User:DavidCary

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Welcome to my little corner of Open Circuits.

I think I first stumbled across Open Circuits on 2006-03-01. I had been starting to set up a electronics-related wiki, but since this one was already here, why bother?

Feel free to leave a note on my talk page.

Electronic projects:

electronics workbench

What exactly do I need for "normal" electronics development? I have a pile of stuff, and I have a wishlist of more stuff ... I hope to document which things are important to have, which things are useful but not immediately necessary, and which things ended up just gathering dust.

data collection network

I'm building a "data collection network" that may end up with hundred of microcontroller sensor nodes, piping data into a PC. This may turn into a serious medical diagnosis tool.

POV display

I'm building yet another "POV display".

I plan on putting a few features into my display that I haven't seen in any other so far:

  • bright blue LEDs (even though blue is usually the most expensive color ... although

sometimes "true green" is even more expensive than blue).

  • no slip rings -- just pumping energy across an air gap
  • ... and a few other features that I'm keeping hush-hush.

I want lots of lumens. Unfortunately, when I go to pick LEDs out of the catalogs, they're not rated in lumens, they're rated in candelas.

Is it even possible to estimate "lumens" from the catalog information?

Do you know what the difference is? Does your flashlight really produce 10 times the light ( in lumens)? Or does the flashlight merely focus its light on a tiny spot, so that that spot gets 10 times as many candelas ?

For example, check out these 2 LEDs: $8.75 SSP-LX6144C7UC : 4000 mcd at 120 mA $8.75 SSP-LX6144D7UC : 1800 mcd at 120 mA

From the mcd rating, it appears that the first one is more than 2wice as bright -- and it is, if you're directly in front of it when you look at it. However, if you're even the tiniest bit off-center, the second one is much brighter -- in fact, the total lumens that second LED puts out (2500 mlm) is slightly more than the total lumens than the first one. If you diffuse the light and try to light up a whole room with an array of them, the second one will make the room brighter.

I'm currently planning on using these in my first POV display:

  • $1.32 Telux TLWB7900 : blue : 330 mlm, 231 mcd at 50 mA. (price in ones from http://Newark.com/ )

Other LEDs I considered using in my POV display (and may re-consider for my next one):

  • $18.89 "Lamina light engine" BL-22B1-0140 : 22000 mlm at 420 mA. (this price includes the required heat sink -- price in ones from http://Digikey.com/ ). This has the most lumens per dollar I've found so far (for blue LEDs).
  • $8.750 Sunbrite LuxLEDs SSP-LX6144D7UC blue: 120 mA, 2500 mlm, 1800 mcd (Odd that the red Sunbrite LuxLEDs are cheaper at Newark, the other colors cheaper at Digikey.) cheapest $/lumen blue LED, except for the "light engine"
  • $2.550 Lumex "DSP LED" 67-1876-ND: blue, 5 mm, 2500 mcd ( DigiKey ) apparently have some kind of internal chip. All colors run at 2.0 V nominal (1.5 V minimum) (rather than running on current like most LEDs. unfortunately, the data sheet doesn't suggest how much current they take -- I presume more than 20 mA).
  • $1.600 Sunbrite "based LED" SSP-01TWB7UWB12 (441-1007-ND) blue 10 mm 20 mA 7000 mcd
  • $5.980 GM5WA06270A SMT RGB (35 mA red, 35 mA green, 35 mA blue) 3000 mcd (full color range -- apparently used for digital camera flash ?) (Digikey)

Spoke-POV and propeller clocks links:

Full-color LED lighting

I'm planning to build a silly little toy with 3 LEDs -- one for red, green, and blue -- to show how "additive colors" work (a "color wheel"). (I might just extend it to have a whole spectrum of visible and infrared LEDs, and a prism to show the little spikes in the spectrum that LEDs generate).

"Red, Green, and Blue LED based white light generation" by Muthu, Schuurmans, and Pashley (2002) http://www.advancetransformer.com/uploads/resources/LED_White_Light_Issues&Control_-_White_paper.pdf

LED illumination applications http://en.wikipedia.org/wiki/Light-emitting_diode#Illumination_applications

"How Many Red, Green, and Blue LEDs to make White" by Don Klipstein 2001 http://members.misty.com/don/ledrgb2w.html

LED Color Shifting http://hackedgadgets.com/2006/02/14/wireless-led-color-shifting/


-- DavidCary

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