AVR-Chat

John Samperi wrote:
> G'day all
> 
> For a few days Yahoo has bumped off the list it seems...
> 
> I posted the following on AVRfreaks so some of you may see this twice.
> I need to know exactly where a stepper motor is positioned at any time.
> By Googling I found some potentiometric position sensors, which I guess
> will do by feeding it into an A/D and reading back the voltage.
> 
> If there is a digital type of sensor that would give me discreet positions
> from 0-255 that would be perfect, and as some of you are geniuses on
> the subject, you may be able to point me in the right direction without having
> to wade some 1600 pages in Google.Basically the program would check where
> the motor is located, find out where it needs to be and issue the correct
> number of pulses to take it there( backward or forward), then check that
> is in fact there. This will be controlling a valve that needs to open a
> certain amount.
> 
> Regards
> 
> John Samperi


Hi John,

If the Valve can go to 0 regularly, it may be easier to home at 0 and 
count up from there (assuming that the valve and stepper have their 
shafts locked (no belt drive) and that the motor is powerful enough to 
drive the valve without slipping)

Another option is if you know you will use set positions, then maybe a 
couple of slotted opto isolators.........


or make your own disk on the shaft, home 0, have the opto on (and a 
second one that only gets light on 0) then count the pulses out as the 
valve moves....

measure the pressure out of the valve / amount in tank etc and adjust 
from that......

a pot on the valve to show the % angle open etc etc.

they are all I can think of for now ;)

Regards,

Kat.