Posts Tagged ‘logic mobot’

Getting started with mobile robots, we definitely need a platform where we can fit the electronics of our robot and make it move. In this tutorial we will be making a cheap mobile robot platform from a toy commonly called as tumbling car here in the Philippines. It can be bought almost anywhere specially on Chinese discount stores at 40-50 pesos.

The Materials:

2 – Tumbling car

1 – Small screwdriver

1 – Side Cutter or small saw

1 – Super glue


Let’s get started:

First, unscrew the top cover by removing the two screws at the bottom side of the toy

Toys with top cover removed

Next, remove the wheels opposite the motor and the gearbox as shown

Trim down the shaft for proper alignment

Put super glue all around on one of the cars


Align and put them together

You may add a plastic or metal link for more strength and ruggedness against bumps like the one shown below

Wait for the superglue to dry and voila!, you now have a less than 200 Pesos robot platform in less than 30 minutes

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.