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An access control circuit

2015-03-02 12:43  
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This article describes an access control circuit. The circuit is very simple, I hope for your help. In this circuit, Q1 form a self-excited oscillator: the output pulse driven into saturation, the third quarter of the second quarter and the LED is off. When contact with the metal part of the body is electrically connected to the wire hook handle, body capacitance suppresses oscillations, Q2 Q1 biased off and the transistor becomes conductive. Thus, the current may flow into the base of Q3 and D3 illuminated. If SW1 is closed, a closed circuit from self-triggering and pagers Q4 & Q5 BZ1 is activated. When the body part to leave the process, resulting in continuous closed but the buzzer sounds, because the behavior of self-enclosed Q4 & Q5. Action buzzer is stopped, the entire circuit must be turned off SW2 open. R3, sensitivity control, can cope with a variety of door types, processing and locks. For formation of the winding L1 of the circuit 20 to 30 rpm 0.4 mm. Enameled wire diameter R2 of the body and across the coil resistance welding result. You should fill R2 body completely with coil windings: the number of the last transfer will be slightly different, depending on the type of 1 or 2 w resistor types actual length (average size is 13-18mm for these components. Length and 5-6mm diameter). Hooks are separated by a non Hotline at 1 - 2 mm. Diameter (brass is appropriate). Its length can vary from 5 to 10 cm. (Not critical). If the device is moved frequently to different doors, trimmer R3 can replace a common linear potentiometer with outer knob is easy to install. Set the device unplanned downtime hook doorknob (in closed doors), open SW1 and connected to the circuit. Adjust R3, until the LED lighting, then slowly backwards screwdriver (or knob) until it is completely closed leadership. At this point, your hands touching doorknobs and LED illumination, should go when the hand withdrawn. Finally, close SW1 and the beeper will sound when the door handle will again be moved, but will not stop until SW2 is opened. In routine use, it is recommended obstacles and power equipment and SW1 open: When all is well resolved, SW1 can be closed. This precaution is necessary to avoid unnecessary triggering of the pager. This circuit is not new, but it proved so useful, simple and cheap, it is worth building.



Door Alarm
R1______________1M   1/4W Resistor
R2______________3K3  1 or 2W Resistor (See Notes)
R3_____________10K   1/2W Trimmer Cermet (See Notes)
R4_____________33K   1/4W Resistor
R5____________150K   1/4W Resistor
R6______________2K2  1/4W Resistor
R7_____________22K   1/4W Resistor
R8______________4K7  1/4W Resistor

C1,C2__________10nF   63V Ceramic or Polyester Capacitors
C3_____________10pF   63V Ceramic Capacitor
C4,C6_________100nF   63V Ceramic or Polyester Capacitors
C5______________2μ2   25V Electrolytic Capacitor
C7____________100μF   25V Electrolytic Capacitor

D1,D2,D4_____1N4148   75V 150mA Diodes
D3_____________5 or 3mm. Red LED

Q1,Q2,Q3,Q5___ BC547   45V 100mA NPN Transistors
Q4____________BC55745V 100mA PNP Transistor

L1_________________   (See Notes)
L2_____________10mH  miniature Inductor

Hook_______________   (See Notes)

BZ1___________Piezo sounder (incorporating 3KHz oscillator)

SW1,SW2________SPST  miniature Slider Switches

B1_______________9V  PP3 Battery

Clip for PP3 Battery


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