Proper sensor for accurate positioning...

Hello everyone...

i need some help for my project. actually i made up automatic link changer system.

now my problem is...

in my project i used stepper motor for accurate sliding movement. so for reach and stop at some fixed position is required. for that i have used TCRT5000 (REFLECTIVE OPTICAL SENSOR) datasheet of that can be download from here

https://tinyurl.com/lxpn4gb

problem with this sensor is its not giving accurate position all the time. in my case aluminum surface as a reflective surface so i think due to oxidation process surface property will change with time and due to that i can't obtain accurate position. so i stick mirror at reflective surface but due to that also i can't obtain accurate position.

so i cant understand what is actually going on...?

please suggest me other method of accurate positioning(without any touching physically like limit switch).

Quite simply, this kind of sensor isn't suited for accurate position sensing.

Thank you for your reply...

can you suggest me right sensor or other thing which i can use...?

and why this sensor is not suited for this application...?

You didn't specify range and intended resolution.

Reflected light intensity can only give a very rough distance estimation

If your stepper motor moves the "thing" along, just count the number of steps. Use a micro switch to calibrate on full withdrawal (sets counter to zero).
Frank
P.S. Real machines use either an acme thread drive or a ball screw to push/pull a nut along which drives the moveable thing. So the stepper motor just rotates the thread and the number of steps is counted, resolution of better then .0001 of an inch is easily achieveable - depending on thread and nut.