Main > Main Forum
Mounting LEDs in translucent happs pushbuttons (joymonkey?)
<< < (3/4) > >>
juggle50:
Joymonkey,

You rule.  Thank you very much for taking the time to do that tutorial.  Excellently done and it should be posted to the FAQ's somewhere. 

Have you ever tried sanding the tops of the LED's?  I've heard that that also disperses the light.
ShinAce:
Wow! A picture is worth a thousand words.

Having done this type of thing many times, I take for granted that instructions are hard to give. Although the first step is unnecessary, you can skip it and go directly to the second pic.

Props on the 3/16" drill bit recommendation...

And now I'd like to give a quick word on LED's. Think of an LED as a switch, because it IS a switch. So let's say you have a red diode rated for 1.9 volts forward drop and 20mA. This tells me that below about 1.5 volts, the LED will prevent any current from flowing, the LED will be off. But once you go above 1.9 volts, the LED lets ALL current go through. It does not limit current in any way. So if you are working with 5 volts, you know the LED will use 1.9 volts and wants a max of 20mA. Now you just need to find a resistor that drops (5-1.9)=3.1 volts and allows 20 mA of current.

R=V/I
If I(current) is always chosen to be 20 mA, the formula becomes
R=50*V
R=50*(3.1)
R=155 ohms, the closest value is 150, so use that.

This is assuming a 1.9 volt drop for the diode, 5 volt source power, and 20 mA current.

Please, if you choose to connect an LED directly to a voltage source, do not tell us about it. You are hurting the community by spreading such disinformation. I myself connected a green LED to a 12 volt battery just to see how bad it would be. The LED was shining red, not green, and I measured 250 mA of current. It burnt out in roughly 5 seconds.
JoyMonkey:

--- Quote from: juggle50 on February 09, 2006, 11:52:17 pm ---Have you ever tried sanding the tops of the LED's?  I've heard that that also disperses the light.

--- End quote ---

I haven't tried that since my LEDs fill the buttons with light well enough without any modification. I can see how it would work though, if you've got LEDs with low viewing angles.
JoyMonkey:
Just for completeness sake, here's the drawing I did from another thread that illustrates how important the viewing angle of an LED is when you're mounting them this way.



You can see how an LED with an acute viewing angle would create an extreme hot-spot in the center of the button (and can be almost blinding if the LED has a high MCD rating). An LED with a larger viewing angle and lower MCD will light up the button much more uniformly and will be less likely to blind your friends.


--- Quote from: JoyMonkey on January 30, 2006, 09:44:03 am ---As Randy has pointed out before, when you're mounting the LEDs so they're pointing straight up through the button (like in the above drawing) the most important factor in choosing an LED is it's luminous flux, which is determined by it's MCD and beam angle.

Here's a nice calculator to help you easily figure out an LEDs luminous flux:
http://led.linear1.org/lumen.wiz

While I'm at it, here's another useful calculator for determining what size resistor each LED needs:
http://led.linear1.org/1led.wiz

--- End quote ---
MovingTarget:

--- Quote from: JoyMonkey on February 09, 2006, 10:00:16 pm ---
--- Quote from: MovingTarget on February 09, 2006, 08:56:53 pm ---Hooking the LED to a 9v battery worked for me but I had a few extra LEDs in case I ruined it.

--- End quote ---

NEVER HOOK-UP AN LED DIRECTLY TO A POWER SOURCE WITHOUT FIRST PUTTING AN APPROPRIATE RESISTOR IN-LINE.

Read up on how LEDs are supposed to be used.
And use this calculator to figure out what kind of resistor your LEDs require.

--- End quote ---

Actually I did have a resistor attached to the LED when I did this.  Should have mentioned that too I guess :/

Also, please don't take what I said out of context.  I was suggesting that he should test his LED in his button to see if he liked the results.  This was for a quick easy (that's why I suggested the 9v) test and not a permanent solution. 

Also, my LEDs must be the more narrow angle ones, they are blue 8000~10000 mcd 20ma.
Navigation
Message Index
Next page
Previous page

Go to full version