IR Object sensing circuit

Hi I am looking for a simple/good circuit to make an IR object seeking robot. I do not wish to use micro controllers because this will be used as a school electronics project (and we are not at that level yet). We have been using Pololu chassis’s with theTamiya Twin gearbox , and mounting our boards on top with great sucess. We have created light seeking and line sensor robots and are looking for a more independent robotic project. Any assistance would be much appreciated.

Many Thanks macman153 :unamused:


Do you know about Sharp’s distance sensors? They have versions that give you an analog reading from which you can determine distance and digital versions that have various trigger distances. The detection range is typically around 10-80 cm. You can see more on their web page:

For shorter distances, up to about a few inches, a simple IR emitter and phototransistor pair can work quite well.

What kind of distance are you looking to detect?

- Jan

Hi Jan,

Thanks for the reply, yes I had seen those sensors on various webistes. I am not looking to get too ambitious at this stage.
Do you think that if I used a pair of Sharp GP2D120 linked to a LM393 comparator that I would get a reasonable working unit? We are just looking for a unit that can roam on its own without too much intervention.


One possibility would be to put one distance sensor on the front of the robot, and use a comparator to determine when an object is within a certain range. Link the output of that comparator to one of the motors, so that the robot turns to one side when there is an object in the way, but otherwise drives straight. Then the robot will circle the room, avoiding objects.

The GP2D120 would be fine, since it has a simple analog output. Just make sure you use a lot of hysteresis in your comparator circuit, or the robot won’t miss the objects, and consider adding a time delay, as well.