Can I draw 3.75 amps from a cigarrette 12v socket?

S

Shannell Sugrue

Guest
Im looking to run a lcd touchscreen in a car from a laptop, the screen has
an ac/dc power adapter that supplies 12v and it draws 3.75 amps, could I
hook this up to the lighter socket, or would I need a better smoother supply
than the 13+V that the car would give?
 
"Shannell Sugrue" <sjs@nella.net.au> wrote in message
news:40e2d752@usenet.per.paradox.net.au...
Im looking to run a lcd touchscreen in a car from a laptop, the screen has
an ac/dc power adapter that supplies 12v and it draws 3.75 amps, could I
hook this up to the lighter socket, or would I need a better smoother
supply
than the 13+V that the car would give?


You'd want to have some regulation and filtering on that supply to protect
Click to expand...
your equipment, things get a bit nasty in a car. In addition to that a car
cig lighter isn't a great connector - if it's just for you in one car, I'd
look at fitting a better quality connector for this.

Ken
 
"Shannell Sugrue" <sjs@nella.net.au> wrote in message
news:40e2d752@usenet.per.paradox.net.au...
Im looking to run a lcd touchscreen in a car from a laptop, the screen has
an ac/dc power adapter that supplies 12v and it draws 3.75 amps, could I
hook this up to the lighter socket, or would I need a better smoother
supply
than the 13+V that the car would give?
Click to expand...
I believe they are usually fused at 10 Amps however you do need to remember
that the 12V from a Car electrical System is not regulated. I believe that
it is generally thought that you need to allow for up to 300V spikes from a
Car Electrical System so some filtering and a Regulator in front of your
Touchscreen is probably a good idea.

Regards
Richard Freeman
 
"Richard Freeman" <deletethisrichard@atps.net> wrote in message
news:2kh1n8F29h92U1@uni-berlin.de...
"Shannell Sugrue" <sjs@nella.net.au> wrote in message
news:40e2d752@usenet.per.paradox.net.au...
Im looking to run a lcd touchscreen in a car from a laptop, the screen
has
an ac/dc power adapter that supplies 12v and it draws 3.75 amps, could I
hook this up to the lighter socket, or would I need a better smoother
supply
than the 13+V that the car would give?

I believe they are usually fused at 10 Amps however you do need to
remember
that the 12V from a Car electrical System is not regulated. I believe that
it is generally thought that you need to allow for up to 300V spikes from
a
Car Electrical System so some filtering and a Regulator in front of your
Touchscreen is probably a good idea.
Click to expand...
The CPU's in the car engine management would fry first if 300V spikes ever
appeared. The battery would have to be dead too. But no harm in adding some
extra protection I guess.

TonyP.
 
On Sat, 3 Jul 2004 02:44:54 +1000, "TonyP" <TonyP@optus.net.com.au>
wrote:

"Richard Freeman" <deletethisrichard@atps.net> wrote in message
news:2kh1n8F29h92U1@uni-berlin.de...

"Shannell Sugrue" <sjs@nella.net.au> wrote in message
news:40e2d752@usenet.per.paradox.net.au...
Im looking to run a lcd touchscreen in a car from a laptop, the screen
has
an ac/dc power adapter that supplies 12v and it draws 3.75 amps, could I
hook this up to the lighter socket, or would I need a better smoother
supply
than the 13+V that the car would give?

I believe they are usually fused at 10 Amps however you do need to
remember
that the 12V from a Car electrical System is not regulated. I believe that
it is generally thought that you need to allow for up to 300V spikes from
a
Car Electrical System so some filtering and a Regulator in front of your
Touchscreen is probably a good idea.

The CPU's in the car engine management would fry first if 300V spikes ever
appeared. The battery would have to be dead too. But no harm in adding some
extra protection I guess.
Click to expand...
Richard is quite correct. Load dumps can cause some very large
spikes in a car system. It's a long time since I looked at the
requirements of the major manufacturers in this area but I seem
to recall that Mercedes had a spec. that OEM module components
must be able to withstand 140V for 300mS and that's an awful lot
of energy. I can't remember what their peak voltage withstand spec
was but 300V seems quite reasonable. Cars are electrically horrible
environments and the more protection you can get the better.

Mike Harding
 
"Mike Harding" <mike_harding1@nixspamhotmail.com> wrote in message
news:vjpbe01l1ujmgblkj3jsn3ur003ji9lkfm@4ax.com...
Richard is quite correct. Load dumps can cause some very large
spikes in a car system. It's a long time since I looked at the
requirements of the major manufacturers in this area but I seem
to recall that Mercedes had a spec. that OEM module components
must be able to withstand 140V for 300mS and that's an awful lot
of energy.
Click to expand...
Sure is when you consider the internal impedance of a car battery in
reasonable condition. The spec probably allows for a disconnected battery or
morons with arc welders.

I can't remember what their peak voltage withstand spec
was but 300V seems quite reasonable.
Click to expand...
Sure, I have a cheap mains filter that claims 4,500A protection too! (yes
41/2 thousand amps) I'm surprised even an advertising exec could accept that
as remotely possible in real life. The pulse duration would have to be far
less than any possible rise time. Looks impressive to some I suppose, just
like IHF power ratings for amplifiers :)

TonyP.
 
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