[PD] PD, xxxduino and adafruitmotor shield

Derek Holzer derek at umatic.nl
Sun Feb 21 13:54:38 CET 2010

All you need to drive a DC motor is simply some kind of transistor. The 
Arduino cannot provide enough current, that is all. With stepper motors, 
it's a bit more complicated since there is a forward and a reverse 
pulse. Also, if you want to be able to change the direction of the DC 
motor, then you will need to use some sort of H-Bridge IC to switch the 
direction of the DC current. IIRC, the H-Bridge simply take High or Low 
to one pin to switch the current from positive-flowing to 
negative-flowing. If you only want one direction for your stepper, you 
could try just sending PWM via a transistor to one leg of the stepper 
and see what happens ;-)

I'm sure others have less Neanderthal suggestions, but these could get 
your started.


JNM wrote:
> Salut
> We are in Dakar, Sénégal, for the second PD/XXXduino workshop in west 
> Africa where we prototype a suitcase for the pedagogy of interactive 
> art.(( http://www.craslab.org/valise (draft, english soon)))
> We try to find a solution to control the stepper motor and dc motor with 
> PD standard firmata 2.1 with the adafruitmotorshield. Servomotors are 
> easy to pilot from PD, but steppers and DC motor are piloted by a chip.
> The docs says (http://www.ladyada.net/make/mshield/faq.html):
>  "The DC/Stepper motors are NOT connected to the Arduino directly. They 
> are connected to the 74HC595 latch which is spoken to by the Arduino. 
> You CANNOT talk directly to the motors, you MUST use the motor shield 
> library"
> Does anyone in the list has found a hack to talk to this chip from PD to 
> pilot the steppers and DC motors ?
> Thanks
> JNM, Jérôme Abel, and 17 Senegalese and Malian students
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::: derek holzer ::: http://macumbista.net :::
---Oblique Strategy # 100:
"It is quite possible"

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