Welcome Guest! To enable all features please Login or Register.

Notification

Icon
Error

Login
LED Question and biasing the current
Options
View
Go to last post Go to first unread
Previous Topic Next Topic
Nakamichi  
#1 Posted : Monday, September 6, 2010 9:33:54 PM(UTC)
Nakamichi

Rank: Member

Groups: Member
Joined: 6/20/2010(UTC)
Posts: 28
Location: Germany
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
Back to top

Wanna join the discussion?! Login to your Twisted Pear Audio Support forum accountor Register a new forum account.
Back to top  
Dingo  
#2 Posted : Monday, September 6, 2010 9:43:21 PM(UTC)
Dingo

Rank: Member

Groups: Member
Joined: 8/3/2010(UTC)
Posts: 25
Location: Australia
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.
Back to top
Brian Donegan  
#3 Posted : Tuesday, September 7, 2010 4:26:21 AM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
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
Back to top
WWW
Russ White  
#4 Posted : Tuesday, September 7, 2010 2:54:05 PM(UTC)
Russ White

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN

Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
If you want better precision in adjustment for higher current application reduce the value of VR1/VR2. Try 20 ohms.
Back to top
WWW
Nakamichi  
#5 Posted : Wednesday, September 8, 2010 3:03:07 AM(UTC)
Nakamichi

Rank: Member

Groups: Member
Joined: 6/20/2010(UTC)
Posts: 28
Location: Germany
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...
Back to top
Rss Feed  Atom Feed
Users browsing this topic
GuestUser
Forum Jump  
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.

Youtube
Copyright © Twisted Pear Audio