>  Joan,
>
>  I know that using the stepper motor is easier to control the its
>  motion, but
>  I happen to have the DC motor and that's what I have to work
>  with.  I have
>  some stepper motor but they run on 12V.  They are quite heavy
>  and it is to
>  large for my tiny robot.  I will use them on my next project.
>

I recently purchased 4 stepper motors from Jameco. Price : 5.95$ (1.8 deg)
and 4.95$ (7.5 deg) per unit. I don't think that cost could be relevant in
this case. But if what you want to do is to control a DC motor ...
You should think that it is very probable that you need a gearbox
(to reduce the speed of motors to an appropriate value for moving
a given joint) and then the total cost you can bet that will be high :-(


>  Regarding your project:  Why don't you just use ONE 16F877 to do all that
>  instead of ONE 16F84 do motor control and ANOTHER one to do the
>  interfacing?

Good suggestion/question. The fact is that I do not have any 16F877 and I
have 4 16F84s. Moreover I do not like 40 pins ICs (small is beautiful) but
I will probably port my programs to a 16F876 (28 pins is not too
much), control the two motors from this PIC and use its UART to
communicate with a host. With this CPU I will have many I/O free pins
for other purposes.

The 16F84 approach has also the advantage of being based on a "distributed"
approach, unloading the main CPU of awkward tasks as motor control, an idea
which I like a lot !

Best regards

Joan

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