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I HAVE A BUG!!! But I dont know why. — Parallax Forums

I HAVE A BUG!!! But I dont know why.

TCTC Posts: 1,019
edited 2013-05-21 03:47 in Propeller 1
Hello all,
My 3D printer project is coming along real nice, but I have a bug and I don’t know why. I am trying to add A PWM controlled fan to it. But when I add the “start” for the PWM my display goes nuts. There are 2 pictures I have added, one is with 
PWM.start(15)
Commented out.
The other picture is when the comment is removed. Other than the display not showing what it should be everything works. I can turn on, and off the fan and adjust the speed from the host software.

Thanks for any input
TC
zip
zip
G_code.zip
15K
IMAG0032(1).jpg
1024 x 577 - 35K
IMAG0033.jpg
1024 x 577 - 41K

Comments

  • kuronekokuroneko Posts: 3,623
    edited 2013-05-19 16:46
    Does the same thing happen when the PWM object is started but the fan isn't connected?
  • TCTC Posts: 1,019
    edited 2013-05-19 16:57
    kuroneko wrote: »
    Does the same thing happen when the PWM object is started but the fan isn't connected?

    No it does not. Did not think of that. Dose that mean i have noise being injected back into the prop?
  • ElectricAyeElectricAye Posts: 4,561
    edited 2013-05-19 20:28
    TC wrote: »
    ... Dose that mean i have noise being injected back into the prop?

    I wonder if changing the frequency of your PWM might help? Perhaps you are hitting some sort of resonant frequency that is amping up the motor noise in your other circuits.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2013-05-19 21:02
    This is probably a ground bounce problem. What are you using to drive your fan, and where do the power leads for it get connected to your circuit?

    -Phil
  • TCTC Posts: 1,019
    edited 2013-05-20 14:38
    ElectricAye wrote: »
    I wonder if changing the frequency of your PWM might help? Perhaps you are hitting some sort of resonant frequency that is amping up the motor noise in your other circuits.

    I tryed that, it works but I have no speed control.
  • TCTC Posts: 1,019
    edited 2013-05-20 14:42
    Phil Pilgrim (PhiPi) wrote: »
    This is probably a ground bounce problem. What are you using to drive your fan, and where do the power leads for it get connected to your circuit?

    -Phil

    I am using a ULN2003 to drive a small PC computer fan. I am using a breadboard so the ground is tied to the prop. bt the 12V comes from a 2A power brick, that also powers my 5V, and 3.3V DC-DC converters.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2013-05-20 15:10
    What is the ground return from the 12V supply connect to first on your breadboard?

    -Phil
  • TCTC Posts: 1,019
    edited 2013-05-20 16:02
    Phil Pilgrim (PhiPi) wrote: »
    What is the ground return from the 12V supply connect to first on your breadboard?

    -Phil

    The ULN2003 would be at the end of the line. I am going to try giving it its own ground path, and see if that helps.
  • TCTC Posts: 1,019
    edited 2013-05-20 16:08
    That did it!!! Thank you everyone for your help.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2013-05-20 16:39
    'Glad you figured it out, TC!

    -Phil
  • ElectricAyeElectricAye Posts: 4,561
    edited 2013-05-20 20:46
    TC wrote: »
    I tryed that, it works but I have no speed control.

    I'm just curious - what sort of fan motor is this? I would think that for most fan motors, only the duty cycle would affect the speed.
  • TCTC Posts: 1,019
    edited 2013-05-21 03:47
    ElectricAye wrote: »
    I'm just curious - what sort of fan motor is this? I would think that for most fan motors, only the duty cycle would affect the speed.

    It is a standard PC computer fan. if I raise the frequency, I get a squeel from the fan. if i lower the frequency the fan hits top speed at around 50%.
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