Thread: 5 Rin Relays

A 5pin relay is NO-COM-NC and 2 coils. That is a standard relay, exactly what the FB is designed for.

"two coils" meaning 2 terminals for the coil.
We know what the Toaster meant.


Does the FB require spike protection? I'd assume so - ie, the diode across the coil - Anode (non-lined) end to coil GND, Cathode to coil+.

Originally Posted by OldSpark

"two coils" meaning 2 terminals for the coil.
We know what the Toaster meant.

Correct, I should have been more explicit.

Originally Posted by OldSpark

Does the FB require spike protection? I'd assume so - ie, the diode across the coil - Anode (non-lined) end to coil GND, Cathode to coil+.

Legal mumbo jumbo from me as Fusion Control Centre: Yes

Me as me: Not always.

The relays I sell specifically for the FB, have no protection diode. But they are also low current and made to minimize spiking on coil release. If you use a standard beefy automotive relay or just whatever you have lying around, I do recommend a supression diode. The Mega and Mini Relay boards have diodes just because it is on a board, and might as well. The FB's FETs are rated to handle high voltage spikes for limited times, so it all works without suppression diodes for what I sell (FB + FB Relays). When you DIY, your FB's life is in your own hands.

That's the beauty of the FB - just buy the RB relay boards. (And sue the designer if they blow ha ha.)

Maybe the FB uses a line drivers (like the ULN2003?? - essentially transistor buffers) that some use. They tend to be quite robust.


I'd say if ever in doubt. add the diode. A mere 20c IN4004 or iN4007 etc could prevent the rear ends of uPC and digital things from blowing. (Relay coils can induce up a a -200V spike, typically 50V-100V are common. Digital circuit typically only tolerate -0.3V to -0.6V.)
But to that I say add it yourself - I don't like relays with inbuilt diodes, I prefer to add my own externally (to the relay base) - in part just in case I was 85 as more +ve then 86. (By convention, relay coils are 86 = +ve, 85 = -ve, hence the diode line end (Cathode) towards 86 +ve).



I just didn't want to see a Fusion Brain get fused.

Each output pin goes through 2 large NPN transistors in a darlington formation between the MCU and the relay coil. You will blow an output driver before harming the MCU, which is a good thing. The older versions went through shared darlingtons. So if you blew it, you might blow 8 channels at a time.