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# Phone Tilt Notes, for RC Car Acceleration

We got our first car working, and figured out that 0 isnt actually 0 but 50, and 100% throttle is actualy 0 or low voltage to the servo controller. We also faced another problem, Reverse! Before we begin understanding reverse, we need to understand the numbers.

The stick on our throttle goes from 0-100, where 50 is neutral, or its ideal position. When you are driving the car at position 49-0 (Note power values are inversed) and pull the throttle back to >= 50 the car does not reverse, but in fact tries to stop it self. It is only when you go back to idle to 50 for a given time that 50-100 responds as a reverse acceleration.

To do this we follow the same procedure on the phone tilt controls. As it is hard to idle a phone at 50, we create a range that is always 50. You can see this represented in Orange in the figure below.

From the diagram above you can see 0 is extended, as we don't want to stop the car just because the person is dropped the phone a little more than the 0 position, It is only when they go past 0 radians that we switch to the dark gray 50 idle position.

## Further notes

We believe that the reverse using tilt is probably not the most intuitive way to perform reverse on a tilt controller. It would be better to use a switch to engage reverse, and then use the normal throttle as you would an accelerator pedal to reverse. This is to be seen.

20th Jun 2013