projects electric vehicle ElektorWheelie The electronics behind a rather special kind of vehicle Chris Krohne (Germany) In this ?rst article describing our DIY self-balancing single-axle vehicle we look at the electronics modules. An ATmega32 processes the controls and sensor data and drives the two electric motors via power driver stages. It keeps the vehicle balanced and can drive it in any desired direction at any desired speed from stationary to about 11 mph. The electronics in the ElektorWheelie processes input signals from a control potentiometer, an acceleration sen- sor and an inclination sensor. It con- trols the magnitude and direction of the torque applied to the wheels via two motors using PWM signals and MOSFET drivers. The sensors provide enough information to allow the vehi- cle to maintain its balance over its full range of speeds, and it can even spin on the spot. Characteristics Sensors: ? Invensense IDG300 (or IDG500) gyroscope ? Two 500 W DC drive motors ? Two 12 V lead-acid AGM batteries, 9 Ah ? Two fourteen-inch wheels with pneumatic tyres ? H-bridge PWM motor control up to 25 A ? Automatic power off on dismount ? Fail-safe emergency cutout ? Analog Devices ADXL320 accelerometer ? Allegro ACS755SCB-100 current sensor Microcontrollers: ? ATmega16 (motor control) ? ATtiny25 (current monitoring) ? Battery charge status indicator ? Maximum speed approx. 11 mph (18 km/h) ? Range approximately 5 miles (8 km) ? Weight approximately 35 kg Compiler: ? BASCOM-AVR Basic compiler 66 elektor - 7-8/2009 A delicate balance For the