Data Logging Part 1 - Acceleration

Its so easy to build circuits and programs with the Arduino that I have a few projects progressing side by side on the same hardware. In this project I intent to record performance data on board my RC Racer then upload the data for analysis on the PC. Something which I see as very simple but very useful is the ability to record and visualise the traction circle for different setups. For my purposes the traction circle will be plotted from the X and Y G-forces acting on my car, to sense and record these forces I am using an ADXL335 3-Axis Accelerometer and a Micro SD Card. Both of these are available on easy to use 'breakout' boards that can be plugged directly into the Arduino UNO. The two plots above are produced from live data coming from the Arduino into my PC, I am using 'Processing' to display the results. The screen area represents +-1G in the X and Y Axis, Z is not plotted. The first plot is generated with the board flat on the table. The second plot is the result of me tapping the side of the table to generate some movement in the X-Axis, then tapping the front of the table to get some action on the Y-Axis, but the really interesting plot is the next one -

Here I have used the constant 1G acceleration provided by good old fashioned gravity. By tilting the board from one side to the other I can use gravity to apply 1G of acceleration to the left and then the right. You can see the result of this in the lines running right, up and down from the center. The diagonal line running from the center to the top right is the result of me trying to 'draw' the line by progressivley tilting the board and letting gravity do the work. This was surprisingly difficult, it had that addictive quality that the simplest of games have - something thats quick and easy to understand, takes a while to master and can always be improved upon. I can think up a dozen gaming applications for this - for example physical tetris where you actually have to rotate the controller to rotate the tiles and then swing the control to the left or right to position tiles. Another application would be target based sports simulations, the sensor is sensitive enough to pick up hand tremors.

Getting back to the main purpose of this project, the left side of the screen shows a sample of a traction circle I have generated by rotating the board which is sensing the constant 1G force of gravity over a range of angles. In practice most of the plot points would be toward the center of the screen but this provides a quick bench test and proof of concept. The sensor I am using can sense up to 3G, and also records the z-axis which I am recording but not currently plotting. I have no idea what to expect in the car, probably less than 1G but will get some plots up with different tyres in the next day or so - I know that racing tyres are worth every penny compared to stock tyres and soon I will be able to prove it !