GRBL Relay Driver Circuit

Here is a quick relay driver circuit showing how to drive a relay from a microcontroller – specifically, one of my GRBLDuino products.


Microcontroller Relay Driver Circuit

Microcontroller Relay Driver Circuit


The circuit as shown is for a spindle control application but the circuit remains the same for any other use. 5V and GND are self explanatory. SPINEN is the signal coming out of the microcontroller and typically 0v DC or 5v DC. Microcontoller outputs can only switch a few mA before damage occurs, but this circuit allows the transistor Q1 to take the load and switch as much as it is rated.

To create a spindle control relay on GRBLDuino products,┬áSPINEN connects to the Sp EN terminal block (the side labeled +). GND is connected to the other side of this same terminal block. 5V must be connected to a 5v source – the simplest way is to use a wire with a Dupont plug to connect to the high side of the Lim. H/L header.

Here are more GRBLDuino posts!