Light Seeking Robot – Seeker BOT

Seeker BOT is nothing but a simple light seeking robot. In this case, light source is the object and theSeeker BOT is moving towards it by comparing the light intensity on left and right sides. Making a light searching robot is not a very tough task.
Seeker BOT presented here can be fabricated within one hour, without using any dedicated microcontrollers!

Schematic of the Light Seeking Robot Circuit

Light seeking robot circuit

Circuit designed, tested and fabricated at TechNode on 17 March 2014

First part of the circuit is a light searching sensor wired around the popular Op-Amp LM358N (U1), which is an 8-pin IC having two inbuilt op-amps. Here the two op-amps are configured in comparator mode, ie the reference voltage is set at the inverting input pin (-), and then it is compared with the input at non-inverting (+) input pin (reference voltage at inverting input pin can be set with the help of associated potmeter). When voltage at non-inverting input pin exceeds this reference volatge, output of the comparator goes high (H), otherwise it remains in low (L) state. 2-channel output from U1 is fed to the inputs of the integrated motor driver L293D (U2), which is an easy-to-use 16-pin IC capable of driving two dc motors at a time in clockwise (CW) and counterclockwise (CCW) direction individually.
Power supply input of the Seeker BOT is 6VDC.

Seeker BOT Parts

  • IC1: LM358N
  • IC2: L293DNE
  • D1, D2 : 3mm/5mm Photodiodes (light level sensors)
  • D3: 1N4007
  • LED1,LED2: 3mm/5mm Red LEDs (only for indication purpose)
  • P1,P2 : 10K multi-turn POTs
  • R1,R3: 10K ¼ w
  • R2,R4: 1K ¼ w
  • C1: 100nF
  • S1: Power Switch SPST
  • M1,M2 : Gear Motors (200 -300 RPM)
  • Battery : 6V (1.5Vx 4)
  • (Accessories: Plastic wheels x 2 , Caster bullet x 2, Motor clamps x 2, Chassis board x 1, etc)

Light seeking robot

Working of the Seeker BOT is simple, and self-explanatory to some extent. Anyway, referring the datasheet of L293D IC is recommended for better understanding of the inside electronics. Logic of the Seeker BOT is:

  • If (light is on left) // Left Sensor Active
  • Turn Left // Right Motor ON
  • If (light is on right) //Right Sensor Active
  • Turn Right // Left Motor ON

Seeker bot breadboard wiring

For implementing this, set up the circuit wiring so that if light source is on the left side of the robot (left light sensor receives more light) the left motor should stop to ensure a left turn with the help of the right motor, and if the light source is on the right side (right light sensor receives more light) the right motor should stop to take a right turn with the help of the left motor. The actual electronics works as shown in the table below, but a special mechanical arrangement (if D1 is your left sensor, then use M1 as right motor, and vice versa ) is necessary to get what you want exactly.


Note that this is a basic design introduction for beginners. Here, the focus is only on taking turns according to the light levels. It is surprising, but it is possible to make Seeker BOT in advanced ways (white line follower, dark line follower, fire fighter…) too by smart circuit tinkering!

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