# 100 leds and 120v

Discussion in 'LEDs and Optoelectronics' started by nitram, Nov 3, 2012.

1. ### nitram

9
0
Jun 25, 2012
Ideally I need to be able to run 100 LEDs off of a standard US 120v outlet. I currently have 100 5mm LEDs that I would like to use but I don't know if its even possible. I could drop the number of LEDs down to 80 but thats it. Any and all help setting up this circuit is greatly appreciated. and Thanks in advance!

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,501
2,841
Jan 21, 2010
I would not recommend it.

Running them from a low voltage DC olugpack is much safer.

In any case, we can't answer your question unless we know the forward voltage of the LEDs

3. ### nitram

9
0
Jun 25, 2012
Oh okay.

The forward voltage is 3.5V for 50 Blue LEDs and 3.6V for the other 50 Green LEDs.

4. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,501
2,841
Jan 21, 2010
What current do you intend to run them at? 20mA?

Depending on how you wire them, you'll need a power supply capable of 10W or more.

12V 1A would be sufficient. You would group the LEDs into strings of three, each with their own resistor.

5. ### CocaCola

3,635
5
Apr 7, 2012
There are an infinite number of ways this can be done, some background on the design or intended use would really help...

6. ### nitram

9
0
Jun 25, 2012
wow i know less about wiring and electricity then i thought i did originally haha oh well time to learn.

Anyway here is the project. I am building a beer pong table with 10 spots on either side that light up. Im wanting atleast 4 LEDs under each cup.

7. ### CocaCola

3,635
5
Apr 7, 2012
You would build two of the attached, one for the green one for the blue side... Resistor value to be determined when the power supply is chosen, and will slightly vary from blue to green... Power supply should be 16V @ 750mA minimum to give a little head room, a little higher voltage won't hurt but don't go too high as it's a waste, although if you want 5 LEDs a cup you will need about 19-20V as a minimum... The mA rating can be higher and it won't hurt anything, and technically could be as low as 500mA but I wouldn't go that low...

Look on Ebay at laptop power supplies, you will easily find one in the 16V-18V range with plenty of mA for this project, and they are low cost...

Example http://www.ebay.com/itm/64W-AC-Powe...03303?pt=Battery_Chargers&hash=item2c6881e147

Remember that would only power 4 LEDs per cup...

Once you have a power supply chosen, then it's just a little math to work out the resistor values...

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Last edited: Nov 4, 2012

25,501
2,841
Jan 21, 2010
9. ### nitram

9
0
Jun 25, 2012
Thank you VERRY VERRY MUCH cocacola this helped at lot!