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Dimmer filtering

  1. Jun 15, 2006 #1
    I have been considering making a dimmer as the first of many projects to come. Searching google I have found quite a few good references. I understand that a inductor (choke) capacitor pair reduces the EMI caused by the rise time of the "firing angle".

    The problem I am having is in how do I size the choke instead of using a value between a max and min range and adjusting accordingly. Looking for a point in the right direction. Thanks in advance

    Just a thought :rolleyes: would this be along the lines of LC filtering in power supplies!
     
  2. jcsd
  3. Jun 16, 2006 #2

    berkeman

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    Staff: Mentor

    Can you post a link to a reference on the dimmer circuit you are looking at? BTW, a dimmer is not generally a good first project to do, since it involves working with AC mains power. AC mains power is very dangerous, even when you know what you are doing and take some basic precautions (like using an isolation transformer). If you haven't designed and built AC mains circuitry before, I'd recommend picking a different first couple of projects. You could do a PWM DC motor drive controller, for example, and get a lot of the same knowledge without the danger or killing yourself.
     
  4. Jun 16, 2006 #3
    The 2 links I have been using are:

    www.ece.utexas.edu/~grady/EE362L_Triac_Light_Dimmer.pdf
    http://www.epanorama.net/documents/lights/lightdimmer.html

    Thank you for your safety concerns and let me assure that I understand the dangers having apprentice with electricians while completing my engineering technology degree (electronic Technologist). Furthermore, I have gone so far as to build a tester where I can connect in series any commercial dimmer to binding post and dim 1-3 loads. In any event still looking into passive LC filtering.
     
  5. Jun 19, 2006 #4

    berkeman

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    The epanorama.net page didn't help me, because the site goes nuts with popups. Yikes. The PDF reference was better, but it didn't show the LC filter that you want to add. Are you just going to add it in series with the Hot and Neutral leads into the dimmer plus bulb? Is the goal to reduce conducted harmonics that the dimmer plus bulb are putting out onto the H-N line? Or are you trying to reduce radiated emissions?
     
  6. Jun 19, 2006 #5
    They are going to be one of the same since the line will be the chief radiator anyway.
     
  7. Jun 20, 2006 #6

    berkeman

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    True, but conducted emissions and radiated emissions generally are in different frequency bands. The radiated emissions testing runs from 30MHz up through a couple GHz, and conducted emissions testing is below 30MHz generally. I'd do filtering differently for each of these two emissions tests.
     
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