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LED Question and biasing the current
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Nakamichi  
#1 Posted : Monday, September 6, 2010 9:33:54 PM(UTC)
Nakamichi

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Hello,
am I stuck with green LEDs? I would like to use blue ones (3.8 Volt)
(Or a non-glowing Type of 2.1Volt)
Biasing the current with VR1/VR2 is a bit tricky.
Quarter of a turn results in in jumps around 50mA , is this normal?
All the best,
Nak
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Dingo  
#2 Posted : Monday, September 6, 2010 9:43:21 PM(UTC)
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I seem to remember (sorry forgot the source) a DIYer that tested the noise generated by different LEDs and zeners for voltage reference usage, like in placid. Of all the LEDs, blue were significantly more noisy.

IIRC green were the quietest, and old school generic type LEDs were better than modern high brightness types.
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Brian Donegan  
#3 Posted : Tuesday, September 7, 2010 4:26:21 AM(UTC)
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The short answer: The LEDs in the kit are not chosen for there looks. They are an integral part of the circuit and should be changed unless you understand the implications and how to compensate for them.

Edited by user Tuesday, September 7, 2010 4:27:14 AM(UTC)  | Reason: Not specified
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Russ White  
#4 Posted : Tuesday, September 7, 2010 2:54:05 PM(UTC)
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If you want better precision in adjustment for higher current application reduce the value of VR1/VR2. Try 20 ohms.
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Nakamichi  
#5 Posted : Wednesday, September 8, 2010 3:03:07 AM(UTC)
Nakamichi

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Thanks!
I guess, I will covber the Diodes with shrink tube. If VR1/VR2 do not drift with temperature/aging, i will not swap them... Does not look like they drift with temperature...
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