Search found 13 matches

by Jarhead
Fri Jan 20, 2006 10:08 pm
Forum: General Discussion
Topic: "Perfect" LED current limiting challenge
Replies: 255
Views: 61571

Re: "Perfect" LED current limiting challenge

Sorry, I forgot to answer some of your other questions. A piece of my job takes me into areas that are related to this article: http://neasia.nikkeibp.com/neasiaarchivedetail/000503 I work as a Senior Avionics Design Engineer, doing EE work, but it takes me into many other disciplines, in order to t...
by Jarhead
Fri Jan 20, 2006 9:56 pm
Forum: General Discussion
Topic: "Perfect" LED current limiting challenge
Replies: 255
Views: 61571

Re: "Perfect" LED current limiting challenge

Okay Chris, you don't seem to want to repent. There is one fella that many electronics and optical experimenters often revere, and is a bountiful source of information for those starting out... Don Klipstein: "Many people have noticed that some LEDs, including most of the multi-LED moving display si...
by Jarhead
Fri Jan 20, 2006 7:16 pm
Forum: General Discussion
Topic: "Perfect" LED current limiting challenge
Replies: 255
Views: 61571

Re: "Perfect" LED current limiting challenge

Chris, You are definitely digging yourself a nice hole from my point of view. Could you please provide this LED pulsing paper you are referring to? I know I've already provided some, showing the decrease in efficiency when an LED is pulsed at higher currents. I've also done the experiement, and shin...
by Jarhead
Thu Jan 19, 2006 11:53 pm
Forum: General Discussion
Topic: "Perfect" LED current limiting challenge
Replies: 255
Views: 61571

Re: "Perfect" LED current limiting challenge

Chris: When I have a constantly on LED, consuming X watts, and this pulsed LED, consuming X watts (not counting losses in the drive circuit), the intensity of the pulse is brighter, but I cannot see the brief pulse and my eye does an averaging or integrating function on it. My test equipment obvious...
by Jarhead
Wed Jan 18, 2006 7:34 am
Forum: General Discussion
Topic: "Perfect" LED current limiting challenge
Replies: 255
Views: 61571

Re: "Perfect" LED current limiting challenge

Chris, I tried your high current rapid pulse, in an attempt to validate your claim that LEDs miraculously get more efficient with fast high current pulses. They don't. The actual pulse, under loaded conditions across the LED: <img src="http://www.molalla.net/~leeper/luxpulse.jpg" alt=" - " /> It act...
by Jarhead
Sun Jan 08, 2006 1:17 pm
Forum: General Discussion
Topic: "Perfect" LED current limiting challenge
Replies: 255
Views: 61571

Re: "Perfect" LED current limiting challenge

Chris, Directly from one of the laser diode manufacturer's websites: Sensors: Laser Diodes Q: What is duty cycle? A: Duty cycle or duty factor (DF) is the length of time the laser diode is actually lasing. It’s also referred to as the “on” time of a laser; and is usually expressed in percentage. For...
by Jarhead
Fri Jan 06, 2006 11:18 pm
Forum: General Discussion
Topic: "Perfect" LED current limiting challenge
Replies: 255
Views: 61571

Re: "Perfect" LED current limiting challenge

DICTIONARY OF TECHNICAL TERMS FOR AEROSPACE USE Web edition edited by Daniel R. Glover, Jr. NASA Lewis Research Center Cleveland, Ohio INTRODUCTION This dictionary was orignally published as NASA SP-7 in 1965. The editor for the first edition was William H. Allen. The introduction to the first editi...
by Jarhead
Tue Jan 03, 2006 10:00 pm
Forum: General Discussion
Topic: "Perfect" LED current limiting challenge
Replies: 255
Views: 61571

Re: "Perfect" LED current limiting challenge

There is more good additional information over at the cpf place:
http://candlepowerforums.com/vb/showthr ... 1&posted=1
by Jarhead
Mon Jan 02, 2006 10:48 am
Forum: General Discussion
Topic: "Perfect" LED current limiting challenge
Replies: 255
Views: 61571

Re: "Perfect" LED current limiting challenge

Ian, Did you read the post where I mentioned this buck chip? http://focus.ti.com/lit/ds/symlink/tps62050.pdf Vin(min) = Vout(max) + Iout(max) * ((Rds(on)(max) + Rinductor)) Using that formula, the circuit will buck all the way down to 3.400328V, at which point it will enter 100% duty cycle. Assuming...
by Jarhead
Mon Jan 02, 2006 12:14 am
Forum: General Discussion
Topic: "Perfect" LED current limiting challenge
Replies: 255
Views: 61571

Re: "Perfect" LED current limiting challenge

I see the reference to 511 on the schematic in pencil, which would be the IRF511. The two transistors written in pencil on there are 123 (2N2222A sub) and 159(forget which one that is), both made by ECG and NTE. NTE123 and NTE159. IRF511 One link: http://www.uoguelph.ca/~antoon/gadgets/irf511.htm EL...
by Jarhead
Sun Jan 01, 2006 8:18 pm
Forum: General Discussion
Topic: "Perfect" LED current limiting challenge
Replies: 255
Views: 61571

Re: "Perfect" LED current limiting challenge

Ian, you might try looking at this buck switcher, with integrated MOSFETs, and this buck converter can go all the way to 100% duty cycle: http://focus.ti.com/lit/ds/symlink/tps62050.pdf Figure 4 sounds the closest to your application (I assume you'd use the adjustable version-this one is fixed, but ...
by Jarhead
Sun Jan 01, 2006 1:35 pm
Forum: General Discussion
Topic: "Perfect" LED current limiting challenge
Replies: 255
Views: 61571

Re: "Perfect" LED current limiting challenge

Hi Chris. I'd suggest you take a look at the OSRAM datasheet yourself. http://catalog.osram-os.com/media/_en/Graphics/00029735_0.pdf Page 4, Radiant Intensity Ie in Axial Direction Radiant Intensity at 100mA, time 20mS = 75 mW/sr Radiant Intensity at 1A, time 100us = 400 mW/sr Notice the difference ...