Author Topic: Also, some LED questions...  (Read 1237 times)

taeagan

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Also, some LED questions...
« on: February 08, 2016, 09:58:04 PM »
I have some bezels (kind of like these dudes here: http://smallbear-electronics.mybigcommerce.com/bezel-5mm-chrome/) and never did quite understand how they're supposed to be all put together.  Does the black plastic piece push on over the little tabs on the LED leads?  Is that how that works?  And then you just solder the led leads to wires (if not directly to the board)? 

Or is the black plastic piece supposed to slip on over your wire AND your solder join making it nice and neat?  I don't see how that would be possible - I can't see those little holes on the black plastic piece slipping over a wire-to-LED-lead solder joint.  But then again if it's not that way then you just have that solder joint twisting out there in the breeze. 

Also, if I have some old LEDs laying around is there a way to test them to figure out what the appropriate resistor is to complete the circuit properly?

Thanks again in advance!

galaxiex

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Re: Also, some LED questions...
« Reply #1 on: February 08, 2016, 10:31:16 PM »
Yep, you have it right. The black piece slips over the LED leads and holds the LED in the bezel.
The wires are soldered onto the LED leads.
They do hang out in the breeze, but the solder join and bare wire should be covered with heat shrink tube.

Google search "LED resistor calculator" and find one you like.
There are lots out there.  ;)

Here's one I found... http://led.linear1.org/1led.wiz
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HamSandwich

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Re: Also, some LED questions...
« Reply #2 on: February 08, 2016, 11:36:00 PM »
If you only want to test the LED, and not select a resistor for brightness, you can use 10k, 22k, 47k, and still get color.

taeagan

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Re: Also, some LED questions...
« Reply #3 on: February 09, 2016, 12:00:06 PM »
Thanks for the link to the calculator. I don't have the specs for the leds that I have. They're somewhere in the yellow-green range so I took some guesses based on that calculator. Everything I came up with was in the 300-400 ohm range. Any reason why all of the madbean specs use 4k7?

HamSandwich

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Re: Also, some LED questions...
« Reply #4 on: February 09, 2016, 12:25:29 PM »
It's a safer bet that your LED won't blow with 4k7. A lot of 'us' are using the water clear/super bright/etc LED's, which need a larger resistor then their diffused, older couterparts. I've used 10k-22k in some builds just so I don't blind someone.

If you really want to get down to it. Put a 25k or so trimmer in series with a 300-400 ohm resistor, or whatever the calculator says, starting with the trimmer at full resistance, and turn it until your LED is at a brightness you like. Add the trim resistance + the resistor and select a resistor of the closest value. Overkill.

davent

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Re: Also, some LED questions...
« Reply #5 on: February 09, 2016, 12:43:13 PM »
Overkill... twenty four steps from 510r - 18k2. Leftover bits put to use. I've all kinds of random leds, i just test them with this as i need them and then put them into use.




dave
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HamSandwich

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Re: Also, some LED questions...
« Reply #6 on: February 09, 2016, 12:45:39 PM »
Yet you make overkill seem so beautiful.