130 LED's on 1 resistor

[greenhill85]

hi I need to wire 130 leds to a 5volt supply is there a way to do this with out using 130 resistors


LED'S used

3mm
10000 mcd (ultra bright)
Forward Voltage : 3.2v – 3.8v
Forward Current : 20mA (Typical) 30mA (Max)

supply

5 volt usb

I would like to know an easy cheap but effective way to drop the voltage to 3.3 so that I can run the led's but not burn them out. prefer not to use 130 resistors as there is not a lot of room

thanks for any help you can give

(complete noob)

 

[Mitchekj]

Sounds like you'd have to run them all in parallel, in that case your USB must supply upwards of 2.6A.

As far as I know, 500mA is the max USB output? Maybe 1A?

 

[Ian]

As far as I know, 500mA is the max USB output? Maybe 1A?

Yep, generally speaking USB 2.0 (most common) is 500mA and USB 3.0 is 900mA

 

[greenhill85]

thanks for the replys you are right the usb is 500ma looks like a rethink is required will probably go for a external plug supply or try to lower the amount of leds and run them on the usb

 

[greenhill85]

hi guys just had a look on ebay and found this external plug supply can i use this or will i have a problem with it being 5 volt

5*Volt*2.6 Amp*DC Regulated Power Supply
Top quality power supply suitable for driving various items of electronic equipment.
This is an AC to DC power supply - it transforms 100-240v AC to 5v DC. It has a regulated 5v DC output and can supply from 0.01a (1ma) to 2.6a (2600ma) making it ideal for any piece of equipment that requires 5v DC at up to 2.6a.
Features:
100v to 240v AC Input
Plugs directly into UK mains socket
5*Volt DC,*2.6a regulated output

once again thanks for all your help

 

[greenhill85]

hi guys if i use the power supply above at 2.6 amps which is needed will i still need a resistor if they are wired in parallel or will they automaticaly share the 2.6 amps between them

 

[(*steve*)]

Read the sticky about driving LEDs.

You should really have 1 resistor per string of LEDs. To minimise the number of resistors, use a higher voltage power supply (say 12, 24, or even 48 volts).

They will not share current. In fact, one will tend to hog the current and blow. Then another will hog the current and blow, then another... (you get the idea)