how to lift and drop a pet door, motorized, remotely

[GaS753]

Pebe, the top of the photo (at Link: http://i17.photobucket.com/albums/b81/l ... ram009.png ) is what I received with my purchase from Ebay. I just went straight across to the connecting points on their diagram of the relays - I translated that to your circuit drawing and marked the corresponding letters at your relays on your diagram. Finally I show the switches S1 and S2 I got off of the net and chose to connect to the “C.” and the “N.C.” on each of them.

[pebe]

Hi Garry,

I cannot find information anywhere on the SC2272T4. I can only find details of the SC2272M4 and the SC2272L4.

The ‘M’ stands for Momentary contacts, ie. the relay releases and soon as you stop keying, and the ‘L’ means the contacts are Latched until you press the button again.

When I looked back again at the ebay link you gave me, then I saw that the receiver was described as ‘self-locking’. So it looks like the ‘T’ is the same as the ‘L’ type. So you have now got several options:

1. You could replace the decoder with the momentary-contact type here

http://www.ebay.co.uk/itm/2PCS-PT2272-M ... 3a6d0f1ba3

But that would appear to be almost as expensive as buying a complete new momentary remote.

2. Stay with what you have got, and:

a) Remember to press the same key again after the door has opened or closed, in order to deactivate the relay that has been activated. If you go down that route you should, ideally, wire a warning LED and limiting resistor across each of the limit switches. When the door had reached its limit the LED would then light up to remind you to press the button again.
OR:
b) You could use a 555 timer and three resistors to remove the power from the receiver when a limit switch had been operated. That would cause the decoder to reset and automatically deactivate the relay. If you want to go that way, I will give you a revised wiring diagram.

[GaS753]

Well if I did it correctly, pebe, pushing either key twice didn’t help or hinder - either on the doors way up or down way or after it hit either limit switch. Although there does seem to be a change in the problem: before when the door hit the bottom limit switch and stopped as it still does, I had to manually lift it off of the switch before pushing the button and that continues to be the case.
When I reached the top limit switch and the door stopped, all I had to do is push the correct key and the door began to lower until it hit the bottom switch and stopped - when nothing would happen until I manually lifted the door off of the switch etc. Now when the door reaches the top limit switch and stops - it is just like the bottom situation and I have to manually move the door from the top limit switch in order for pushing of the correct key to work.
In other words I now have the same problem at both the top (S1) and bottom (S2) limit switches. I really did not change anything physically as I only tried numerous combinations of key pushing as you suggested.
I hope this helps you pebe. Again I can not say how much I appreciate your help. It is really neat to see work at least partially. Thanks again. Garry (GaS753)

[pebe]

Hi Garry,

What you say is happening is illogical. Here is what should happen (the contact letters are as your drawing).

At Start:- B to C contacts of both relays are closed. When the door is closed, S2 is open. When you open the door, relay A switches contacts A to B. With S1 closed, current flows from +12V through S1, relay A (contacts A to B), left to right of motor and through relay B (contacts B to C) to 0V. As the door rises, S2 closes but that does not affect the movement. At the end of its travel, the top switch S1 opens to stop the motor.

To close the door, Relay B switches contacts A to B. Relay A must be de-energised so its contacts B and C close. Current then flows through S2, through relay B (A to C), right to left through motor, and through relay A (B to C). When the door has fully closed, S2 opens. Relay B must then be de-energised before the opening cycle can be repeated.

We are now back at the start and the process can be repeated. Note that it does not matter what the state of S2 is because current does not flow through it during the door-open cycle.

If you agree with that, then either you have a faulty receiver or there is a mix up with the terminals somewhere. You can perform these tests to find out which.

Remove the wiring from all six relay connections, then power up the receiver.

1. Check on relay A that there is continuity between contacts B & C, and there is no contact between A & B.
2. Press transmitter button to turn on relay A.
3. Check that contacts B & C have opened, and contacts A & B have closed.
4. Press button A for a second time.
5. Check that B & C have closed and A & B have opened, as at the start of the tests.
6. Now repeat the tests for relay B.

If all those tests are satisfactory, then make sure the receiver resets itself when power is removed:

1. Power up the receiver.
2. Check B & C are connected on both relays.
3. Press A button. Then press B button.
4. Make sure A & B connect on both relays.
5. Remove power from receiver.
6. Repeat 1. and 2.

Will you let me know the results?

[GaS753]

Thank you for your usual quick reply pebe. I will certainly let you know the results as soon as I get it all checked out. Thanks again for your wonderful help! Garry (GaS753)

[GaS753]

I started the tests pebe. I removed the wiring from all six relay connections and powered up the receiver ( did this by plugging in the circuit via the AC plug of the power supply as I regularly do). Your step #1 checked out - continuity between contacts B & C, and no contact between A & B. Moved to step #2 and pressed transmitter button to turn on relay A. Then step #3 and found no change from step #1 so I pressed button again and still no change. So I moved to step #6and repeated above for relay B and got the same results - no change after button for B was pushed. OK, what can I do now? Thanks for your help as always. Garry (GaS753)

[pebe]

Well, according to those tests the receiver is not working at all ! But it worked before so this is defying all logic!

Are you sure the receiver powered up OK, and that in step 2 you were keying the correct button for A?
Try steps 1 & 2 again but this time press each button in turn at step 2. Then check continuity of A to B, and B to C of both relays.

[GaS753]

As a beginner pebe, I am not much help to you and it is frustrating.

Before with everything connected the receiver starts the motor and the door either goes up or down depending on which button is pressed - and the door stops when it hits either limit switch - so I think that much is working or was working so then wasn’t the receiver powered up and the correct button pressed? The problem starts after the door is stopped by either limit switch and needs to be manually moved off of either switch before pressing either switch to start the motor in either direction again.

Sp I tried step 1 and 2 again pressing each button in turn at step 2 and the results were the same - no change - continuity A to B and no continuity B to C with both relays.

So the light comes on for me about your power question. I plugged in the power supply into the wall outlet just I did before disconnecting the six relay connections, but are you saying that the relay wasn’t getting power (despite the seeming phenomena) even originally?

Is there a way that I can check it? If so, please give this beginner the details on how to verify that. Thanks again pebe for all your help. Garry (GaS753)

[pebe]

I think it must have been working before, otherwise the motor would not have moved. With B & C connected together on both relays there would be no volts across the motor. To make the motor move, contacts A & B must have been connected on one of the relays, and B & C on the other. And that means the receiver must have been powered.

I assume you are checking continuity of relay contacts with a multimeter, so use the voltmeter section of it to make sure you have voltage at the 12V connection. Switch it to an appropriate range (say, 20VDC). The voltage supply must be the right way round, ie. positive relative to negative. If you hold then hold the receiver up to your ear you should be able to hear the relay click in and out as you press the transmitter buttons. Is there an LED on the transmitter, and does it light up when you press a button?

But if you have power OK to the receiver, and the transmitter works OK and it still doesn't work, then it looks like the receiver is faulty and you will need to contact Ebay for a replacement. But it still doesn't make any sense.

[GaS753]

pebe I am using a multimeter to check continuity. I not sure how to check for voltage at the 12v connection: “Switch it to an appropriate range (say, 20VDC). The voltage supply must be the right way round, ie. positive relative to negative.”

Let me be very basic - on the PCB there is a double connection with two terminal screws - one neg. and one pos. - the two that were not disconnected with the other six. On my Craftsman multimeter I have a black lead plugged into the jack marked common and the red lead plugged into the jack marked V/ohm/mA. So if I put the switch to 20VDC with the black lead on the Negative electrode as marked on Ebay’s drawing and the red lead on the Anode as marked on Ebay’s drawing I should see the 12V on the meter and therefore making sure I have power. Beginners have a lot to learn don’t they.

There is a tiny LED above and between the buttons on the transmitter and it lights up red when the appropriate button is pressed.

I will be listening for the relay click when I hear back from you pebe that I am doing the voltage check correctly. If there is 12V does hearing the click mean it is working and not hearing a click mean it is a bad receiver? How loud of a click is it - Is it loud enough that I will know it is not clicking or I am just not hearing it? Thanks again for all you help. Garry (GaS753)

[pebe]

Hi Garry,
I thought I would try to replicate your problems, so went looking for a latching receiver that I had bought in error about six months ago. I found it a box with some other leftover items and fixed it up.

First, I found out it did not work as I expected. In fact, pressing A button turned on the A relay, but pressing it again did nothing. Pressing button B turned on the relay B and released relay A. Pressing B a second time did nothing. So it looks like the action of the relays is this:
Pressing A turns on A and turns off B.
Pressing B turns on B and turns off A.
My receiver has two small LEDs to indicate which relay is switched on.

Second, I found the unit failed after about 10 operations. The keypad LED was not particularly bright so I opened up the transmitter and checked the battery. It was a Chinese VAVTT 27A 12V battery and it had gone down to 8.2V – obviously low enough to stop it encoding properly. There was no indication of its type so I assume it was a cheap zinc/carbon type, rather than an alkaline type. Installing a good battery fixed the problem.

So to come back to your question. Yes, the way you have described measuring the voltage is correct. The actual voltage reading will depend on your power supply – it may be anything between 10V and 15V, but anything over 9V will be OK. Make sure that there is not a minus sign in front of the reading (ie. -12.00 instead of 12.00). That would indicate wrong polarity.

If it all measures OK then press the A and B buttons alternately. On my receiver I can easily hear the relays clicking when the receiver is two feet away on the bench. If yours does not work, then open up the transmitter and check its battery (zinc/carbon batteries have a very short shelf life, and you do not know when the unit was manufactured).

If all is now OK we can go on to stage two of the diagnosis.

[GaS753]

pebe you are a great tech and mentor as I have said before and I reiterate it again that you actually replicated my project! WOW!

When I went to measure the 12VDC on the PCB I thought I noticed the wires were hooked up wrong - now I’m thinking it can not be after checking them twice and then having both my wife and daughter check them - but as a beginner I thought I’d better do it again marking with masking tape each and every lead. Oh my gosh I found 1 wire that was connected incorrectly. I had connected the +12V correctly everywhere else but the wire lead that was to go to the diode went to relay A - terminal A. All else was OK. How all 3 of us missed that and I missed it twice . . . You probably seen it right away. Anyway I decided after again rechecking everything, to hook it all back up and hope.

After some experimenting the door worked - well I have some work to do with the cord and finding the correct spring - but it works.

When I had it all set up, with the door down, I pressed A (locked padlock symbol on left) and the door rises until its hits limit switch S1 and stops. Next I press B (you can definitely here the clicks!). Now I press A again and the door lowers until it hits S2 and stops.

NOTE: If I hit B before the door hits the S1 or S2 limit switches, it just stops where ever it is. In running many tests I need to note for you that there was a time or two it seemed to hiccup and I needed to manually move the door off of the limit switch and then it was back to the usual operation.

Press A and the door goes up and hits S1 and stops. Press B and here that click. Press A and the door goes down and hits S2 and stops. As it did hiccup a time or two, I hope to install the warning LED with limiting resistor across S1 and S2 for my wife, she is really the user. Here is that beginner again - does “across the switch” mean the LED and resistor are wired in series or parallel with each other and how does one determine the specs of these?

Also about replacing that transmitter battery - those screws are tiny, even my set of eyeglass screwdrivers are not small enough to fit them. Do you know what size they are, and a place on the net you recommend to order them? Do I have to worry about any springs jumping out or buttons flying?

Again I sure glad to work with you. Thanks. Garry (GaS753)

[GaS753]

A later continuation . . .
It is several hours later and I have continued to operate the door while trying to find the right length of cord and the proper spring size and tension. Just when I was satisfied with their operation the motor doesn’t seem to be able to lift the door without my physical help. Could this be a problem with the battery in the transmitter or now what? Thanks again. Garry (GaS753)

[GaS753]

As an another added note pebe, it is Wed. and almost noon and I have pondered the situation most of the morning. How many times have I read - don’t forget to check the obvious. Everything is working as it was - I checked the pulley shaft and it had loosened some from the motor shaft - tightening up the screw solved the problem of the door lifting. So it is back to where we were. Thanks again. Garry (GaS753)

[pebe]

Hi Garry,

You say that when the door is moving and you press button A, the door stops. Under those conditions both S1 and S2 are closed, ie. their contacts are ’made’ and they will pass current. So provided the door has not activated S1 or S2, then pressing A or B should reverse the direction of the motor.

You also say in your next posting

…..the motor doesn’t seem to be able to lift the door without my physical help.

Taking those two statements together, and the fact that the circuit hiccups sometimes, could it be that your12V source is low, and there is not enough power to drive the motor properly? Try connecting your multimeter, set at 20Vdc, across the motor while you are testing. That way you can see whether it is low voltage, or something wrong with the relays or limit switches, that is causing your problem.

If you can hear the relays clicking when you key the transmitter, then the transmitter is OK. But to answer your earlier question:

I think that most of these small transmitter fobs are built the same way. If you take off the keyring and unscrew the two screws holding the halves of the case together, it will release the printed circuit board that has the battery clipped in place on it. The buttons are part of the board so you should have no problems with bits falling out. You need a small crosshead screwdriver for the job. I bought something like this from the local dime store.
http://www.ebay.co.uk/itm/SILVERLINE-JE ... 35c1a425c8