Re: 12Vdc Solenoid Driver Circuit requ'd.

From: Joerg (notthisjoergsch_at_removethispacbell.net)
Date: 10/06/04 

Date: Wed, 06 Oct 2004 16:38:47 GMT

Hi Frithiof, Hi Pete,

>That's really hard to do without all sorts of complexity - the
>force/displacement characteristics is very nonlinear and position control
>would be hard.
>
>
That's right, it is hard. There are ways to do that though. For example,
you could send an increasing current through it and measure how much
current you need for each millimeter. Or tenths of millimeters if you
need to be more precise. Then look at the curve to see if it can be
mimicked with analog circuitry. If it can't, you could then store the
response digitally in a ROM or flash chip. When the button is pressed a
counter would clock out that memory into a DAC which sets the current
corresponding to each memory position. Plus a powerful current driver,
of course.

If the ROM method costs too much in hardware there is the analog way:
Set up a diodes-resistors ladder which approximates the desired slope.
It can be temp compensated in case that is an issue.

It would not be very accurate but maybe it is enough for your appliccation.

Regards, Joerg

http://www.analogconsultants.com