Make 12 volt christmas lights

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bug73 · #1 Post by **bug73** » Thu Nov 27, 2008 1:23 pm

This may need to be posted in off topic, not sure...

It might be easier to just buy them, but I cant stand to spend money on something if I can make it a lot cheaper. Most of the time my labor for myself is free.

I buy the cheap 100 light bulb strings after christmas on sales from 1-2 bucks a box.

Here is the Schematic for rewiring normal 120 lights to run on 12 volt so you can run them on your boat or in your car or what ever...even run them on a couple of 6 volt flashlight batteries wired in series. You can run them on 9 volt batteries also but they dont last long. for 9 volt battery operation just wire 4 bulbs together instead of 5. The schematic says it all.

rewire.JPG

kimbercarry · #2 Post by **kimbercarry** » Wed Dec 31, 2008 10:21 am

To reduce the current draw, purchase the 60 light,

LED strings. Each LED requires 3 volts to operate so use the same wiring diagram and use 4 LED's. Current draw for each LED at 13.8 volts is only 13ma so for a string of 60, there is only about 3/4 amp total draw. this will allow several strings to be connected end to end without depleting the spare battery too quickly.

I found the LED's at Wallyworld for 3.50 each (1/2 price) and they are available in white,blue (my favorite), red and green.

The only drawback that I can see is that if one of the 4 LED's burn out, the voltage (3.4 volts)is shared by the other 3 LED's which results in a voltage increase to 4.6 volts and could result in frying the other 3 LED's but LED's typically have a life of over 200.000 hrs I didn't consider it a problem

bug73 · #3 Post by **bug73** » Wed Dec 31, 2008 4:39 pm

I havent had a chance to tear apart an LED string yet.

Dont those have a resistor in there somwhere to limit the current? You may have to put a limiting reistor in there to limit the current if you rewire one if they dont have one already built in somwhere, possibly in the plug.

It would for sure draw less current.

bug73 · #4 Post by **bug73** » Wed Dec 31, 2008 4:51 pm

as I suspected...there is a resistor in there somewhere...here is an large article about modifying them and how they work...interesting if your an egg head like myself...you would have to make sure you get the resistor back in there if you cut it out or you will have VERY bright LEDS for about 1/10th of a second...LOL...Looks like if you have all red LEDs then the wiring is different yet according to this article...

http://www.ciphersbyritter.com/RADELECT ... DLITES.HTM

kimbercarry · #5 Post by **kimbercarry** » Thu Jan 01, 2009 10:20 am

Actually there are two resistors. 18k each I did not use them because the 4 LED's seem to work great with the voltage divide.
Used the brute approach Increased DC voltage until they had a brite glow. Seems to be durable and bright at 3.45 vdc and 13ma. Current draw seems to be in the proper range. Had them on for ~4 days with no problems. Dont recall how RMS works on a Diode

kimbercarry · #6 Post by **kimbercarry** » Thu Jan 01, 2009 10:29 am

Just read the link you provided and it looks that I wasted some time because the connections will corrode and fail in a damp environment. Thanks for the link, back to the drawing board.

kimbercarry · #7 Post by **kimbercarry** » Fri Jan 02, 2009 10:52 am

Solution 0: 4 x 1 array uses 4 LEDs exactly
+13.8V
+ -|>|- -|>|- -|>|- -|>|- -/\/\/\- + R = 1 ohms
The wizard says: In solution 0:

* each 1 ohm resistor dissipates 0.4 mW
* the wizard thinks 1/4W resistors are fine for your application Help
* together, all resistors dissipate 0.4 mW
* together, the diodes dissipate 276 mW
* total power dissipated by the array is 276.4 mW
* the array draws current of 20 mA from the source.
Looks as if the 4 LED wiring will work but with the LED leads being steel, they will rust out on a pontoon boat in short order.

bug73 · #8 Post by **bug73** » Sat Jan 03, 2009 6:38 pm

maybe coat each one in either silicone sealant or maybe some silicone grease, wont take much. Another labor intensive way would be to tin each one but if your tinning isnt good by missing just one spot, rust will get to it, maybe use a solder pot? but you could still miss a lot of the lead and is still labor intensive, I think I would be willing to try silicone sealant in the sockets and on the leads...

not sure what your last post with all the symbols and such meant though...

Here is another site I found with a quick search...good info..

http://www.theledlight.com/LED101.html

you must have the bright white type, in that case 4 of them in series across the battery would work great without the resistor as you figured. Great to know.

when I played with LED's before we only had to worry about 15 ma and about a voltage drop of approx 1.7 volts....now with so many differnt types and powers things have changed dramaticaly. Have not dealt with them in awhile. I do have some super bright ones in my junk bin but have not figured out or needed them for any projects lately...although I do have a project in mind involving a headlight on my snowblower made from them...they came out of one of those super bright led flashlights.

#9 Post by **HandymanHerb** » Sat Jan 03, 2009 9:43 pm

Between 2 houses I think I put up 35 sets, I liked the fact that you could hook up 87 sets together, that's over 2000 feet of lights .

kimbercarry · #10 Post by **kimbercarry** » Sun Jan 04, 2009 9:20 am

Cut and paste did'nt work that well on the symbols, they origionally had a drawing of 4 LED's in series left to right and a 1 ohm resistor at the right end.
Thought about pulling the light through a 1/2 ID plastic tubing and sealing around the ends with silicone to protect them from the elements before mounting them under the pontoon but after reading the article on the link you provided, it appears that using a more expensive LED string (Phillips) did not provide the reliability present in regular bulb type so the el cheapo wallyworld brand may be even less durable. I plan to stay on the lookout for LED strings that have copper leads. Might be better off to go ahead and put out the bucks on the LED rope but it would'nt be as much fun.

#11 Post by **HandymanHerb** » Sun Jan 04, 2009 12:44 pm

I want to see if I can buy bulk strings of lights to decorate homes with and make my own lengths, I did three homes this year not even trying if I can give them a good deal on light prices, I can get a bunch more to do.

bug73 · #12 Post by **bug73** » Sun Jan 04, 2009 4:31 pm

kimbercarry wrote:Cut and paste did'nt work that well on the symbols, they origionally had a drawing of 4 LED's in series left to right and a 1 ohm resistor at the right end.
Thought about pulling the light through a 1/2 ID plastic tubing and sealing around the ends with silicone to protect them from the elements before mounting them under the pontoon but after reading the article on the link you provided, it appears that using a more expensive LED string (Phillips) did not provide the reliability present in regular bulb type so the el cheapo wallyworld brand may be even less durable. I plan to stay on the lookout for LED strings that have copper leads. Might be better off to go ahead and put out the bucks on the LED rope but it would'nt be as much fun.

You still might get some corrosion on the copper from electrolysis if the bases are not sealed well. It just takes a little bit of moisture and a little current between the leads and the copper, tin, lead or whatever they are made of will migrate over to the positive terminal in a DC circuit. Wont happen as much in an AC circuit though.

I tried to seal some regular christmas light bulbs in 1/2 inch tubing once. Had a hell of a time pulling it through the last 4 feet or so even with soap without breaking the string. The stickyness of the tubing added up when more of the lights got inside. Might work better with 3/4 inch but I didnt try it after the 1/2 inch disaster.

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