advice: 4-pin DC cable shield
Ben Lowry
cable (2 cond. + shield)? I plan to tie the shield to pin 1, along
with "-" conductor, on both ends of the cable.
So... will the braided shield help reject interference in this
application? Any reason to connect it differently? Any minimum gauge
needed for basic on-cart uses? Any suggestions for making DC cable
extra resistant to RF ?
Thanks!
ben
Ben Lowry
Sound Mixer for Film and Video
Austin, TX
Eric Toline
advice: 4-pin DC cable shield
Group: rec.arts.movies.production.sound Date: Wed, Aug 25, 2004, 7:22am
(EDT-3) From: blo...@bga.com (Ben Lowry)
Why go to all that trouble? Go to Home Depot and get a piece of 2
conductor jacketed 16 or 18 ga electrical wire and you'll be fine. Even
16 or 18 ga zip cord (speaker cable) will work with no problems. AFAIK
RF interference in DC cables is a non issue.
Eric
Douglas Tourtelot
guage. I was looosing a whole 1vdc with the 16 guage wire I had, but I do
have "tons" of 12vdc gear on my cart. I am probably pulling nearly 4A!
D.
"Ben Lowry" <blo...@bga.com> wrote in message
news:6d2ef188.04082...@posting.google.com...
Eric Toline
Re: advice: 4-pin DC cable shield
Group: rec.arts.movies.production.sound Date: Wed, Aug 25, 2004, 9:58am
(EDT-3) From: tour...@nospanspeakeasy.net (Douglas Tourtelot)
Try and go with a larger guage wire. I just upgraded my DC system to 12
guage. I was looosing a whole 1vdc with the 16 guage wire I had, but I
do have "tons" of 12vdc gear on my cart. I am probably pulling nearly
4A!
D.<<<<<<<<<<<<<<<<<<
how do you connect 12ga wire inside a 4 pin xlr?
Eric
Raymond Collins
>
> how do you connect 12ga wire inside a 4 pin xlr?
>
> Eric
>
With a welder and a hammer? ;-)
Douglas Tourtelot
distro, 16 guage 4-pin XLR from there.
D.
"Eric Toline" <Audi...@webtv.net> wrote in message
news:26229-41...@storefull-3251.bay.webtv.net...
Kurt Albershardt
> Don't use 4-pin XLRs for the 12 guage; Neutrik Speakon connectors to the DC
> distro, 16 guage 4-pin XLR from there.
Just be sure nobody plugs your distro into a power amp!
I use Anderson SB series connectors for this sort of thing <http://www.andersonpower.com/products/mp/sb.html>
Douglas Tourtelot
connectors; take LOTS of amperage. If I notice anyone bringing a power amp
around to plug into my distro, I'll ask them not to<g>. (That doesn't keep
inexperienced electricians from somehow plugging diferent color Camloks
together however. Guess he was color-blind. Good thing my cart was wearing
a condom; too bad the video assist's wasn't <he-he>)
D.
"Kurt Albershardt" <ku...@nv.net> wrote in message
news:2p4ginF...@uni-berlin.de...
Ben Lowry
Marty
power on a sound cart? Are you guys trying to run a golf cart or sound
recording gear? How large is the distro that has 6 speakon outputs?
Geezzze! According to standards (and one very good calculator I use),
the power loss of 16g stranded copper wire should be no more than a few
mV per meter depending on it's construction.
If we are talking about powering wireless receivers, mixers, an LCD
monitor, even a hard disk recorder, and they are all on the same cart
within a 6 foot cable's distance of the distro, then 4 pin XLR's are a
quasi standard. Remote Audio makes the Hot Box, which is a 6 output 4pin
XLR distro for sound carts.
If on the other had, if you are working ENG style from an audio bag on a
harness, then either coaxial d.c. pin plugs or 4 pin mini QG (aka TA4)
connectors are standard (such as on Remote audio's 6 output BDS box).
For either connector, the pinout standard is 0V (gnd) on pin 1 and +V on
pin 4.
Output wire gage should be able to handle the load of the device it's
plugged into, which in most cases is between 50mA and 1 Amp. For low
power devices, I often use a 22g stranded wire which will have a voltage
drop of 16mV/foot, and can handle a max of 4A. This is good for the
smaller connectors.
Input cable from the battery to the distro should be able to handle the
sum total current from all loads plus at least a 25% safety margin. A
16g stranded wire has a power loss of 4mV/Foot and can handle a max of 15A
The insulation used will, in part, determine the maximum power the wire
can handle as it relates to meltdown temperature. The figures I gave are
examples only and do not account for any specific wire or insulation type.
Marty Atias
ATS Communications
Douglas Tourtelot
pulls nearly 5A when it is all up and running. The 1vdc loss was measured,
with a meter, not guessed at, and I have regained that volt by re-wiring my
DC supply with 12 guage and Speakons. True, I could power my M4 on 22
guage, just not my cart. Okay?
D.
"Marty" <Ma...@atscomms.REMOVE.com> wrote in message
news:WcAXc.5180$Y%3.4...@newsread2.news.atl.earthlink.net...
John B., Indianapolis
Voltage drop in the wire is a function of the resistance of the wire,
therefore, the lower the resistance of the load (which is inversely
proportional to increased current draw of the load) the higher the
voltage drop in the wire.
According to some hastily made computations: 11 feet of 16 gauge wire
would drop about a quarter of a volt with a 5 amp load. This, of
course, doesn't take into account the resistance of any connectors or
switches, which will add to the voltage drop. 12 gauge wire has about
40% of the resistance of 16 gauge wire, so it can be two-and-a-half
times as long for the same voltage drop.
Five amps at twelve volts would mean the load has an equivalent
resistance of about 2.4 ohms.
I found the following chart online (I haven't confirmed its accuracy):
Wire Gauge Resistance per foot
4 .000292
6 .000465
8 .000739
10 .00118
12 .00187
14 .00297
16 .00473
18 .00751
20 .0119
22 .0190
24 .0302
26 .0480
28 .0764
Therefore the computations (volts dropped across 11 feet of 16 gauge
wire with a 5 amp load) would be:
12/5=2.4
11*.00473=.05203
2.4+.05203=2.45203
2.45203/.05203=47.1272342
12/47.1272342=.254629837
With that high of current draw, any resistance in connectors and
switches would definitely contribute to the loss.
Gosh, math is fun!
John Blankenship,
Indy
John B., Indianapolis
But -- hold the phone -- the loss would be twice what I figured. Who
can tell me why?
(I'm pretending I know something here.)
John Blankenship,
Indy
Jay Rose CAS
> But -- hold the phone -- the loss would be twice what I figured. Who
> can tell me why?
Well, sort of. You're passing through one conductor in each direction, and
one contact pin per direction... but only 1 set of switch contacts for the
whole circuit.
--
Correct address is spell out the letter j, AT dplaydahtcom
Clio- and Emmy-winning sound design
Learn audio for video at www.dplay.com
John B., Indianapolis
Jay Rose CAS wrote:
>>But -- hold the phone -- the loss would be twice what I figured. Who
>>can tell me why?
>
>
> Well, sort of. You're passing through one conductor in each direction, and
> one contact pin per direction... but only 1 set of switch contacts for the
> whole circuit.
>
That's why I like this group -- it's loaded with folks who are as picky
as I am. And to think, I almost fooled myself on that one. All said,
it would appear that the one volt drop is reasonable.
John Blankenship,
Indy
Brad Harper
that pulled about 3 amps all by itself. The cable would hardly fit into the
connector and eventually shorted. I have since remade my mixer and recorder
power cables from 14 gauge 2 conductor cable. It fits much better into an
XLR connector and offers good size to flexibility ratio.
I run two 40 amp gel cells into a PSC Power Max using the same 14 gauge
cable. I can go for days without A.C.
Brad Harper
Glen Trew
news:kweYc.252300$eM2.199362@attbi_s51...
Sorry you cable failed, Brad. I'll have it shipped back to see what
happened. It's a tight fit, but with the cable we use it is normally
reliable with an XLR (it's what I use).
But I'm glad to see this topic discussed. It's one of those things that's
too often ignored like the seatbelt instructions given by a male flight
attendant. The difference is that the wire size and connector type of your
power system will always have a measurable negative affect. For those
powering their rigs with a single battery, wire size and connectors have a
direct affect on how long you can operate between recharges.
It is quite possible that a large battery will adequately power a cart rig
for several hours longer if proper wire size and connectors are used. For
example, consider a 60 amp lead acid 12V battery powering a cart drawing
about 10 amps. (Ten amps is considered high for a location cart, but is
becoming more and more common). 4 feet of a feeder cable that would be more
than adequate for a Nagra or PD-4 can easily have more than a 2V loss when
feeding a 10 amp rig. When this is the case, when critical equipment fails
to operate below 10.5 volts (the PD-4 comes to mind), then you will be in
trouble when the battery drops below 11.5V - even though the battery may
still have half of its capacity remaining.
An easy way to check power loss within your system is to measure the
voltage, with your equipment turned on, as close to the power source as
possible (such as the battery terminals), then measure the voltage at the
connector mounted on each device (mixer, recorder...). The difference in
voltage is the amount of loss in your cable and connectors. You'll probably
be surprised at the difference.
Glen Trew
Marty
corrected. At 5 amps, according to my calculations, there should be
about a .5V drop over 22 ft of 16g wire.
I thought I remembered Neutrik marketing a 2 pin XLR for D.C. power.
They no longer list it, but they do have a "PowerCon" 3 pin model. Funny
though, it has half the current capcity (per pin) of the 2 pin Speakon,
and is no smaller in size.
John, I saw that chart and others. I also found a very extensive free
calculator program that does all kinds of cool tricks at
http://hjem.get2net.dk/hkj/miscel.html
Thank you,
Marty
Richard Crowley
> I thought I remembered Neutrik marketing a 2 pin XLR for D.C. power.
> They no longer list it, but they do have a "PowerCon" 3 pin model. Funny
> though, it has half the current capcity (per pin) of the 2 pin Speakon,
> and is no smaller in size.
Aren't those made for mains (110/220V) use? Don't need the high current
capacity at those high voltages.