RC Tank Project

Here is a rough outline of a RC Tank project of mine that I did a few years ago. Hopefully this will inspire the budget robot builder on to build one themselves. With some IR sensors, the platform could easily be adapted to an autonomous mode. So, the main thing is to get creative, add your improvements, style, and above all, have fun!

Transmitter Receiver

The RC control employed was a 6 channel Vex Robotics transmitter and receiver add on kit. It was commonly available several years ago for $30 or less, when there seemed to be a glut on the market.

As an added note, a Futaba 75 Mhz FM receiver was successfully tested to operate a servo with the Vex transmitter, by swapping in the Vex receiver crystal. Using a Futaba, or compatible, receiver would relieve the burden of decoding the Vex receiver signal.

The tank used a PIC16f684 to decode the raw receiver PPM signal. The Vex receiver signal is best explained by looking at the output with an oscilloscope. There is a writeup by Jon Williams on the Vex receiver pinouts, and how to decode the inverted PPM signal http://www.allelectronics.com/mas_assets/spec/JS-6.pdf

Base Platform and Motors

The RC tank's base platform used was the Tamiya Tracked Vehicle Chassis Kit. If I had it to do over again I woud use the Track and Wheel Set, along with the Universal Plate set for the convenience of the pre-drilled holes

The motor and gearbox combo used was the Tamiya Double Gearbox. Tamiya also has a Twin Motor Gearbox that could be a viable alternative. The 114.7:1 gear ratio was selected to provide a balance between speed and torque. Switching to a higher speed ratio couldn't get the tank's heavy battery pack moving. A li-po battery would lighten the load considerably, with a chance at higher speeds.

The Brains and Power

The RC Tank uses a Pic16f684 to decode the Vex receiver PPM receiver signal and to control the SN754410 dual H-Bridge chips. I upped the ante by using a single chip for each motor, thereby doubling the stated output rating of 1A to 2A. A couple of led's were added to each motor h-bridge input, for a little bling factor, using green for forward and red for reverse.

PWM was not used for motor control, because the gearing, tank weight, and low motor power proved a little too much for the tank.

A low dropout 5V regulator was used to power the PIC from the six AA ni-mh batteries.

Using the 6 AA's, is running on the hot side for the 3V mabuchi motors, and could be the reason why one of the motors isn't currently working. Will blow off the dust someday, and have a look see. The 16f684 has a PWM output to play with, so that could be put to good use on reducing the average motor voltage.

Conclusion

This was one of my most fun projects. Lot's of room for future improvements.