i am using uln2004 as a driver for stepper motor control. Using this i have given about 30v dc. and pulses given from microcontroller as program written by me. at that time the problem is that, when i increased speed of motor by decreasing pulses duration by controller, motor loosing its torque. i know that speed and torque are inversely proportional. but still i have daught about driver that i have used or pulses pattern that i have applied by controller.

please send me help if anybody can.

thanking u,
sumit dave

 

The motor torque is proportional to its current. You can know the stepper motor coiling has some inductance. When you use a plain control, without switching control, the current increase as a ramp, where di/dt is proportional to applied Voltage and inverselly to the inductance. Also the current must be ideally zero before the next current pulse, to not reduce torque. This way, you must take care to use a resistor in paralel to each motor coil in order to maximize the di/dt between each command.