Bistable relays, limit switch and remote control

[crossup]

I'm trying to basically duplicate the functions of a garage door opener using a linear actuator to raise/lower a "bridge" .
The problem is basically that I want to use a garage door 3 button control to run 2 receivers, one for up and one for down. The receivers unfortunately only pulse a relay so I thought I might use that to change the state of a 2 coil bistable relay, which would "hold" the circuit on. The problem with that idea is that a limit switch wont provide a pulse to control the reset coil on the BS relay so the actuator will go off at end of travel and be ready for a reverse

 

[Leftyretro]

I'm trying to basically duplicate the functions of a garage door opener using a linear actuator to raise/lower a "bridge" .
The problem is basically that I want to use a garage door 3 button control to run 2 receivers, one for up and one for down. The receivers unfortunately only pulse a relay so I thought I might use that to change the state of a 2 coil bistable relay, which would "hold" the circuit on. The problem with that idea is that a limit switch wont provide a pulse to control the reset coil on the BS relay so the actuator will go off at end of travel and be ready for a reverse

I suspect this design will take two relays, one to 'remember' which direction to go next and one to remove power when either limit switch is activated.

A simple 8 pin PIC chip would make quick work for the logic to be performed and to drive a power switching device or relay for the motor, for a minumum parts count solution.

Lefty

 

[ljcox]

Here is a relay garage door controller that I designed when the electronics in mine failed and the company would not give me a circuit for it. The IC is a 40106 Hex Schmitt trigger. The 3 unused inverter inputs are connected to gnd.

The Up Down & Stop inputs are connected to the output of the radio receiver and to push buttons.

I intend to replace it with a PIC version one day since there is no protection against overload if the door was obstructed by something. (once our deaf cat's head was caught as the door came down, fortunately this was before the electronics failed so the electronic overload sensor turned the motor off).

It does not use bistable relays.

I bought a radio receiver and remote control transmitters from Oakley Electronics who are located in Sydney.

 

[crossup]

Let me clarify: I have already purchased the remote, receivers, actuator and controller with handheld. And it works except for the nagging detail that a command only causes about 1/2 second of actuator activation due to the short control pulse.
So at this point I'm looking for solutions that uses what I have. Basically I need something to do a latch function that can be unlatched when full travel is reached.
While a PIC would be a nice solution, (I have only 12C509s and 16F603(?)) but regardless, time to code, design a circuit, design corresponding PCB and fab would be about 10x the time it would take with relays and basic discreet components. Not to mention , someone may have to fix this after I'm gone.

 

[crossup]

Also let me reiterate that I'm controlling this from the control side, I dont want to cut the motor control cable which has a water tight connector to the controller/powersupply. This unit is going to operate on a salt water dock so its IP66(?) spray proof etc. It has overtravel protection from the electronic standpoint.

 

[ljcox]

If all you need is a latch, then a relay with a holding contact would do the trick.
The holding path would be via a contact that opens when the full travel is reached as in my circuit posted above.

 

[crossup]

Okey, well I'm not wed to bistable relays, just a thought. All I'm trying to do is to use the output relay in the remote control receiver to control the actuator via the wiring for the handheld control, which has momemtary up and down switches. For the purposes of this discussion, lets just talk about a single function, as I'm using a seperate receiver for up and down.
As I've mentioned the problem is the receiver relay does NOT stay pulled in by design, its just activated for an instant. Since this is a standard garage door remote and receiver I'm just trying to do the same thing the controller does in a a commercial garage door opener. The bistable relay only needs a short pulse to reset so one approach would be a one shot capacitor circuit fired by the limit switch, that would additionally potentialy give the ability to have reverse polarity(compared to the receiver relay output) allowing me to use a single coil bistable instead of a harder to find and more expensive dual coil

 

[ljcox]

My concerns about the bistable relays are:-
1. If the reset pulse does not occur (for some reason) the motor will keep running.

2. A bistable is not necessary.

3. You would need extra circuitry to generate the pulse.

Here is the basic idea of how I would do it.

Note that both contacts on X are N/O (normally open).

Edit. Attachment replaced. The diode was in the wrong direction.

 

[crossup]

Well Sir, I have to say, who needs a stinkin' bistable relay? I presume your diagram is the 'hold' relay idea which did not sound feasible to me but silly me did not think of a DP relay. This is exactly what I was hoping for...simple, fool proof and no special parts. Thank you very much and Happy New Years.

 

[ljcox]

Well Sir, I have to say, who needs a stinkin' bistable relay? I presume your diagram is the 'hold' relay idea which did not sound feasible to me but silly me did not think of a DP relay. This is exactly what I was hoping for...simple, fool proof and no special parts. Thank you very much and Happy New Years.

You're welcome. Happy new year to you too.

The use of holding contacts has been used for many years in relay systems.

I suggest you think about the prevention of possible misoperation, for example, if the up button is pressed while the door is going down (or vice versa) you don't want the motor to reverse. In my garage door circuit (that I posted previously), you will see that the motor is stopped if either the up button is pressed while the door is going down or vice versa.