# 12 Volt Regulated Supply

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

1. ### Dave.HGuest

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
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.HGuest

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. ### Paul E. SchoenGuest

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.HGuest

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.HGuest

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.