# LEDs in Parallel - 12v

Discussion in 'The Projects Forum' started by Lewisjenkins1, Jul 11, 2015.

1. ### Lewisjenkins1 Thread Starter New Member

Jul 11, 2015
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Hi everyone, I'm new to this forum so I apologize if this seems to be a question asked a lot.

I am planning a project to create LED stips to illuminate all the walls of my room.
I am just wondering however- how many LEDs can be connected in parallel on a power supply providing an output of 12v DC (600mA 6VA)? I plan to make 2 strips of 25m- with an LED every 10cm (Total of 250 LEDs per strip). Is this too many or is this possible?

At the moment I am connecting the LEDs to 510 ohm resistors in parallel.

2. ### Alec_t AAC Fanatic!

Sep 17, 2013
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Welcome to AAC!
You'll need a bigger power supply.
What are the current rating and colour of the LEDs (white LEDs have a higher Vf rating than red)?

3. ### #12 Expert

Nov 30, 2010
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As a very crude estimate, you are talking about 50 watts of power...depending on how effectively the LEDs are arranged to achieve the best efficiency.

Jul 11, 2015
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5. ### Boxy New Member

Jul 11, 2015
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If the supply that you are going to use is 12v, 600mA max, then you can only add 30 leds on that power supply (with no safety factor). For your 250 Leds, you are going to need a power supply that can output > 5 amps @ 12 volts.

250 Leds * 20mA = 5 ampers (desired case, 1 led strip)

600mA/20mA = 30 Leds (with your supply)

6. ### Lewisjenkins1 Thread Starter New Member

Jul 11, 2015
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Thanks for the support.

So if I obtain 2x 12v 5w power supplies, I will be able to correctly power said LED strips in separate circuits without a problem right?
If so I will replace my power supply.

7. ### Boxy New Member

Jul 11, 2015
3
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No, you are going to need 60w+ Power supply for 1 strip.

250leds*20mA = 5 Ampers,

Reqired power in watts = 12v*5 = 60w

8. ### #12 Expert

Nov 30, 2010
16,705
7,358
The specs on those LEDs are kind of wide resulting in numbers from 90 ohms to 150 ohms to run 3 LEDs in series. Better wait until they arrive and find out what their real voltage is so you don't run some at 20 ma and some at 5 ma. First guess would be 120 ohms in series with 3 LEDs. Do that 83 times using 1.66 amps at 12 volts. That's 19.92 watts.

and, no, 5 watts is NOT 5 amps. 5 amps times 12 volts is 60 watts.
My proposal uses less than 2 amps and just about 20 watts.

If you want to run one LED per each resistor, you would be better off buying a 5 volt power supply. 250 LEDs x 0.02 amps = 5 amps
total power = 25 watts.

Last edited: Jul 11, 2015
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9. ### Boxy New Member

Jul 11, 2015
3
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+1 what has been said here.

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10. ### Lewisjenkins1 Thread Starter New Member

Jul 11, 2015
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Oh, I misread that last post thinking it was 5w, apologies.

Thanks very much, I will certainly try that.