DC power circuit

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Old 07-19-13, 05:18 PM
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DC power circuit

Folks, I'm brand new here so go easy--I've got plenty of questions.

I want to power a 10 X 10 tent canopy at music festivals so we can jam at night with instruments. Power would come from motorhome 12V DC deep cycle batteries. I have ideas of what I want to do but want to know the best way to go about it.

Canopy would be @30 ft from MH. I want to run a direct line from the battery to the canopy, go thru a dimmer, from the dimmer splitting the line to 2 lines, one to each LED strip light. Each LED strip is 24 Watts and they would be 5' apart. I would run them for 3-5 hours a night. I would like some sort of quick connect/disconnect prior to the dimmer and one after the dimmer. The one after the dimmer would split the line from one to two, one to each light, if they make such a thing. I would also like to make up two additional lines with quick connect/disconnects, each line 10', that I could add in the event the canopy ends up further away from the MH than 30'.

I have a roll of 12 awg and 18 awg speaker wire, the LED strip lights, the dimmer, and alligator clips to attach to the battery terminals.

I would like to know what the best way to quick connect/disconnect and where to find these parts? Also, does it sound like I'm on the right track on what I want to do?

Thanks for any help--joe
 
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Old 07-19-13, 05:42 PM
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Welcome to the forums.

At 24 watts per string you could use either size wire. You could run #12 to the point where the strings combine.

If you didn't want to use a dimmer......you could put the two strings of LED lights in series and they will run at half brightness.

A 10 amp fuse should be used in the main line at the battery for wire protection.

The quick disconnects in the pic are inexpensive, reliable and easy to come by. They come in #20 - #10 wire size.

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Old 07-19-13, 05:46 PM
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Do these LED strips run at 12VDC? If not then you'll need to put a resistor in-line to lower the voltage or you'll need to run them in series in order to get the voltage right.

I'm not all that skilled with DC, but years ago I did build a lockout buzzer system like game shows use for panelists to buzz in. I used modular connectors similar to older hard disk drive molex connectors, though more robust. Thing is, the amount of power drawn through what I made is very small and only used sporadically. I would be a little concerned about continuous DC over a distance as it has a tendency to heat up wires. You'll need a much thicker gauge wire than you'd need for AC.

Come to think of it, you may want to look up microphone XLR connectors to see if they're robust enough, provided that you can avoid mixing up ports and blowing equipment. They're available weathertight, they're fairly common so finding them at parts places should be easy, and they don't just pull apart.

As for a dimmer, you need to know that LEDs do not dim in the traditional way. LEDs are often unforgiving of having their voltage reduced too low or ramped up too high, and dimming LEDs often will kill them. A better way to dim would be to turn off banks of individual LEDs on a given strip, but that would require controls that are probably impractical in this solution.
 
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Old 07-19-13, 08:01 PM
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It all depends on the type of led lights you have, if they plug in to a wall outlet then they are half wave rectified to create the DC voltage to run them (meaning there are some diodes in or near the plug that filter out negative voltages), if they are DC LEDs then tell us the brand and model or any info on their power hook up.

If they are made for automotive then they are already built for 12vdc and you can dim them with series resistance to limit the current (at 24 watts, this resistor will get HOT! So it will have to be rated accordingly).

I haven't looked, but I'm sure there are all kinds of products to use for the dimming, let us know how the LED chains are powered!
 
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Old 07-19-13, 08:05 PM
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Inline LED Dimmer - Remote Control LED Dimmer Switch - ElementalLED.com

Since your a rock star, this may be the only way to go!
 
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Old 07-19-13, 10:32 PM
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Thanks, folks.

PJmax: like those disconnects pictured. Do you know what they're called and where can I get some??

mnmattmn: I'll let you know when I'm "known". Doesn't happen too often to banjo players.

The other questions raised: I got the 12VDC LEDs from FlexfireLEDs.com. I ordered the Ultra Brights, warm white, which give 4800 lumens per 16' reel. Pretty expensive but very bright. They're also sending me the dimmer that they use that's rated at 96w, same rating as the 16' light string. I plan on cutting the string into quarters, using 2 four footers which will give 2400 lumens which may be a little too bright. The usual power source is a transformer plugged into 120VAC but because I'm going to use them from my motorhome, I'm going to pull 12VDC directly from the deep cycle batteries. The LEDs are 12VDC.

I ran an online calculator concerning volt drop and it shows a run of 30 to 35', 12AWG, would give me resistance of .098 ohms, volt drop of .39, voltage at fixture of 11.61 . What I'm not sure of is how much resistance am I adding by cutting the line and adding the quick disconnects??

Again, where would I buy the connectors from PJmax's photo?

Thanks for all the help.
 
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Old 07-19-13, 11:58 PM
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OK, I located the connectors online-2 pin flat SAE connectors. Any idea as to how much resistance is added by splicing in each connector? thx joe
 
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Old 07-20-13, 05:46 AM
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Looks like they are configured in sets of 3 LEDs in series, which is about right as white LEDs have a 4v voltage drop each.

You don't need a power supply if you're using a 12vdc battery, but the battery will provide anywhere from 11 to 14.5 volts at unlimited current so i would add a fuse and definitely use the dimmer. Always have the dimmer turned down 10% just to avoid over driving the LEDs at 14.5 volts.

I recommend buying an inline fuse holder with a 5 amp slow blow fuse (which will allow up to 60watts at 12 volts but is really to protect the LEDs from a short circuit). If you're using the accessory port (the automotive lighter port) you can find those with fuses built in (screw cap)

I wouldn't worry about voltage drop from connectors, its going to be negligible at such low power.

Few other things: the LED strips are made to be installed once, it looks like they're on a flex circuit which is not very durable so you will have to handle them very carefully when transporting them. You could get some 3/4" vinyl tubing and make your own rope light. Also, speaker wire will be fine but some sort of coax cable would work nicely too as it can handle being handled a bit more because the shield is a nice strain-relief. Finally, the website you mentioned offers solder less splice kits to interface with the led chain, be very careful with these splices as they will be the most fragile connection in your circuit.
 
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Old 07-20-13, 08:20 AM
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OK, all that sounds good. I'll get a 5 amp inline fuse from the battery. I built two 7' plywood -U- channel "fixtures" two inches wide with 1/2" lips and the LEDs will be afixed on the plywood and hung in the canopy rafters so people won't bump into them. When I take them down, I can disconnect each fixture, face the U channels together and bungy cord them together for transport which will protect the LEDs on the inside. Once I get them made and start using them, if I find I have a weak point, I can modify it as I go along. Right now, this is just to get me started to see how well they function. If they work OK, I think a lot of other players may want to do the same as everyone uses something different and most of what's used is pretty harsh on the eyes. Thx for all the help.
 
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Old 07-20-13, 08:53 AM
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I'll let you know when I'm "known". Doesn't happen too often to banjo players.
I know a banjo player named Joe Bethancourt. Got a couple of his albums too. It can happen.
 
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Old 07-20-13, 08:55 AM
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The power disconnects I mentioned above can usually be found at most chain auto supply stores like Pep Boys, Car Quest, Auto Zone, etc.

In case you still need to order parts there is a big company in Ca. that has a lot of parts...... David Levy.
Quick Disconnect Leads - David Levy Company
 
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Old 07-20-13, 10:14 AM
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I like the David Levy contact but I'm scratching my head about why I would want to connect a red female to a black male plug/connector which is what they show in the photos?
 
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Old 07-20-13, 10:21 AM
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I see what you are saying.......the ones I showed earlier are one female and one male is red and insulated.

On the DLC site the females are both insulated. I'm not sure if that's an error in the picture or the way they sell them.


ON EDIT:
That is really strange..........DLC is the only site to show those connectors that way. I checked at a dozen other sites and they are all as same as the one I posted above.
 
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Old 07-20-13, 11:41 AM
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I looked at a bunch of other sites also and the prices are higher than Levy. I sent them an e-mail asking about it and will let you know what their response is. I feel that the only stupid question is the one I don't ask.
 
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Old 07-21-13, 05:58 AM
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I like the David Levy contact but I'm scratching my head about why I would want to connect a red female to a black male plug/connector which is what they show in the photos?
Maybe that's why they're cheaper?

T-W-X, microphone XLR connectors could work but they are not at all weatherproof. The pins and sockets will start to rust in no time. They also have to be soldered. At $5 each it's also more $$ than PJ's solution.

Barclay, those connectors are "2-way flat trailer connectors." For multiple circuits, use a 4-way flat trailer connector.

 
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Old 07-22-13, 05:10 PM
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Rick, thanks for the info but I'm only running one circuit.

David Levy Co. sent me an e-mail first thing this AM and said their web page photo was wrong, They assured me that both ends plug into each other with red to red and black to black. I ordered connectors and fuse holders and they were shipped by noon. Very responsive company.

Thanks all for the help and I'll let you know how it works out.
 
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