# 24vdc to 12vdc

Discussion in 'Electronic Basics' started by Chris Serra, Aug 2, 2003.

1. ### Chris SerraGuest

Hi all. I have a pretty simple question. I am looking at reducing 24vdc to
12vdc. I am new to making circuits, but I fix video games for a living, so
I know my way around most pcb's. I am not sure the best way to do it, using
resistor, caps, or if a simple 7812 will do the trick. I am not looking for
someone to make the circuit for me, but just nudge me in the right
direction.

Thanks alot.

Chris Serra

7812

3. ### William HayesGuest

A couple of 5w 10 ohm resistors and a unijunction transistor would be more
of a challenge with a 10 ohm pot off the collector of the unijunction
transistor. (assuming the 24vdc potential has less than 503 ma of current
and ignoring the 12v zener hanging off the emitter going to "ground" the
negative pole) But then, I digress...

24vdc to 12vdc

4. ### BlakeGuest

There are two options - a linear or a switcher. A linear (7812-type)
solution will dissipate power equivalent to 12V (the amount dropped) times
the current your load will draw. With a big heatsink, you can drop a lot
of power. You will have to do the math to be sure that the 7812 will not
get too hot.

A switcher will dissipate a lot less heat, maybe 5-30% the heat of the
linear. There are some small switchers that you can drop in that are easy
to design because the datasheet spells out what to do. But a divide-by-two
switcher can be as easy as a 50% duty-cycle switch followed by an LC
circuit.

Blake

5. ### Leigh W3NLBGuest

We need to know the current drain: minimum, average and maximum, if
it varies. Can't design a regulator until we know that information.

73 de Leigh W3NLB

6. ### Brian LundGuest

Hi all. I have a pretty simple question. I am looking at reducing 24vdc
to
It depends on how much current you need, the 7812 is often a good choice,
but for circuits requiring a lot of current you need something else. You can
get the as 7812 as a low power model, it is called 78L12 and can maximally
deliver 100 mA.
http://www.el-supply.dk/elpix/7B.GIF

The regular (TO220) can deliver 1-1.5A depending on the manufacturer.
http://www.el-supply.dk/elpix/17B.GIF

And for high-power requirements there is a 3A model in a TO3 package.
http://www.el-supply.dk/elpix/23A.GIF

Always remember to use a heatsink for the later two models as they do get
pretty hot when they have enough load.

Brian Lund