PS_ON driving a normal relay ?
-
So I'm just wondering if the PS_ON pin can be used to activate a normal relay or will the back EMF blow the FET? Current limits, etc ? SSR's are cheap, however I'm still nursing my wounds from last years printer budget. I have about 50 assorted relays of various voltage ratings, sizes etc. and I would really like to turn on and off the main PSU as it keeps fans running, LED lighting running, etc. I also have a few small 5v switchers floating around, looking at one now with 3A rating about 75 x 45mm with screw mounts.
I realize the PS_ON pulls down to activate so a 5V relay safe to use ? Add a snubber for safety ?
Thanks,
Jeff
-
I actually figured out I can answer this question on my own by looking at the schematic for the board. The PMV40UN2 Fet used can more then handle the 50ma I need for a 10A 5 volt relay. The Fet also has a diode built in which might handle the issue of reverse EMF from the relay coil when de-energized. I may toss a fast diode in reverse on the coil just to be safe. FET's are cheap, time is not.
Jeff
-
You definitely need to connect a flyback diode across the relay coil, to protect the PS_ON mosfet from the back emf. Or use a solid state relay.
-
You definitely need to connect a flyback diode across the relay coil, to protect the PS_ON mosfet from the back emf. Or use a solid state relay.
Thanks for responding, I was planing on doing so as I'm a bit paranoid on that subject however it's good to get that you better or else feedback. I think an SSR would be the best method, The boss says no more spending so I'm going with a 5V coil 10A relay for now. I'll toss in something fast to snub those spikes. Need to get my standby PSU in a small case now, good thing I have a 3D printer.
Thanks,
Jeff
