maximum length of wire?

Guest
I have some video equipment i need to power off directly from my car's
battery. I need a wire that is not too big, because i need to solder
on a special quick-release connector that will be used to easily
disconnect the cable from my video equipment. The cable requires 2
wires inside, one for positive and one for negative on the battery.
The biggest cable i found with 2 conductors, has 2x 22AWG wires
inside. Some tell me that it is too small and some say it will work no
problem. I don't want the wires to start melting and cause a fire! The
video gear will draw no more than 1 amp total, directly off the car's
12V battery. My question is, what is the maximum length of cable i can
use to remain safe? Thnks for your advice.
 
rose250@hotmail.com wrote:
I have some video equipment i need to power off directly from my car's
battery. I need a wire that is not too big, because i need to solder
on a special quick-release connector that will be used to easily
disconnect the cable from my video equipment. The cable requires 2
wires inside, one for positive and one for negative on the battery.
The biggest cable i found with 2 conductors, has 2x 22AWG wires
inside. Some tell me that it is too small and some say it will work no
problem. I don't want the wires to start melting and cause a fire! The
video gear will draw no more than 1 amp total, directly off the car's
12V battery. My question is, what is the maximum length of cable i can
use to remain safe? Thnks for your advice.
Click to expand...
There is no maximum to remain safe.

To actually _work_, the voltage drop from the battery to the camera has
to be fairly low. Make the cable too long for the wire size and your
camera won't work (but nothing will burn up). So try it out...

You can get wire as big as you want and connect pigtails to the ends to
step the wire size down for your connectors.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
 
On Nov 15, 3:45 pm, rose...@hotmail.com wrote:
I have some video equipment i need to power off directly from my car's
battery. I need a wire ...2x 22AWG wires
inside. Some tell me that it is too small and some say it will work no
problem. I don't want the wires to start melting and cause a fire! The
video gear will draw no more than 1 amp total
Click to expand...
The fuse limit for typical insulation on 22AWG wires is well over
2 amps, so PROVIDED WITH A SUITABLE FUSE it's safe to
connect it to the 12V battery. Your battery does NOT connect
directly to this wire, it connects THROUGH A FUSE (1.5A
would be a suitable size).

The important part here, is that the fuse prevents the wire
from burning up under ANY fault condition, including higher
current than your intended device (the video gear) uses.
 
On Sat, 15 Nov 2008 15:45:18 -0800 (PST), rose250@hotmail.com wrote:

I have some video equipment i need to power off directly from my car's
battery. I need a wire that is not too big, because i need to solder
on a special quick-release connector that will be used to easily
disconnect the cable from my video equipment. The cable requires 2
wires inside, one for positive and one for negative on the battery.
The biggest cable i found with 2 conductors, has 2x 22AWG wires
inside. Some tell me that it is too small and some say it will work no
problem. I don't want the wires to start melting and cause a fire! The
video gear will draw no more than 1 amp total, directly off the car's
12V battery. My question is, what is the maximum length of cable i can
use to remain safe? Thnks for your advice.
Click to expand...
For some back o' the envelope approximations...

We'll assume that your equipment load is about 1 A, as stated. The
battery will really be about 13 V when not loaded but we'll swag the
equivalent load resistance at 12 ohms.

AWG 22 cable is about 16 ohms per 1000 feet, so using a 100 ft run, you
would add 1.6 ohms on "either side" of your existing load. The total
load, which is now about 15 ohms, will draw about 0.85 A from a 13 V
battery and you'll have a bit more than 10 V to work with at your load.
Your equipment may not be happy with that.

If you follow Tim's recommendation and use heavier gauge cable with
short transition pieces to the necessary wire size for the connector,
things look a bit better.

With regular 14 AWG zip cord, you're now running only about 2.5 ohms per
1000 feet. That 100 foot run now only adds 1/4 ohm to each leg, so your
total draw (with that same 13 V battery) is pretty close to 1 A, with
only about 0.5 V lost in the cabling. Happy equipment!

As whit3rd mentioned, fuse it. Preferably run from a polarized aux
connector to a spare fuse on the vehicle's fuse box, rather than hook
directly to the battery. (Nobody would EVER hook black to positive, red
to ground, would they?)

If you ever intend to run from an operating vehicle, be aware that the
equipment will see some nasty transients. If the stuff is designed to
run from a car's electrical system, you're good. Otherwise, be aware
that the magic smoke may come out. See the link for a description of
some issues http://www.industrologic.com/autotransients.pdf

--
Rich Webb Norfolk, VA
 
Rich Webb wrote:

With regular 14 AWG zip cord
Click to expand...
Good thing he's in N. America (Canada) or he wouldn't have an earthly clue
what an AWG is. Does Canada use AWG or have they fully metricated now ?

Graham
 
On Sun, 16 Nov 2008 04:51:40 +0000, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

Rich Webb wrote:

With regular 14 AWG zip cord

Good thing he's in N. America (Canada) or he wouldn't have an earthly clue
what an AWG is. Does Canada use AWG or have they fully metricated now ?
Click to expand...
One may note that the OP mentioned that the "cable i found with 2
conductors, has 2x 22AWG wires" and infer from that statement that he
indeed has some clue (earthly or not, to be determined).

--
Rich Webb Norfolk, VA
 
On Sun, 16 Nov 2008 04:51:40 +0000, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

Rich Webb wrote:

With regular 14 AWG zip cord

Good thing he's in N. America (Canada) or he wouldn't have an earthly clue
what an AWG is. Does Canada use AWG or have they fully metricated now ?
Click to expand...
---
Don't you have access to Google in the UK on Sunday?

From:

http://www.electrical-online.com/cableandwire.htm

"In Canada and the United States there is a standard by which we measure
wire. This standard is the A.W.G. (American Wire Gauge)."

JF
 
On Sun, 16 Nov 2008 04:51:40 +0000, Eeyore wrote:

Rich Webb wrote:

With regular 14 AWG zip cord

Good thing he's in N. America (Canada) or he wouldn't have an earthly clue
what an AWG is. Does Canada use AWG or have they fully metricated now ?
Click to expand...
The OP wrote: "I need a wire ...2x 22AWG wires"

Says it all.

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)
 
John Fields wrote:
On Sun, 16 Nov 2008 04:51:40 +0000, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



Rich Webb wrote:

With regular 14 AWG zip cord

Good thing he's in N. America (Canada) or he wouldn't have an earthly clue
what an AWG is. Does Canada use AWG or have they fully metricated now ?

---
Don't you have access to Google in the UK on Sunday?
Click to expand...

Access, and ability to use are two different things.


--
http://improve-usenet.org/index.html

aioe.org, Goggle Groups, and Web TV users must request to be white
listed, or I will not see your messages.

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm


There are two kinds of people on this earth:
The crazy, and the insane.
The first sign of insanity is denying that you're crazy.
 
In article <Ruednc1DrqATDb3UnZ2dnUVZ_iydnZ2d@earthlink.com>,
mike.terrell@earthlink.net says...
John Fields wrote:

On Sun, 16 Nov 2008 04:51:40 +0000, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



Rich Webb wrote:

With regular 14 AWG zip cord

Good thing he's in N. America (Canada) or he wouldn't have an earthly clue
what an AWG is. Does Canada use AWG or have they fully metricated now ?

---
Don't you have access to Google in the UK on Sunday?


Access, and ability to use are two different things.
Click to expand...
Ability to use and ability to think are two different things.

--
Keith
 
<rose250@hotmail.com> wrote in message
news:8d288801-86bb-4573-9751-a6147e38ddf8@a3g2000prm.googlegroups.com...
I have some video equipment i need to power off directly from my car's
battery.
Click to expand...
just a quick note, is the equipment designed to run directly off a car
battery? or are you powering an item that has a 12 volt DC input from a
power adaptor (wall wart)

just that video equipment will be pretty sensative to noise and spikes, and
you get a lot of them on a car's electrical system, also the voltage at the
battery terminals will vary from 11 volts to 14.8 volts, depending on if the
engine is running or not.

i've run my hard drive camcorder fixed to my dashboard whilst driving in my
motorhome last year, it too wants a 12 volt DC supply at 1 amp max, but no
way i'd feed it with the power directly from the battery/alternator.

i was going to get one of the proper 12 volt camera power supplies to run
it, but it was easier for me to run an extension cable from the living area
of the motorhome to the dash connected to the main inverter, part of that
reason was the 12 volt Dc power supply was about 50 quid, the extension
cable was 2 quid, and i use the mains adaptor and that has the neccisary
filters to take out any noise on the power.
 
On Sat, 15 Nov 2008 15:45:18 -0800, rose250 wrote:

I have some video equipment i need to power off directly from my car's
battery. I need a wire that is not too big, because i need to solder on a
special quick-release connector that will be used to easily disconnect the
cable from my video equipment. The cable requires 2 wires inside, one for
positive and one for negative on the battery. The biggest cable i found
with 2 conductors, has 2x 22AWG wires inside. Some tell me that it is too
small and some say it will work no problem. I don't want the wires to
start melting and cause a fire! The video gear will draw no more than 1
amp total, directly off the car's 12V battery. My question is, what is the
maximum length of cable i can use to remain safe? Thnks for your advice.
Click to expand...
Go to Radio Shack and pick up a 12V lighter adapter.

Good Luck!
Rich
 
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