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Need to replace some PIRs. The out going unit uses 4 of the 6 wire. Red and black and positive and negative supply as expected. The next bit is what has me a bit flummoxed though.
The first of the n/c alarm contacts has a single wire to it. The second tamper contact has a different wire to it. At the sides of the contacts are pins with resistor ratings along side them. The 4k7 pins are shorted with a plug in box next the the alarm side and the 2k2 pins are shorted on the tamper side.
Two unused wires are just cut back in the housing.
So far, I think I'm okay with this until I tried to replace them. The new sensors have 6 terminals, as you'd expect but if I want to set up a supervised system, I'll need to add some conventional resistors to the contacts. I'm just not 100% certain where to put them.
Can anyone help?
Are the markings on the PIRs the same? If so, just wire exactly as before.
You are not clear about the resistors - are they soldered on the PIR?
If not, just reuse them.
What are the markings on the old PIR and new??
Black and red are usually wired as the 12v + & -, a resistor between + and Ta, and a resistor between + and T. Only 4 wires needed.
You have end of line resistors which help tamper protect the circuit. Sounds like they are normally open .... Long time since I did this though. Check out this article
Yep, happy with the idea of end of line resistors, that makes sense. My problem is, with the current until and its pins instead of physical resistors, I can't see the actually connects of the 4k7 and the 2k2 resistors so that I could replicate them on the standard pir connector block on the new unit.
I'm thinking it should be alarm wire to alarm contact 1, 4k7 between alarm contact 1 and alarm contact 2 and then a 2k2 from alarm contact 2 to tamper contact 1.
yep, you want one core coming to pin 1 of the alarm contacts, 4k7 resistor from pin 1 to pin 2 of alarm contacts, 2k2 from pin2 alarm to pin 1 tamper, remaining core into pin 2 of tamper.
Breaking tamper circuit will read an open circuit, everything closed will read 2k2, tamper closed but alarm open/active will read 6k9 in total.
that's assuming the jumper pins on your old one are 4k7 alarm and 2k2 tamper, usually the jumper pins are on the same sides as the relevant terminals but always worth a check
Cheers, thanks for that. 4k7 pins on the left, nearest alarm contacts and 2k2 pins in the right nearest the tamper.
Looks like I need to go resistor shopping.