Posts Tagged ‘mobots’

Line Follower
Here is a low cost line follower for steer type chassis like the one used in remote control car toys.

The circuit consist of three parts, the sensor, logic, and speed controller for the drive motor. The sensor is formed by two IR pairs and fed to a comparator to condition  the signal before it goes to the logic circuit. The logic circuit is basically a SR latch formed from NAND gates. Since the output of the SR latch is logic 1 for Q and ~Q when the input is both logic “0” we invert this to protect the h-bridge. We used the two remaining NAND gates to become an inverter. Thus the logic circuit is only a single chip using a quadruple two input nand gate 74LS00.  The logic truth table is show below:

One problem that I encountered during my early design of this kind of mobot is controlling the speed of the drive motor.  When the mobot is too fast and the steering  of the car is not good the mobot might get out of track. In this version I added a PWM controller using a 555 timer with varying pulse width to control the speed of the drive motor.