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12 Volt Regulated Supply

Discussion in 'Electronic Basics' started by Dave.H, May 1, 2008.

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  1. Dave.H

    Dave.H Guest

    I was looking at a 12 volt regulated power supply at Dick Smith
    Electronics cat. number M9935 @ www.dse.com.au for a regen radio I'm
    planning on building (http://www.schmarder.com/radios/tube/
    1-12af6.htm) but the AU$24 is a bit too high for my liking. I was
    thinking of using a center tapped transformer, 6.3-0-6.3V @ 500mA, in
    series with a 1.3 watt zener diode, I need help with obtaining 12.6
    volts from a center tapped transformer, I never had to do it before.
    I thought that the two positive primary leads were connected, I don't
    want to blow the transformer if this isn't the case.

    Any help appreciated,

    Thanks
    Dave

    Transformer is M2853, and zener diode is Z3543 @ www.dse.com.au
     
  2. Dave.H

    Dave.H Guest

    How would I install the zener diode? I thought they were used in
    series with the voltage source much like a rectifier diode, but I just
    read that they're used in parallel to the source. Excuse the dumb
    question, I've only ever had experience with rectifier diodes like the
    1N4007.

    Thanks
    Dave
     
  3. There were several power supply designs offered in response to your post on
    a voltage doubler. The same principles apply to your 12 VDC circuit. It
    would be good for you to become familiar with LTspice where you can try
    different configurations and do experiments without blowing something up or
    hurting yourself.

    For the components you have, you will need a full wave bridge made from
    four 1N400x diodes, a capacitor of about 1000 uF 25 VDC, and a resistor
    that will drop about 5 volts at the current you need to draw, plus the
    zener current. With a 1.3 watt 12 V zener, its maximum current is about 100
    mA, so the maximum current draw for your supply should be about that much.

    Paul
     
  4. Dave.H

    Dave.H Guest

    I like that 7812 idea. The tube (12AF6) draws 150 mA, then there's
    the current draw of the 12 volt B+, a zener won't handle all that. A
    5600 MFD 40 volt capacitor is AU$7.30, I don't like paying that for
    low quality Asian capacitors, so I'm paralleling 3 2200 MFD 25 volt
    caps in series to give a total 6600 MFD. Each of these caps cost $0.97

    Dave
     
  5. Dave.H

    Dave.H Guest

    Oops. Didn't mean to say that that they were in series. I'm only
    paralleling them. I already have one 2200 uF 50 volt cap I'll use.
     
  6. How about $7, delivered to your door:
    http://cgi.ebay.com.au/Switching-Po...ryZ20589QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

    Dave.
     
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