I have been investigating stepper motor control for the last couple of months. I've been looking at lots of different solutions and right now I think that using the l297 chip is probably the best balance of features, price and useability.
First, here is what I have found about this chip that might be useful for others interested in stepper control.....
some useful docs....
STmicroelectronics l297 notes... http://www.st.com/stonline/products/literature/an/1734.pdf
STmicroelectronics l297 datasheet... http://www.st.com/stonline/products/literature/ds/1334.pdf
my understanding and brief summary....
The l297 can create the control signals for bipolar, unipolar and variable reluctance stepper motors.
In all cases, you can digitally select full stepping, half stepping and wave stepping modes.
The motor takes one step for each pulse sent from the arduino board. Direction is decided by taking a pin HIGH or LOW.
The l297 has another important feature. It includes two PWM chopper circuits to regulate the current in the motor windings. ??? what does that mean?? well, i found this page...
It's a nice and easy going explanation on stepper motors in general and it includes this bit on chopper control of steppers...
'To increase the torque at higher speeds, stepper motors are driven at several times their voltage rating. A designer might use 5 volt steppers and then run them at 12 or 14 volts. To avoid destroying the motors, the current through the windings is monitored and power is cut off when the current reaches a critical level. When it falls back down, the power is reapplied. This technique is known as "chopper drive" and it allows the motor to increase its top speed.'
So that kinda explains the functions of the chip.
I don't yet understand how to implement the chopper drive properly. Also, I have not yet tried any circuits!! but from reading and researching, I believe the following to be true....
If you don't want the chopper drive......
If you want to control a bipolar stepper, you can use the l297 with the l293.
If you want to control a unipolar stepper, you can use the l297 with the L702B or any darlington transistor array. I'm not sure if you would need a buffer.
If you do want the chopper drive......
If you want to control a bipolar stepper, you can use the l297 with the l298.
If you want to control a unipolar stepper, you can use the l297 with the ULN2075B
In all cases, you will need a few extra components to complete the circuit.
So, now I have some questions for you!
Does anybody have any experience using the chip?? or any good circuit designs for using it??
The chip has an input Vref. This is used for giving the reference voltage for controlling the Chopper circuit. Can anybody explain how to connect up this pin??
I would like to compile circuit designs using the l297 to control bipolar and unipolar steppers, with and without chopper control. I want to find the easiest possible solution for each circuit. ;) Please post if you already have a good solution for one of these circuits.
I will now start trying some circuits, i'll post when I get one working.
PS. maybe I made some mistakes above. Please correct me! I'm just a beginner still!