CAMERA_ALARM_TRIGGER

Published:2009/7/9 1:36:00 Author:May | From:SeekIC

Transistor Q1 remains off until the magnetic switch connected to J1 closes. When that happens, the 9 V is connected through R1 to Q1'S base. Q1 turns on, thereby charging C2 through relay K1, which causes K1's contacts to close. Since the contacts connect via J2 to the remote control jack in the camera, which in turn connects to the camera's shutter release, the closure of K1's contacts will cause the camera's shutter to trigger. After C2 charges, K1 opens because current through its coil ceases; the camera won't take another picture. If Q1 turns off because the magnetic switch on the window or gate opens, C2 discharges and the circuit is ready for another cycle. As long as Q1 remains on, C2 stays charged and prevents K1 from triggering more photos. Capacitor C1 bypasses spurious magnetic switch noises from physical phenomena, such as a rattling window or a gate shaking in the wind, thus reducing the likelihood of an unwanted picture. Resistor R2 biases Q1 and dampens K1/C2 oscillations which might cause contact bounce. Diode D1 prevents C2 from discharging through K1; the relay coil isn't polarity conscious and C2 discharging through it would trigger an unwanted picture.



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