Re: Does this pot exist?
- From: "Chris" <cfoley1064@xxxxxxxxx>
- Date: 10 May 2005 13:02:47 -0700
steamer wrote:
> --Howdy! I've been fiddling around with using a pot to position a
> "servo". I'm using the teeny weeny one from Parallax that needs to be
> turned with a screwdriver. The application is to drive one of those
> surplus windshield wiper motors; I'm using the PWM output to send
signals
> to a Victor motor controller and this is working very well.
> --The trouble is determining, with certainty, that the motor is in
> "neutral", so to speak. What I'm trying to do is use the motor as a
winch
> to move a small load up and down on an art car I'm building. The
winch
> will position the load one way when the vehicle is in motion and in
> another when it's parked. Although it's tempting to use a DPDT
switch, I'd
> prefer to control the rate of the load's position change with a big,
easy
> to grasp knob on a pot that could be located a few feet from the
Stamp.
> What's needed is a tactile feedback of some kind so that I know when
the
> motor is in "neutral", so that the motor isn't creeping. Text and
photos
> of project to date at: www.nmpproducts.com/artcar.htm.
> --TIA,
>
> --
> "Steamboat Ed" Haas : The other night I
> Hacking the Trailing Edge! : dreamed about wasabi...
> http://www.nmpproducts.com/intro.htm
> ---Decks a-wash in a sea of words---
Lookin' good, Ed. The model sitting in the cart in Fig. 2 is very
complimentary to your project -- easy on the eyes, and a definite plus
for the Art Cart team.
Have you considered using a "rocker pot" joystick? You can easily
program in a big enough dead zone for any variability in supply voltage
and pot manufacturing. This will definitely give you a "neutral"
position with feedback -- you just let go of the joystick or let it
spring back to its center position, and the motor stops. You would be
using the pot to determine motor speed and direction rather than
absolute position. You also might just use a couple of microswitches
on the winch to determine end of travel positions (this prevents winch
overtravel and/or overloading the motor). If you were interested in
saving a few clams (and possibly provide some flair of a commercial
sort to your project) you might want to look at some old joysticks (you
can feel if they're just switches by the "click" on end of travel --
stay away from those), and only use the X- or Y-axis (depending on
whether it's going up/down or side-to-side). Many of the older ones
were made to be rugged, have a good plastic/rubber boot over the stick,
and might withstand an onslaught of sand pretty well.
Good luck
Chris
.
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