Timeline for How to calculate the tolerance of this constant current circuit?
Current License: CC BY-SA 4.0
19 events
| when toggle format | what | by | license | comment | |
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| Apr 4 at 6:36 | comment | added | jonathanjo | @RussellMcMahon Got an up-to-date link for SNSLIGHTS? "Account is temporarily unavailable for non-technical reasons." | |
| Apr 4 at 6:35 | comment | added | jonathanjo | @rohmeooo 1) The general 2:1 number is supported by camera stops/shutter speeds, which go in 2:1 ratio; 2) For a scientific overview, have a look at Transmission and display of pictorial information, D.E. Pearson 1975, esp chapter 2, Properties of the eye affecting system design. It's old, now, but summarises well and is a great starting point. (archive.org) | |
| Oct 1, 2024 at 8:17 | comment | added | Russell McMahon♦ | @rohmeooo Possible value - and this- Google searches. | |
| Oct 1, 2024 at 8:12 | comment | added | Russell McMahon♦ | @rohmeooo That's based on my research 15+ years ago and my following experience. There will be similar on web. I hada quick look now and while I found several links that agree roughly with me they are informal. || I designed several solar powered LED lights and 300,000+ were made. My above mentioned 'research' was with a view to understanding the relatve merits of various power levels. || For interest - what is your appliation? || Some of my lights - scroll don't click bit.ly/SNSLIGHTS | |
| Sep 30, 2024 at 16:48 | comment | added | rohmeooo | @RussellMcMahon, do you have a source for those subjective measures of a human's ability to discern different lumens? I'm curious for different colors, not just White, as well, if you have it to share. | |
| Sep 30, 2024 at 16:17 | history | edited | Null♦ | CC BY-SA 4.0 | added 17 characters in body; edited tags |
| Sep 28, 2024 at 14:35 | comment | added | jonathanjo | @user57037 In case that link expires, Bob Pease collected articles at Arhive.org include the Vbe one: web.archive.org/web/20240715110955/https://www.changpuak.ch/… | |
| Feb 21, 2020 at 3:00 | history | tweeted | twitter.com/StackElectronix/status/1230688689950527488 | ||
| Feb 19, 2020 at 14:57 | vote | accept | Sonder | ||
| Feb 16, 2020 at 21:54 | comment | added | Russell McMahon♦ | Data point only: If those are white LEDS used for illumination AND if light output is what's of interest THEN it probably doesn't matter. Viewed physically separately (in space and/or time) you need about a 2:1 variation in lumen output for it to be discernible to most people. Put the two lights "near each other" and it drops to around 50% +/- some. Wall washing side by side it's usually 10-15% difference before it can be discerned. | |
| Feb 15, 2020 at 15:24 | answer | added | Tony Stewart EE since 1975 | timeline score: 4 | |
| Feb 15, 2020 at 9:15 | comment | added | user57037 | Just look at the one called "what is all this vbe stuff" it explains in detail the relationship between vbe, current and temperature. | |
| Feb 15, 2020 at 6:50 | answer | added | jonk | timeline score: 36 | |
| Feb 15, 2020 at 4:51 | comment | added | jonk | @Sonder Yes, and the expression I gave you does that. It tells you what percent change in LED current to expect for a given percent change in absolute temperature. That actually includes the base emitter voltage change. | |
| Feb 15, 2020 at 4:41 | comment | added | Sonder | @mkeith thanks for the gift. It is really overwhelming document for me but I will keep it in my library. I will go throught the index first. | |
| Feb 15, 2020 at 4:38 | comment | added | Sonder | @jonk Sir, I want to calculate the deviation in the LED current due to variation in the VBE due to temperature rise. Forgive me for not being clear to ask. | |
| Feb 15, 2020 at 3:45 | comment | added | user57037 | Maybe the famous Bob Pease article "What's all this Vbe stuff anyhow" would be useful. It is hard to find online nowadays. This link will probably stop working but it works for now. Just look for the Vbe article. changpuak.ch/electronics/downloads/www-national-com_rap.pdf | |
| Feb 15, 2020 at 3:20 | comment | added | jonk | It sounds like you are asking for the sensitivity equation: \$\frac{\frac{\text{d}\,I_\text{LED}}{I_\text{LED}}}{\frac{\text{d}\, T}{T}}\$. Is that it? Or something else? | |
| Feb 15, 2020 at 3:10 | history | asked | Sonder | CC BY-SA 4.0 |