All About Circuits Forum 12 5mm led to 12V DC 1000mA adapter
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#1
11-20-2010, 07:16 PM
 oupulino New Member Join Date: Nov 2010 Posts: 3
12 5mm led to 12V DC 1000mA adapter

Hi can someone help me out how to connect 12 X 5 mm leds on 12 V DC 1000mA adapter here is spec for led they are pre wire with own resistor any wiring diagram is really appreciated
The led are rated for 12V

The resistor = 470 ohm 1/4W.

The LED voltage = 3.0v - 3.4v

The LED amp = 20mA

If the adapter output = 1000mA then it is sufficient to connect more than 40 LED together. How to do it Im using it as a background
#2
11-20-2010, 07:24 PM
 tom66 Senior Member Join Date: May 2009 Location: Basingstoke, UK Posts: 2,613

I use this website: http://led.linear1.org/led.wiz

It suggests putting 3 LEDs in series in 4 parallel chains. Each has a 150 ohm resistor in series to limit current.

Be careful with your wall wart. Very likely it isn't outputting 12V - it is probably unregulated, basically a transformer, diodes and a capacitor. In order to get it to output 12V you need to load it down with the maximum 1A - otherwise the output can be as high as 18V, which will overheat your LEDs.

Perhaps try a switching power supply which should keep 12V or thereabouts no matter what the load, up to 1A. CUI supplies are quite popular. Ideally, chose a 9V supply, which would allow you to put 3 LEDs in series with no resistors maximising efficiency.

Also you might want to follow the buck regulator thread where a single LED supply is being designed, however it should still work with series LEDs.
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#3
11-20-2010, 08:21 PM
 oupulino New Member Join Date: Nov 2010 Posts: 3

the power adapter is Regulated and this led are pre wire so each led has already resistor 470 ohm 1/4W.How to wire 12 of them to one 12V DC 1000mA adapter do I have to add another resistor or cut of existing resistor
#4
11-20-2010, 08:37 PM
 SgtWookie Expert Member Join Date: Jul 2007 Location: In the vast midwest of the USA; CST Posts: 22,030

Just wire them all in parallel.
Since each LED-resistor string will draw ~20mA current, you can connect up to 1000mA/20mA = 50 pairs.
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#5
11-21-2010, 06:02 AM
 oupulino New Member Join Date: Nov 2010 Posts: 3

Quote:
 Originally Posted by SgtWookie Just wire them all in parallel. Since each LED-resistor string will draw ~20mA current, you can connect up to 1000mA/20mA = 50 pairs.
Thank you very much it work I was posting every were about this issue and only you resolve it properly other recommended replacing resistor,cutting of existing ones all nine yards long story

Thank you one more time SgtWookie
#6
11-24-2010, 05:00 PM
 Bill_Marsden Super Moderator Join Date: Mar 2008 Location: Dallas, TX (GMT-5 w/ DST) Posts: 19,022 Blog Entries: 5

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"Good enough is enemy of the best." An old engineering saying, Author unknown.

General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input. Thanks for the verbage Wookie.

 Tags 1000ma, 12v, 5mm, adapter, led

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