Stepper Motor Driving at High speed

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samirprabhudesai

Joined: 06 Apr 2006
Posts: 4

06 Apr 2006 19:20 driving a stepper motor using l297

Hi

I have the basic circuit for driving a stepper motor using L297 and 298. I am able to drive the motor at a particular speed. But i have a machine in which they have used the same circuit and achieved a high speed that i m unable to obtain. I checked the CLK waveform of L297 for this speed. It appears that there is a single pulse when the motor runs at high speed and not a series of pulses when it is running at a lower speed. I tried to apply the same pulse by modifying my microcontroller software. But the motor jams and doesnt run. What may be the cause? How can i make it run at very high speeds ?

Regards
Samir

roy mathew

Joined: 19 Feb 2004
Posts: 27

07 Apr 2006 7:00 l297 speed

You should apply more voltage to the motor coil as speed increase. Generally a chopper driver with current limittation is used to drive stepper at high rpm . canyou post your schematic.

samirprabhudesai

Joined: 06 Apr 2006
Posts: 4

07 Apr 2006 7:56 stepper circiut high speed

Hello

Thanks for the reply. But the supply available is 24V 4A max . The schematic is the one present on page 1 of the attachment. Can u elaborte it more?
Thanks

Samir

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H_u_n_t_e_r

Joined: 24 Nov 2001
Posts: 207
Helped: 4

07 Apr 2006 9:44 l297 port schematic chinese

first of all your supply should be 40V (max 50V)
i had encountered same problem
your application circuit has missing part which its 470uF 63V capacitor..
you should use L298 datasheet http://www.st.com/stonline/products/literature/ds/1773.pdf
PAGE-->8
hope this helps

samirprabhudesai

Joined: 06 Apr 2006
Posts: 4

07 Apr 2006 19:13 driver stepper high speed

Hi

Thanks for the reply. But if you refer to my previous post then pls check that there is a difference in the pulse that is applied to the CLK pin when the motor is driven at high speed. I have trapped this pulse on the oscilloscope. I generated using the same pulse using my controller. But the motor doesnt run in this case. What may be the cause?

Samir

H_u_n_t_e_r

Joined: 24 Nov 2001
Posts: 207
Helped: 4

08 Apr 2006 10:02 speed and schematic stepper motor

i dont know what kind of clock feeding scheme but i had another problem with clock and it was;

if you feeding clock over resistor reduce resistor value to typical 470 ohm

you should give complete sch which you used in your application..
Best Regards

samirprabhudesai

Joined: 06 Apr 2006
Posts: 4

08 Apr 2006 18:03 high speed stepper

Hi Hunter

The schematic is the same as given in L297 datasheet. The values of RS1 and RS2 are 68ohms and 2W. the clock pin is directly connected to a port pin of microcontroller (I am using Texas MSP430F149 controller).
The clock applied is a PWM similar to the one shown in the datasheet. I am driving the motor in Half step mode.The waveform is on Pg no 5 in the L297 datasheet. I hae already attached it.

Hop i m clear now

Thanks in advance

Samir

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H_u_n_t_e_r

Joined: 24 Nov 2001
Posts: 207
Helped: 4

09 Apr 2006 9:19 stepper 298

no i dont mean current sense resistors..i mean, is there a resistor between ucontroller clock out and L297 clcock input? if so, this resistor should be low as 470ohm..
try with 555 oscillator instead microcontroller as clock source ..
..and pls use L298 (pg "8") datasheet instead L297