Advice with replacing a schematic input voltage

Discussion in 'General Electronics Chat' started by doby, Jun 28, 2015.

  1. doby

    Thread Starter Active Member

    Aug 17, 2011
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    I want to use a schematic that is designed to run on 12V, if I were to change this to 4.5V what alterations would I need to make to the circuit?

    I presume the resistors would need changing, is this just an ohms law calculation? What else would need changing?

    Thanks

    (Schematic attached)
     
  2. dl324

    Distinguished Member

    Mar 30, 2015
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    You wouldn't be able to run 3 LEDs in series. Depending on the forward voltage, you might have to run them all in parallel with their own current limiting resistor.
     
  3. doby

    Thread Starter Active Member

    Aug 17, 2011
    43
    0
    Yeh I don't intend to, I should have said that, sorry. That side of things I can make sense of anyway, it's everything else I need help with!
     
  4. dl324

    Distinguished Member

    Mar 30, 2015
    3,242
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    The only other thing to worry about is the threshold voltage of the MOSFET; it needs to be low enough that it turns on completely at the lower voltage.
     
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