>
>
> Ok, this morning I set up the bot so that I could measure the
voltage to the
> motors. When I set the motor speed at 127, the voltage across the
motor pins
> was 8.7, which is pretty reasonable. When I changed the motor speed
to 120,
> the voltage across the pins was just below 1. It held steady around
0.6V.
> That's certainly a bit low for those motors.
>
> The second time I tested this, I got the same voltage at 127, the
same at
> 120, about 0.4V at 100, then I tried 126. The voltage first showed
about 2V,
> at which the wheels bumped forward some, but the voltage dropped rapidly
> down to 0.8V.
>
> That's not a very smooth curve. Can you point me towards a solution?
>
What did you get at the OOPic pin?
This sounds like the kind of thing that happens when the motor power
supply ground wire is not connected to the logic ground.
As discussed in another thread a couple of days ago, you need to
create a STAR ground at the motor controller chip. The logic ground
and the motor ground tie individually to that point. The objective is
to keep motor ground current off of the logic ground wire.
There is a wiring diagram for the L293D (a predecessor to the 754410)
at the bottom of the oDCMotor2 object reference.
Richard
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