relay contact problem with remote control gate opener

[chansen1963]

hi, I have riged up a 12V remote control 4x4 winch as a gate opener. The mechanicals work fine, and open the sliding gate nicely. The rpoblem I am experiencing, is that the relays used seem to wear out the contact about every 6-8 months. The gate is operated at least twice a day , and I think that the 4x4 Winch is not designed for such frequent operation.
The circuit uses 2 x 80/100 Amp changeover relays to give forweard and reverse of the 12V Dc motor.
Is there some way to protect the contacts ? the relays are quite expensive in this AMP rating, and it was actually cheaper to buy a whole new winch kit and just grab the relay/remote switch from it to keep the existing one working.

I have considered Solid state DC relays, but as these do not seem to be available in a 5 pin changeover configuration, I do not know how to wire up some SSR's to control the DC motor for foreward/reverse operation..

can anyone help with a suitable circuit, using SSR's to control a 12V DC motor.. as this would elimimnate the relay contact ware.n.tear problem.

 

[alec_t]

One solution would be a power-FET H-bridge. The choice of FETs would depend on the motor current rating. What is it?
I'd be very surprised if a 4x4 winch isn't designed to operate more than twice a day!

 

[BrownOut]

You probably need diodes across the relays to suppress the inductive kick-back from the wench motor. If you show a schematic of how it's connected to the relays, we might be able to suggest how to connect them.

 

[chansen1963]

Thanks for the quick reply guys...
I will open up the control box and trace the circuit and get the motor ratings..
I'm pretty sure the Relays are rated at 80A because I have replaced them now three times...

a 4x4 winch would normally only be operated a few dozen time per year.. not many times per day.. so I think the relays are underrated..

 

[alec_t]

kick-back from the wench motor (post #3)

Thought-provoking indeed!

 

[carbonzit]

[bad joke alert]

That reminds me of the only joke I've ever made up.

Q: What did Jack the Ripper say when he was working on his car?
A: "Hand me a wench!"

(Who knew that he had a speech impediment, too?)