Hi there!
I am currently building a stepper motor circuit for a small robot. The circuit consist of the L297 and SLA7024M motor driver. I have now constructed two of these and both seems to have some issues.
I intend on driving both in half step mode, but I have tried both for testing purposes. For both circuits it seems like the L297 works as it should, as I have looked at the outputs on a oscilloscope, and the sequence match what I want. I have never worked with steppers before so not sure what to expect, but I think something is wrong here.
In both cases I used a 1ohm 2.5W resistor as current sensing resistor, and used a potentiometer to limit the Vref to 0.5V. From the datasheet this sould result in a Iout of 0.5A.
Circuit 1:
The motor spins slow and steady at 50Hz, but as I increase the frequency (100-700Hz) the motor starts twitcing in the same spot. At high frequencies(>1kHz) the motor runs fine but the speed is a little higher then I need. Also as the frequency is increased the the motor randomly change direction. I use an arduino with a simple code I found online, the arduino is controling the pulse(speed), direction(cw/cww) and enable pins of the L297. The half/full is connected to the 5V bus which will set it in half step mode (it also work on full step).
Circuit 2:
This circuit really buggs me, it was working fine at one moment, but now it seems that the circuit don't supply the motor from the high voltage line. The motor rotate at 50Hz but only pulls about 0.05A. If I increase the frequency the speed goes up, but not nearly as fast as the other one. Obviously because it dosent get enough current. So I'm wondering if the IC might be destroyd? I would think it would be wierd since I have used a bench supply and never alowed more then 1.5 A. I have trippled checked all connection and they all seem fine.
Here's the links to the datasheets.
Motor: RS 440-420 5V, 0.5A Unipolar Stepper http://docs-europe.electrocomponents.com/webdocs/001c/0900766b8001c018.pdf
L297: http://www.st.com/web/en/resource/technical/document/datasheet/CD00000063.pdf
SLA7024M: http://www.futurebots.com/7024.pdf
I also have some questions regarding the datasheets.
L297:
It is stated that the minimum clock time is 0.5us, is this really the clock signal? Wouldnt that be 2MHz? The motors run at 50-2000Hz but over that the motor stops and get very warm.
Some other information
This chip is a nightmare to work with as the pin layout does not match up with standard protoboards or veroboards. My solution was to solder a piece of wire to each pin which I then soldered to the verobord.
The IC is literally two of the same circuit to drive each phase of the motor. The datasheet provides a circuit diagram on how to connect it. The changes I have made is to use a 1Ohm resistor for Rs and a potentiometer for R2. I have meassured the pins and they show a 0.5V on Vref, which should be right.
hope someone can help me!
Please let me know if I left something out.
I am currently building a stepper motor circuit for a small robot. The circuit consist of the L297 and SLA7024M motor driver. I have now constructed two of these and both seems to have some issues.
I intend on driving both in half step mode, but I have tried both for testing purposes. For both circuits it seems like the L297 works as it should, as I have looked at the outputs on a oscilloscope, and the sequence match what I want. I have never worked with steppers before so not sure what to expect, but I think something is wrong here.
In both cases I used a 1ohm 2.5W resistor as current sensing resistor, and used a potentiometer to limit the Vref to 0.5V. From the datasheet this sould result in a Iout of 0.5A.
Circuit 1:
The motor spins slow and steady at 50Hz, but as I increase the frequency (100-700Hz) the motor starts twitcing in the same spot. At high frequencies(>1kHz) the motor runs fine but the speed is a little higher then I need. Also as the frequency is increased the the motor randomly change direction. I use an arduino with a simple code I found online, the arduino is controling the pulse(speed), direction(cw/cww) and enable pins of the L297. The half/full is connected to the 5V bus which will set it in half step mode (it also work on full step).
Circuit 2:
This circuit really buggs me, it was working fine at one moment, but now it seems that the circuit don't supply the motor from the high voltage line. The motor rotate at 50Hz but only pulls about 0.05A. If I increase the frequency the speed goes up, but not nearly as fast as the other one. Obviously because it dosent get enough current. So I'm wondering if the IC might be destroyd? I would think it would be wierd since I have used a bench supply and never alowed more then 1.5 A. I have trippled checked all connection and they all seem fine.
Here's the links to the datasheets.
Motor: RS 440-420 5V, 0.5A Unipolar Stepper http://docs-europe.electrocomponents.com/webdocs/001c/0900766b8001c018.pdf
L297: http://www.st.com/web/en/resource/technical/document/datasheet/CD00000063.pdf
SLA7024M: http://www.futurebots.com/7024.pdf
I also have some questions regarding the datasheets.
L297:
It is stated that the minimum clock time is 0.5us, is this really the clock signal? Wouldnt that be 2MHz? The motors run at 50-2000Hz but over that the motor stops and get very warm.
Some other information
This chip is a nightmare to work with as the pin layout does not match up with standard protoboards or veroboards. My solution was to solder a piece of wire to each pin which I then soldered to the verobord.
The IC is literally two of the same circuit to drive each phase of the motor. The datasheet provides a circuit diagram on how to connect it. The changes I have made is to use a 1Ohm resistor for Rs and a potentiometer for R2. I have meassured the pins and they show a 0.5V on Vref, which should be right.
hope someone can help me!
Please let me know if I left something out.