Need tips for reducing EMI, circuit picking up +700mv noise from High bay lights.

Discussion in 'General Electronics Chat' started by Mrdouble, Jul 5, 2015.

  1. Mrdouble

    Thread Starter Member

    Aug 13, 2012
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    View attachment 88075 I'm trying to build a transistor small motor controller but I realiz image.jpg ed today that the noise that has been intermittently present is coming from the high bay lights in my shop. The problem is that I use a resistor in parallel with the transistor BE junction. Sometimes the noise is so high that it triggers the transistor to conduct. Any easy solution to fix or reduce this noise?
    Thank you in advance.
     
    Last edited: Jul 5, 2015
  2. DickCappels

    Moderator

    Aug 21, 2008
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    The simplest solution is to turn the lights off. If that isn't practical then the general approaches of shielding and bypassing are probably what you should try.

    It would be very helpful if you were to post the circuit that you believe is picking up the interfering signal. Photographs of the subject circuit would probably be helpful too.
     
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  3. bertus

    Administrator

    Apr 5, 2008
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    Mrdouble likes this.
  4. Mrdouble

    Thread Starter Member

    Aug 13, 2012
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    i attracted a 5" jumper wire to the probe and set a 600mv trigger. Took about 1 min. Bam! I guess what I'm asking is we have old transistor radios and I'm wondering did they take EMI precautions or just design them to work with EMI. I can't really give schematic right now as I don't have an updated one but will certainly try tomorrow. Thank you for the prompt responses
     
  5. Mrdouble

    Thread Starter Member

    Aug 13, 2012
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  6. Mrdouble

    Thread Starter Member

    Aug 13, 2012
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    I got it working. I put a ferrite bead over the base and working like a champ. Thanks for all the advise.
     
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