Membrane switches - anyone have experience with them?

[badugi]

Any of you know much about membrane switches?

Just curious if it's worth my while to try to take apart a membrane switch on an appliance and wire it to some sort of device to control the appliance.

More specifically, want to be able to turn devices without auto-power-on on/off remotely.

I guess by taking it apart I could trace what button goes where? How would I go about attaching a wire to the conductive circuit on the PET layers? Is there any other simple way? Gotta be an easier way.

 

[Haps]

I think my pecker is one one, still works pretty good after over half a century.
Hehap

 

[XIII]

Sorry if this is me being dense but out of curiosity what's the advantage of a membrane switch over a mechanical one?

[I'm assuming you're applying this to a grow design, it has obvious advantages otherwise!]

 

[kaljukajakas]

Membrane switches are not designed to handle heavy currents and high voltages, they trigger relays etc. So you can't just take a membrane switch from a pocket calculator and use it to turn on your 1000W lights or probably anything much more powerful than a pH-meter.

The easier way is to just go to a radio shack and buy a small switch that's rated to handle your power requirements.

 

[badugi]

What I want to do is be able to turn on an A/C w/o auto power-on via the membrane switch. I'm well aware that it can't carry high voltages and heavy currents, just wondering what the best way to go about connecting to it.

After a little thought I'm thinking the easiest way would be to:

1) Get an A/C with auto-restart (not that important, A/C thermostat works great)
2) Solder a wire at the PCB, where the membrane switch connects, for that button

As mentioned, A/C thermostat works well... but even being a window unit, it still sucks out some inside air/CO2 while the fan is running. And no way to shut off the fan (even when compressor isn't running, even with fan on "auto" mode) w/o turning it off. So what I'd like to do is have my environmental controller (Sentinel CHHC-1) send a "press" signal to the A/C's On/Off button toggle membrane switch, so that the fan doesn't run when the A/C (compressor) isn't needed.

Again, I could just get a new unit with auto power-on but the idea of taking this thing out, making a new hole, popping in a new unit, etc, isn't that appealing.

 

[kaljukajakas]

Thanks, much clearer now.

You might try electrically conductive silver paint for making connections straight to the switch, if other options fail. Paint on two thin wires and cover the entire thing with hot-melt glue:

http://www.maplin.co.uk/Module.aspx?ModuleNo=36275&doy=27m12&C=SO&U=strat15

 

[PharmaCan]

Wouldn't it be easier to just get a line-voltage thermostat that turns the entire a/c unit on/off?

PC

 

[badugi]

I'm not sure how that would solve anything.

 

[PharmaCan]

I'm not sure how that would solve anything.

A line-voltage thermostat would switch the power to the a/c on and off at a pre-set temperature. (The a/c would be controlled by the thermostat, not by your Sentinel CHHC-1.)

Or you might be able to switch power to the a/c on/off with a relay controlled by your Sentinel CHHC-1.

IOW - you set the a/c thermostat to a low temperature so that whenever the power is on the entire a/c unit is on, essentially bypassing the a/c unit's thermostat. When the desired temp is reached, the a/c is powered off completely.

PC

 

[badugi]

A line-voltage thermostat would switch the power to the a/c on and off at a pre-set temperature. (The a/c would be controlled by the thermostat, not by your Sentinel CHHC-1.)

Or you might be able to switch power to the a/c on/off with a relay controlled by your Sentinel CHHC-1.

IOW - you set the a/c thermostat to a low temperature so that whenever the power is on the entire a/c unit is on, essentially bypassing the a/c unit's thermostat. When the desired temp is reached, the a/c is powered off completely.

PC

I know, but I thought I wrote in the first post that the A/C can't auto-power-on and the whole point was so I can turn the device back on via membrane switch? So I can't really see how switching off the device's power, whether through a separate thermostat or through the CHHC-1's thermostat, would really change anything.

 

[PharmaCan]

Apparently I don't understand what you mean by auto-power-on. Do you mean that when you unplug the a/c the settings are lost so that when it is plugged back in it is "off" and you have to reset the temperature etc.? If that's the case then what I suggested would be useless.

PC

 

[badugi]

PC, yup that's the case; thanks, regardless.

What type of device would I use to send a quick on/off (connect/disconnect) signal to the membrane switch, to simulate someone pressing the "On/Off" toggle button?

A SPDT relay wouldn't work so well since that'd be similar to holding the toggle button down, which powers on the unit but disconnecting (releasing button) doesn't cycle any additional action, only the next button press. That means that with a relay, the controller will need to power cycle the relay twice to turn the A/C on, then off (or vice versa). Rather than the A/C being powered on when the relay is on, and A/C being powered off when the relay is off.

So I need an electrical device, that upon being given power, simply connects & disconnects (~1 second within connecting, or so). Does that make sense? What are they called?

 

[kaljukajakas]

Couldn't you just disconnect and bypass the electronics in the AC and find the fan and compressor leads, which you'd then twist together and connect to the environmental controller (which would then act as the sole thermostat)?

 

[Bozo]

I understand problem I just aint smart enoug to solve it
Seems like youd have to convert back to the membrain switch voltage and tie into the switch somehow
Wish I had better advice but I'm sure theres an answer out there and it would solve the non autorestart problem people have using controller that shut power to devices off then back on (just like pulling the plug )
Would it be easyer to convert back to the A/C thermostat but that doesnt take care of the fan issue GL findin yer answer I know its out there

 

[badugi]

Couldn't you just disconnect and bypass the electronics in the AC and find the fan and compressor leads, which you'd then twist together and connect to the environmental controller (which would then act as the sole thermostat)?

That would definitely be a possibility, if I were a little more knowledgeable about this type of stuff. I'm not sure exactly what I'd connect & where, esp. since I don't already know how simple the wiring inside might be. I'm trying to avoid taking the unit out of its installed location right now at all costs, and access to the membrane switch on the front might be pretty easy.

In short: I'm skurrred.

 

[badugi]

I understand problem I just aint smart enoug to solve it
Seems like youd have to convert back to the membrain switch voltage and tie into the switch somehow
Wish I had better advice but I'm sure theres an answer out there and it would solve the non autorestart problem people have using controller that shut power to devices off then back on (just like pulling the plug )
Would it be easyer to convert back to the A/C thermostat but that doesnt take care of the fan issue GL findin yer answer I know its out there

I don't mind using the A/C thermostat at all in terms of temperature control... but the A/C likes to have its fan running at all times, and I believe there is a little bit of CO2 leakage. Fan runs on low when on "Auto" & compressor is idling, which helps. But I'd like to turn it off altogether when the compressor isn't running.

 

[PharmaCan]

How about if you run a leg from the thermostat-controlled hot leg of the compressor to a relay which would then switch the hot leg of the fan motor on/off? That would be a pretty simple thing to wire and relays are cheap and simple to install.

PC

 

[imnotcrazy]

You're looking for either a "One-Shot" or Off Delay Timer...