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[SOLVED] Bi-Polar Stepper Motor Direction Control L297

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Junior Member level 3
Jun 23, 2013
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Hello Sir..
I am Using L297 and L298 Stepper Drive with Bi-polar Stepper Drive.
I just gave the 1 to the direction pin but the motor changes its direction unconditionally. Some time it goes clockwise direction and sometime it goes anticlockwise direction. I just feeling helpless nothing comes in my mind. :(

I check the circuit many times it seems all okay. even I changed the L297 IC But still Problem remain continue.
I Develop the code by changing the ramp speed in clock form low to high too and drive the motor without Load but still the problem remain continue.

Im using Bi-Polar Stepper Motor and running load is not so heavy. So run it safer and cooler Im running it below 1A.
The circuit parameters are

Vref pin no 15= 0.45 V
Current sensing resistance = 0.5 ohm ( 1 ohm 2 watt , 2 resistance )
Control Pin no 11= 1
Osc pin no 16= Coupled with 22k and 3.3 nF capacitor
Enable and Reset connected together to the output of 74HCT14N

Same way Direction and Clock pins are also connected with 74HCT14N. I also attached pull up resistance to the input side of 74hct which is connected to the output of the optocoupler el817 for the isolation to the microcontroller.

Im great thankfull to you


where does your clock come from? (If it is a switch then it may bounce, and this causing problems)

What is your clock speed.

Is it two coil bipolar stepper? maybe you need to change the polarity of one coil..

Hope this helps

Perform single steps, either in half- or full-step mode. Verify the individual A-D and motor phase signals.
@ Klaus St

Sir , Im giving clock around 1khz from pic microcontroller which is connected with opto then opto is with 74hct and further L297

It is a Bi -polar motor i changed the polarity but problem stills.


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Sir , Im running the motor in full mode by giving ground to the pin no of L297
the polarities are identified.

Im using 20 Mhz clock for pic18f85j11

Starting a step motor with 1 kHz rate is likely to fail. Use acceleration/deceleration ramps.

As already suggested, test with single steps to see if the phase current sequence feed to the motor is basically correct.

There may be a trivial wiring problem as well.

Sir i just want to rotate the motor for two or three steps only. Is this acceleration and deceleration ramps are necessary .? can you tell me what is the value for the ramps i have to select for it..?

the wiring is seems too be alright even i can posted the schematic if you want to see

thanks in advance :)

You can operate the motor at a constant low rate, maximal at the start/stop frequency.
I found the error it is in the pcb track which is internally cracked and shorted to neighbour capacitor..

thank you sir for help :)

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