aftermarket remote unlock

[Rawze]

(06-25-2026 )barf Wrote:  I'm definitely not an electrical engineer. I understand what you've done there Rawze. I don't understand why or how that makes relays last longer....

(its my OCD kicking on mostly)...

Because any motor/mechanism/coil, solenoid, etc. that has inductive back-emf will cause an arc across the relay contacts every time the power is released, especially if that door mechanism that likely pulls a few to several amps when activated. Depending on how many amps it pulls, this could be a lot of arc-wear on the relays. I have even seen relays contacts burn/wear out when the amperage is only 30-40% of the contact ratings.

The diodes (if rated properly) installed will negate any back-emf, causing it be re-routed back into the mechanism instead of arcing across the relays. The relay on the right also has a capacitor as to add a slight delay so that this can happen in the proper direction, no matter the polarity supplied to the mechanism. The capacitor should be sized as to not release the right-most relay until about 0.2-0.4 seconds or so after the first one releases.

You need to remember that I was a controls system design engineer for some very, VERY large machinery (hundreds of tons kinda big) that often had hundreds or thousands of inductive load currents across some mighty big relays. Without this type of protections, a relay can arc/flash over and burn out (wear out) the contacts rapidly, or weld them shut.