Computing stuff tied to the physical world

Meet the DC Motor Plug

In Hardware on Nov 30, 2010 at 00:01

Here’s a new I2C plug to drive two small DC motors. The DC Motor Plug has 2 H-bridges on board, which can drive each motor in forward or reverse. An additional 4 I/O pins are available, for limit switches, quadrature encoders, whatever:

Dsc 2310

Here is a test setup with a couple of (different) geared motors, driven from a 4x AA battery pack, plus the usual AA Power Board for the JeeNode itself (these could also have been combined):

Dsc 2309

All I/O is done via I2C, using the MCP23008 expander chip (same as used on the EP, LP, and OP plugs).

Here is a sample sketch called dcmotor_demo.pde which briefly drives each of the motors in both directions:

Screen Shot 2010 11 29 at 13.02.38

One notable detail about this plug is that it uses TC4424 chips which are in fact not DC motor drivers at all but MOSFET drivers… it turns out that these are also well suited for small DC motors, and should be able to handle up to 1.5A @ 4.5..18V.

A small bipolar stepper will probably also work, but I haven’t tried that yet. This board has a jumper to select between I2C addresses 0x26 and 0x27, so two of these can be daisy-chained on a single port.

Speed control should be possible using software PWM, but not at very high rates, since the I2C bus will be the limiting factor.

One use for this in the context of home automation would be to drive small highly-geared 12V motors to adjust the position and raising/lowering blinds.


Docs added to the café and kit in the shop, as usual.

  1. Wow, this will come in handy for home automation thats for sure! I hope you will post your setup when you found a motor that works well.



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