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Date:	Fri, 24 Apr 2015 01:21:45 +0200
From:	Bernd Walter <ticso AT cicely7 DOT cicely DOT de>
To:	geda-user AT delorie DOT com
Subject:	Re: [geda-user] Stepper driver issues
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On Thu, Apr 23, 2015 at 06:43:49PM -0400, Rob Butts wrote:
> My application: I'm a quadriplegic and I want to get out in a kayak with my
> kids.  I bought a small 12V trolling motor.  I raped the trolling motor
> where I'm just using the shaft and propeller.  I have two joystick (one to
> be mounted on each side of me).  I designed a controller board where one
> joystick (only operable in the x-axis) shifts the trolling motor up through
> the 5 forward gears or back through the 3 reverse gears.  This part works
> great.
>
> I'm using the stepper to turn the shaft of the trolling motor.  The
> trolling motor shaft turns very easy by hand and is about 1 inch in
> diameter.  My machinist mounted a 100 tooth gear to the trolling motor
> shaft.  He then mounted the stepper with a 48 tooth gear on the trolling
> motor (that's why I'm locked into the nema 23 size and footprint).
> 
> I only want the trolling motor to turn 180 degrees maximum.  I don't need
> the stepper to run fast and since the torque is low (I went with the nema
> 23 just to be safe) the torque does not need to be high.  I have a 12V
> marine battery that will be mounted in the kayak so my stepper voltage
> supply will be 12V.
> ???

Not sure why you need that stepper.

> From reading your reply I think I should be ok using the DRV8825.

You should try, but I think it will be Ok.
Don't forget to setup the current on that board.
With your use case I think you should go much into microstepping and just
use half steps.

> What really erks me is that the stepper was working at one point with the
> On Semiconductor STK682 driver and the circuit I designed.  I just don't
> know what changed since that time.  It's been a while since then and I
> spent six months in the hospital soon after that.

Was the trolling used in the meantime?
If it drives the stepper shaft the stepper can induce current into the
circuit.
Some drivers don't like this.


-- 
B.Walter <bernd AT bwct DOT de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.

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