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5v Regulator(s)

Discussion in 'General Electronics Discussion' started by cjdelphi, Oct 26, 2011.

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  1. cjdelphi

    cjdelphi

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    Oct 26, 2011
    I bought 3 voltage regulators from Jaycar, I get them wired up, and it works perfectly, >7v in 4.95v out, i can get 2 amps from it as well with good heatsinking, works perfectly and circuit, anyway It turns out these are discontinued now...

    So after testing voltage/current i plug in my phone, and I think the voltage is just a tiny bit too low, power supply USB is 5.5v and these smart phones are picky my samsung galaxy refuses to charge from that voltage...., so question?..

    anyone seen any 5.5v voltage regulators (as USB power source) ?

    Cheers.
     
  2. cjdelphi

    cjdelphi

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    104
    Oct 26, 2011
  3. Resqueline

    Resqueline

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    Jul 31, 2009
    I've not seen fixed 5.5V regulators. The ordinary 5V regulators have a 5% tolerance and so may be a little high or low. Try using the adjustable LM317 for example.
    Ordinary 7805's may also be tweaked up in output voltage by a resistor and a potentiometer.
     
  4. cjdelphi

    cjdelphi

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    Oct 26, 2011
    it is? cool, I thought only the adjustable vout reg's had that ability? Learn something new everyday, not that I know much, i just tinker around until i see a poof of smoke and try something else :D
     
  5. cjdelphi

    cjdelphi

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    Oct 26, 2011
    Guess what i'm going to ask now, lol, where exactly have you seen this type of circuit? where would the resistor connect? between ground and the + rail?
     
  6. Externet

    Externet

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    Aug 24, 2009
    Check if other of the regulators you bought outputs a little more voltage; if not, you can insert a 0.6 V silicon diode between that 4.95V 7805 ground pin and ground, it will rise its output by 0.6V
     
  7. Resqueline

    Resqueline

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    Jul 31, 2009
    Lol, I saw it coming allright.. The methods to do it is all over the net, just Google adjustable 7805 for example.
    The "only" difference between an adjustable and a fixed regulator is the current coming out of the Gnd or Adj pin.
    In adjustable regulators this is a very small and constant/fixed current, so it can usually be disregarded, leaving resistor choices very "roomy".
    In fixed regulators it's a relatively high current and it's not entirely constant and it also varies between batches and types/ brands. It needs to be considered/calculated.
    I've found it to be around 4-6mA for the 1A 7805 regulators, and around 2-4mA for the 0.1A 78L05's.
    A single resistor/potentiometer (R2) could be used but the results becomes more predictable when adding a constant current via R1.
    Using a diode instead of R2 as Externet suggests is also a common way of adding a predictable voltage to the output.
    Sometimes it's beneficial to add a capacitor across this diode/ R2 to improve the stability of the regulation.
     

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  8. davelectronic

    davelectronic

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    Dec 13, 2010
    You could add a few usb sockets to a modded atx power supply, charge all usb gear, your phone thats fussy probably needs an inrush current limiter, nokia's do, put one in the circuit and it should charge.
    Dave. :)
     
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