One of my kids came home from Xmas shopping with a very tasteful(??)
illuminated Xmas decoration for her bedroom, but when she got in she
discovered that unfortunately(??) it had a cigar lighter plug and was
intended for use in a car.

This "thing" includes ten 2.5V 0.5W bulbs, and the blurb says it wants a
12V/5W power supply (and must be used only with a car battery etc etc).
I tested it with a spare wallwart from my Useful Box, rated at 9V /
200mA / 1.8VA and it illuminates the bulbs fine. But could someone just
confirm it's OK to do this long-term, ie that I can't overheat the PSU
or something daft?

Thanks
David

On Tue, 06 Dec 2005 11:24:22 GMT, Lobster
wrote:

But could someone just
confirm it's OK to do this long-term, ie that I can't overheat the PSU
or something daft?

Sounds like you're under-running the bulbs. I'm guessing that they're
wired as two paralel strings of 5 bulbs in series, thus expecting a
design voltage of 12.5V. Running this on 9V will make them glow, but
more orange and at a fair bit less power. If your PSU was providing 12V
then it would probably be significantly under-powered at that current
rating. However at 9V if it's working OK so far, then I'd be happy to
use it - the total power demand drops off a lot because you're
under-running them.

Don't wrap the PSU in anything flammable and check that it isn't running
too hot (by touching it). Apart from that, I'd happily use it.

In article , Lobster
writes
One of my kids came home from Xmas shopping with a very tasteful(??)
illuminated Xmas decoration for her bedroom, but when she got in she
discovered that unfortunately(??) it had a cigar lighter plug and was
intended for use in a car.

This "thing" includes ten 2.5V 0.5W bulbs, and the blurb says it wants a
12V/5W power supply (and must be used only with a car battery etc etc).
I tested it with a spare wallwart from my Useful Box, rated at 9V /
200mA / 1.8VA and it illuminates the bulbs fine. But could someone just
confirm it's OK to do this long-term, ie that I can't overheat the PSU
or something daft?

Although the lights will use less power on 9W, the supply you're using is
waaay underrated for the job having only 40% of the required capacity and
will almost certainly overheat. Get digging in the bin again & find one rated
9V 400mA or 12V 500mA :-).
-
fred
Plusnet - I hope you like vanilla

Lobster wrote:
One of my kids came home from Xmas shopping with a very tasteful(??)
illuminated Xmas decoration for her bedroom, but when she got in she
discovered that unfortunately(??) it had a cigar lighter plug and was
intended for use in a car.

This "thing" includes ten 2.5V 0.5W bulbs, and the blurb says it wants a
12V/5W power supply (and must be used only with a car battery etc etc).
I tested it with a spare wallwart from my Useful Box, rated at 9V /
200mA / 1.8VA and it illuminates the bulbs fine. But could someone just
confirm it's OK to do this long-term, ie that I can't overheat the PSU
or something daft?

Thanks
David

Watts are the same as VA for a load like this - your lights would need a
5W supply at 12V (probably 3-4 W at 9V) but yours is rated at less than
2W. These wallwarts usually have a fuseable link built-in to the
transformer, I wouldn't be too surprised if it gave up after a while.

Dave

In article ,
Lobster wrote:
This "thing" includes ten 2.5V 0.5W bulbs, and the blurb says it wants a
12V/5W power supply (and must be used only with a car battery etc etc).
I tested it with a spare wallwart from my Useful Box, rated at 9V /
200mA / 1.8VA and it illuminates the bulbs fine. But could someone just
confirm it's OK to do this long-term, ie that I can't overheat the PSU
or something daft?

A 12v 5 watt supply suggests at basics that the load is 29 ohms.

9 volts into 29 ohms will draw 0.31 amps, or 310 mA.

All approx, of course, but you're sailing very close to the wind.

A 12 volt 500mA wall wart shouldn't cost much. If they are incandescent
lamps you could probably use an AC one.

--
*It's not hard to meet expenses... they're everywhere.

Dave Plowman London SW
To e-mail, change noise into sound.

I tested it with a spare wallwart from my Useful Box, rated at 9V /
200mA / 1.8VA and it illuminates the bulbs fine. But could someone just
confirm it's OK to do this long-term, ie that I can't overheat the PSU
or something daft?

It will probably burn out the transformer. If it was a resistive load, it
would draw 2.8W (or 2.8VA) which is considerably larger than the rating.
However, the bulbs are probably not ohms-law compliant and the situation
could actually be worse than this.

Christian.

One of my kids came home from Xmas shopping with a very tasteful(??)
illuminated Xmas decoration for her bedroom, but when she got in she
discovered that unfortunately(??) it had a cigar lighter plug and was
intended for use in a car.

This "thing" includes ten 2.5V 0.5W bulbs, and the blurb says it wants a
12V/5W power supply (and must be used only with a car battery etc etc). I
tested it with a spare wallwart from my Useful Box, rated at 9V / 200mA /
1.8VA and it illuminates the bulbs fine. But could someone just confirm
it's OK to do this long-term, ie that I can't overheat the PSU or
something daft?

Thanks
David

Well according to that lot your either fine or about to be toasted. I can't
decide which. Lectrics are confuddling.
Suzanne

On Tue, 6 Dec 2005 11:24:22 UTC, Lobster
wrote:

One of my kids came home from Xmas shopping with a very tasteful(??)
illuminated Xmas decoration for her bedroom, but when she got in she
discovered that unfortunately(??) it had a cigar lighter plug and was
intended for use in a car.

You can get 12V PSUs (try a caravan shop) with cigar lighter sockets
fitted! Useful for priming those coolboxes, too.
--
The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
Avenue Supplies, http://avenuesupplies.co.uk

Dave Plowman (News) wrote:
In article ,
Lobster wrote:

This "thing" includes ten 2.5V 0.5W bulbs, and the blurb says it wants a
12V/5W power supply (and must be used only with a car battery etc etc).
I tested it with a spare wallwart from my Useful Box, rated at 9V /
200mA / 1.8VA and it illuminates the bulbs fine. But could someone just
confirm it's OK to do this long-term, ie that I can't overheat the PSU
or something daft?

A 12v 5 watt supply suggests at basics that the load is 29 ohms.

9 volts into 29 ohms will draw 0.31 amps, or 310 mA.

OK... I also have an old 14V / 500mA wallwart (that's the nearest
alternative):

So, 14V into 29 ohms = 483mA! Sounds like that would that run OK
without setting fire to my daughter, then?

A 12 volt 500mA wall wart shouldn't cost much. If they are incandescent
lamps you could probably use an AC one.

Not a chance! This monstrosity she's bought only cost her a quid (it
uses Xmas tree bulbs AFAICS) and I'm not going out to buy one
specially... no further than a rake through the garage!

Thanks
David

In article ,
Lobster wrote:
A 12v 5 watt supply suggests at basics that the load is 29 ohms.

9 volts into 29 ohms will draw 0.31 amps, or 310 mA.

OK... I also have an old 14V / 500mA wallwart (that's the nearest
alternative):

So, 14V into 29 ohms = 483mA! Sounds like that would that run OK
without setting fire to my daughter, then?

Should be OK - if they really are designed for a car this is about the 'on
charge' voltage.

--
*If at first you don't succeed, then skydiving definitely isn't for you *

Dave Plowman London SW
To e-mail, change noise into sound.

Lobster wrote:

So, 14V into 29 ohms = 483mA! Sounds like that would that run OK
without setting fire to my daughter, then?

Yes, but you will shorten the bulb life considerably. They'll burn
bright though!

Thinking about it, it's likely that this decoration will be thrown out
after xmas, right? Go for it.


Not a chance! This monstrosity she's bought only cost her a quid (it
uses Xmas tree bulbs AFAICS) and I'm not going out to buy one
specially... no further than a rake through the garage!

I must have half a dozen 12V 500mA and anther half dozen 12V 1A psus in
my drawer. Unfortunately the time and hassle of packaging and posting is
just a little too high :-(


--
Grunff

Lobster wrote:
One of my kids came home from Xmas shopping with a very tasteful(??)
illuminated Xmas decoration for her bedroom, but when she got in she
discovered that unfortunately(??) it had a cigar lighter plug and was
intended for use in a car.

This "thing" includes ten 2.5V 0.5W bulbs, and the blurb says it wants a
12V/5W power supply (and must be used only with a car battery etc etc).
I tested it with a spare wallwart from my Useful Box, rated at 9V /
200mA / 1.8VA and it illuminates the bulbs fine. But could someone just
confirm it's OK to do this long-term, ie that I can't overheat the PSU
or something daft?

2.5/0.5W = 200mA.
So, 400ma for 2 strings.

In other words, yes, you are probably running the PSU at somewhere over double
its ratings.
Probably the cheapest PSU would be an old PC one...

Ian Stirling wrote:

2.5/0.5W = 200mA.
So, 400ma for 2 strings.

In other words, yes, you are probably running the PSU at somewhere over double
its ratings.
Probably the cheapest PSU would be an old PC one...

It would have to be a very old one then. Most computer PSUs will not
output 12 Volts until the mobo gives the thumbs up on the 5 Volt line.

Dave

Ian Stirling wrote:
Lobster wrote:

One of my kids came home from Xmas shopping with a very tasteful(??)
illuminated Xmas decoration for her bedroom, but when she got in she
discovered that unfortunately(??) it had a cigar lighter plug and was
intended for use in a car.

This "thing" includes ten 2.5V 0.5W bulbs, and the blurb says it wants a
12V/5W power supply (and must be used only with a car battery etc etc).
I tested it with a spare wallwart from my Useful Box, rated at 9V /
200mA / 1.8VA and it illuminates the bulbs fine. But could someone just
confirm it's OK to do this long-term, ie that I can't overheat the PSU
or something daft?


2.5/0.5W = 200mA.
So, 400ma for 2 strings.

In other words, yes, you are probably running the PSU at somewhere over double
its ratings.
Probably the cheapest PSU would be an old PC one...

Hey, I'd forgotten all about that as an option!! I've got an ancient
one here which says: max output 145W; then
DC Voltage /Max current = +12V / 4.2A

Sounds like just the job, yes?!!

David

In article , Lobster davidlobster
writes
Ian Stirling wrote:
Lobster wrote:

One of my kids came home from Xmas shopping with a very tasteful(??)
illuminated Xmas decoration for her bedroom, but when she got in she
discovered that unfortunately(??) it had a cigar lighter plug and was
intended for use in a car.

This "thing" includes ten 2.5V 0.5W bulbs, and the blurb says it wants a
12V/5W power supply (and must be used only with a car battery etc etc).
I tested it with a spare wallwart from my Useful Box, rated at 9V /
200mA / 1.8VA and it illuminates the bulbs fine. But could someone just
confirm it's OK to do this long-term, ie that I can't overheat the PSU
or something daft?


2.5/0.5W = 200mA.
So, 400ma for 2 strings.

In other words, yes, you are probably running the PSU at somewhere over double
its ratings.
Probably the cheapest PSU would be an old PC one...

Hey, I'd forgotten all about that as an option!! I've got an ancient
one here which says: max output 145W; then
DC Voltage /Max current = +12V / 4.2A

Sounds like just the job, yes?!!

By the time you've finished faffing around sorting out a dummy load for the
5V to make it start up properly you'd be as well using the 14V number and
live with the fact that the tree bulbs will be a bit short lived. Sounds like
you wouldn't shed a tear if it popped before the new year & it would be a
useful education for your daughter in the what-do-you-expect-for-a-quid
rules of life ;-)

The plugin would be safer too, no open slots.
--
fred
Plusnet - I hope you like vanilla

Dave wrote:
Ian Stirling wrote:

2.5/0.5W = 200mA.
So, 400ma for 2 strings.

In other words, yes, you are probably running the PSU at somewhere over double
its ratings.
Probably the cheapest PSU would be an old PC one...

It would have to be a very old one then. Most computer PSUs will not
output 12 Volts until the mobo gives the thumbs up on the 5 Volt line.

Or until you jumper the correct 2 wires on the PSU.
I forget which two - they are next to each other on the plug though.

And IME, most PSUs work just fine with no load on 5V.
YPSUMV.

In article , davidlobsterpot601
@hotmail.com says...
Ian Stirling wrote:
Lobster wrote:

One of my kids came home from Xmas shopping with a very tasteful(??)
illuminated Xmas decoration for her bedroom, but when she got in she
discovered that unfortunately(??) it had a cigar lighter plug and was
intended for use in a car.

This "thing" includes ten 2.5V 0.5W bulbs, and the blurb says it wants a
12V/5W power supply (and must be used only with a car battery etc etc).
I tested it with a spare wallwart from my Useful Box, rated at 9V /
200mA / 1.8VA and it illuminates the bulbs fine. But could someone just
confirm it's OK to do this long-term, ie that I can't overheat the PSU
or something daft?


2.5/0.5W = 200mA.
So, 400ma for 2 strings.

In other words, yes, you are probably running the PSU at somewhere over double
its ratings.
Probably the cheapest PSU would be an old PC one...

Hey, I'd forgotten all about that as an option!! I've got an ancient
one here which says: max output 145W; then
DC Voltage /Max current = +12V / 4.2A

Sounds like just the job, yes?!!

As long as it's AT rather than ATX it should work fine. Otherwise some
fiddling will be required.