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[wbrells]

I have an alarm system that provides a NC set of contacts which I plan to connect to an X10 Powerflash module. In addition to sending out an X10 signal, though, I was hoping that the Powerflash unit could be modified to operate a locally-connected (reed?) relay (which should save space & money as well as being more reliable & faster responding compared to using an X10 Universal module). If anyone has any thoughts on such a modification to a Powerflash module I would be very interested in hearing from them! (BTW, the NC contacts on the alarm system are not "robust" enough to operate a relay directly.) Thanks, Wayne

[-Bill- (of wgjohns.com)]

What are the alarm's NC contacts rated at then?

I would think that if they could handle triggering a powerflash, they could handle the current for a small relay coil.

An option I have used in the past with alarm panels that had a really poorly rated transistor output is to use an optoisolator so the panel only basically has to light an LED (within the optoisolator chip) and run the relay current through the optoisolator's output.

I'm sure I could be of more help with more information about your alarm system and its output.

[wbrells]

I plan to connect the (supposedly) NC output jack of a Skylink Audio Sensor (model AS-101) to the Powerflash module. It is difficult to get detailed specifications about that feature of the AS-101, but Ohmmeter measurements show the resistance increasing from a couple of thousand ohms to near infinity when the device is triggered. I have not actually connected the AS-101 to a Powerflash module yet (I have an extra Powerflash on order) but I've had good luck using that module in somewhat similar applications. I'll update this post in a few days when I have more information!
 
BTW, I did a test by connecting a 1K resistor (to simulate a small relay) in series with a 5VDC power supply to the NC jack of the AS-101, but the voltage across the resistor only changed a small amount when I triggered the unit - not what I was expecting based on the Ohmmeter measurements! I assume the Ohmmeter is using a lower voltage & a much smaller amount of current???

Wayne

[Brian H]

The output may not be a real relay. Could be a solid state device. Could also be polarity sensitive.
Also when I used a solid state device [ELK Doorbell Sensor]; I found that the sensing voltage on the terminals is + on the screw marked - and - on the screw marked +. The markings on the Powerflash are in relation to a DC input not the sensing voltage there when in the Dry Contact Mode.