I would appreciate some basic info about using a 12VDC "wall wart" to
power or charge a device using a car cig lighter attachment.

In other words, I'd like to take the power cord that normally plugs
into a car cigarette lighter power source and connect it to a power
supply I plug into a wall outlet.

I know a little about electricity so I know the amp rating of the
power block must be sufficient. I can figure out the correct polarity.

What I AM confused about is why I plug a 12VDC power brick in and
measure it with my tester to find they read about 15 or 16 VDC with no
load. I know cars supply about 12V when off and perhaps 13-14V when
running. I do NOT want to damage anything and am concerned that 16V
is too high unless this is normal and it will be less when it is
actually powering something.

Any comments or things to watch out for would be appreciated. I was
thinking of charging my GPS for which I do not have a house charger
for and things like that.

Thanks very much!

On 2010-01-09, TedVerizon wrote:

power block must be sufficient. I can figure out the correct polarity.

the pin part of the lighter plug is positive

What I AM confused about is why I plug a 12VDC power brick in and
measure it with my tester to find they read about 15 or 16 VDC with no
load. I know cars supply about 12V when off and perhaps 13-14V when
running. I do NOT want to damage anything and am concerned that 16V
is too high unless this is normal and it will be less when it is
actually powering something.

this is the difference between a regulated and an unregulated supply.
a regulated supply will not produce a voltage significantly higher
than its rating. unregulated supplies may produce 50% more when not
being used to full capacity.

Any comments or things to watch out for would be appreciated. I was
thinking of charging my GPS for which I do not have a house charger
for and things like that.

start with a regulated 12V 2A wall wart (last time I looked that was
the sweet spot on the price-cost curve, and that should be enough to
power pocket-sized appliances like phone and GPS chargers) and wire
it to a lighter socket.


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This is interesting but I, too, know just enough to be dangerous...

How does one tell the difference between a regulated and unregulated
supply? Do they say or do you just have to measure the unloaded voltage
and guess?

Is there an inexpensive part from Radio Shack that can 'fix' an
unregulated supply? I've heard the term 'voltage regulators' but don't
know much more than that.

If not, where is a good place to find a rugulated 12V supply like you
mentioned?

Thank you for this information.

Mike



On Sat, 09 Jan 2010 05:28:45 -0500, Jasen Betts wrote:

What I AM confused about is why I plug a 12VDC power brick in and
measure it with my tester to find they read about 15 or 16 VDC with no
load. I know cars supply about 12V when off and perhaps 13-14V when
running. I do NOT want to damage anything and am concerned that 16V
is too high unless this is normal and it will be less when it is
actually powering something.

this is the difference between a regulated and an unregulated supply.
a regulated supply will not produce a voltage significantly higher
than its rating. unregulated supplies may produce 50% more when not
being used to full capacity.

Any comments or things to watch out for would be appreciated. I was
thinking of charging my GPS for which I do not have a house charger
for and things like that.

start with a regulated 12V 2A wall wart (last time I looked that was
the sweet spot on the price-cost curve, and that should be enough to
power pocket-sized appliances like phone and GPS chargers) and wire
it to a lighter socket.

On Fri, 08 Jan 2010 19:27:47 -0800, TedVerizon wrote:

I would appreciate some basic info about using a 12VDC "wall wart" to
power or charge a device using a car cig lighter attachment.

In other words, I'd like to take the power cord that normally plugs into a
car cigarette lighter power source and connect it to a power supply I plug
into a wall outlet.

I know a little about electricity so I know the amp rating of the power
block must be sufficient. I can figure out the correct polarity.

What I AM confused about is why I plug a 12VDC power brick in and measure
it with my tester to find they read about 15 or 16 VDC with no load. I
know cars supply about 12V when off and perhaps 13-14V when running. I do
NOT want to damage anything and am concerned that 16V is too high unless
this is normal and it will be less when it is actually powering something.

Any comments or things to watch out for would be appreciated. I was
thinking of charging my GPS for which I do not have a house charger for
and things like that.

Thanks very much!

You are correct about the voltages a discharged car battery will measure
up to 14-15 volts when the car is started and usually shows 14v when fully
charged.

Unregulated wall warts are able to produce higher voltages depending on
how much current they were rated at for that output voltage.

But there are plenty of switching regulated wall warts avialable that will
prduce a steady 12v output at all times and should be perfectly safe for
charging your GPS

This site has a very good assortment of power adapters at reasonable
prices.

http://www.allelectronics.com/make-a...upplies/1.html


They even have this one that plugs in and provides a cigarette lighter
socket at 1 amp.

ttp://www.allelectronics.com/make-a-store/item/PS-1201/12V-1000MA-CHARGER-W/CIG-LIGHTER-SOCKET/1.html


I doubt that you will need anything heavier than 1-2 amps for charging
that unit.


Gnack

On 2010-01-09, Mike wrote:
This is interesting but I, too, know just enough to be dangerous...

How does one tell the difference between a regulated and unregulated
supply? Do they say or do you just have to measure the unloaded voltage
and guess?

regulated ones will be labeled as such on the packaging.

Is there an inexpensive part from Radio Shack that can 'fix' an
unregulated supply? I've heard the term 'voltage regulators' but don't
know much more than that.

one such part is LM7812 (not sure what stock number RS uses on that) but you'll
probably also need a heatsink, etc and also need more supply voltage ...

If not, where is a good place to find a rugulated 12V supply like you
mentioned?

seing as you mentioned radio shack.
(try http://www.radioshack.comhttp://www....goryId=2818335 )

here's a big one, massive overkill (good for automotive-powered appliances upto 200W)
things like car sterios, portble refrigerators, coffee heaters, and spotlights.

http://www.radioshack.com/product/in...uctId=39644771

here's a smaller one.

http://www.radioshack.com/product/in...ductId=3875403

should be strong enough to power your GPS charger.

and here's one with an in-between size.

http://www.radioshack.com/product/in...ductId=3875404


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Well it all depend what power supply is going to be use for,
However you saying that you would like hook up GPS to
your house source yes that is not problem but you have not
stated what power does your GPS takes my takes 5 vdc
and yes you can use 6 vdc source but I would not go any
higher even so I had mine hook up for while on 9 vdc it seemed
it survived one time but I would not do it again.
Keep in you mine that most of batteries need at list 10-20% more
voltage to take charge and to stored that power.


"TedVerizon" wrote in message
...
I would appreciate some basic info about using a 12VDC "wall wart" to
power or charge a device using a car cig lighter attachment.

In other words, I'd like to take the power cord that normally plugs
into a car cigarette lighter power source and connect it to a power
supply I plug into a wall outlet.

I know a little about electricity so I know the amp rating of the
power block must be sufficient. I can figure out the correct polarity.

What I AM confused about is why I plug a 12VDC power brick in and
measure it with my tester to find they read about 15 or 16 VDC with no
load. I know cars supply about 12V when off and perhaps 13-14V when
running. I do NOT want to damage anything and am concerned that 16V
is too high unless this is normal and it will be less when it is
actually powering something.

Any comments or things to watch out for would be appreciated. I was
thinking of charging my GPS for which I do not have a house charger
for and things like that.

Thanks very much!





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