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Fan (industrial) control with a triac and optoisolator?

Discussion in 'Electronic Design' started by Rodo, Oct 8, 2007.

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  1. Rodo

    Rodo Guest

    Hi all,

    I need to set the speed of an industrial fan to either full speed (12amps),
    half speed or off. I also need to isolate the driving circuit from the ac. I
    thought an optocoupler (led to triac) should do it but I couldn't find
    anything that can handle the power in Digikey. Is there such a beast?

    Thanks
     
  2. Huh? Your trying to deliver the power through the optocoupler? I don't know
    much about this area but I would imagine you won't find any optocoupler that
    can do that. (all I've seen are < 1A)

    I would think the standard method is to run the power directly through the
    triac and use the optocoupler on the gate of the triac. Ground the chasis
    of the device using the fan and you are pretty much set.

    The gate current is significantly smaller than the drive current so you can
    use a normal optocoupler.

    If you just need half power and not variable power then I'm sure you can
    just use a switch and some diodes. Not sure how well this would work with an
    ac motor though as it might cause some problems. (essentially either using
    direct AC or a half wave rectifier cutting the power used in half but
    unfortunately probably won't work with an AC motor or will probably atleast
    cause some problems)

    I imagine what your trying to do is extremely typical and so if your having
    trouble finding the components then your probably going about it the wrong
    way.

    Anyways, thats my 2c's. (Someone will correct me if I'm wrong. I'm sure Phil
    or Eyeore will call me a moron or some shit too...)
     
  3. Phil Allison

    Phil Allison Guest

    "Jon Slaughter"

    ** Exactly correct assessment.


    ** You have got me & Graham all wrong - Jon.

    Both of us really *love* you a whole lot !!!!!

    But we are fearful that if we ever told you so

    - it would go straight to your head.





    ....... Phil
     
  4. neon

    neon

    1,325
    0
    Oct 21, 2006
    I think if i remenber correctly there is a photocoupler to triac 8 pin MC3022 where ypu can find it is at elexp.com for 120v a 1.5k to the gate should do it to the external triac, at half speed you will need to synch the 60 cycle with a delay to half wave or fire one shot and disable the fireing for Ms as required. need more help ask.
     
  5. Guest

    Go to:
    http://www.st.com/stonline/stappl/p...roduct$$view=table&querycriteria=RNP139=124.0
    Regards,
    Kral
     
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