Is Speaker Wire OK for LED hookups?

[nyyanx18]

So I have asked this question to a few friends with more electronic experience than I have, and the they all say "ehhhh I wouldn't," but none could say why, which still leaves me questioning...


I have a whole bunch of decent quality speaker wire looks about 16-18awg. I need wire to hookup a few LEDs (TIR3 and similars). Is speaker wire ok for this use?

 

[zsiya]

Yes.

 

[calebsheltonmed23]

So I have asked this question to a few friends with more electronic experience than I have, and the they all say "ehhhh I wouldn't," but none could say why, which still leaves me questioning...

I have a whole bunch of decent quality speaker wire looks about 16-18awg. I need wire to hookup a few LEDs (TIR3 and similars). Is speaker wire ok for this use?

Some LED lights (smaller ones) have 20 and 22 AWG, so that's fine.

 

[Steve0625]

So I have asked this question to a few friends with more electronic experience than I have, and the they all say "ehhhh I wouldn't," but none could say why, which still leaves me questioning...

I have a whole bunch of decent quality speaker wire looks about 16-18awg. I need wire to hookup a few LEDs (TIR3 and similars). Is speaker wire ok for this use?

It needs to be stranded wire. Solid wire is almost always a no-no in automotive applications. Stranded wire handles flexing and routing much better. I have a roll of 18-2 jacketed wire in my materials crate. It's useful for a number of different applications.

 

[nyyanx18]

It needs to be stranded wire. Solid wire is almost always a no-no in automotive applications. Stranded wire handles flexing and routing much better. I have a roll of 18-2 jacketed wire in my materials crate. It's useful for a number of different applications.

It is stranded!

 

[FollowingNFront]

I've used 18g speaker wire to extend my the length of the wiring for my rear light bar. I've also used it to hookup my grill lights. Works just fine.

 

[Tom]

We use mostly 14awg wire but 18awg should be OK for you to use

 

[nyyanx18]

So i tested it out and the light brightness was significantly decreased.

 

[mm2k5]

For the most part, copper is copper. Try to determine if the wire that is NEEDED is the same or better. You mentioned the output decreased, did you double check your connections to make sure both hot/ground had a good connection?


I deal with wiring (not vehicle installation) all the time. The main thing is jacket that is over the copper would be more what I would worry about, rather than if the wire is good enough itself (assuming the gauge is heavy enough for the application) .

 

[Phillyrube]

Run down to best Buy, get some of that Monster cable that makes your stereo sound better, then separate the conductors.

 

[Kent@MoveOverOutfitters]

So i tested it out and the light brightness was significantly decreased.

I would say there is something else going on unless its 40gauge wire or 1000 feet long. Electrically speaking its mathematically impossible to dim significantly without a bad power source or connection.

 

[tvsjr]

So i tested it out and the light brightness was significantly decreased.

Then you wired something up wrong. Copper is copper. Watch out... I'm going to drop some more science on you:


First, let's assign a few variables:


Characteristic resistance of the wire in ohms per foot - Rc


Lighthead's peak current consumption - I


Length of the wire - L


We'll use Ohm's law to determine the voltage drop present:


I=V/R


The lighthead's current consumption is fixed at I. We are seeking V (voltage drop), and we can find R by multiplying the characteristic resistance by the length of the wire - Rc * L. By substitution:


I=V/(Rc*L)


Let's plug some values in. You mentioned TIR3 lightheads. Let's be generous and say the peak current consumption - I - is 2A.


Next, let's use a chart to determine Rc. http://www.seas.gwu.edu/~ecelabs/appnotes/PDF/techdat/swc.pdf


Assuming you are using 18ga. speaker wire, composed of 16 30ga. strands, our resistance is 6.48 ohms/1,000 ft, or 0.00648ohms/ft.


We'll be generous and say your run was 25ft.


Plug those numbers in.


2=V/(0.00648*25)


2=V/0.162


0.324=V


Total voltage drop through this system would be 0.324 volts. If your input voltage was a nominal 13.8VDC, the lighthead would have been seeing 13.476V during its peak current consumption. This is well within the tolerance of the lighthead and certainly wouldn't have caused the brightness of the heads to be "significantly decreased".


Most likely, these numbers are inflated... I suspect your run wasn't 25 feet, I know a TIR3 doesn't consume 2A even at peak, etc.


Now, we have neglected a few things:


High-resistance connections - a poor connection will add substantially more resistance than some 18ga. wire. You did solder and heat-shrink all of your connections, right? At a minimum, you used good quality, properly sized butt connectors with a reliable crimp tool, yes?


Length of wire - I assumed you were testing this for a POV. If you're running this through a whole spool of wire, you will have challenges if the spool is big enough.


Personally, I have a spool of Belden jacketed 18/4 wire that I use for all lightheads, which brings power, ground, sync, and pattern back to a barrier strip. This allows easy reconfiguration of patterns, sync strategies, etc., along with troubleshooting of problematic lightheads (nothing like having a LINZ6 crack and fill with water, and have that cause a whole string of lights to shut down because of wonky voltages on the sync bus). I also have some 18/2 for running lightheads that require a flasher, with the same techniques.


At the end of the day, copper is copper. If you used proper wire connection/termination techniques, aren't trying to run a dozen lightheads, and aren't testing it through a 500' spool of wire, it should work just fine.

 

[Kent@MoveOverOutfitters]

^ exactly

 

[minig0d]

This is what you do... go google the lights you are trying to run... you'll see somewhere in the specifications where it talks about "maximum amperage draw" (amperage is abbreviated amp sometimes)... It may say something like "Maximum Current Draw: 4 amps"... Now figure out how far you are trying to run the wire (total length of your wire run)... Now look at this chart below... Wire gauge numbers are the inverse of what you would think (22 gauge is thinner than 20 gauge)... look at the next largest amperage draw (in the case that your light uses 4 amp look at the line in the chart that says 5 amps) and then move across to the first distance in feet larger than the length you are trying to run... (if you are trying to run that 4 amp current 10 feet, you would go over til you see the 15 (since 9.5 ft isn't long enough)) then look UP to the top of the chart... that will tell you the MINIMUM AWG (American Wire Gauge) for stranded copper wire... (in my example it would be a minimum of 18 AWG wire)...


Most speaker wire is marked in tiny print along one side of it (either in a colored ink or imprinted into the wire) with the AWG of the wire... again you want this number to be a SMALLER NUMBER (THICKER) OR EQUAL to what the chart says...


One thing to keep in mind is that pure copper is the most conductive common wire material (but it is also more expensive than cheaper alternatives), so cheaper speaker wire may be made of aluminum or some other blend of metals that aren't as conductive, so you would need a THICKER wire to compensate. Copper wire is usually copper colored... if its silver in color assume its a cheaper alternative and that you need to use a thicker wire...





SHORT ANSWER: if its a small single lighthead like a grill light, most of them draw less than 1 amp, which can use a super tiny 24 gauge wire for the entire length of a vehicle and still not overload the wire... if we are talking lightbars, speaker wire may not be sufficient... sounds to me more like a poor ground or really really low quality speaker wire though...


Footnote: Electronics gurus please don't bother correcting my use of conduction into "resistance" and such... I tried to make this as simple as possible for the guy...


PS (the above chart is for stranded copper wiring, and I believe it has a 3% tolerance value built in but don't recall the exact amount)

 

[minig0d]

Most of the reason people moan and groan about using speaker wire for automotive runs is that most "speaker wire"'s is designed for home/interior use and the sheathing is not designed to be heat and chemical resistant. Automotive rated wires have a higher heat tolerance and chemical tolerance and usually have a thicker sheath to protect against abrasions (there are different standards)... but as long as you keep them away from sources of heat, chemical exposure, and abrasion it will be fine! I would say it does make it more important to use a proper fuse though, as the sheathing isn't as sturdy you do run more of a "risk" of it abrading/melting through and causing a short... with proper placement/grommets/etc you minimize these risks but still should always use an appropriate fuse.


All you have to do is add up all that maximum amperage for each light that will be running off the wire (as discussed in my post above) and add AROUND 10-20% leeway and that will tell you what size fuse you need (this value should always be less than the capacity of the wire according to that chart)... for example if you have two 4 amp lights running off the wire, that's 8 amp maximum draw, use a 10 amp fuse and make sure the wire can handle 10+ amps according to the chart for that distance...

 

[tvsjr]

One thing to keep in mind is that pure copper is the most conductive common wire material (but it is also more expensive than cheaper alternatives), so cheaper speaker wire may be made of aluminum or some other blend of metals that aren't as conductive, so you would need a THICKER wire to compensate. Copper wire is usually copper colored... if its silver in color assume its a cheaper alternative and that you need to use a thicker wire...

Oh noes! You mean all the harnesses that Motorola includes with their radios are cheaper alternatives? Shit, I better rebuild my whole truck.


In fact, wire that isn't copper colored can be better. If you're dealing with automotive wiring, you're most likely looking at tinned copper wire - which is actually equal in conductivity and superior in durability to straight copper. There is some minor chance that you might be looking at aluminum wire - which isn't a problem if your connections are rated for it. But it's very rare to see small gauge aluminum wire.


By the way, aluminum is actually more conductive than copper (lower resistance for equivalent length and size). It got a bad rap in household wiring because people were using aluminum wiring into connections rated for copper - causing galvanic corrosion, eventually leading to a high resistance connection, heat, and fire. Check out any utility pole - see all that wire up there? How it's all silver colored? Guess what? All aluminum.

SHORT ANSWER: if its a small single lighthead like a grill light, most of them draw less than 1 amp, which can use a super tiny 24 gauge wire for the entire length of a vehicle and still not overload the wire... if we are talking lightbars, speaker wire may not be sufficient... sounds to me more like a poor ground or really really low quality speaker wire though...

Not really. If you bothered to understand the equations I laid out above, you would know that 1 amp through 25' of 24ga. wire would result in 0.64V drop... that's pushing 5% and will start resulting in fairly substantial heating of the wire. Get into bigger lightheads or longer lengths and you will be in trouble soon. Whelen recommends 18ga wire for their lightheads for a reason.

Footnote: Electronics gurus please don't bother correcting my use of conduction into "resistance" and such... I tried to make this as simple as possible for the guy...

Simplifying is one thing. Being wrong is quite another. Please avoid confusing the OP with information that is incorrect.

 

[minig0d]

Oh noes! You mean all the harnesses that Motorola includes with their radios are cheaper alternatives? Shit, I better rebuild my whole truck.

Ummmmmm possibly... I don't know what they use in their wiring... fact of the matter is they usually compensate for resistance with larger gauge wiring... obviously their is voltage drop as well but being that they generally can accept anywhere from 9-16 volts, the drop is minimal...

In fact, wire that isn't copper colored can be better. If you're dealing with automotive wiring, you're most likely looking at tinned copper wire - which is actually equal in conductivity and superior in durability to straight copper. There is some minor chance that you might be looking at aluminum wire - which isn't a problem if your connections are rated for it. But it's very rare to see small gauge aluminum wire.

If the tip of the wire has SILVER COLOR SOLDER on it yes that is not what I'm referring to... aluminum wire is EXTREMELY common... go to autozone and buy one of those $5 LED light strips... it will be aluminum wiring or some cheap blend... if you buy a $50 surround sound speaker system from walmart, that speaker wire will almost definitely be not pure copper... not only is it cheaper but it is physically LIGHTER (even in the increased gauge to compensate) which makes manufacturing costs less, not to mention the extremely high price of copper in general at the moment)

By the way, aluminum is actually more conductive than copper (lower resistance for equivalent length and size). It got a bad rap in household wiring because people were using aluminum wiring into connections rated for copper - causing galvanic corrosion, eventually leading to a high resistance connection, heat, and fire. Check out any utility pole - see all that wire up there? How it's all silver colored? Guess what? All aluminum.

I have no idea what's on a utility pole... it would definitely make sense though regarding corrosion but I'm not going to speculate about something I don't know about... but where do you get that aluminum is more conductive? Copper is 98% conductive, aluminum 60%... The last article mentioned something that probably has a lot to do with your use on utility poles... the non magnetic properties during thunderstorms...


Copper-Versus-Aluminum Conductors


http://www.geindustrial.com/Newsletter/Aluminum_vs_Copper.pdf


Resistivity of Aluminum

Not really. If you bothered to understand the equations I laid out above, you would know that 1 amp through 25' of 24ga. wire would result in 0.64V drop... that's pushing 5% and will start resulting in fairly substantial heating of the wire. Get into bigger lightheads or longer lengths and you will be in trouble soon. Whelen recommends 18ga wire for their lightheads for a reason.

Um... ok... so a car running at 13.8v with 24AWG wire.. you have a voltage drop of .65v, which is a resulting voltage of 13.15v... which is still under 5% (which is more than acceptable in automotive wiring)... using 22 gauge would be recommended for this run as it results in a 2.99% loss (13.39v resulting)... you still don't have a point... I mean if you want to go into technicality... if you look at the chart in WHELEN'S OWN MANUALS, their chart looks like around a 3.5% drop is acceptable (if you look at their recommended gauges/distances)


EDIT: Lets also add that you used a value of 25 feet... as per this website the average length of a car is somewhere around 13.5 ft and 16.5ft for a SUV... in my example I said a common single lighthead drew less than 1 amp... the OP mentioned a Whelen TIR3 light which uses 390 mA... but we'll even give you the benefit of the doubt with that 1 amp... so 1 amp @ 16.5 ft would be a 3.13% drop... which is within Whelen's own recommendations... since you wanted to get technical and all... are you planning on going boo hoo and saying that the 25 feet was so you could route a wire along the entire perimeter of the car from the grill all the way to a distribution block located in the liftgate or something? come on dude... I'm trying to give this guy no frills advice that it doesn't take a mathematician or rocket scientist to utilize (aka follow this chart)... and you want to throw in equations that no one cares about? If you're really that bored why don't you calculate for us the temperature rise in that 16.5 or 25 ft section of 24 AWG stranded wire due to the resistance... I'd like to know what the temperature of the wire at the 3.5% resistance that Whelen uses on their chart and at the 4.9% which the 24ga wire would have at your 25 ft length. you can impress us with your electrical engineering and physics skills... don't forget to take into account thermal dissipation and you can assume the outside temperature is say 77 degrees when computing the rise and for the resistance value in general... oh and assume pure copper as well... clock starts NOW...

Simplifying is one thing. Being wrong is quite another. Please avoid confusing the OP with information that is incorrect.

So would you like to explain how I'm wrong?

 

[Flashguy]

I just want to go on record as saying you two are waaaaay to smart. All of the advice is appreciated and I believe his question has been answered by BOTH of you. Thank you...

 

[foxtrot5]

I'm finding the technical discussion very enlightening and useful. Thank you both for providing such in-depth information.

 

[ncfireman1918]

Ohm's law and all the electrical theory have been thoroughly discussed, so my only input here is going to be that I have used a spool of 18 AWG outdoor UV resistant speaker wire in my personal installations for years. I picked the spool up at radio shack for $15, and it is good wire. I can't (visually) tell the difference between my wire, and the factory wire on my DashKing, Dashmiser, or Flatlighter. It is identical in appearance, and has performed very well.