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Help finding LED and suitable resistor for CK2III

post #1 of 11
12/28/09 at 12:36am
Thread Starter 
Hi.

I'm building a CK2III and ordering parts for it now. For some reason I have difficulties finding the right kind of LED and a resistor for it. The partslist says "Your Choice", and that doesn't really help me.

A blue one is what I'm looking for. I'm about to order some other parts from Digi Key, so it would be cool if you guys could help me finding one there.

Thank you

EDIT: Can I use this? When I use the Led Calclator, it tells me "With a supply voltage of more than 24V, you'll dissipate excessive heat in a current-limiting resistor." The supply voltage is going to be 30V, will that be a problem?
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post #2 of 11
12/28/09 at 12:48am
i'm quite partial to this one:

Digi-Key - 751-1092-ND (Manufacturer - TLHB4400)

Unfortunately out of stock right now.

I wouldn't use the one in your edit - 2500mcd will be rather bright.
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post #3 of 11
12/28/09 at 1:14am
Thread Starter 
Okey. Do you know about any alternatives to that one? Should it be Vishay, or could other brands do a decent job to?
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post #4 of 11
12/28/09 at 1:22am
This one might be an option:

Digi-Key - 67-1748-ND (Manufacturer - SSL-LX3044USBD)

I like the diffused lenses as they help deal with the fact that blue LEDs tend to be quite bright (like a flashlight in a dark room). You will also want to make sure you likely run it with about 1-2mA current only.
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post #5 of 11
12/28/09 at 3:36am
Thread Starter 
Sounds good, thank you!

Quote:
Originally Posted by cobaltmute View Post
You will also want to make sure you likely run it with about 1-2mA current only.
So that it doesn't get to bright? A resistor between 10k and 15k ohms will be good then?
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post #6 of 11
12/28/09 at 4:43am
Vishay TLHB4400 is also available at Mouser and they currently have plenty in stock. The default 10K resistor will be fine.
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post #7 of 11
12/28/09 at 4:57am
Thread Starter 
I guess I should have asked you guys about this last week, before I ordered parts from Mouser then. So I think I will go with the LED from Digi-Key.

But I just found out that OPA2134PA is out of stock at both Mouser and Digi-Key. Do you know about any other store that might have it?
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post #8 of 11
12/28/09 at 5:04am
You can use OPA2132PA instead. More than double the price, though. Many other FET-input opamps can be used, such as OPA2604AP, or even TL072, LF353...
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post #9 of 11
12/28/09 at 5:10am
Thread Starter 
Allright, thank you very much for your help!
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post #10 of 11
12/28/09 at 10:10am
Quote:
Originally Posted by Mariuslk View Post
Sounds good, thank you!

So that it doesn't get to bright? A resistor between 10k and 15k ohms will be good then?
Yes. 10K = ~2.5 mA 15K = 1.75mA

If you are putting the LED on the front panel, you want it to be indication, not illumination. So not too bright is a good thing. It can be really annoying to have your amp act as a flashlight and light up that dark room you are listening in.
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post #11 of 11
12/28/09 at 8:18pm
Thread Starter 
Thats very true, I don't want it to light up the room. I ordered a couple 15K and 12K ohms resistors, as well as I have the default 10K ohms resistor for it, so I will try the 15K first.
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