[TriEmbed] Raspberry Pi GPIO

[Scott Hall]

Give me a week or so to get past Easter and the RARSfest, but I'll dig up
an article in Elektor Magazine or Circuit Cellar magazine from about a year
or more ago precisely about this.

The author shows how to fab up your own (or you can order PC boards from
him -- all open source) a circuit that totally galvanically isolates GPIO
from the R-Pi and external devices.  It contains its own power management,
is 5V compatible, and uses optoisolators.  He also shows how to
specifically interface to a motor (and motor driver) and avoid any current
kickback even to the new circuit.

The motivation for the author at the time was that the original R-Pi's did
not have much GPIO (no analog at all), that what was there was 3.3V
interface only, and that the current sourcing and sinking capability was
minimal.  And that the Gertboard Motor Controller (Gertboard Addon Motor
Power Control
<http://www.newark.com/gertboard/gertbot/add-on-board-motor-power-control/dp/93X7452>)
was both overkill in some respects, and not sufficient for some general I/O
projects in other respects.

P.S.  The open-source circuit from the article might also gleam you some
insight as to how to modify your own circuit.

- sgh

On Mon, Mar 30, 2015 at 2:06 PM, Grawburg <grawburg at myglnc.com> wrote:
> I will never attach anything that even looks or smells like it could send
current back to the RPi by connecting directly to the GPIO. I just crapped
out a Pi while working with a stepper motor, and I'm not really sure how.
I was trying to set up a transistor to switch the power on/off to the
control board (the Enable option still allows current to the motor) and
something happened that fried the Pi.
>
> If I can't fully isolate the Pi with a logic level shifter or I/O port
expander I don't think I'll try to hook up a project. And I'm sure not
going to use a transistor without a shifter.
>
>
> Brian Grawburg
>

-- 
Scott G. Hall
Raleigh, NC, USA
scottghall1 at gmail.com
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