Hooking LED's to 9 volt? What else do I need?

[Egon Spengler]

Hooking BLUE LED's to 9 volt? What else do I need? I remember I had to have something else the last time I did this. I'd like to hook as many as 5 LED's to one 9volt.

Thanks

 

[NakedMoleRat]

You'll need resistors set to the positive annode. What size you need, depends on what voltage LED you have. Also, to do five, it would be best to run them in series with all the negative annodes to a single point.

 

[Darth Cross]

You need a current limiting resistor. As the name implies, this will limit the current applied to the LEDs and keep them from burning out. You can use Ohm's Law (Voltage = Amps x Ohms) to calculate the value of the resistor.

For example: say you want to use 4 LEDs and they each draw 1.5 volts at 300 milliAmps (the info should be on the LED packaging). If you wire them in series that will be a total voltage drop of 6 volts.

Subtract this from the battery's voltage to get the amount dropped across the resistor: 9 - 6 = 3 volts

Now divide the voltage by the current (in amps) and you will get the resistance (in ohms) 3 / .3 = 10 ohms

This is how to calculate the size resistor you need. Just plug in whatever values you are working with. I hope this helps.

Richard

 

[CessnaDriver]

There are a few online LED resistor value calculators you can use too, just do a google search. Find one you like and plug in your known values.

 

[Egon Spengler]

Thanks everyone. I just found a really bright LED that might keep me from having to buy 5 of each.

http://www.radioshack.com/product/i...&origkw=blue+led&support=support&tab=features

Typical voltage: 3.7, with a maximum voltage of 4.5V

20mA (max.)

 

[WookieeGunner]

Don't know much about it, but here is one that is brighter and cheaper:

http://www.mouser.com/search/Produc.../Hvirtualkey60400000virtualkey604-WP7113PBC/H

 

[exoray]

Thanks everyone. I just found a really bright LED that might keep me from having to buy 5 of each.

http://www.radioshack.com/product/i...&origkw=blue+led&support=support&tab=features

Typical voltage: 3.7, with a maximum voltage of 4.5V

20mA (max.)

270 ohm resistor in series

BTW if you just need a few super bright blue LEDs drop me a PM, as I purchase them by the 1000s and get much better prices, even with shipping to you I can save you some money and I'll even include the resistor...

 

[FXArtist]

There are a few online LED resistor value calculators you can use too, just do a google search. Find one you like and plug in your known values.

This is super helpful for my project. Thank you! I am glad I found this old thread.