Stepper motor control

quium · Joined: 19 Jan 2007 Posts: 27

Hi
I am controlling the stepper motor(Bipolar 12V). I am using the chip UDN2916B for driving the stepper motor. I was wondering how I am going to set the pulse from PIC to drive the above IC. I mean what should be the pulse on time to turn the pic for five steps apon the information obtained from analog input to the PIC.

Any ideas and suggestions?????
Kind Regards
Quium

Ttelmah · Guest

If you want to send a pulse to move the motor, you are going to need a different chip. The A3977 supports step/direction control like this. The UDN2916, requires you to control the lines feeding the phases yourself, and 'step' through the required patterns on these pins to move the motor. the minimum number of connections, is two, using two external inverters, with one signal feeding the phase pin, with the invert of this signal fed to the other phase pin, and a second feeding the two inputs on one bridge connected together, and this signal inverted feeding the inputs on the other bridge. Then stepping through these signals, in the pattern:
0 0
1 1
1 0
0 1

Gives single step operation. going beyond this needs more pin connections (four for 1/4 stepping).
You need to put out the required pattern on the pins, then wait, and change to the next pattern. The delay time needed, will depend on how high the drive voltage you are using is, relative to the staticrated voltage for the motor (for example, on 48v industrial systems, it is common to use 1.8, or 3.6v motors to get fast movement), and the inductance of the motor coils.

Best Wishes

quium · Joined: 19 Jan 2007 Posts: 27

If I am having 1.8 degree step and I want to rotate it by five steps so what should be the delay in between any two pulses and I am using SN754410 to drive my motor

Ttelmah · Guest

You need an enormous amount more , including the inertia of the system. Inductance of the motor coil. DC resistance in the motor and driver. Voltage being used. etc. etc..
However typically speeds around perhaps 200Hz, are commonly used on small motors, when not being driven with more sophisticated controllers.

Best Wishes