What should I use instead of a battery?

Question

I have a matrix of LEDs run in parallel. http://www.instructables.com/id/RGB-LED-Mood-lighting/ besically this, but I plan on doing several other boxes along with it, so about 500 LEDs running with a forward current of 20mA and a voltage of 3V i guess. So I'm planning on making this array as square as possible, but it would take a LOT of 9 volt batteries to power it. So how should I power it?

Answer 1

I downloaded this but I can't really see how the LEDs are connected. It makes a lot more sense to have more LEDS in series and run them from a higher voltage. For example, 4 x 3V diodes in series, and 100 of these strings in parallel, will give you 20mA x 100 or 2 amps A 12 volt battery or a beefy (2amp) mains adapter could supply all these LEDs.

Or 8 LEDs in each string and 2 x 12V batteries in series to feed them, or a 24V mains adapter, the current would now only be 1 amp so the battery/adapter could be smaller.

You only need a series resistor if the voltage is too high for the LED, but if you put them in a series string you can organise it so the voltage for each diode is less than Vmax, the highest voltage that can safely be applied. A series resistor adds to the load so you need a bigger power supply, sometimes it takes more power than the LED ! A higher voltage and more LEDs is better.

You may find that the light emitted is acceptable at a significantly lower voltage than Vmax. so you could put more LEDs in each string.

Answer 2

Dern right it would take a lot of 9V batteries - you'd need one for each LED!





500 X .020 A = 10 A.





Use a 15 amp (or larger) power supply.



Any of these would work for your purposes:



Samlex SEC-1223



MFJ 4225



Astron RS-20A



Jetstream JT Mini 15 (not a good choice, but it's cheap)





All of these are 12V supplies.

I would use a separate resistor for each LED:

It's much easier to be certain of the correct value,

and if any LED or resistor failed,

the rest of the LEDs would still light up.

Answer 3

Get five 5V 2.5A supplies. Run 100 per supply. Size the resistors for 5V supply. 2.5A gives things breathing room.