Used an alarm motion sensor to switch on an LCD inside the door showing the person at the door

So I just finished probarbly the 3rd iteration of the front door cam I've been building. Currently it has a colour camera with IR LEDs for night time, this is outside facing the door. On the inside there is a LCD I got off the internet for around $20, which was much of the motivation to build this project. Also there is a PIR sensor outside which activates the camera, although the PIR doesnt stay active long enough for me, so I added a timer circuit I copied off the internet. The timer simply uses a capacitor to keep a transistor active for around half a minute. I have included the schematic for the wiring below.


testing out values for the resistors to get the analog timer to work


Schematic for the electronics box. There are 4 transistors, just to make sure everything works. As the signal comes in from the PIR sensor, as a normally closed circuit, I ran it through a resistor then a transistor, probarbly not necessary in retrospect. Then this goes to another transistor, this time as an inverter circuit, the output of this inverter isnt that strong, as it is a 12v signal inline with a 1000K resistor... it think. Anyway this then goes to a capacitor circuit which servers as an analog timer (woo analog electronics), and because this output isnt that strong, this then goes through a darlington pair, before switching the relay. Done!

LCD inside, with modified cable to look less obtrusive.

Also the whole system can be put online by piggy backing the video cable to a USB CCTV capture card ($10 ebay), using an RCA plug splitter. Fits nicely into an always on server running win xp (the one I got isn't win 7 compatible). Otherwise there are ethernet video servers for standalone video serving to the net.