HIGH POWER OPTO ISOLATOR?

Discussion in 'General Electronics Chat' started by dougalere, Jul 7, 2015.

  1. dougalere

    Thread Starter Member

    Mar 4, 2015
    128
    5
    HI
    i need to switch 1 amp at 12 volt, with isolation from the signal.
    at around 20 times per second.
    i was hoping to find an opto coupler or opto isolator that would do the job without an external output stage,preferably cheap, as i need 6 channels
    i have done some searching, but the output current is 'never' stated in the specs.
    if any members have any suggestions, it would be much appreciated.
    tthank you
    dougal
     
  2. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Well... Inasmuch as it seems you do not wish to follow a 'standard' isolator with a power semiconductor (why not?) -- you could use 'solid state relays' (many of which incorporate 'opto-isolated' inputs) -- Note, however, that you will require devices designed to switch DC (i.e. GTO output) -- else the input signal will 'lose control' following 'turn on'...

    Best regards
    HP
     
  3. ScottWang

    Moderator

    Aug 23, 2012
    4,855
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    What you care about is cheap, that is less money, but the current more higher of components will be need more money and that it is not cheap.

    I would suggest that you to using 6 photocouplers as PC817 and 6 stages of N mosfets.

    How about the channels, is that 6 to 1 or 6 to 6 independent control?
     
  4. dougalere

    Thread Starter Member

    Mar 4, 2015
    128
    5
    hi
    thank you for your repliies and prompt responses,
    the way to go is of course an external driver stage, but with so many channels
    i i would look to see if there were any alternatives.
    i did look into ss relays but they costed out at around £40-£50,plus postage. hence my mention of price.
    something that did come up was the 8 channel arduino relay boards, these are quite reasonable,but few if any in the uk, could work round 5 volt input i suppose.

    i didnt mean to come across as cheapskate and lazy, but i suppose i am.

    it was just a thought.

    thanks again
    dougal
     
  5. ScottWang

    Moderator

    Aug 23, 2012
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    The relay only suit for works under 10 times/sec.
     
  6. OBW0549

    Well-Known Member

    Mar 2, 2015
    1,319
    888
    IXYS make optically coupled MOSFET switches which can be used for DC. Not sure where you would obtain them in the UK, but here in the States they're available through Digi-Key:

    http://www.digikey.com/product-search/en?pv434=72&pv434=152&pv434=73&pv434=75&pv434=76&pv434=78&pv434=79&pv434=117&pv434=80&pv434=116&pv434=121&pv434=120&FV=fff40010,fff80058,fffc00d4,1c0002,1c0003,1c0006&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

    Perhaps one of those might do the job...
     
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  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    The LCA717 looks good enough. Not wild about the turn-on/off times, but they combine to less than 3% of the period (typ.).

    ak
     
  8. dougalere

    Thread Starter Member

    Mar 4, 2015
    128
    5
  9. ian field

    Distinguished Member

    Oct 27, 2012
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    There is an optocoupler with MOSFET output often used as the hookswitch function in modems.

    It can handle about 230V, the current rating is higher than a typical opto but I can't remember exactly how high.
     
  10. dougalere

    Thread Starter Member

    Mar 4, 2015
    128
    5
    euraka/ish
    might have found it, and a fiver for 5 on ebay.
    im not well up on optos, could i ask someone to see if this would do the job,
    only snag, theres always a snag . the supply rail needs to be 6v above output
    voltage.als would have preferred through hole,
    FOD3150S, OPTOCOUPLER, DIP-8, 1A, SMD

    optoshttps://www.fairchildsemi.com/datasheets/FO/FOD3150.pdf
     
  11. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Maybe not. At 1 A current there is 6 V of drop across the output terminals. That 6 watts of internal power dissipation, enough to kill the part in seconds. Plus the datasheet notes that the 0.25 W power dissipation is not for continuous conditions. Sorry, keep looking.

    ak
     
  12. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Last edited: Jul 9, 2015
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