Hello all,

So I've made a circuit that actuates a solenoid using a relay. The relay is getting a 5V signal from a microcontroller. I've been advised to add some capacitors to filter out any noise for the signal on the relay. Does anyone have any input on what I should be looking for in terms of capacitance and how I should add the capacitor in the circuit (in series with the signal, or in parallel across the relay?)

Attached is a drawing of the circuit.

 

You have the diode to catch the back EMF from the solenoid so I don't think it needs anything added. The solenoid is on a different supply to the microcontroller so they shouldn't interfere with each other.

 

You could use a BEMF diode across the relay coil also maybe.
Had you considered a logic level Mosfet in place of a relay?
Max.

 

You could use a BEMF diode across the relay coil also maybe.
Had you considered a logic level Mosfet in place of a relay?
Max.

I've been considering adding a flyback diode on that side of the relay. Do you have any resources or recommendations for a MOSFET instead of the relay?

 

If out of the current range of the 2n7000 then a IRL540.
Max.