This is a simple obstacle avoiding robot with two wheels that can be fabricated using a handful of generally available and inexpensive discrete components. The robot can perform avoidance manoeuvres whenever it detects an obstruction in its path. The electronic part is simple and can be built on a small piece of prototyping board. Although not terribly complicated, the mechanics do require a little care all the same. ROBBOT can be operate by a 6V (1.5x 4) battery pack.
Circuit Diagram
Working
ROBOT uses a front facing Infrared LED (Tx) to scan its path and a Photodiode (Rx) to detect light reverted from the obstacle by reflection. As soos as an obstruction is detected, ROBOT goes into reverse direction, and set off the locomotion in another forward direction. The sensor electronics is wired around the small Op-Amp LM358N (IC1), which is an 8-pin chip having two inbuilt Op-Amps. One part of IC1 used here is configured in comparator mode. The sensitivity of the circuit is controlled by the reference voltage at pin 2 of IC1 using a 10K trimpot (P1). P1 will help to reduce unwanted detections caused by external light sources.
Parts list
Symbol
|
Name
|
Value
|
IC1
|
Op-Amp
|
LM358N
|
T1
|
Transistor
|
BC547
|
D1,
D2
|
Diode
|
IN4007
|
LED1
|
Green
|
5mm
|
Tx
|
Infrared
LED
|
3mm
|
Rx
|
Photodiode
|
3mm
|
RL1
|
DPDT Relay
|
6V
|
M1,
M2
|
DC
Motors
|
|
S1
|
On/Off
Switch
|
|
R1
|
Resistor
|
150
ohm
|
R2
|
Resistor
|
10K
|
R3
|
Resistor
|
120K
|
P1
|
Potentiometer
|
10K
|
C1
|
Capacitor
|
100uF/16V
|
C2
|
Capacitor
|
100nF
|
Robot Parts
- Single Shaft Plastic Gear Motor x 2
- Plastic Wheel x 2
- Plastic Chassis Board
- Plastic Castor Bullet x 2
- DC Motor Clamp x 2
- 4 x AA Battery Compartment/Holder x 1
Important Note
Normally relay RL1 switches the positive and negative supplies to both motors M1 and M2. In case of an obstruction detection, RL1 switches to reverse the polarity of the motor connections. D2 now becomes reverse biased and hence supply to M2 is not available. Now only M1 goes into reverse mode. When RL1 switches back (no obstacle detection) Tiny BOT returns to the initial condition.
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