LIGHT FOLLOWING ROBOT
This robot moves in the direction of light. The robot is very simple to design as it doesn’t use any microcontrollers (no need of programming).
LDR - 3 MM type
U1 - ua 741
U2 - l 293
Q1 - BC 548
R1 - 5k1
R2 - 1k
R3,R4 - 10K
RV1 - 10k preset
The circuit uses two IC’s , LM741 op-amp, which is used as a comparator and L293, which is the H bridge used to control the motor direction. The two light dependent resistors used are connected as a voltage divider, so if LDR1 is exposed to more light, the voltage at point A moves towards Vcc & if LDR2 is exposed to more light, the voltage at point A moves towards ground. This voltage is given to op-amp’s non-inverting terminal. The op-amp compares this voltage with the voltage present in the inverting terminal, so if the voltage at point B is more than point C the output of the op-amp is high & if it is vice versa, the op-amp output is ground. The voltage at point C can be set using RV1 which is configured as a voltage divider, which enables us to adjust the sensitivity of the LDR’s. Transistor Q1 is used as an inverter so whenever the output of the op-amp is high, the collector of Q1 goes low. The Q1 along with op-amp output gives the control signal for the H-bridge.
For H-bridge:
IN1
|
IN2
|
DIRECTION
|
0
|
0
|
No motion
|
0
|
1
|
Clock-wise
|
1
|
0
|
Anti-clock wise
|
1
|
1
|
Not allowed
|
Since we have the signals controlling IN1 & IN2 as complement to each other, only clock wise & anti-clock wise motion of the motor occur. Connect the H-bridge to the motor of a robotic car. Place the LDR’s in opposite directions in the car. Power the circuit using a 6 V source (4 * 1.5 V AA batteries).
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