Now that I have a microcontroler I can desgin the rest of the controller. For the sensors I chose to use:
- X and Y axis Gyroscope: Invensense IDG-500
- Z axis Gyroscope: Invensense ISZ-500
- 3 axis Accelerometer: Analog Devices ADXL335
- Pressure Sensor: Bosch BMP085
- Compass: Honeywell HMC5883
The Accelerometer and Gyroscopes will be used to control the rotational axis’. I chose to use analog snsors to beable to have the fastest update rate. Had I used I2C digital sensors the max possible update rate would be much slower since the ACD conversion time i significantly less than the time it takes to read data from an I2C sensor at their max baudrate of 400kHz. Thee are some downsides I am going to have to live with since I am using the analog sensors I need to have a stable and accurate volatge reference for the ADC, in whch I chose the:
National Semiconductor LM4132EMF-3.3
- 0.5% Tolerance
- 30ppm/°C Temperature Coefficient
- 50ppm Long Term Stability
Other downsides are to the anaog sensors are the 10bit ADC on the micro controller, which only gives 1024 counts which could be a problem. Also Analog sensors are going to be more suceptable to EMI which cold be thrown off from the brushless motors. Even though the downsides I finished the design with the analog sensors and sent the Gerber files off for the boards to be made.
Schematic:
Quadcopter Controller Rev 0
Andrew