Monday, 20 May 2013

my Pi-Car

Pi-Car is a Raspberry Pi (RPi) controlled RC (remote control) car, for details click on the link. In brief Pi-car runs without pressing the remote buttons, instead we will send the instructions by a computer program. I have used the basic Pi-Car kit and Raster RC car Porche GT3 RS from Argos.

How it works?
We connect the RC circuit Left, Right, Forward, Backward button points and 0V points with RPi GPIO pins, using Pi-Car circuit which is made of 4 FETs and 4 Resistors. Need to write Python program that controls the behaviour of pressing the L/R/Frwd/Bkwrd button of the remote. For detailed instruction for building a car like this follow the instructions provided here http://pi-cars.com/2013/01/24/pi-cars-factory-beginners-tool-kit/

Here are the pictures of my setup

1. RC Circuit of Raster RC Car Porche GT3 RS from Argos

2. Make 5mm hole on back of the RC to create a passage for wires

3. Final setup looks like this

4. Here is a video showing how it works, doing one forward and backward loop, there is a sleep of 10 sec in between to change the position of the car



5. This video is showing car following the carpet perimeter forward and reverse



6. Sample Python script, here is link to my Python script, which is a modified version of the sample script provided by Pi-car.com
https://googledrive.com/host/0BwDWZ6lzXD51eXV3d2dvdGVEMkE/PiCarTest1.py

Lessons Learnt
I think overall its a great project for any 10+ years old to learn computer programming in fun way. I found that even the five years olds were quite excited and amazed watching the car run by a computer instead of a remote, all they have to do is hit the enter key :-). They also got a hang of it, Big Computer talking to small one, Small one (RPi) is talking to remote and remote is talking to a car. :-)

Controlling a RC car is not that easy, as the basic car doesn't have speed control or break system. It simply runs based on how long a button is pressed, so getting a time accuracy is bit of tedious job and require lots of trial and error. Also it may not run the same distance on and off carpet due to variation in friction. The charge of the battery will also affect the distance it covers in a given time, for example with full charge it may cover 3 ft in 1 sec but with low charge it may be able to do only 2.5 or 2 feet. I think once you get hang of it its fun.

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