16-11-2010, 07:36 PM
[attachment=7219]
DESCRIPTION AND WORKING:
This automatic door opener can be made using readily availablecomponents. The electromagnetic relay at the output of this gadget can be used to control theDC/AC door-opener motor/solenoid of an electromechanical door opener assembly, with lightintervention in its electrical wiring.
A laser diode (LLED1) is used here as the light transmitter. Alternatively,you can use any available laser pointer. The combination of resistor R1 and diode D1 protectsthe laser diode from over-current flow. By varying muliturn trimpot VR1, you can adjust thesensitivity.(Note that ambient light reflections may slightly degrade The performance of hisunit.))Initially, when the laser beam is falling on photo-transistor T1, it con-ducts to reverse-biastransistor T3 and the input to the first gate (N1) of IC1 (CCD4001) is low. The high output atpin 3 of gate N1 forward biases the ED-driver transistor (T4) and the green standby LED(LLED2) lights up continuously. The rest of the circuit remains in standby state. When someoneinterrupts the laser beam, photo-transistor T1 stops conducting and transistor T3 becomesforward-biased. This makes the output of gate N1 go low. Thus ED-driver transistor T4becomes reverse-biased and LED2 stops glowing. At the same time, the low output of ate N1makes the output of N2 high. Instantly, this high level at pin 4 of gate 2 triggers the monostablemultivibrator built around the remaining two gates of IC1 (N3 and 4).Values of resistor R8 andcapacitor C1 determine the time period of the monostable.
DESCRIPTION AND WORKING:
This automatic door opener can be made using readily availablecomponents. The electromagnetic relay at the output of this gadget can be used to control theDC/AC door-opener motor/solenoid of an electromechanical door opener assembly, with lightintervention in its electrical wiring.
A laser diode (LLED1) is used here as the light transmitter. Alternatively,you can use any available laser pointer. The combination of resistor R1 and diode D1 protectsthe laser diode from over-current flow. By varying muliturn trimpot VR1, you can adjust thesensitivity.(Note that ambient light reflections may slightly degrade The performance of hisunit.))Initially, when the laser beam is falling on photo-transistor T1, it con-ducts to reverse-biastransistor T3 and the input to the first gate (N1) of IC1 (CCD4001) is low. The high output atpin 3 of gate N1 forward biases the ED-driver transistor (T4) and the green standby LED(LLED2) lights up continuously. The rest of the circuit remains in standby state. When someoneinterrupts the laser beam, photo-transistor T1 stops conducting and transistor T3 becomesforward-biased. This makes the output of gate N1 go low. Thus ED-driver transistor T4becomes reverse-biased and LED2 stops glowing. At the same time, the low output of ate N1makes the output of N2 high. Instantly, this high level at pin 4 of gate 2 triggers the monostablemultivibrator built around the remaining two gates of IC1 (N3 and 4).Values of resistor R8 andcapacitor C1 determine the time period of the monostable.
