# use AC lights on DC circuit

Discussion in 'Electronic Basics' started by [email protected], Feb 13, 2007.

1. ### Guest

My son and I have a project that involves converting a strand of
christmas lights(110AC) to run off of 12v DC,no AC input.Is this
possible? If so what is involved?
Thank you for your help.

2. ### John PopelishGuest

You buy a power inverter that converts the DC voltage to AC
and steps it up to line voltage. For example:
http://www.dcacpowerinverters.com/itemdesc.asp?CartId={20DEVEREST41BBC-EE6E-4B3E-B0C9-991BE2E4B5F5}&ic=PW200-12

3. ### Stephen J. RushGuest

The quick way is to buy a small inverter that chops the DC to AC and
transforms that to 110V. Small ones aren't expensive; look at
auto-accessory stores, Wal-Mart (if you're in the USA) or even big
drugstores. If the string is one of those that has a lot of low-voltage
lamps in series, you could cut them apart and reconnect them in
series-parallel to run on 12V. If, for example, you have 40 3-volt lamps
in series, breaking up the string into 4-lamp strings and connecting those
in parallel will work. If the string has screw-in lamps, they are
probably 120-volt C7 or C9 lamps, so an inverter is the only way to go.

If you do have a string of miniature lamps, connect an AC voltmeter across
one lamp and light the string to see what kind of lamps you have.

4. ### Rich GriseGuest

Count the number of bulbs in the string. Divide 110 by this number,
that will give you the voltage rating of each bulb. What you do
at this point might vary, depending on the individual bulb voltage;
if they're 3V, you put 4 in a string, if they're 6V, put 2 in a
string - I don't know exactly what to recommend if it's something
like 8V - that's kinda in the middle.

Assuming that you can get little strings of bulbs that take 12V
each, cut up the series string, and put the little strings in
parallel. You'll need heavier supply wires, so that the bulbs
at the end of the parallel set don't get current-starved by
the wire's resistance.

Hope This Helps!
Rich

5. ### jasenGuest

unravel the wiring,
your string will be electrically like a loop of lamps

.-------------------------------------------------------------.
| This is an ascii schematic, if the diagram appears garbled |
| try switching to a fixed-pitch font (courier works well) |
| pasting it into notepad works well on ms-windows. |
| in google groups selecting 'fixed font' (top right of page) |
| or view source (options) work too. |
`-------------------------------------------------------------'

eg if they are 3V lamps there will be 40 in the string

--o-o-o-o-o-o-o-o-o-o-...-o-o-o-o-o-o-o-o-o-o-.
----------------------...---------------------'

cut it into 10 pieces with the same number of lamps in each.
connect one end of each to the positive terminal and the other
to the negative terminal

|-o-o-o-o-|
|-o-o-o-o-|
|-o-o-o-o-|
|-o-o-o-o-|
(+)|-o-o-o-o-|(-)
|-o-o-o-o-|
|-o-o-o-o-|
|-o-o-o-o-|
|-o-o-o-o-|
|-o-o-o-o-|

if you want to make it string-shaped again get some do this

(+)---+-----------+-----------+-----------+-----------+---------- ...
`-o-o-o-o-. `-o-o-o-o-. `-o-o-o-o-. `-o-o-o-o-. `-o-o-o-o-.
(-)-------------+-----------+-----------+-----------+-----------+ ...

Don't try to convert it back to 120V, it's not worth the risk.

Bye.
Jasen

6. ### JeffMGuest

Google broke this in their latest "improvement".
There is no longer anything to click.
You can make it work by appending &fwc=1 to the URL.

Note: All Google Groups pages thereafter
will display in monospaced font
UNLESS you close all Google Groups thread pages but one
then add &fwc=0 to its URL, access the page, and close it.
Yup. That still works.

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