Help Choosing MOSFET

Discussion in 'The Projects Forum' started by Chris15, Jun 4, 2010.

  1. Chris15

    Thread Starter Active Member

    Apr 15, 2009
    252
    0
    Hello Again
    I have a small circuit that is made to switch 5, 5mm LED's on and off randomly, i want to add more LED's and larger ones so i though about a relay but they aren't fast enough. i cant really measure the voltage as when i connect the multimeter it changes too fast to get an average. i need a MOSFET that will turn on easily with the 5mm LED voltage

    Thanks, Chris
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,694
    904
    If you can't measure the voltage at the LED, what is the voltage at the supply? Some mosfets are made that turn on with as little as 2.5V (e.g., STS5PF20V, which is P channel)? Can you provide your schematic?

    John
     
  3. John P

    AAC Fanatic!

    Oct 14, 2008
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    Or, use a bipolar transistor and a base resistor that give you a reasonable base current (say 1/20 of the desired LED current). That could be operated off any voltage down to less than 1.
     
  4. Chris15

    Thread Starter Active Member

    Apr 15, 2009
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    The supply is 9V
    When i measured it i saw it jump from 1.5v up to 8v, the circuit is a TIP31C Transistor with an audio (P2) connecter, you plug it into an audio output and it beats the the music.

    So that is all of the specs i can give now i just need the MOSFET
     
  5. Chris15

    Thread Starter Active Member

    Apr 15, 2009
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    0
    This is the schematic i put an arrow where i want the mosfet to be so i can connect about 30, 10mm white/Blue LED's

    Chris
     
  6. Chris15

    Thread Starter Active Member

    Apr 15, 2009
    252
    0
    Any one know any answers?
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    Take a look at Bill's thread on:
    LEDs, 555s, Flashers, and Light Chasers
    http://forum.allaboutcircuits.com/showthread.php?t=19075

    Bertus

     
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