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# battery power supply for LED light

Thu 24 Jun, 2010 02:54 pm
I want to use a 12 Volt DC LED light in an art project. I've purchased the LED bulb, now I need to know how to connect it to battery power. How many double AA batteries does it take to come up with 12 volts? All the battery holders I find are for 9 volts. Any help would be appreciated.
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Type: Question • Score: 4 • Views: 3,599 • Replies: 6
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talk72000

1
Thu 24 Jun, 2010 03:39 pm
@TarrArt,
Look at the label. I think they are usually 1.4 volts.
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BillRM

1
Thu 24 Jun, 2010 03:57 pm
@TarrArt,
Eight batteries now the second question is how many millamps does this LED light draw and how long do you wish the light to be on.

Off hand I think you can get around 500 mill-amps hours out of the AA batteries but I would need to google that to be sure.

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Rodger Hooks

1
Sat 22 Sep, 2012 03:27 am
Hi all,

LEDs are as small as traditional string light bulbs, but they last up to 100,000 hours, use up to 90 percent less power, and they are almost indestructible under normal conditions. This makes them ideal for homemade battery-powered string lights.Determine the desired length of the string and the number of LEDs to be included in it. Divide the length of the string by the number of LEDs to establish the gap required between the LEDs for a string of equidistant lights. For example, in a 500 cm long string containing 100 LEDs the distance between the LEDs should be 500/100, or 5 cm. To the length of the light string, add sufficient extra wire to reach from the start of the lights to the battery. Cut two wires to this length. Strip the insulation from the final 5mm of each wire. Cut the LED legs to the desired length, and then solder the first LED across the ends of the two bare wires. Remember that all subsequent LEDs must have the same polarity, so be sure to note the orientation of the first LED. Work backward from the end of the light string, removing about 2mm of insulation from each wire at every equidistant point along both wires. Solder one LED across each pair of bared points along the wires. Connect battery clips to the ends of the wires. Connect the battery clips to the battery terminals, observing the correct polarity. Check the light string for LEDs that fail to illuminate. Identify the "dead" LEDs, disconnect the battery, unsolder the relevant LEDs and rotate them through 180 degrees. Re-solder them, reconnect the battery and check again. Replace any LEDs that still fail to illuminate.

Best Regards,
Rodger Hooks
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john hassen

1
Mon 24 Sep, 2012 01:30 am
@TarrArt,
Hello community group,

LEDs find wide use in emergency lighting because of their high efficiency and control simplicity. The circuit provides a highly efficient and reliable design for emergency LED lighting at 3 to 6W. The circuit's input is 12V ac, which the full-wave bridge rectifies and one or two capacitors filter into dc.. The battery is a 12V lead-acid type. IC1 compares the battery voltage to the supply voltage. When the rectified voltage drops below the battery voltage, the battery takes over to provide LED power. The circuit has some small switching losses, which should be acceptable as long as IC2, a 12V PB137 battery-charging circuit from STMicroelectronics. To get 12V ac, you can use an electronic transformer. These transformers provide 12V at a higher frequency, so a 10-µF capacitor can hold the voltage high as well as provide a high power factor.

Best Regards,
John Hassen
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MontereyJack

1
Mon 24 Sep, 2012 01:42 am
You can find strings of battery -operated LED lights as Xmas decorations for a couple bucks, which obviates the need for you to do any wiring yourself. If you can use ten or a dozen small LEDs in a string, or bunch them up in a ball to act as more or less a single light source, that would be a simple and cheap way to do it. I've already seen some Xmas decorations for sale (I know it's not even Halloween yet, but there they are) in some of the more mercenary chain stores. They usually run on 2 or 4 AA batteries, which would be either 3 or 6 volts. They'll burn for hours. They may also make Halloween battery LED light strings, which would probably be orange-and-yellow bulbs. Walgreens usually seems to do a lot of Halloween deco stuff, or Target. You can also find 9-LED up to 36-LED flashlights, which are pretty small, and compact, running on 3 or more AAs widely available, again for a buck up to maybe 5 bucks. They'd probably run several days on one set of batteries, maybe more. If you don't need a naked bulb, radiating light in all directions and very small, those are a couple options you might explore.
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Steven Brooks

1
Mon 24 Sep, 2012 09:29 pm
@TarrArt,
Hello Members,

To operate an extra-bright LED, first find out the voltage required by the specific LED you want to use. Most extremely-bright LEDs need at a power source of at least 4.5V to operate at full intensity. Most LEDs use so little current that AA cells will run them for a good long time, but a set of 4 D cells or a 6V gel cell may be better suited to your project. Find a knowledgeable electronic hobbyist near you for hands-on assistance.

Light Emitting Diodes:
LEDs emit light when an electric current passes through them. LEDs must be connected the correct way round, the diagram may be labelled a or + for anode and k or - for cathode (yes, it really is k, not c, for cathode!). The cathode is the short lead and there may be a slight flat on the body of round LEDs. If you can see inside the LED the cathode is the larger electrode (but this is not an official identification method). LEDs can be damaged by heat when soldering, but the risk is small unless you are very slow. No special precautions are needed for soldering most LEDs.

Thanks and Regards,
Steven Brooks
0 Replies

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