This is a car security system that will start a camera recording when someone touches your vehicle. It can be run off it's own 12v power supply or you can wire it to the car battery and use a switch or relay to turn it on. Alternatively, it could be placed inside a building, near a door, and detect people when they walked up outside.
DEI 508D Proximity Sensor $28
DEI 528T Pulsetimer Relay $18
Fuse and Holder
Dash Cam HD Camera ($100)
Step 1: Plan
I'm testing the circuit first on a board, before installing it in a small plastic box in the car glove compartment. The plan is to eventually have an auto tech run a female cigarette plug, behind the dash, into the glove box. It is important that the cigarette plug provides 12 volts ONLY when car is not running. It's a small job and should cost under $100 in any good shop. Have the auto tech use a relay that is normally closed when the car is not running, so it doesn't drain the car battery when parked. Optionally a rechargeable 12v battery with an on/off switch could be used.
Include are the supplied installation instructions for the motion sensor and relay.
Step 2: Fuse
Solder the fuse to the positive wire (centre pin) from the male cigarette plug. It is a good practice to have a fuse protecting the electronics.
Step 3: Positive and Negative Terminals
I'm using 2 copper tacks hammered into the board as my connectors. The positive lead from the fuse and the negative lead from the male cigarette connector are just wrapped around them.
Step 4: Proximity Sensor Power
Connect the Red (+12volt) and the Black wire (- Ground) from the Proximity sensor to the correct terminals.
Step 5: Power Relay
Attach the Relay's Red (+12v) and Black (-ground) to the terminals.
Step 6: Relay Common
Connect the yellow Relay (Common) to ground (-).
Connect the positive female cigarette wire (centre contact) to the positive terminal.
Connect Relay Brown (normally open) to the (-) wire of the female cigarette plug.
Step 9: Trigger
There are two trigger wires from the Proximity sensor. The first stage (green) and second stage (blue). The first stage field is larger than the second stage and will detect movement at a greater distance. If you are parking on the street and worry about passing cars triggering the camera, you might go with the second stage. Both fields are somewhat adjustable with a screwdriver. Since I'm mostly parking in driveways, I'm going to use the first stage.
Connect Proximity Sensor Green (first stage warn away) to Relay Black with White stripe (trigger input).
Step 10: Unused Second Stage
If you are not using the proximity sensor second stage wire (Blue) , wrap the end with electrical tape to stop it from touching anything.
Step 11: Unused Orange
Wrap the end of the Relay Orange (normally closed) with electrical tape.
Step 12: Camera
A car dash camera will have a male cigarette plug connector and they will start recording as soon as they receive power. There are a lot of DVR cameras intentionally mislabelled as HD. Do some research before you buy.
Step 13: Adjusting
With a screw driver turn the relay adjustment to maximum. You should get about one minute of power to the camera every time the Proximity Sensor is triggered.
Try for maximum distance with the first stage Proximity sensor trigger. The car body will affect the field so it may take some tweaking to get it right. The green led will light for the first stage, red for second.
Step 14: Conclusion
The camera was helpful in finding out who was trying to break into neighbourhood cars. Looking at the diagram again, it might have been best to wire it slightly differently, but it seemed to work.