remove interfering noise from power supply

Discussion in 'The Projects Forum' started by smilem, May 4, 2011.

  1. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Hi, I have 2 noise sources on my PSU.

    1. Here is IR kit that I use
    http://www.velleman.eu/distributor/support/downloads/?code=MK120
    The transmitter http://www.velleman.eu/downloads/files/schema/transmitter.jpg
    Frequency mesured 6Khz


    2. I use PWM motor driver http://www.velleman.eu/distributor/support/downloads/?code=K8004
    Frequency measured 38Khz

    How can filter the noise from each device so that my PSU wont be distorted and other electronics would work ok?

    Would this DC-DC converter (for IR module it needs only 100mA) with galvanic separation make the frequency isolated from my main PSU? For PWM motor I really don't know how to do it.
    https://www.elfa.se/elfa3~lt_lt/elfa/init.do?item=69-560-98&toc=0
     
    Last edited: May 4, 2011
  2. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    I have used shielded cable now for my PWM signal, and placed 0.33uf cap on my motor, that made huge impact ant I can only measure around 6Khz only frequency that I was unable to filter using 2 caps and some toroid that I placed on that circuit power cable.

    So any ideas or do I have to use DC-DC converter ?
     
  3. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    I'm not sure what you're building because two of your links brought me to a home page. I was able to view the .jpg though. I would say try a 10Ω in series with the supply line with .1uF caps to Gnd on both ends but you said that you tried that with a toroid.
     
  4. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    A full PI filter would be where I begin, where the coil is on both the ground and hot wires.
     
  5. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Hi, My circuit looks like this. I don't know inductor value, it's from scap I have desoldeted a while ago. Have a few more but without LC meter I cant measure them :(
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    I was thinking in line of a second inductor, make the circuit symmetrical on both axis.
     
  7. smilem

    Thread Starter Active Member

    Jul 23, 2008
    132
    0
    Added another inductor but no difference, inductors are not the same.

    I desoldered the filter circuit and just connected it to the transmitter power circuit positive and negative terminals. Then I connected frequency meter and I can't measure any frequency after the filter.

    So why then the filter connected in the power line to the transmitter doesn't work the same way (filter noise after itself?)
     
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