03-11-2012, 01:38 PM
LASER GUIDED DOOR OPENER
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ARCHITECTURAL OVERVIEW
The block diagram will help you to understand the project in the simplest way. In the
block diagram the components that are used play vital role for the development and building of
the other circuit diagram and different internal architecture view of component successfully.
The other circuit diagram and internal architecture views are also shown one by one
carefully and by keeping in mind to show the entire significant components that are used in the
project (Laser Guided control) is shown in the next part.
DESCRIPTION AND WORKING:
This automatic door opener can be made using readily available
components. The electromagnetic relay at the output of this gadget can be used to control the
DC/AC door-opener motor/solenoid of an electromechanical door opener assembly, with light
intervention 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 protects
the laser diode from over-current flow. By varying muliturn trimpot VR1, you can adjust the
sensitivity.(Note that ambient light reflections may slightly degrade The performance of his
unit.))Initially, when the laser beam is falling on photo-transistor T1, it con-ducts to reverse-bias
transistor T3 and the input to the first gate (N1) of IC1 (CCD4001) is low. The high output at
pin 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 someone
interrupts the laser beam, photo-transistor T1 stops conducting and transistor T3 becomes
forward-biased. This makes the output of gate N1 go low. Thus ED-driver transistor T4
becomes reverse-biased and LED2 stops glowing. At the same time, the low output of ate N1
makes the output of N2 high. Instantly, this high level at pin 4 of gate 2 triggers the monostable
multivibrator built around the remaining two gates of IC1 (N3 and 4).Values of resistor R8 and
capacitor C1 determine the time period of the monostable.
The second monostable built around IC2 (CD4538)is enabled by the highgoing
pulse at its input pin 12 through the output of gate N4 of the first monostable when the
laser beam is interrupted. As a result, relay RL1 energises and the door-opener motor starts
operating.LED3 glows to indicate that the door-opener motor is getting the supply. At the same
time, Piezobuzzer PZ1 sounds an alert. Transistor T5, whose base is connected to Q output
(pin10) of IC2, is used for driving the relay. Transistor T6, whose base is connected to Q output
of IC2, is used for driving the intermittent pi-ezobuzzer.‘On’ time of relay RL1 can be adjusted
by varying trimpot VR2. Resistor R9, variable resistor VR2 and capacitor C3 decide the time
period of the second monostable and through it on time of RL1.
DESCRIPTION OF CD 4538:
The CD4538BC is a dual, precision monostable multivibrator With independent trigger
and reset controls. The devices retrigger able and reset table, and the control inputs are internally
latched. Two trigger inputs are provided to allow either rising or falling edge triggering. The
reset inputs reactive LOW and prevent triggering while active. Precise Control of output pulsewidth
has been achieved using linear CMOS techniques. The pulse duration and accuracy are
determined by external components RX and CX. The device does not allow the timing capacitor
to discharge through the timing pin on power-down condition. For this reason, no external
protection resistor is required in series with the timing pin. Input protection from static discharge
is provided on all pins.