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Thread: K8004 problem with PWM controller noise

  1. 15th July 2009 12:01 PM #1
    smilem
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    Default K8004 problem with PWM controller noise

    I have a problem with PWM controller.

    I use velleman K8004 PWM controller card to drive DC motor. I have a problem that when I choose low frequency (by rotating resistor) the motor vibrates, when I set high frequency (5000Hz) I hear high pitch whine noise.

    Is it possible to make the noise inaudible?

    Manual:

    http://www.velleman.be/downloads/0/i...k8004_rev3.pdf
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  2. 15th July 2009 12:20 PM #2
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    You need to change the components in the oscillator section...C3 and R3....try making C3 around 22nf

    Making the frequency around 18khz will make it inaudible
    Last edited by Chippie; 15th July 2009 at 12:22 PM.
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  3. 15th July 2009 12:52 PM #3
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    So I should change C3 form 100nF to 22nF. And the resistor change to what?
    Won't it bother my cat?
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  4. 15th July 2009 01:06 PM #4
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    Quote Originally Posted by smilem View Post
    So I should change C3 from 100nF to 22nF. And the resistor change to what?
    Won't it bother my cat?
    Make one change at a time....Change the capacitor first and see if that makes it better....Leave the resistor as is for now...

    Put the cat outside...
    Last edited by Chippie; 15th July 2009 at 01:06 PM.
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  5. 15th July 2009 03:39 PM #5
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    Quote Originally Posted by Chippie View Post
    Make one change at a time....Change the capacitor first and see if that makes it better....Leave the resistor as is for now...

    Put the cat outside...
    Well, changing the capacitor improves it but I still can hear it a bit myself, don't know about the cat

    What lower value I can try because the higher the frequency the lower the torque of the motor, I mean it has less power right?
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  6. 15th July 2009 03:45 PM #6
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    You'll have to experiment unitl you find a cap that doesnt affect your hearing.....or else change the value of the 2k2 resistor by half...The effect of that would be to reduce the charging time for the cap so the RC time constant is shorter and the frequency should go up...

    You could always wear earmuffs....
    Last edited by Chippie; 15th July 2009 at 03:46 PM.
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  7. 15th July 2009 03:54 PM #7
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    Thanks, is it normal that the FET is dead cold, and SG IC chip is a bit warm, doesn't it require a heatsink?
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  8. 15th July 2009 04:16 PM #8
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    Quote Originally Posted by smilem View Post
    Thanks, is it normal that the FET is dead cold, and SG IC chip is a bit warm, doesn't it require a heatsink?
    The fet may warm up depending on the load current it is switching...

    as for the chip....shouldnt get too hot...You could add a small dip heatsink if you wanted...
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  9. 15th July 2009 08:12 PM #9
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    thanks for help
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  10. 15th July 2009 08:25 PM #10
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    To get stable motor speed do I need to use LM338 or can I just use A diode bridge with transformer as power source?

    Also isn't is possible to calculate the required frequency?
    Last edited by smilem; 15th July 2009 at 08:30 PM.
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  11. 16th July 2009 12:49 AM #11
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    18kHz is easily heard by young people who are not deaf.
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  12. 18th July 2009 11:05 AM #12
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    So do I need to feed this circuit from LM or it will work fine simply by using diode bridge with capacitor?
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  13. 18th July 2009 01:59 PM #13
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    Have a look at figures a,b, and c in the manual
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  14. 18th July 2009 10:46 PM #14
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    Quote Originally Posted by Chippie View Post
    Have a look at figures a,b, and c in the manual
    The manual lists: 8-35VDC unregulated and figure A shows a simple diode bridge with capacitor as power source. But since I use configuration C that shows internal reference voltage used as control coltage. This means if my DC current is unstabilized by LM338 the motor speed will change as voltage changes right?

    I will use slowest motor rotation mode possible so that means that LM338 is a must no?
    Last edited by smilem; 18th July 2009 at 10:46 PM.
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  15. 19th July 2009 08:25 AM #15
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    If you use figure C, just connect a potentiometer value 1k as per the drawing, using Vref,
    connect your dc power supply as shown, the motor speed is then controlled by the new 1k pot....
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