Connect with us

12v to 5v

Discussion in 'General Electronics Discussion' started by spike47, Oct 18, 2015.

Scroll to continue with content
  1. spike47

    spike47

    11
    0
    Aug 11, 2009
    Hi

    I am making a simple voltage regulator using a TS7805 , as per the diagram attached , to light up some led's in a PC Gaming machine I am building , can I fit another spec of capacitor instead of the ones shown :

    1x TS7805 5 volt regulator
    2x 1uf capacitor
    1x power plug (or other connector)
    1x 220 ohm resistor
    1x Blue LED (I used a diffused one)

    I have plenty 16v 22μf capacitors ! , I have seen simular voltage reducers using a TS7805 and using different spec capacitors .

    question : how do you work out in that simple circuet what size capacitors to use .

    cheers

    spike
     

    Attached Files:

  2. davenn

    davenn Moderator

    13,671
    1,892
    Sep 5, 2009
  3. Colin Mitchell

    Colin Mitchell

    1,417
    312
    Aug 31, 2014
    The minimum is 1,000u per amp.
     
  4. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    spike,
    If all you need is TO light a LED(s) you don't need to step-down the voltage!
    Connect the LED directly to 12V with a series resistor(just like you do with 5v).
    The resistor value will be different that is all.

    For the LED you used above with 220 Ohm Calculate R for 12V:

    R=220+7000/i ; i=LED current in mA

    for 5ma ---> R=1.6k
    for 10ma ---> R=910
    for 20ma ---> R=560
     
  5. spike47

    spike47

    11
    0
    Aug 11, 2009
    Hi davenn

    12 v feed is from the PC's power supply , as per my first post ! .
     
  6. spike47

    spike47

    11
    0
    Aug 11, 2009
    Hi dorke

    the LED in the pic is only to show power is there .
     
  7. spike47

    spike47

    11
    0
    Aug 11, 2009
    Hi Colin

    I have about 12 led's to light inside the PC , I have no idea what there load is to work out what Capacitors I would use , I think I will go for a resister instead of the TS7805 , i was only going that route because I have a spare TS7805 .

    spike
     
  8. spike47

    spike47

    11
    0
    Aug 11, 2009
    Hi dorke

    I have no idea what amperage the led's draw ! .
     
  9. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    Then you have little hope of driving them correctly.

    Using the 12V power is actually more efficient than reducing it to 5V because you can put several LEDs in series and reduce the total current you draw.

    You need to determine the forward voltage and current that the LEDs are designed to operate at.

    Bob
     
  10. davenn

    davenn Moderator

    13,671
    1,892
    Sep 5, 2009
    that was very unclear as the power source
    My answer could have been very different

    Colin's comment ONLY applies if you are supplying from an unregulated source

    if it is indeed a reasonably standard PC supply ??
    then his comments are spot on use the 12V rail as he said, or if you want to, just use the existing 5V rail
    there no need to have another 5V reg line


    If they are standard 5mm LED's then around 20 -30mA,


    Dave
     
  11. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    Well you can easily measure it .
    Connect like you intended ( 5v, led,resistor).
    use a resistor =1k potentiometer in series with 100 ohm.
    Get the correct luminescence you need from the led
    -important start with the pot. at max value and lower the resistance!

    VF==> measure the voltage on the led.
    IF ==> measure the voltage on the 100 ohm and calculate the current through it.
     
    Last edited by a moderator: Oct 18, 2015
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-