CurtPalme.com Home Theater Forum

[tri_joel]

My Draper has the simple togle switch, one position for up, one for down, and center for stop. I would like to add the screen to my Crestron program, but don't want to drop a couple hundred bucks on a Draper IR switch, low voltage controller, etc. It seems like it should be fairly simple to build a 12v relay with a 120 volt contactor to activate the screen. Any good ideas how to do this? I'm pretty good and putting things together, but not so good and figuring out all the pieces.

Thanks,
Joel

[ecrabb]

Joel, I built a box for a Stewart powered roll-down screen that was probably exactly like what you want. A couple quick questions...

Do you know if your Crestron controller has relay triggers, just dry contacts, or both? The switch for the Draper... Do you have to old the switch in the "up" and "down" positions, or can you just flip it down, the screen rolls down, and it just sits that way. Also, do you want to be able to stop it in intermediate positions, or just roll it all the way down and all the way up?

SC

[tri_joel]

Let's see - I have the CNMSX/AV which has this relay:



The Draper switch is a rocker switch that you do not need to hold, if I press "down" and let go then the screen lowers and the switch remains in the "down" position.

There are two conductors (red and black), a neutral (white), and a ground (bare) between the motor and the switch. The switch simply energizes the "up" or "down" wire to the motor. (It's really changing polarity). I don't have any other equipment to put on the Crestron relays, so I suppose I could use one relay port to a 120 volt contactor for "up" and a separate relay port and contactor for "down". It would be a nice to have but not necessary to have control over the "stop" position, but I'm not sure how to do that since it's nothing more than breaking contact so neither "up" or "down" are energized.

[ecrabb]

Cool... This is easy, Joel... The Crestron relay outputs are just dry contacts (relays), so you just need a 5- or 12-volt wall wart to drive the relay coils, and a couple of relays.

If you wire your relays "normally open", you don't need to worry about "off" because like you said - if you drop power to the "up" or "down" side of the motor - it'll stop.

So, use two relays (SPST is fine, but SPDT is more common and is also fine), one for each motor direction/winding. Wire them so the secondary (switched 120vac) side is using the relay in "normally open" condition - in other words, the circuit won't be hot until you power the relay coil.

Then, wire each of your 1- and 2- relay outputs in series with your relays, with power from the wall wart.

The only question is the current draw on the Draper motor. If it's pretty light (like <1A), you can get by with a 5v micro-relay. If it's heavier, you'll need to use a heavier (usually 12v) relay. Both are available at Rat Shack if you're an instant gratification guy like me, but you can find stuff much cheaper online.

You can set up your Crestron program however you want, then. Just make sure no condition can exist where both relay outputs close simultaneously. It could be set up as momentary where you have to hold the button down to make it roll and unroll.

It could also be set up to hold the relay closed for x+1 seconds, where x is the number of seconds it takes to roll or unroll the screen completely, and you could use a third to button to turn off both relay outputs to open both relays to stop the screen wherever you want.

Make sense? I can sketch a diagram if you want.

SC

[tri_joel]

Thanks Steve. I sounds like it is as easy as I thought it would be, which is unusual for me. I just want it to lower when I turn on the PJ and raise when I turn off the pj, so when I program my Crestron it should never be a condition when both are closed.

[tri_joel]

Okay, so I get the concept well enough, and I have a basic understanding of relays and contactors ((considerable experience in HVAC project management) but very little experience in the hands-on aspect). Stopped at Rat Shack and found the parts drawers pretty much empty, the employee working that evening didn't know anything about parts so was completely unhelpful (but he could help me choose a mobile phone or sell me a Livestrong Calendar).

So I went to Pats Express, Grainger, and Amazon searching for relays and am now completely overwhelmed at the exact requirements. I went to Kals electricbrewery site because I was sure his control panel would have some type of LV control in it, but it appears to be all line voltage.

So, to stop beating around the bush here, Steve - I would like to take you up on your offer to provide a sketch if you don't mind.

Thanks,
Joel

[tri_joel]

Never mind, I found this tutorial http://www.sparkfun.com/tutorials/119 which answers all of my questions.