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12 volt diode question

Discussion in 'Members Lounge' started by hot rod otis, Feb 27, 2008.

  1. hot rod otis

    hot rod otis New Member

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    i need help finding the right diode for a project i am working on. the diode i am looking for will work on 12 volts dc and need to handle 20 amps. any help would be great!
    thanks
    -otis
     
  2. Rolf

    Rolf Member

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    Welcome Otis! You can help us help you if you indicate in what part of the world you live.
    Ebay has plenty, that is the first please I look because of the usually low shipping cost small items:
    http://cgi.ebay.com/35V-20A-Schottk...ZWD1VQQ_trksidZp1638.m118.l1247QQcmdZViewItem
     
  3. hot rod otis

    hot rod otis New Member

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    thanks rolf! i live in omaha, nebraska. i will check out the link you sent and i will keep checking back here too.
    thanks again!
    -otis
     
  4. dave

    Dave New Member

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  5. hot rod otis

    hot rod otis New Member

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    i looked at that and the question i have now is will that work on 12 volts? i noticed it says 35v. and, i'm sure i will catch some guff for this question, why does that diode have 3 terminals on it and not just 2?
    thanks again
    -otis
     
  6. blueroomelectronics

    blueroomelectronics Well-Known Member

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    What's the deal with the lack of capitals with new posters? Did they not teach them in Omaha, Nebraska?
     
  7. hot rod otis

    hot rod otis New Member

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    If I start using caps will you help me with my question?
    -Otis
     
  8. blueroomelectronics

    blueroomelectronics Well-Known Member

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    Sure, the 35V 20A is the maximum rating for the part. It'll work fine with anything below those numbers.
     
  9. Rolf

    Rolf Member

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    You always want some cushion because you newer know when you will have a voltage spike. A few hundred percent don't hurt.
    Google for the data sheet, I suspect the three pins are connected in parallel and the heat sink is the other; this is in order so that this fairly small package can handle the current and the associated heat.

    PS. You still have not filled in your location!
     
    Last edited: Feb 27, 2008
  10. gerty

    gerty Member

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  11. blueroomelectronics

    blueroomelectronics Well-Known Member

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    It's amazing the TO-200 case can handle 30A, does it require a large heatsink?
     
  12. hot rod otis

    hot rod otis New Member

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    thanks, oops, Thanks guys. I did check that out and it looks like like the outside terms are common anodes and the center pin along with the base are common cathodes. This is where my lack of knowledge is getting in my way. I am wanting to put this diode inline on a 12 volt wire, just an in and out. Would i just use one anode and one cathode and get a one way current through this thing?
    Thanks
    -Otis
     
  13. blueroomelectronics

    blueroomelectronics Well-Known Member

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  14. Rolf

    Rolf Member

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    I Goggled "diode theory" and found this:
    "The diode is to electrons exactly as a check valve or one-way valve is to water. Electrons can easily pass in one direction but are prevented from traveling through the diode in the reverse direction. This is great for changing Alternating Current (AC) where electrons go back and forth inside the wire, to direct current (DC) where the electrons always go the same direction. The diode merely refuses to let the electrons go backward when the voltage reverses. There are literally thousands of other uses for the common diode (sometimes called rectifiers) other than that though."
     
  15. hot rod otis

    hot rod otis New Member

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    That is great stuff rolf. That was why the 3 terminal thing was throwing me off. I just need in and out, so why 3 terminals? If I understand this right, I can use the terminal that flows in the direction I need and leave the other open and call that done. Sound good?
    Thanks again!
    -otis
     
  16. Rolf

    Rolf Member

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    I was not aware that it was actually two diodes in the TO220 case.
    Connect pins #1 & #3 together and connect to the positive side of your circuit and pin #2 and the case to the negative.
    This will put the two diodes in parallel.
     
    Last edited: Feb 27, 2008
  17. hot rod otis

    hot rod otis New Member

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    We have 14 of em on the way (thanks Gerty). I will keep ya posted on the project.
    Thanks
    -Otis
     
  18. shokjok

    shokjok Member

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  19. RODALCO

    RODALCO Well-Known Member

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    Just get a block rectifier. Many of these are rated at 35 Amps, cost only a couple of bucks.

    Only use one diode of it and leave the others not connected.

    As long you put it on a heatsink. 20 Amps at 0.7 Volts gives 14 Watts in heat to be dissipated.
     
  20. hnoor0077

    hnoor0077 New Member

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    That was why the 3 terminal thing was throwing me off. I just need in and out, so why 3 terminals?????
     

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