What diode is this...

Discussion in 'The Projects Forum' started by VUK, Oct 20, 2009.

  1. VUK

    Thread Starter New Member

    Oct 20, 2009
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    I am not an expert lol

    I have been trying to find out what kind of diode this is.

    SMD diode, silver ends, 2 bands = white and purple

    CAR application off 2001 BMW m5 variable valve timing (vanos)

    circuit board powers 4 solenoids

    Schematic attached

    Thanks! :D
     
    Last edited: Oct 20, 2009
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Don't know. Was is across the coil of the solernoid perhaps? If it was it is there to prevent the coils from making a high voltage spike, which can damage other electronics. If not, I have no idea.
     
  3. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
    16
    It could be an inductor, perhaps 97μH (according to the bands). Diodes don't have the color bands on them and if it is a diode they usually just have one band to note the cathode. If you have a meter you can check if it's a diode or not. It should have a high resistance one direction and a lower resistance the other direction. If it doesn't, I can almost guarantee it's a inductor. Just to make sure, though, measure the inductance with a meter also.
     
  4. VUK

    Thread Starter New Member

    Oct 20, 2009
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    Thanks for yours help

    I measured with a multimeter that I have laying around, I got a reading ONLY 1 WAY and here is what I got.
     
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  5. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
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    If you get 0.800 for the diode measurement then it definitely is a diode. But try measuring the resistance the opposite way and record the difference between the two.
     
  6. VUK

    Thread Starter New Member

    Oct 20, 2009
    5
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    Thats the thing, I get no reading the opposite way. I tired all OHM functions on the meter and the dioide test, none work the opposite way.

    :confused:
     
  7. VUK

    Thread Starter New Member

    Oct 20, 2009
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    All I want to know is what kind of diode I need that will take care of the inductive flyback on the solenoids, any ideas?
     
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Last edited: Oct 21, 2009
  9. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
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    Good! Then it's a diode! ;)
     
  10. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
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    Did the empty pads next to this Diode contain a fried one? I ask because there's no need to replace a Diode that tests good, as this one did.
     
  11. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
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    Indeed, the diode looks fine. Did you intentionally disconnect the diode yourself as shown in the picture due to the measurements? Or, what it like that when you saw it? Maybe you could just solder it back on.
     
  12. VUK

    Thread Starter New Member

    Oct 20, 2009
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    I fried 3 by reversing polarity when testing, this was 1 good one left :)
     
  13. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
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    Are they all the same type of diode? You should definitely replace the damaged ones and resolder the one shown in the picture.
     
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