those radio shack LEDS ?

[adamtekh]

so i was just wondering if those those radio shack LEDS are any good , r they bright ???

 

[Iron Hawk]

they are just as good as any, if you put the correct voltage through them. Blue Leds require more voltage than other color leds so if you run a blue led (3.8v) off of a red led's 2.0v it will not appear very bright.

 

[Fraggle]

what resistor would you use for the power on that 3.8v? run it off the 5v i assume? Can you tell from the LED what voltage it is? I have some I scavenged, but don't know their power requirments. their dual color, and appear to have different requirments (i.e. 12v fried the red side, but not the green. small amp, max 500ma off this powersupply)

 

[adamtekh]

i do belive they sell some 12v ones , thats what i was asking about

 

[MechCD]

I'd say 12v is a lil high for an LED

A good guess is 3v and 20ma. You cna go up or down from there. you won't burn an LED at 3v, unless it has way too many ma going through it.

I have some 2.8v 30ma LEDs that are slightly brighter at 3v, 20ma. They don't get warm to the touch. If an LED is warm, it has too many volts or mas going through it

 

[Fraggle]

how did you get 3v 20ma??

 

[Ottoman]

I bought 4 12v led's linked them together... gives nice hue, not too bright.. just enough to highlight the inside... a subtle touch

 

[Iron Hawk]

reds oranges and yellows generaly use 2.0-2.5 volts green 2.2-3.2v & blues 3.6-5.0v. this is just general, there are many diferent types of leds, some even have resistors wired into them.

 

[MechCD]

how did you get 3v 20ma??

I bought an LED with those specs. And then I used a variable resistor from a 5v source to find the proper voltage and MA rating. Once i found what resistance to sue, I got a fixed resistor out of my junk box and used that.

All that isn't needed just for motherbaord power and hdd connectors. That dandy LED was for a gel-cell charger

 

[WillysNut]

what resistor would you use for the power on that 3.8v? run it off the 5v i assume? Can you tell from the LED what voltage it is? I have some I scavenged, but don't know their power requirments. their dual color, and appear to have different requirments (i.e. 12v fried the red side, but not the green. small amp, max 500ma off this powersupply)

Not sure about 5v but you need a 470 Ohm resistor on the postive or negative lead to run an LED on a 12v line.

Edit: Checked a couple sites, and it appears that you need a 330 Ohm resistor to run most standard LED's on a 5v line. Not quite sure how that would affect the blue unit but...

 

[robertm]

Ok here is the deal with LEDs LED stands for Light admitting diodes. Doide have a voltage drop and this voltage drop is the voltage rating of the doide.

How bright and how long an LED lasts depends on the current the LED is driven at. I have run red 1.2 volt drop LED from 48 Volts DC and its not a problem as long as you know the value of the resistor you need to drive the LED.

If you look at the specs on an LED you will see the max current rating for the LED go over this current for any long amount of times and the diode will burn up. To make a LED as bright as it can you drive it very close to this limit. Most ofen you design for 1/2 to 2/3s max current depending on the use of the led.

So to figure out what Resistor you need to drive an LED do the following. current = I voltage= V and resistance = R.

I=V/R

This reads Curent is equal to Voltage divided by resistance.

So if you want to drive an LED at 20mA (mili Amps) At 12 volts then you do this

R= V/I

R=12/0.02 (Current is expressed in Amps)

R= 600 Ohms

So to drive an LED at 20mA from a 12 volt line use a 600Ohm resistor.

So know the max current of the LED you want to use then figure the resistor to match the voltage you want to run the LED from.

 

[WillysNut]

Thanks for the info robertm...very much appreciated!!

 

[robertm]

I hope thats why most of use are here to pass along and gather information.

 

[WillysNut]

I hope thats why most of use are here to pass along and gather information.

That's the idea I got when I started posting here. We can't possibly know everything now can we? You scratch my back and I'll scratch yours...and we all make out for the better. Unfortunantely at times a few of the masses spoil things. Best to just stay calm and post with detail and fact instead of frustration. I know the feeling your post is expressing!!! Thanks again!

 

[Iron Hawk]

One of us alone may not know everything, but the 15834 currently registerd members put together must know a LOT!

 

[robertm]

I hope thats why most of use are here to pass along and gather information.

Its realy bad when you cant understand your own post LOL

Well I learning that at times your better off not to post when confronted. Let poeple take or leave your advice or comments as they are But its hard t times

 

[Fraggle]

ahhh. then I was looking for the wrong information. Thanks for clearing that up for me.
According to Radioshack's web site most LED's run on 10-20ma so I'll assume that a safe place to start (I have about 25 of these things.)


One of these days I'll borrow a camera and post some pix of my case up here. I've gotten alot of kewl ideas from this site. You guys rock!!

 

[Yakbak]

What is the Radio Shack part number for a good blue LED? Or just all of them they have...

 

[robertm]

What is the Radio Shack part number for a good blue LED? Or just all of them they have...

Radio Shack list two Blue LEDs

900-7861
900-7860

They sell nether in there stores you have to get them online or on the phone. There stores will also order them for you.

I would look for them at Digikey there about half the cost only problem is they have a 5 dollor change on orders less then $25 so buy 10 and sell some to your friends Digikey part and link is below

P465-ND

Digikey

 

[adamtekh]

i just bought 3 red leds fomr radio shack

they come in this tube with the resitors and all , all u have to do is wire them to the 12v line

now my comp kinda reminds me of HAL