pwm in stepper

[kumar_prashu]

Hello Everybudy
can anyone tell me how to stop the stepper motor running at full steps/secs (full speed). I know that it operates on pulses but i have to put heavy load on the motor shaft so because of pulling action of load the motor may slip from the commanded position. My question is Can I apply the Pwm principle as applicable to the DC motors to completely stop the motor at its position.
Also i want to know is that can motor be made to able holding more torque than the "Rated Holding Torque".

[ante]

Kumar,

You must use a motor rated for the load in your application then you can stop it just by stopping the pulses. PWM is used for other kinds of motors. If you exceed the holding torque by applying more current you will damage the motor in a very short time. It is possible to use some kind of mechanical brake to hold the shaft but this will complicate the construction.

[MP]

Kumar,
Your stepper should always have the same pulse width on the pulses sent to it.
What circuit are you using to run this stepper? There is a delay in between each of the motor pulses. You add to the delay time in between the steps to slow the motor down. It is hard to explain how without knowing the circuit used.

MP

[surajbarkale]

The effective voltage generated by a PWM is directly proportional to the Duty Cycle. The relation is -
Ton * Vpeak
Veff = ----------------------
Ton + Toff

The DC motor can be controlled by using this voltage. However this is not the case with stepper motor. If you need more torque, you should put more current into the motor (without burning it ;)).