Journal CW23 - bjornburton/champbot GitHub Wiki
Geared motors are a necessity to match the low speed, high thrust we will be running, but geared or belted RC motors are expensive! The answer is three surplus B&D 12 V drills for main motors; one is a spare. These are way cheaper at only $13 each.
We now have a remote. One key aspect of a diving machine's RC is the ability to receive signals under water. High freq. units in the upper MHz and GHz can't penetrate water well so we have an old 27 MHz unit. They say 40 MHz will do too. This is a nice used digital unit only costing $20.
Saturday we put the receiver on the scope and found the signal was just as expected, a 20 ms period with 1 to 2 ms pulses. That range includes the full trim so I will need to keep in mind that the stick only covers +/- 0.4 ms.
We are going to convert the two PWC signals (throttle and turn) to two PWM signals (port and starboard) in firmware. The $5 Trinket (ATtiny85) processor doesn't have the pins or resources to take 2 PWC, do math to resolve the radius, and generate 2 PWM with direction control outputs. So it has been replaced with a $10 Pro Trinket (ATmega328p). I have half a plan for the code. Those signals will drive the H-Bridge. The H-Bridge will be modulate the 24 VDC to whatever we need to the motors (0 to +/-12 VDC).
We still need to encase the motors to create the water-tight drive units and mount them to the carrier assembly.