Garage door openers

[cathead]

I now have three boards on the work bench, the nonfunctional one(O) that was originally in the opener, the one I call "A"
because it shows a little activity, and "B" which does nothing at all. The circuit diagram I have isn't a complete diagram
since there are parts on the board not indicated on the circuit for some reason. There is a voltage regulator (78L08)
on the boards so I did a little testing on A and B to measure the output voltage while the boards are plugged into the
opener. Interestingly B has the proper 8 volt output but A reads 3 volts. Board O sits off to the side at the moment
because it shows a short on one of the pins on the main chip so considering it as a parts board presently. I have some
regulators(78L08) ordered so will put one in A and see what happens when they arrive. A complete circuit would be
quite helpful but so far have not come up with one. Of course voltage testing on the components would be a big help too
but will have to pull the opener off the ceiling as it is not practical with it overhead standing on a ladder. As a side note,
I wonder if any of you remember "Sam's Photofacts", a publication by Howard W. Sams from before the age of
computers. I did check there but found no reference to Stanley openers so it was mostly for radio and TV stuff.

 

[markba633csi]

I do remember Sam's Photofacts, my library had them
On the regulator issue it could be a bad one, low input voltage, or something is loading it down-
You can remove it then tack it back in leaving the output pin free to test. Avoids having to cut traces
78LO8s can only deliver 100 mA to a load max

 

[cathead]

I do remember Sam's Photofacts, my library had them
On the regulator issue it could be a bad one, low input voltage, or something is loading it down-
You can remove it then tack it back in leaving the output pin free to test. Avoids having to cut traces
78LO8s can only deliver 100 mA to a load max

Thanks for the PDF. I find it completely amazing all that circuitry is in that little TO-92 package.

 

[markba633csi]

Not to mention what's in your phone

 

[rwdenney]

@rwdenney Aren't ZAP the maker of 'Liftmaster' openers? I have some very serious concerns about the security of liftmaster. Defcon (5 I think) demonstrated an easy way to defeat the RF opener using a kids toy...

FYI I keep my door locked with a padlock in the track. I never remotely open it. (and now there is no motorized opener)

No, I don't think Zap has any relationship with Liftmaster. The U.S. company that sells them also sells Liftmaster stuff, but I think that's the extent of any relationship.

Zap openers only include contact closure points for remote switching devices. I used Liftmaster transmitters and receivers and wired the receivers into those points, but I think any transmitter/receiver with a contact-closure output will work. One could just as easily wire in a physical key-operated switch mounted on the garage exterior adjacent to the door to avoid an RF remote.

By the way, if I need to secure the doors, all I need to do is slide over the latch mounted on the door to create a positive lock on the inside. No need to defeat the opener--Zap uses DC motors and senses the slight rise in current when the door strikes an obstacle. It will not try very hard to overcome that latch even if the opener is actuated. But one can also easily release the belt tensioner (which is how one defeats the opener in case of a power outage).

Rick "Zap appears to be British-made" Denney

 

[cathead]

Here's a little update on my garage opener project. The COP411L 20 pin chip is an N channel microcontroller
and has an oscillator in it running at I think 500 kilohertz. I did a bit of testing with an oscilloscope and found
that two of the three boards have a running oscillator. It looks like I will have to get some 20 pin chip sockets
and several COP411L chips as even though they oscillate, they may not be functional. I did apply 1.5 volts
to the base of the driver transistors for the relays just to see if the drivers and relays were good. They were good.
Knowing that pretty much puts the magnifying glass on the microprocessor chips I think. So I need to order some
parts before I can progress much further.

 

[chip maker]

For all the time you have put into this repair almost a month, I believe you would have been better off just getting a new opener. Just about the time you get this to go up and down something else may give up and you'll be in the same boat and be working on it again. I really like keeping and repairing alot of things but you have to draw a line at some point. Good Luck !!!!!

 

[Dabbler]

I think @cathead is a hero of herculean proportions! It isn't about the bottom line, it is about rescuing a relic - go go go!!!

 

[cathead]

I could go to plan "B" if needed. Since I can open and shut the door by applying a small voltage to the base of the two
driver transistors and since the limit switches work, all that I would have to do would be to tap off the low voltage
supply using a voltage divider and feed each one using a momentary switch one for up and one for down. All that
would be needed would be two resistors, some wire and one more momentary switch.

On the other hand it would be nice to have the original board working as it was intended. In the process, I am learning
some things and get to do some experimenting at a time when the weather is generally unsavory. We have 6 inches
of new wet snow, you know the kind... the perfect snow for snowballs and a snow man.

 

[homebrewed]

Not to be too much of a debbie downer, but the original processor's ROM almost certainly has code specifically for the application. Often, the code in earlier processors could be extracted -- with the right H/W and S/W. Then you need some way to program a new one. Lacking that, buying a replacement COP411L probably won't get you where you want to go. Newer processors are designed to keep the code private (if the manufacturer wants it that way), so no one can copy their code.