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PC controlled burglar alarm

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2010 - » Archive through 28 July, 2011 » PC controlled burglar alarm « Previous Next »

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kayjay
Regular Contributor
Username: kayjay

Post Number: 46
Registered: 10-2009

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Posted on Thursday, 14 July, 2011 - 05:05 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

OK, I've finally got round to completing this project

I have a problem with wiring in the PIR I bought for it, I'm only using the one sensor as the alarm is only covering my model rail workshop in the garden so the PIR will cover the room, this means that I don't need to loop the PIR with anything.

OK, this is where I'm stuck, the alarm accepts signals from sensors through one bit of the B port but the PIR signal is via two pins. I'm guessing that one pin goes to the PIC pin and the other PIR pin goes to either +ve or 0v.

The pinouts of the PIR are, left to right, -LED, next 2 pins are Tamper, next two are N/C (normally closed) and the last two are 0v and +12v.

If the alarm had dual inputs for the PIR signal I'd been fine but this single pin signal has me a little puzzled.

Thanks guys .... Keith
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echase
Frequent Contributor
Username: echase

Post Number: 503
Registered: 07-2007

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Posted on Thursday, 28 July, 2011 - 02:23 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I had a PIR like that and could not work out if the N/C pins were truly volt free as they did not seem to be connected to a relay contact in the PIR but to some semiconductor output which would struggle to be volt free. But it was not an opto output either as it could deliver more current than an opto could. I tied one pin to +12V and switched a relay coil off it and that seemed to work.

(Message edited by echase on 28 July, 2011)

(Message edited by echase on 28 July, 2011)
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kayjay
Regular Contributor
Username: kayjay

Post Number: 50
Registered: 10-2009

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Posted on Thursday, 28 July, 2011 - 03:51 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I tried activating the PIR and holding my meter leads across the terminals in continuity mode, it showed 0 ohms so I reckoned that it would be as you figured except it needs to be tied to 0v rather than 12v as the PIC port is held high at 5v. I've not actually tested it yet but I'm happy that it's going to work.

Thanks for your input though I appreciate it.

Keith

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