In message , Stephen
writes
Hello,

I bought a roller door from a well known auction site ;(

The problem is that the box of electronics controlling it has got two
relays. I imagine one for up and one for down. The "up" relay is
sticking so that the door will not open. I have opened the box of
electronics and given the relay a tap and it is working for now but I
expect it to stick again soon. How can I prevent it from sticking in
the future?

Angle grinder

Is there anything I can do? I guess I really need to get
out the soldering iron and replace it before it fails completely.

No - I think you should stay away from things you don't understand

There is no such thing as a "sticky" relay, what do you think "sticks"
??

So, you tap it and it works ?

sounds like the coil voltage is borderline, or you have a cracked joint
or something

Don't just replace the relay, I doubt it will have any effect


Does anyone know the schematic for these boxes of tricks? I presume
the relays isolate the electronics from the motor? Is the switch side
of the relay connected to the mains on one side and the motor on the
other? Is the relay output open circuit when he door is stationary? If
so I was wondering whether I could put a switch in parallel with the
relay so that I have an emergency override? Is this possible?

My worry is that if the relay output is connected to ground when
stationary, I don't want to blow a fuse when I switch the override!

I notice there is a spark when the relays open. I'm not sure whether
that's the reverse emf in the coil or just the mains jumping the
contacts as they separate. Possibly this is welding the relay stuck.
Do you think I should add diodes?

yeah - pour a couple of dozen on top, see what happens

Honestly, I think you should let someone with a clue have a look at it,
it doesn't sound like something you should be diving in to, you are
likely to do more harm than good


The box is branded Nico IIRC.

Thanks,
Stephen.

--
geoff