What’s Inside It? – Line Following Robot Tank

One day while looking around a toy store near my workplace I found this nice little line following robot tank on sale. Originally, the tank cost around Php400 but then it was sold at around a hundred less. Without thinking twice I know I had a great offer so I decided to buy the toy.

I played it for a while but then I got a little bored so I finally decided to crack it open.

 

The toy is powered by four small button cells. Two of the cells power the motors while the other two power the control board.

 

Opening the toy was quite a bit tricky. The track belt needs to be removed first and the middle wheels must be pulled out to reveal the two screws joining the tank’s upper body to the lower chassis.

Inside it is a little circuit board centered around an SMT IC. Guess what it is, a microcontroller? Eeeeeh!!! You’re wrong. It is controlled by a dual comparator IC which is pin to pin compatible with LM358 (the body marking says it’s “0358”).

Inside the gearbox are two small DC motor no bigger than a cellphone vibrator motor that differentially drive the tracked wheels and, of course, a couple of gears.

 

 

Optical sensors are located at the bottom. The main part are the phototransistors (dark part) that detect the reflection (indication that the surface is not black) of the light emitted by the red LEDs (transparent part). The outputs of the comparator provide the drive signal to turn on/off the motors of the tank.

The main switch is also mounted on the component side of the board.

 

It was easy to trace the circuit’s layout since few component resides on the circuit board. Looking at the circuit, we can clearly see a window comparator that turns either of the motor off when the voltage produced by the phototransistors divider network goes beyond the window voltages (most of the time phototransistors are shorted but it opens when it senses a black line).

~ by glutnix_neo on December 18, 2009.