12V - 7.29A ac/dc converter project Need Help

Discussion in 'The Projects Forum' started by Butterworth, Nov 6, 2011.

  1. SgtWookie

    Expert

    Jul 17, 2007
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    They are not Zeners. They are Schottky diodes.

    You could use 1N5821 or 1N5822 Schottkys, or other >=2A Schottky diodes.
     
  2. Audioguru

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    Dec 20, 2007
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    There are no zener diodes.
     
  3. Butterworth

    Thread Starter Active Member

    May 6, 2009
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    Ok thanks for the clarification.

    Sorry, I read the symbol wrong. They are similar looking when small. :)
     
  4. Audioguru

    Expert

    Dec 20, 2007
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    Sorry. I didn't know you looked at the schematic on a tiny cell phone.
     
  5. Butterworth

    Thread Starter Active Member

    May 6, 2009
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    Hmm well my phone isn't exactly small... its about the same size as the dell streak.

    I found the following shottky diodes, 1n4508 &1n5844, i know they are not the 5822's listed but they should work still? Can I mix the two styles?
     
  6. SgtWookie

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    Jul 17, 2007
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  7. Butterworth

    Thread Starter Active Member

    May 6, 2009
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    Alas, I have but 1pc of the 5844... Such is life, however, I will need to pick up the 555 Timer and the mosfet anyway, so I might as well grab a 4pk of the schottky 5822's.

    I wanted to put a power indicating led (red 3mm 2.2Vf @ 10mA) Can I place this between the switch and the 555 timer? It is so I can see if the unit is on or not, being IR leds, I don't want people looking at it when it is on full blast... preventative measure.

    I found a transistor comparable to the bc... it is an NTE123AP, datasheet located here http://www.nteinc.com/specs/100to199/pdf/nte123ap.pdf

    I think it is higher in capacities, but will still do the job I am hoping.
     
    Last edited: Dec 9, 2011
  8. SgtWookie

    Expert

    Jul 17, 2007
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    It never hurts to have a few extra on hand.

    I forgot about that.

    Yes, you can connect a single LED and a series resistor.

    Connect it after the two diodes from the bright and dim terminals to ground (the supply negative terminal) with a series current limiting diode.
    Since your supply is 12.82v, and the diodes will drop ~0.5v, a 1K resistor in series with an LED will give roughly 10mA current flow through the diode. You will need to use a 1/4 Watt resistor. Might as well use 1/4 Watt resistors for everything; they will work.

    You can use just about any small-signal NPN transistor; 2N2222, 2N3904, 2N4401, etc - it does not have to sink much current to keep the 555 timer disabled and the output switched on.
     
  9. Butterworth

    Thread Starter Active Member

    May 6, 2009
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    Awesome. Thank you for the info, yet again you have saved one of my projects. :)
     
  10. Butterworth

    Thread Starter Active Member

    May 6, 2009
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    Ok so the test board circuit was made and it working using only a single string of 1.42V irleds. The question I propose is this, looking at the led strings you have arranged them in 7 -led strings and the last 4 strings are 6 leds... what values did you use to calculate the series resistors for each string?

    *BUMP* - Sgt.Wookie, can you advise on the led order you used? I cannot get the value resistors that you did, Thanks!
     
    Last edited: Dec 19, 2011
  11. Butterworth

    Thread Starter Active Member

    May 6, 2009
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    *BUMP* Sorry guys, didn't know that edits to posts doesn't refresh the thread standing in the forum. :p
     
  12. SgtWookie

    Expert

    Jul 17, 2007
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    Use the values that were calculated some many posts back when I had you using 8 in series.

    I'm not going to look for it.
     
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