Arduino Obstacle avoider is now popular in the DIY field. I made one using cheap available components.
Hope it will entertain you.
Things you need:
1. Any cheap Arduino UNO R3 (clone)
2.Adafruit Motor Shield v1
3.A pair of DC motor and wheels
4.Micro 9G Servo
6.Some connecting wire
7.Some Plexi Glass
8.Battery pack for arduino and motor shield
Step 1: Chassis
From plexi glass cut your bot design using hacksaw or cnc or laser cutter.
I made round one using hacksaw. Then place the DC motor with glue. I prefer super glue or fevikwick as the are strong than hot glue. Then attach the wheels to the motors.
Attach the SR04 sensor to the micro servo using glue and place the servo in other piece of round design.
You done your work with chassis.
Now attach the motor shield to the UNO board. Connect dc motor to the motor shields M1 and M2 port.
Connect the servo to the Servo_2 port of the motor shield. Now connect the SR04 to the analog pin as I mention
Trigger Pin to A0
Echo Pin to A1
Now connect the batteries to the arduino and the Motor Shield.
Upload the sketch that I made and you done.