As to first issue, I assume any DPST relay with contacts rated at 20a 120v ac will work, but is it necessary? Tables show different starting watts for different type 1/2 hp motors so I still need to know what type of motor this is: split phase, capacitor start or induction. (Is the capacitor used here for starting purposes or for isolation or some other purpose? Not savvy enough to know.) If the motor is pure induction, 1300w, for capacitor start, 1800w, according to tables. If induction, I wouldn't be so concerned with directly connecting the relays in the kit. Your thoughts?

Please refer to my posted schematic for answer to second question.

Could you please suggest a heavy duty relay for this application (assume I will need two.) I was looking online for a 12v with 20a@120vac contact rating. I saw a couple of cheap automotive relays on Amazon rated at 20a but obviously that was a DC contact rating.

 

I use the P&B (Tyco) PRD series for this type of application.
www.farnell.com/datasheets/1573070.pdf
Max.

 

As to first issue, I assume any DPST relay with contacts rated at 20a 120v ac will work, but is it necessary? Tables show different starting watts for different type 1/2 hp motors so I still need to know what type of motor this is: split phase, capacitor start or induction. (Is the capacitor used here for starting purposes or for isolation or some other purpose? Not savvy enough to know.) If the motor is pure induction, 1300w, for capacitor start, 1800w, according to tables. If induction, I wouldn't be so concerned with directly connecting the relays in the kit. Your thoughts?
.........................

It would appear to be a capacitor-start or capacitor-start-run motor.
For 1800W the starting current would be 15A, which I think would be pushing the 10A relay a bit. The problem is that there is always some contact bounce when a contact closes, which causes a small amount of arcing that degrades the contacts. It may work for awhile but the long term reliability could suffer.
But since you don't operate the gate very often (I presume) then the relay reliability may still be adequate. It's somewhat of a WAG.

A related question is how to wire the relays to control the motor. You may have to add additional relays just to get the proper connections for that.
Edit: One thing to consider is that pushing both buttons on the remote energizes both relays (I think) and you need to make sure that doesn't cause a problem with the motor (perhaps by wiring the motor power is series through the two relays so that both being on won't power the motor).

 

The relays I showed I have used for Garage door type operations, they are DP and are rated 50amp contacts.
BTW the DC contact rating you mentioned is higher than for an equivalent AC load.
Max.

 

Below is my take on how to control the motor from the control board (per Mike's diagram for the motor).
RY1 and RY2 are the relays on the control board.
RY3 and RY4 are added 12V coil power relays.
RY1 and RY2 are connected so that the motor stops if both are energized at the same time (the alternate remote button pushed while the gate is moving). This is a safety factor as the gate will thus stop if either button is pushed.
You likely will have to experimentally determine how RY4 needs to be connected to the capacitor get the open and closed direction synced to the desired remote push-button (1 or 2).

 

Below is my take on how to control the motor from the control board (per Mike's diagram for the motor).

How do you get any current to flow through the lead winding? Now you understand about my question on why the OP's motor has four wires???

 

How do you get any current to flow through the lead winding? Now you understand about my question on why the OP's motor has four wires???

I misunderstood.
I thought your circuit diagram was a correct representation of how the motor is wired.

Edit: So I guess the question is: exactly how does P1 make the connections to the capacitor and motor(?).

 

...
I thought your circuit diagram was a correct representation of how the motor is wired. ...

It is a correct representation of how the motor was wired in the schematic posted by Frank. I question how the motor is wired internally?

 

Thanks so much, Crutschow, for your circuit! I have ordered the board from Carl's which should be arriving soon. However...
Some time ago I designed a simple circuit to operate curtains on my home theater. It had no solid state parts at all and all switching was done with mechanical relays.
Based on Mike's circuit showing the gate's motor wiring, I wondered why the attached circuit wouldn't do just fine, without Carl's board. Please let me know if I have missed something or have created a circuit that is somehow impractical. The reason I am trying to avoid electronics is because of the Cape Cod dampness that has caused problems before with the board. (We had gone through a couple of replacements when the board was still available.) For ease of maintenance my circuit employs a plug-in relay for which we would keep a spare. My goal is to keep everything as simple as possible. If this would work, it would have the advantage of allowing me to continue to use my old single button 24 vac Liftmaster transmitter/receiver combo, with several existing remotes that are now used by neighbors.
There may be reasons why my circuit would be incorrect and/or troublesome. I will probably end up by going with your plan, but I would appreciate it if you and others might evaluate my circuit, as it is very similar to my curtain closer which has worked fine for many years.


I'll wait for your replies.
Frank

 

Note to Max and others: I am aware that 16a relay contacts (resistive) are probably not adequate, would plan to address this if the circuit is found to be generally acceptable.

 

...I'll wait for your replies....

Unless I am mistaken about how the motor is wire internally, your proposed wiring leaves 120Vac on the motor winding between Wht and Brn forever. You really need to Ohm out that motor....

 

Unless I am mistaken about how the motor is wire internally, your proposed wiring leaves 120Vac on the motor winding between Wht and Brn forever. You really need to Ohm out that motor....[/QUOTE

Aside from that, does the rest of the circuit look OK? I was aware of the "forever" issue, but why is that a problem? Would the coil overheat? If so I can do another relay to connect the Wht/Brn winding only when the Liftmaster transmitter/receiver is activated (I think...)
If I can fix that, will this work? (Thanks.) (Note: Assumes your theory about internal motor winding is correct...will eventually check resistance.)

 

That "latching" relay needs to be an alternate action impulse type relay.
Is that the type you selected?
You can't leave any power connected to the motor when it is not running. That would likely burn it out.

Edit: Below is my take on a circuit using your Liftmaster signal to control both the motor power and direction.
RY1 is a DPDT impulse type latching relay.
RY3 and RY4 are 24VAC coil power relays.

 

T
Edit: Below is my take on a circuit using your Liftmaster signal to control both the motor power and direction.

Maybe I am missing something but I don't quite see how the phase shift winding is powered?
The current sense is, is that the motor is the type with identical windings so each can do double duty as main and phase shift in order to reverse easily.
Max.

 

Maybe I am missing something but I don't quite see how the phase shift winding is powered?
The current sense is, is that the motor is the type with identical windings so each can do double duty as main and phase shift in order to reverse easily.
Max.

Yes, that's the question being pondered.
How would you connect the motor to do the reversing?

 

If the motor corresponds to post #12 where the windings are Wh to red and Br to Bl, then this is the normal way for a motor with identical windings.
The OP seems to have it covered in post #29, but only if the motor corresponds to this format.
A reading across the motor leads are needed.
Max.

 

Yes, that's the question being pondered.
How would you connect the motor to do the reversing?

While you await an answer from Max, I have a couple of questions;
(1) Can any damage be done if the motor is connected according to your latest diagram, or would it just not run? (I can do a winding resistance check probably as early as Tuesday but I would like to try whatever circuit you and Max agree on right away as my time is limited next week.)
(2) I assume the limit switches are NC, as in my original circuit, yes? (Sorry I don't always completely understand schematic symbology.)
(3) The contact rating issue on the relays still looms. Max had suggested a very heavy duty P&B relay (50a) for the power relays but I wondered if I could get by with less for a 1/2hp motor. The 1800w starting current figure that I saw for a 1/2hp capacitor start motor would suggest that 16a is adequate. It's also very hard to find a latching relay with a contact rating of greater than 16-20a, and those are generally resistive not inductive. Your thoughts?
I sincerely appreciate your ongoing help. Looks like we're almost there!
Frank

 

You can get a way with smaller relays, just that I have used them in past where a contactor is overkill.
The smaller plug in relays usually max out at 10amps.
If you need a latched relay, you could always use a smaller signal relay type and latch it in and use it to operate the motor relay.
If the motor is not the identical winding type, then you have to identify the main and phase shifted winding and the power would be applied to the main winding and the P.S. winding would have the capacitor permanently in series with it.
The series pair and the main pair would then have to be reversed across the supply to achieve reverse direction.
Max.

 

......................
If the motor is not the identical winding type, then you have to identify the main and phase shifted winding and the power would be applied to the main winding and the P.S. winding would have the capacitor permanently in series with it.
The series pair and the main pair would then have to be reversed across the supply to achieve reverse direction.
Max.

I assume you only reverse one pair of windings since, I would think, reversing both pair would have no effect on the motor direction in a AC circuit.

 

Sorry, yes, should have read reverse one pair WRT the other.
Max.