Do Some PWM's Run on 110VAC?

Discussion in 'The Projects Forum' started by Tom Kay, Feb 17, 2009.

  1. Tom Kay

    Thread Starter Active Member

    Feb 10, 2009
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    Hello All;

    I would like to know if any PWM circuits are designed to run on 110VAC.

    I have found much on this forum, and on Google outlining the design and operation of 555 timer IC's being used to create Pulse Width Modulation circuits. This would offer the proper and adjustable waveform that could potentially dim a series of LED lights, assuming that all else is designed and assembled as it should be. These, however, typically run on around 10 to 15 VDC.

    I am interested in knowing if any PWM circuits run on line voltage, 110 VAC in North America.

    If you happen to know of such a circuit, preferably fairly simple construction, I would appreciate knowing about it, either in a reply, or in a link to another website.

    Incidently, I have done a quick search on this forum, regarding the educational treatment and discussion of 110VAC circuits. It is clear to me that discussing such circuits has been undertaken on an ongoing basis in the past, typically without the need to step in and end the discussion for any reason, real or imaginary.

    Second, I have read the rules of this forum very carefully, and while Point 7, paragraph 2 gives moderators the right to terminate any thread without explanation or recourse (ie, the right of the person posting the thread to ask "why did you cut me off?") it is also clear that discussing items which have been discussed in different applications at different times in THIS forum, should be viewed as PERFECTLY ACCEPTABLE.

    Thank you for any well-intended help on 110VAC PWM circuits. Tom Kay.
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    PWM is for DC, not AC. Try a search on "triac" for attenuating AC.
     
  3. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,692
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    Look up treadmills.

    John
     
  4. Tom Kay

    Thread Starter Active Member

    Feb 10, 2009
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    Hello;

    Thingmaker3, you raised a point which I may have made an error on. Although I did ask about PWM's for 110VAC, there's no critical reason for keeping it AC. My goal is to modulate a wave form that is fed to a series of LEDs, so I probably should have asked about 110+ VDC PWM's.

    If I were to think of this in block diagram form, it would be 110VAC into a system, then rectified, then PWM'd and then fed to the bank of LEDs. In my mind I put the PWM first before the rectifier.

    So, let me ask, any PWM circuits for 110 VDC?

    Jpanhalt. Treadmills?

    Thanks, Tom.
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    There are plenty of circuits for 110VDC PWMs. Use any old low-side PWM and insure your MOSFET or IGBT is appropriately sized. Make sure the transistors are protected from that inductive kick!

    For making 110VDC out of 110VAC, you'll need a 10:7 turns ratio power transformer in addition to your rectifiers and capacitors. You may have considerable difficulty finding such a transformer.

    I also suggest you get a thousand hours or so worth of projects done at 50V or less before attempting to work with lethal voltages.
     
  6. Tom Kay

    Thread Starter Active Member

    Feb 10, 2009
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    0
    Thingmaker3;

    Now THAT is what I call a comprehensive, and frankly quite helpful reply. Thank you.

    So I've learned that it is possible to modulate a LED feeder supply at 110 volts DC, some ways to go about it, and pitfuls to be wary of.

    You've also worked in both your concern for another person's safety, and the answer I was looking for in another thread about the size of output voltage you'd expect from rectifying 110VAC, with your reference to a 10:7 transformer. What you're saying is that a 30% step-down is needed to stay at 110VDC.

    I thank you for your help. This is the kind of thing I was hoping for when I entered this forum. Much appreciated.

    Best Regards, Tom.
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
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  8. Tom Kay

    Thread Starter Active Member

    Feb 10, 2009
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    Thingmaker3;

    Another excellent tutorial. Thanks for the link.

    Tom.
     
  9. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    You might look for references on "On-line" regulators, which combine rectification and regulation with minimum components.

    eric
     
  10. Tom Kay

    Thread Starter Active Member

    Feb 10, 2009
    35
    0
    Eric;

    Thanks. I'll do some searching.

    Cheers, Tom.
     
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