Designing a line follower robot - Part 3

Follow up from "Designing a line follower robot - part 1" and  "Designing a line follower robot - part 2":

So, by now I should've had the first part of code ready to be tested, but unfortunately there was a delay in getting the PIC and PICKit.  I went ahead and assembled the chassis and drive system which I will be using.

I cheated a little and bought a neat little kit.  I say 'cheated' because that doesn't include any designing, only had to research a few options and choose one closest to my needs.  I chose this kit from Tamiya, which comes in three parts.  The gearbox-motor assembly (first picture), the universal mounting plate (forms the base/chassis for the whole thing and the tank-tracks.  The second picture shows the complete assembly.  This little gearbox/motor  kit has two configurations for two different ratios; 58:1 and 204:1.

Tamiya twin-motor gearbox
Figure 1
Here are the technical specs for the gearbox:

• Gear Ratios: 58:1 207:1
• Motor: FA-130
• Motor RPM: 12300 (9710 Maximum Efficiency)
• Motor Voltage: 1.5-3V (1.5V Recommended)
• Motor Stall Current: 2.1A
• Free-run current: 150mA
• Motor Stall torque: 36 g-cm     


I bought mine from MicroRobotics in Centurion.  Click on the link to find out more about them.  They distribute +Arduino boards and +Atmel Microcontroller and programmers and a host of other electronics.  I also bought an h-bridge from them, which will enable the microcontroller to drive the motors.

Tamiya twin-motor and gearbox complete with chasis
Figure 2
Check out +Pololu Robotics and Electronics for more information about the h-bridge, or click here for the one that I bought.

I could not help myself, and had to test the tank drive system after I had assembled it, so I stripped the control circuit off a robot kit I had built previously, the Hexpod obstacle avoiding robot (Shown below)







HexaPod robot
Figure 3

The tank drive worked perfectly and a lot smoother than the leg drive system of the Hexapod and this was the result of the test system:

Line Follower chasis and drive system

The only snag I have picked up is that the robot doesn't run in a straight line, but that I will sort out later.  It could be that the one motor is being driven harder by an imbalance in the electronics.   I will first go ahead and concentrate on the fun part of building and programming the control system, then we can find out if there really is a problem with the drive system.





Getting up to speed with my dormant programming skills proved harder than I anticipated.  See the next post in this series: Microcontroller Basics
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