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[REK636]

This project I have been working on for at least a few weeks now and I am not sure how to run power to all the LEDs. The PCB is set up in 15 series of 6 LEDs and 6 series of 3 LEDs. The IR LEDs are rated at 1.5v @ 50mA each.

I thought about 12v because I have a few power supplies that went to rechargeable flashlights that died. But now I want to go portable and go with batteries instead of a power cord.

Thinking of several 9v ones for either 18v or 27v. Then I'll just need to recalculate for the resistors. I don't have capacitors, because I don't know how to use them or figure them in.

[REK636]

Anybody? Just need a power supply and I can get this done.

[trials_modder]

could you rephrase/explain further how that pcb is set up?

[REK636]

I didn't have room on the board for the resistors they are on another board. Each searies of leds gets power from a wire on the other board.

Not actual size.

[trials_modder]

correct me somebody if i'm wrong but:

to run the series of 6 LEDs,  you'll need 6*1.5 = 9 V, 300mA per series*15 = 4.5 A total
and the series of 3 LEDs is 3*1.5 = 4.5 V, 150 mA per series*6 = 900mA total
108 LEDs

total = 5.4 A of current required? that would mean a battery rated for 5.4 AmpHours would only last... an hour? if those calculations are correct then i think the bigger problem is finding a suitable battery (i'm not sure how portable it would be).

again, correct me if i'm wrong as this current seems rather large

[REK636]

That makes sence about the current not working well for a battery. Looking at taking out the 6 series of 3 leds and replacing with somthing with less mA or a diffrent color.

Still the  6 x 1.5 = 9 V, 300 mA per x 15 = 4.5 A fot the 90 LEDs

[trials_modder]

so say if you use a decent 12 v battery (laptop lithium ion maybe?) then...

on each series of 6 LEDs you'd need (12v-9v/0.3A) = 3 ohm resistor per branch = essentially no resistor?
and (12V-4.5V/0.15A) = 50 ohm resistor per branch

i think those calculations are set up so that the resistor lowers the 12volts to the amount needed by the LEDs in series to run

[viridius]

You might try strobing the LEDs to conserve power.  Other than that, infrared is the most efficient color in terms of electricity to light.  Don't run them without a resistor.

[REK636]

Strobe them. Using a 555 or somthing.

[viridius]

Strobe them. Using a 555 or somthing.

Well, 555s can only source a few mA, so you'd have to use a logic level MOSFET or something but yeah.