# 12v dc power distribution circuit

Discussion in 'Electronic Basics' started by John Popelish, Apr 11, 2007.

1. ### John PopelishGuest

Might be easy, might not.

How much current do each of the 3 volt loads need?
Do any signals communicate between these 4 circuits?
This is a way of asking if these circuits need to be
isolated from each other or may share a common negative or
positive supply rail.

2. ### asmoGuest

Hi I'm building a circuit bent instrument with several circuits in it.
I want to run them all off one power supply rather than several
different battery packs, I want to run 4 3v dc circuits from a 12v dc
power supply, can anyone point me to a schematic?

Cheers
Ed

3. ### ehsjrGuest

-----
+12 ---+---Vin|LM317|Vout---+---+---> +3
| ----- | |
| | | |+
[C1] +----------+ [C2]
| | |
| [R2] |
| | |
Gnd ---+---------+--------------+

C1 = .1uF
C2 = 10 uF
R1 = 240
R2 = 336

Above is a simple voltage regulator circuit based on
the LM317 chip that will provide 3 volts output.
you can use it in your project.

Ed

4. ### asmoGuest

I'm not sure about the current, it consists of the circuits from 2
vtech tiny touch phones,early learning toys, which run on 2 AA
batterys each.
The 16 pins from each IC are routed to a patch bay so, yes there is
some cross wireing, the other 2 circuits are simple 555 astable
circuits which act as LFO's which can be patched into various points.
Ed

5. ### John PopelishGuest

The simplest way to get several different 3 volt supplies
from a 12 volt main supply is probably to use linear
regulators, like LM317T, programmed with a pair of resistors
to produce a 3 volt output. If the 3 volt loads draw more
than about 50 mA, you will need heat sinks on the regulators
to keep them from overheating.

See:
http://cache.national.com/ds/LM/LM117.pdf

This arrangement would require that the negative side of the
12 volt main supply were common to all loads.