Modifying the Universal Module for double momentary relays
By The Home Automation Forum Users

DISCLAIMER:This is just an example of what I have done, intended for ideas only. Experiment at your own discretion and only if you're qualified.

The X10 universal module gives you one dry normally open contact for use in triggering things. It can work latching ON or OFF via x10 commands, or be "momentary" pulsing for about a half second.

I hate adding extra power supplies and I wanted to use a relay (DPDT) in the garage project, to break/make two different circuits at once.

Upon inspection:

I saw that inside, there was a clear plastic box (bottom) with a solenoid on each side. One causes the contacts to be ON and the other OFF. The solenoids pulse to move this switch.

Well, since they pulse why not try a relay? So I snipped the wires off the right side as shown (black and yellow). My equipment is lacking, I had no way to measure such a quick pulse. The only thing I could discover was that the coil measures 40 ohms, and it draws 1ma when idle.

I just tried a 12vdc PC relay, which measures 200 ohms. It worked fine, and drew the same current when idle, without triggering.

Now the tricky stuff. Why voltage when idle? The right side turns out to be the OFF side. When I tried the ON side on a relay, it failed!! Why? After experimenting, I found that the OFF side must have a relay on it, or the ON side will not operate.

I'm guessing this is a safety precaution so if in the standard setup, the OFF relay burns out, you won't be able to switch the thing on and have it not shut off. This is important because when it runs as "momentary" it really just energizes the ON solenoid, waits, then energizes the OFF. If the OFF burned out, the momentary would be stuck next time you tried it. BTW the OFF side seems to work regardless of the ON side being connected.

Here's a pic of mine modified, just four wires out the side:

Have fun in your experiments! I wanted to use one side for my garage door to pulse the opener, but alas it is too quick. If anyone measures the duration, voltage etc., please let me know so I can update this!