Let's Make Robots!

low current motors for very lightweight robot design

Hi all.

Has anybody encountered any VERY small motors that can be controlled directly from an arduino without an H-Bridge, motor shield, or similar?

I think the max current on a pin is 40-50 mA (please correct me if I'm wrong)

I know some small pager motors draw that or less, but was wondering if there was something a little bigger that the robot community uses for small robot projects.

 

thanks

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The  "D" in L293D is for "diodes". It is these diodes that will help prevent the EMF feedback that everyone mentioned above.

thats all I need to hear.  L293D it is!

the D is "dual" right? (so I only need one for two motors)...correct?

You can get small motors designed for use with solar cells with a low current draw but as mentioned above, it will cost you a lot more to replace your fried controller than what it cost for a few L293D chips. Even if the back emf didn't damage your controller it is likely that the electrical noise would constantly reset your processor.

In short - never try to drive a motor directly from a controller unless the controller has a motor driver built in like the Micro Magicians do.

Mosfet, fine, but when I think "mosfet" I think T-220 case, 40 amps and a big heat sink. At 40-60mA, you could make an H-bridge (or even just a simple on/off) with tiny little SMD 2n3904's and 2n3906's (or really, whatever "general purpose" transistors are handy. I think they are maybe a penny a piece on ebay. Maybe a buck or two if you are only buying 10 or so.

no problem with using them...it was more of a "keep it simple" thing.

can I use a mosfet instead of an h bridge?  (I'm more familiar with how mosfets work)

motors, as well as any other coil based devices, produce back emf when stopped/reversed. If you don't have diodes in place you will let the magic smoke out of your microcontroller. I would, however, imagine that any small robots that use motors still use some kind of h-bridge. With an L293 only costing about $1, where is your problem with using one?