[simpits-tech] load cell amp...

[Gene Buckle]

On Mon, 6 Jul 2009, Roy Coates wrote:

> There seem to be a new breed of DC LVDT's but my understanding of the
> typical setup is that you feed an AC signal into coil A, and then read
> that signal back from coil B.  The magnet which forms the moving part of
> the device causes a phase-shift between input and output - it is this that
> gives you your position, normally presented as a voltage thanks to the
> clever black boxes you normally hang these things on.
>
Right.  My (faulty) understand was that they were a form of load cell. 
Google rapped my knuckles about that. :)

> Anyone know anything about the uber-sweet new hall-effect devices that can
> be used as a straight swap for pots?
>

They're not that new.  Hall effect based replacements for pots have been 
around quite a while.  In Mike Powell's new book, he's got a project that 
uses a device called "A1301 hall sensor".  It's a three wire part, very 
similar in size to a 2N2222 transistor.  He uses it as a 0..5V voltage 
divider.  When he first posted info about it, I bought 5 of them from 
DigiKey and they were less than a buck each.  If you head over to his site 
(http://www.mikesflightdeck.com/) and scroll down a bit (or search for 
"A1301" you can see how he's using it.  If you scroll to the bottom of the 
page and click on the "previous rants" link you will find a little more 
info on it under "Position Sensors Chapter Revisions" about the middle of 
the page.

As far as I can tell, you can use these devices as a direct replacement 
for a 5v based voltage dividing pot.

I know that there has been a lot of success in replacing the jitter-prone 
pots in the Cougar stick with a couple of hall effect devices.  I think 
there is someone selling a refit kit for something like $60, but this was 
some time ago.

g.

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