5V signals to the relay. After test with stronger signals from a battery the relay did switch.

Is is possible to solve this without buying new relays?

The supply to the relay circuit needs to be 9V or so. The voltage to the relay doesn’t have to be 5V.

Make sure the MOSFET is logic-level, otherwise it won’t work properly.