Two NC switches, OR logic, with Timer

[hwmonkey]

I am a hobbyist. I have used automation systems and repaired damaged PCBs and stuff, but my training is limited to a course when I was about 10 years old which was a long time ago. Usually, I am a hobbiest out of necessity. I used to have some nearby friends to consult about issues, but we moved. I am hoping to find some assistance here.

Context: I have a commercial garage door opener. It operates perfectly when opening. Closing is now an issue. When I push close, it will not stop trying to close. It has two normally closed switches in the circuit. Both switches are operating perfectly. Without a switch in the circuit, nothing operates. I have concluded that the logic chip on the circuit board is damaged. I cannot find the logic chip to purchase anywhere. The circuit board was discontinued and the replacements costs $150. https://www.powermastergateopeners.com/Powermaster-Circuit-Board-PBR2-PRB3-PBRSS_p_515.html which is more money than I can afford right now.

Solution: Break the circuit at the point of the switches and create my own sub-circuit. The sub-circuit would simply break the 110V supply (relay) when either switch A or switch B is tripped. The circuit would break for 4-10 seconds then return to normal state.

HELP: The concept seems simple in my mind. I have the two NC switches. I just do not know what to insert for the OR logic or timing. In my mind, the following is the logical circuit:


Thank you for the help!!

 

[MikeMl]

Circuit link is broken.

 

[dr pepper]

Its discontinued but still available at 150, they mean the price just went silly.

Google 555 monostable circuits you ought to find something meaniningfull.
One thing you need to think of is safety, if the door is powerfull enough to squish someone precautions have to be taken, something better than a 555 might be required, or maybe shell out for the new pcb.

 

[AnalogKid]

The chip is an Atmel microprocessor or logic array. Either way, you would need its firmware to make it operational. Have you tried ebay? Lotsa people sell cannibalized things.

ak

 

[hwmonkey]

Google 555 monostable circuits you ought to find something meaniningfull.

Thanks, will do.

One thing you need to think of is safety, if the door is powerfull enough to squish someone precautions have to be taken, something better than a 555 might be required, or maybe shell out for the new pcb.

Not worried about safety. The existing setup has nothing like infrared sensors or anything. This is not on my primary garage, where we have that. This is on my workshop. Right now, I wait until the door is close to closed before I flip the breaker to stop it. I try to stop it early to that it does not throw the chain. Thanks for bringing up an important issue.

 

[hwmonkey]

Have you tried ebay? Lotsa people sell cannibalized things.

Yes. Thanks. I would LOVE to find one on ebay, but no luck so far.

 

[Les Jones]

In your original post you say "Both switches are operating perfectly. Without a switch in the circuit, nothing operates" This seems to be a contradiction as the door closed switch being operated is the same as it not being connected. Are the switches in series or does each switch go to a separate pair of terminals on the unit. When you say the switches work perfectly did you test continuity at the switch of at the ends of wire from the switch to the control unit. If you only tested at the switch then there could be a short on the wires to the switch. With the unit powered
up what is the voltage across the switch contacts when they are operated. (Contacts open.)

Les.

 

[hwmonkey]

Les -

When I said both switches, I mean one that is on the wall and one that is an inch away. The one that is an inch away is a limiter switch. As the door closes, a mechanical rod pushes this limiter switch until it is fully engaged. At that time, the door should stop moving. I tested for continuity on the switch, and it was good. Without the switch in place, the door does not operate. The switch is labeled as a NC, the wiring diagram lists it this way, and there is continuity across the NC poles until the switch is engaged. My conclusion is that the switch is therefore good.

The second switch is on the wall. I tested the switch for continuity at the switch itself and did not test at the terminals 16' in the air. It has different terminals for each switch.

I will post voltage later (hot out there right now and even hotter high up on the ladder).

Thanks

 

[Tony Stewart]

What you can do is locate if it has remote switches for open and close and see if they operate with an ohmmeter.
Verify if the problem is the switch or the board or wiring.

If the closed indicator switch is not working, replace it.

Can you measure the voltage across the closed wire pair pins? ( with door open/closed) then check resistance?
If there is 5V or 12V or such across the contacts at all times, then the switch has failed. The switch can either be disconnected, faulty mechanically or electrically. If electrical and it would have been intermittent before. A large polarized cap can help de-oxidize the contacts, it you can trigger it to close once.

 

[Les Jones]

When you said that there was two switches I assumed that one was the closed limit switch and the other was the open limit switch. Is the switch on the wall to operate the door ?(To open and close the door.) if so is there a third switch that is the open limit switch ? Can you draw a diagram of the wiring to ALL the switches or if you have the installation manual can you scan it and attach it to a post as a .PDF file. (or .JPG or other image file type.)
What is the model number of your door opener ?

Les.

 

[mbarazeen]

Some doors will not have two switches instead it will have an arangment to measure the distance travelled and it has to be programed for open and close limits. did you go through instruction manual of the controller? do you see a sensor wired to the board that send pulses by counting a rotating wheel to measure the distance travelled?