Flyback diode

[Mike_2545]

I am building a circuit where a 5v relay will be operating a 24v solenoid. I have put a flyback diode on the relay. Do I need a diode across the solenoid as well?
They are both on different power supplies and don't even share the same ground.

Would it be wise anyway, just to save the contacts of the relay?

 

[dknguyen]

THe diode is not needed because the relay is not as sensitive to inductive spikes as the transistor is. Having it present will result in reduced stress on the main terminals of the relay at the expense of the current in the inductor taking a longer time to decay (ie. turn off).

 

[MrAl]

Hi,

Using a diode there means the contacts will not arc over as long when they
open up when the relay coil turns off. This means it's a good idea to have one
connected at all times.

 

[Ubergeek63]

or a snubber