StarWreck's Journal: Automated RC Car

So far the RC Car is coming along nicely. Andre and I finished writing the assembly for the motorolla chip so when you pulse port A1 low it turns right and when you pulse port A2 low it turns left. The wiring job we did was pretty shoddy but it was only for basic testing, when we are ready for open road testing we'll be sure to put it together a little bit better. The servos for the steering, shifting, and throttle are all using pulse-width modulation, all with only 1ms duty cycle difference between the maximum and minimum values. Luckily, pulse-width modulation lets you use any frequency you want as long as the period is long enough for you to squeeze in adequate duty cycles. The original radio receiver used 50Hz singals (20ms period) and we're using closer to 300Hz (if I remember right less than 4ms period). We could only get it down to that frequency because the maximum scalar divisor for the output is 128... so to get a lower output frequency we would have to lower the speed of the processor. The motorolla chip can go anywhere from less than 1MHz to 40MHz, if we get it much lower than 18MHz the signal starts to freak out... like the board is having trouble generating it. We're just lucky that the frequency we got it down to works perfectly with all the servos.

Next up, sending GPS data over a GPRS cellular modem to an SQL database via the internet and then pulling up the data with a GUI on an internet connected computer.