# Constant Voltage DC & LED's

Discussion in 'LEDs and Optoelectronics' started by hannibal, Jul 27, 2011.

1. ### hannibal

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Jul 27, 2011
I am planning on building a grid of 64 leds. Assuming each takes 10ma to light the entire grid up would require considerable current. My question is, if I buy a 5v 1000ma Dc constant voltage power supply would this effectively power the entire grid, and if I'm only running 1 led, the psu won't blow out the led, will it?

My foray into the world on electronics is just beginning, so thanks for any help!

443
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Jun 10, 2011
Welcome to the forum! What exactly are you trying to accomplish with this array of LEDs?

If it's to display things like messages, a commonly-used technique is to display only one row or column at a time and do it fast enough so that your eye thinks they're all on at once.

As long as you have the proper resistor on each LED, your power supply won't harm one LED.

3. ### hannibal

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Jul 27, 2011
I'm planning out an led cube, which would multiplex by layer, i'm not sure if a microcontroller could update row by row by layer quick enough for the leds to appear not to be blinking.

I'm not sure what you mean by the appropriate resistor. Will the psu always output 1000ma or is it just capable of that? If i put a large resistor on each led, then when all 64 turn on, will it draw too much current from the psu?

4. ### BobK

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Jan 5, 2010
The current rating of a power supply is the maximum current it can provide. The amount of current it actually applies depends on the circuit it is powering. If you apply a 5V 1A power supply to a 100 ohm resistor it will supply (by Ohm's law) 50ma. If you apply to same 5V to a 10 ohm resistor, it will supply 500 ma. If you apply it to a 1 ohm reistor it will try to provide 5A and will either blow up, drop the voltage, or shut off depending on how well protected it is.

5. ### trueblue

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Jul 26, 2011
Most power supplies include an overload protection which causes the power supply to shut down to protect itself. A fuse is an effective way to disconnect the power supply to the load if too much current is drawn and most power suppiles come equiped with one.

trueblue

Last edited by a moderator: Jul 27, 2011
6. ### hannibal

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Jul 27, 2011
@BobK

Thanks! That's what i was wondering about.

7. ### TBennettcc

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Dec 4, 2010
Last edited: Jul 27, 2011

443
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Jun 10, 2011
The LED displays you commonly see everywhere are often multiplexed to reduce current requirements. I don't think you'll have any problems.

Are you considering making a 4x4x4 cube?

9. ### hannibal

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Jul 27, 2011
Yeah, I figure it'll be fun, and a good teaching experience for improving my sodering and electrical abilities.