When lever microswitches go bad.

[wilfred]

I am dealing with a set of new(ish) gate operators (Elite SGO-1) that are intermittently operating erratically. The two symptoms are the gates overlap, ie close in the wrong order, or only one of the pair moves.

Now I have been told that this can be explained by faulty limit switches giving the controller a false idea of the position of the gate and that seems plausible. However my specific question is what is the failure modes of such microswitches and new ones in particular? And intermittent faults at that. The gates could work 60 or 70 times before showing a fault.

New ones will be installed on Tuesday and I'll know one way or the other soon after. But I'm happy to take opinions. Remember these are new motors and hence new microswitches. The old units lasted reliably for 11 years and the motor brushes were the reason for replacing them.


What are the chances a microswitch expert will read this and give me a link to some industry report on microswitch failures? I'd read it.
 

[floobydust]

The Elite SGO-1 manufacturer's service manual specifies "Zippy" brand microswitches VMH 15H 04 C they sound so reliable.

Check the current rating on the replacement microswitches, as they widely vary.
If the limit switches are in series with the motor, that might be why they don't last- carrying the motor's high current. Some machines do this with limit switches so that even a MCU failure will not cause troubles, the limit switches alone are a safety function.

Zippy VMH I cannot find datasheets for. The VM is rated 5A, so the VMH might be a special version.

Microswitch (Honeywell) V15 series have higher current 16A, 22A, 26A ratings or gold contacts for MCU logic inputs, if contact oxidation there is your problem.
What goes bad - is it the contacts, the mechanical toggle etc. ?

[wilfred]

I'm pretty sure the microswitches are just to monitor the gate open and close positions. The controller has relays to drive the motors. there are three wires for the two switches and two wires for the motor.


Thanks

[Muttley Snickers]

I'm pretty sure the microswitches are just to monitor the gate open and close positions. The controller has relays to drive the motors. there are three wires for the two switches and two wires for the motor.

Many early gate openers incorporated adjustable cams which dictate the timing and limit sequence in regards to the microswitches, these switches were wired directly to the controller board as you mentioned. I would suspect a sticky switch which has been subject to contamination such as dust or lubricants, either that or they have been poorly aligned, mounted or tensioned.