These curves are for a white LED with nominal and maximum forward
currents of 20 and 30mA, respectively.

--
JF

On Sat, 28 Jan 2012 12:39:20 -0600, John Fields
wrote:


These curves are for a white LED with nominal and maximum forward
currents of 20 and 30mA, respectively.

---
"Connect-the-dots" works wonders. :-)

--
JF

"John Fields" schreef in bericht
news
On Sat, 28 Jan 2012 12:39:20 -0600, John Fields
wrote:


These curves are for a white LED with nominal and maximum forward
currents of 20 and 30mA, respectively.

---
"Connect-the-dots" works wonders. :-)

--
JF




Well, it tells what you and I - and several others - knew and told already.
If one realizes that this curves are typical values that may vary even for
LEDs from the same batch and also depend on temperature he'd have to agree
that constant voltage to drive a LED is bad engineering practice.

petrus bitbyter

On Mon, 30 Jan 2012 11:42:54 -0800, John Larkin
wrote:

On Sat, 28 Jan 2012 21:32:15 +0100, "petrus bitbyter"
wrote:


"John Fields" schreef in bericht
news
On Sat, 28 Jan 2012 12:39:20 -0600, John Fields
wrote:


These curves are for a white LED with nominal and maximum forward
currents of 20 and 30mA, respectively.

---
"Connect-the-dots" works wonders. :-)

--
JF

Well, it tells what you and I - and several others - knew and told already.
If one realizes that this curves are typical values that may vary even for
LEDs from the same batch and also depend on temperature he'd have to agree
that constant voltage to drive a LED is bad engineering practice.

petrus bitbyter


"Bad engineering practice" is an interesting term. I think it means "I
don't approve of that."

---
Then you'd approve the use of a constant voltage source to drive an
LED?

--
JF

On Mon, 30 Jan 2012 18:38:16 -0600, John Fields
wrote:

On Mon, 30 Jan 2012 11:42:54 -0800, John Larkin
wrote:

On Sat, 28 Jan 2012 21:32:15 +0100, "petrus bitbyter"
wrote:


"John Fields" schreef in bericht
news On Sat, 28 Jan 2012 12:39:20 -0600, John Fields
wrote:


These curves are for a white LED with nominal and maximum forward
currents of 20 and 30mA, respectively.

---
"Connect-the-dots" works wonders. :-)

--
JF

Well, it tells what you and I - and several others - knew and told already.
If one realizes that this curves are typical values that may vary even for
LEDs from the same batch and also depend on temperature he'd have to agree
that constant voltage to drive a LED is bad engineering practice.

petrus bitbyter


"Bad engineering practice" is an interesting term. I think it means "I
don't approve of that."

---
Then you'd approve the use of a constant voltage source to drive an
LED?

Approve? I'm not in the approval business.

I might do it. If it was volume production, low cost, and I could
depend on the LEDs to be consistent. Like an LED flashlight, for
example. A small white LED and a couple of alkaline cells is a common
design, and seems to work just fine.

Or if I had some other reason, like wanting to drive an LED really
fast, for example.

"Good engineering practice" is doing what works.




--

John Larkin, President Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

John Larkin wrote:
On Sat, 28 Jan 2012 21:32:15 +0100, "petrus bitbyter"
wrote:

"John Fields" schreef in bericht
news
On Sat, 28 Jan 2012 12:39:20 -0600, John Fields
wrote:

These curves are for a white LED with nominal and maximum forward
currents of 20 and 30mA, respectively.
---
"Connect-the-dots" works wonders. :-)

--
JF



Well, it tells what you and I - and several others - knew and told already.
If one realizes that this curves are typical values that may vary even for
LEDs from the same batch and also depend on temperature he'd have to agree
that constant voltage to drive a LED is bad engineering practice.

petrus bitbyter



"Bad engineering practice" is an interesting term. I think it means "I
don't approve of that."


Howsomever, the "constant voltage" scheme is eXtremely (yes, "X"
rated) common way to drive parallel LEDs..three 1.5V cells in series
driving a number of LEDs in parallel (have a light with 24 LEDs driven
that way, NO resistor).