knowing position with dc motor / stepper mottor

[pw444]

Hya,

any hint in how to calculate the position of a DC motor or stepper motor? beginning at 0 finnish at 100..

Thx for any advice.

BR

[TD-er]

For a DC motor it is next to impossible to determine its position, unless you use some sensor connected to the motor axis.
The rotational speed of a DC motor depends on voltage/current and torque needed to rotate.

A stepper motor can be "tracked" if you know the begin position and number of steps made. (assuming the stepper motor did not miss a step)

When controlling a curtain, you could position an end stop switch so you know where to 'reset' the position.
Or using a potentiometer coupled to the rotation of the driving motor.
You can either using some gears to reduce the number of rotations, or use a multi-turn potentiometer.
Then you know the absolute position and only need to calibrate the start/end position.