Nomad

An autonomous car!

Website

What does it need to do?

• Follow a set of waypoints

• Too fast - while steering and throttle worked well the car itself didn't like moving at low speeds. Instead it was too fast for easy testing.
• Short Battery Life - the main power pack was 7.2v and didn't contain much charge - therefore the car could only be tested for a short period of time before it was necessary to recharge for 30mins.
• Direction - as GPS was being used to decide the direction that the vehicle was facing it was necessary for the car to move before this direction could be found. A digital compass on the i2c interface could be used to overcome this problem (however calibration might be an issue).
• Messy - the construction was rushed resulting in a messy construction.

Upgrade - Bought a r/c hovercraft from Maplin for £24.99 - 3 motors, one for lift and the other two for left and right. No servos instead it moves like a tank. Didn't take long before I'd taken it apart, the decoder chip is PT8A97BPE and after a bit of searching I managed to find the data sheet. As the left and right motors are either on or off there is no need for a PWM signal. Instead I identified the pins from the decoder chip to the individual motors and found that by applying 3.3v the motors turn (I guess it goes through some more circuitry). i therefore attached some wires to the correct pins on the decoder chip, also added a ground wire and wired this up to the I/O pads on the waysmall.

Todo

• Check that flicking the state of the GPIO is sufficient to start and stop the motors.
• Add GPS
• Check range of radio modems and add them
• Sort out power for all the components
• Perhaps increase power supply for lift motor
• Add i2c digital compass
• Write simple waypoint following software.