DC Motor Control

Hello Guys
I am going to work on a new project.In this there is a 24V-DC Motor whose shaft is joined to a roller (for fabric rolling purposes). The fabric comes from the machine and roller rolls the fabric on it. As the fabric becomes loose between the machine and the roller the motor automatically runs and rolls the loose fabric on it and the cycle goes on.So i am not able to understand wether the motor is running through PWM or as the fabric becomes loose, the load on the motor decreases and it sense the current then turns the motor ON.So please guys need your help on it.

I’m not sure from your Post if you are wondering how a specific existing machine works or whether you are just thinking out loud trying to find a solution without any example to copy.

If you imagine a motor being fed with a fixed voltage (the average of the PWM pulses) then if the load is lower the motor will naturally speed up even though the motor current will reduce.

It doesn’t seem to me that that is sufficient for your project as you you have described it.

If it was my problem I think I would have a small jockey pulley running on the fabric and swinging on a lever arm. If the fabric tension reduces the sag will allow the lever to turn and trigger a micro-switch.


Robin;s answer has to the correct one. You didn't mention the diameter of the roll of fabric is continuously increasing, so if it was powered by PWM, that would also have to slow down as the diameter increased. Since you didn't mention a sensor for diameter, PWM is out.