My college has entered an annual racing competition called Greenpower, and it's been agreed to use a Raspberry Pi as the car motor controller. Since I am the only knowledgeable one in the group where Electronics and Programming are concerned, I'm managing most of this myself.
The regulations have limited the amount of power we are allowed to use to 2x 12v lead-acid batteries, as well as 6x 1.5v AA batteries. We are additionally allowed a 3v coin cell battery. I was planning to power the pi using 3x AA's(totalling 4.5v), and have the other 3 AA's hooked up in parallel to double the capacity. As well as the Pi, there will be 2 other electronics using the battery, including a 3.6v sound system, and a 1-watt amplifier.
On the dashboard there will be 3 status indicators, a Red LED (11mA), a Green LED (1mA), and a Yellow LED (9mA). There is an additional buzzer on board (1mA) which will sound if an error occurs. All these status indicators share the same ground, and have independent inputs with different value resistors (for brightness) and a 10v zener diode. These have all been tested using a voltmeter and a 3.3v power supply. These will be hooked up to the Pi's GPIO ports. These have already been soldered to a board, but another can be made
There will be 2 relays controlling the motor output, only one of which will be active at a time. The relays I've tested so far are 6v relays (3mA), but only activate at 3.45v(Pi may not power them).
There will be 3 inputs: Acceleration, Gear 1(16v to motor) and Gear 2(24v to motor). I am completely unfamiliar with sending an input to the Pi.
The code which will be controlling these has been written already, but has empty spaces where it will check and set inputs/outputs.
The race is in October so there is plenty of time for changes to be made. It is 90 minutes long, and batteries cannot be changed for the duration of the race. If the Pi dies, I'm planning to setup an emergency switch to power the Motor at full 24v.
I am running Raspbian with Mono installed.
What I would like to know...
Regarding power, is there any way I can optimise the current setup?
Additional suggestions and improvements are welcome.