OBSTACLE AVOIDING ROBOT

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

Robot Circuit Parts

IC1    : LM358N

T1     : BC547

D1,D2  : 1N4007

LED1   : Green 5mm

Tx     : Infrared LED 3mm

Rx     : Photodiode 3mm

RL1    : 6V/DPDT Relay (also tested with a 5V Relay from O/E/N)

M1,M2  : DC motors (Single Shaft Plastic Gear Motor)

S1     : On/Off Switch

R1     : 150 Ohm

R2     : 10K

R3     : 120 Ohm

P1     : 10K

C1     : 100uF/16V

C2     : 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.