Let's Make Robots!

Servo Controller: A thought experiment

First up, this is at best a work in progress, at worst only ramblings.

I have seen members asking about driving more than a handful of servos and getting the response that they can either use an arduino and its assorted libraries to drive 12+ servos, correction, up to 20 servos or get a dedicated controller board that seems to cost in the area of 50USD. I spent an hour or so knocking up an idea. I want to lay out my thoughts and see where it could or should go.

 

Saves time and avoids many related coding mistakes.
I have been learning about programming for years. More recently, I have been taught that magic numbers or constants should not be hard coded deep in your program. … Read more

Shared microcontroller pin

A quick search here did not give me any relevant hits. So, I was hoping to ask the electronic gurus here if my plan/idea will work.

My thinking is that the photoresistor will be able to be read by the analog input and, because of the diode, the LED will not light unless the microcontroller is set as an output and set LOW.

EDIT:

Based on the input so far, I have redrawn the circuit. I hope the collective doesn't mind helping me get circuits straight.

Charlieplexing for sensors, is it possible?

I was wondering if it would be possible to use charlieplexing as a way to select sensors. If so, what is the minimum number of pins required for charlieplexing to work?

Tank track construction ideas

I was reading Hackaday and saw a post that I thought might interest builders here.

http://www.rctankcombat.com/articles/track-systems/

One pin dual outputs

I have an inexpensive R/C car w/ the TX2/RX2 chipset. Typically, one would use a single pin per function on the RX2. Using that logic on an 8 pin PIC would leave me with 2 pins, one input and one output. After reading about the Ladybug Clone, I wondered if could get away w/ splitting the output of a single pin, one inverting and one non-inverting using a NOT gate and tri-stating the pin when I didn't want either output high.

Schematic concept

Alternate 3 pin dual motor drive?

I know enough to be dangerous to components.

I had thought about using 2 4427 MOSFET drivers and tying one input from each driver together to a single uC pin. I could then control fwd/rev with two digital pins and put a pwm signal on the shared pin. The 4427 data sheet says the input current is 10uA per pin and PIC pins are supposed to be able to source 25mA max. Is there a flaw in my thinking?

As far as a schematic, I imagine many of you have seen what David Cook has posted on his RobotRoom site.