Constant to pulse, how? - Page 2

e30_droptop · 12-02-2007, 07:48 PM

Now that you guys made quick work of that question I have a similar application for a relay that uses the constant to momentary to create a button press.

I have read the posts concerning the Constant to Momentary Circuit and believe that it will help with the final circuit that I need to build.

Here is what I need to do. Connect two wires (short them) for a small duration as if someone pressed a button for a moment.

Essentially I have a home automation system and would like to use an existing Applainace Control Module to simulate someone pressing my interior button of the garage door opener.

The Applicance Module will respond to commands and provide a constant 120 Volt AC output and then respond to another command to remove the 120 V AC output.

I have gone this far.

Hooked up a standard (cell phone charger transformer) ( 120 V AC to 9 Volts DC ) to the Applicance module. So when the appliance module is on and supplying 120 V AC I get 9 Volts DC over the two wires that come off of the transformer. Ran the 2 wires from the transformer to a standard SPST Relay on pins 85 and 86. This DOES latch the relay and the coil is energised as long as there is power supplied. This creates a connection ( continuity) between pins 30 and 87. I could connect the 2 wires from the garage door button to these pins , but that would just simulate the button being pressed indefinately. I need the connection to drop away after a second or so.

Then it would be great if then when the applicance module turns off and removes the 120v AC->9 volt DC source voltage then the contacts are shorted or closed again briefly.

This would allow me to press once on the home automation controller and supply 120 V AC- >9 V DC and short the connection thus opening the garage door and then press again and remove the 120 V AC -> 9 V DC souce Voltage and then short the connection again thus closing the garage door. And over and over...

I really cant visulaize how to do the entire circuit so I thought I would post up .
Thanks mucho!

e30_droptop · 12-02-2007, 07:49 PM

Oh, I dont need a pulse I just need contact closures so that the wires on the garage door opener find a path to allow current to flow.

h3rk · 12-02-2007, 08:51 PM

I'm thinking 30 to one side of your garage door opener switch and 87 and 87a both in parallel to the other side. When you say that you don't need a pulse, you mean that if you push the button and hold it, the door opens and doesn't reclose until you release and push the button again? The break-before-make aspect of the realy would simulate this.
But if you're trying to implement logic wheras the state of the home automation relay is in sync with the door (1=open, 0=closed); you'll need to make sure that it can't get out of sync. There has to be something in the garage door opener itself that knows wether it's closed or open, like a limit switch (probably 2 of them). The best way would be to put it so that the limit switch that closes when the garage door is open is in series with the 87a(close) terminal wire to the button, and the limit switch that closes when the garage is closed is in series with the 87(open) terminal wire to the button. Then, since you're up in the actual opener, you could not interface with the button by the door, just interface with the terminals on the opener itself (where the wires from the remote switch go to). Use diodes to isolate your circuit from the existing controls and capacitors to increase the timing of the switching effect, and maybe it might work.

Another way has to do with using the controlling station to do the logic, (software?) If, let's say you are using a program to do this, it would be useful to not only send the open/close signal to the door, but to also know the state of the door. then the logic could be done in software, with more functionality. Then the switches in series with 87,87a could be eliminated.

e30_droptop · 12-03-2007, 10:14 PM

Thanks for the reply.
Sketched this in paint to show what I have as an idea so far. Where to go from here? Add to sketch?

h3rk · 12-03-2007, 10:34 PM

At this point you really need to do some investigating to determine how the controls on your door work.
Here is a good example, but I'm not going to go through applying what you want to this example, because it may do you no good.

h3rk · 12-03-2007, 11:56 PM

Considering that the signal going through the control circuit is AC for the generic door opener I linked to, the limit switch setup will be more difficult, so I left it out. Simply, this circuit will take a "on" signal from the automation device and turn it into a pulse to close across the open/close switch connection (I'd use the pulse).

e30_droptop · 12-04-2007, 02:21 AM

Awesome. Thanks very much. Ill build it and try it to see how it works. Ill post back with the outcome.