i2c
I2C-based H-bridge controller with PWM
ian – Tue, 2006 – 07 – 04 10:42
During development of my Sumo robot, I ran into some problems around controlling the H-bridges:
- If you're going to use PWM, the PWM signals on each input of the H-bridge need to be synchronised (phase-coherent), and there's no such guarantee when using an AVR to drive them. If they're not phase-coherent, the H-bridge will get hot and not drive the motor properly.
- I wanted to use braking on the H-bridge, which means I need independent control of all four H-bridge inputs. The ATMega32 that I was using has four PWM channels - more than most microcontrollers - but still only enough to run a single H-bridge.
Controller hardware
ian – Tue, 2006 – 05 – 16 15:07
The controller is based around a PIC16F84A. It has 13 I/O's, a timer, and not a lot else. To program it I'm using JDM programmer hardware, ICProg software, and the excellent Microchip MPLAB suite to compile and simulate the software.
H-bridge controller schematic
The controller board, attached to the main control board: Note the I2C cable running between them, which provides the main control board with power.
