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This board and CPU is no longer available for purchase Features:
This board was designed to be as small as possible. The upper surface is a complete ground plane which also serves as the heat sink for the voltage regulator and the TI 754410 motor driver chips. Although each channel is capable of 1.1 amps the practical limit will depend upon the total heat dissipation of the board. With a cheap Tamiya dual motor gearbox, one R/C receiver and a servo the board became warm to the touch when loading down the motors and actuating the servo. If the board becomes hot it would be easy to super-glue additional heat sink material to the top of the motor driver chips. Assembly Guide for the board (500k PDF) The Atmel AVR micro-controller is In System Programmable; look in my tools page to find examples of how to build your own programmer (it is really simple). I used an SMT voltage regulator which was interesting to solder in place. Fortunately holding the board up to the light verified I had no solder bridges. The R/C pulse is measured in 10 us steps for a range of +/- 50 over the 1.0 ms range of control. The PWM output is +/- 32, which means that full power is obtained at +/- 320 us from the center of the R/C range, or a total of .64ms of control range. It turns out that a typical R/C receiver (Hitec) has just about this much range. The additional +/-160 us is used by the trim pots. If having greater range of PWM control is important, it would be easy to modify the software to have +/- 50 levels of PWM, then, the entire 1.0 ms control range could be used. For that matter, any control pulse range (within limits) could be used. Here is a .zip file with the schematic and software. The software was written for the atmel at92s1200 which is no longer being made, but should work on any small AVR with minimal or no changes. The software is written using the gnu avr-gcc compiler v3.0 which is quite old as of 2007. Some editing may be needed to compile the software with the latest versions. All Barello.net designs are available for personal non-profit use for a licensing fee of $0.00.
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