Strangely I think it might Strangely I think it might work. The motors will work more slowly than normal, since they are sharing in some cases. Might be enough were some motors stop since the other is having less resistance, taking more current.
The bold columns are new. I also included the electrical states for four pins on the picaxe (28x1) that correspond with A1-B2.
The real question for me is how the resistances in the motors compare to each other. And if it matters at all. Consider the fourth line in the table.
cmd A
cmd B
4 = A1
5 = A2
6 = B1
7 = B2
A1 - B1
A2 - B2
forward
halt
sink
source
sink
sink
center
rightmost
Motor A will run forwards because lead A1 is sinking current wich is sourced by lead A2. The GM10 connected to A1-B1 sees two sinking leads and therefor will not get any voltage or current. The other GM10 (A2-B2) sees lead A2 sourcing and the other lead, B2 sinking. But lead A2 is now sourcing current for two motors. Which motor shall receive the brunt of it?
If Motor A (unspecified type) draws all the current because it is some heavy duty, no resistance to speak of, kinda supermotor, the current will choose that path. The GM10 will not move.
If the situation is the other way around, the GM10 will draw all the juice and Motor A will remain still.
And even if all motors are nicely balanced (say they are all the same make/model/type/age), you would see some differences under varying motor loads. A stalling motor would draw away all current from other motor(s) that happen to be connected in parallel at that moment.
Still, this would be an awesome hack. Maybe a diode or two would make it work nicely. Even if it would reduce the number of permutations in the logic table. Or would it?
To stay on the cautious side, youd could breadboard the whole cricuit, send pwm signals to the L293 inputs, measure current flowing throught V+ into the chip, maybe even put in a fuse at say 1 or 2 A.
Program your Picaxe to give off a modest mark/space rastio at first, slowy crank it up while cycling through the permutations in the table.
PWM not on the projectboard I may be mistaken, but I believe it is not possible to wire the picaxe projectboard to do PWM through the L293D. That’s why I suggest you put the L293 in a breadboard. And then connect all the other thingeys.
What if you added relays or What if you added relays or additional external transistors so that each motor had its own current source? Now you would get the same control, but the motors don’t share current.
