Siemens IR 120c  (PIR)

Forum 2005-2010 (read only) Hardware Interfacing
1

Hello all,

I'm trying to get some use of an old motion detector we had lying around, but I can't seems to get my head around it. Hopefully some here can shed some (IR) light on my problem.
The PIR involved is a Siemens IR 120c (datasheet: http://www.sourcesecurity.com/docs/fullspec/IR120C.pdf)

There is a small note inside the unit with a pin wiring schematics, for power supply and alarm relay.

The issue: The power is straight forward enough, but I can't seem to get any output on the alarm relay. I's assuming that when motion is detected, some output would be send to the two pins for the relay.
I have tried testing this by measuring voltage on those pins (direclty on the two pins and each pin seperatly with connection to ground).
Try as i might, I simply don't see anything happening on the relay pins.
So, my question really, can someone tell me if this is a good approach? Is my assumption correct that I should see voltage running on the relay pins when it triggered?

Any insights would be greatly appreciated!

Leen

EDIT:
Just had an idea myself..I suspect the relay is just acting as a switch!

2

I suspect the relay is just acting as a switch

That's what relays normally do. So measure the resistance between the two with a meter.

Alternately put one contact to ground and the other contact through a resistor (1K to 10K) to +5v, then you should see a voltage change on the contact / resistor junction as it switches.

3

It indeed was just me thinking about this the wrong way...
Works like a charm, thanks!