New controller board
November 29, 2010
Hello, it's been a really long time, since I last posted something on LMR, but now I've made a new controller for my robot and I thought I'd blog about it.
The controller features
- 2 Atmel Tiny26 chips. 1 is for motor control and reading of encoders and 1 is for overall control and interfacing with other modules that will appear along the way - a line sensor module is up next and is also based on Tiny26.
- 2 2.5A H-bridges interfaced using a L239D chip. The bridges are transparent in the sense that you could plug 2 motors directly to the L293D without changing your code. The bridges can be made to handle 5A each by replacing 8 1k ohms resistors with 470 ohms resistors, but the motors I use have a stall current of less than 2.5A. I decided not to buy driver chips like for example L298, since I already had a number of L293D chips and a lot of transistors available.
- Two-wire-interface (I2C) ready. This is how the overall controller will talk to the motor controller and any modules that are plugged in.
- MAX232 level-shifter for connecting a PC via serial cable (DB9 form).
The H-bridges use darlington transistors (TIP125 and TIP120) so they drop around 2.8V in the transistors, but this is not a problem for the motors and battery packs I use.
By the way I still need to add a few wire connections since this is a single-sided board and it was not possible to route all traces in one layer, so the board will look a bit messier when it's done :-).