Things You'll Need

Instructions

1

Open the motion sensing door chime (availabe online or at electronic retailers such as Radio Shack) by unscrewing the back and prying the two molded plastic halves apart. Remove the circuit board and motion sensor from the speaker using the soldering gun at the speaker connections. The circuit board and sensor are the only parts you need from the casing. Make sure you don't disconnect them from each other.
2

Using a USB mini DVR with a 5 mm pinhole video camera with audio, remove the micro-switch attached to the DVR (it's about the size of a match tip). Solder a standard diode (e.g., a 1N4007) to the switch contacts. Note the striped side (the cathode side) of the diode. Solder the diode with the cathode side away from the switch to the negative terminal of a 220uF capacitor. The other side of the diode is hot glued to the other Reed relay terminal. (Remember these are the two inside Reed relay connections). Hot glue the other side of the diode to the Reed relay. In effect, when this small contraption is turned on, the motion sensor will send continuing pulses to sense motion. The capacitor will limit the sensor to one "trigger," in effect making it a momentary switch.
3

Connect (solder) the positive side of the capacitor to one motion detector contact and connect (solder) the non-striped end of the diode to the other contact on the motion detector. The two outside contacts from the relay should then be soldered to the DVR, completing the circuit.
4

When finished with all connections, install a 9-volt battery onto the circuit board. Don't worry, you'll see the preconnected battery pad that is already attached to the circuit board. After 15 seconds, move your hand in front of the sensor and the spy cam will detect motion and turn on the DVR.