I'd like to ask for some general help on where to start with the lighting component for this project. I'm building my own Polynomial Texture Capture Rig: http://www.wessexarch.co.uk/book/export/html/2617
I first started looking into building my own shift registers etc but have since found things like addressable LED strips could suffice. However I've done some tests and all the strips I've found so far won't be bright enough, and maybe impractical for placement on the inside of a hemisphere (could still work I guess). I want to keep the depth of field on the cameras as wide as possible which means keeping the lens aperture small so I'll need to throw a bit of light onto whatever I'm capturing to keep the ISO low.
The overall design I'm thinking of is an Arduino Mega or Due (mostly so I can build future versions of this with more lights etc) to control the LED and camera shutter sequencing + RasPi to aid in the image capturing (download and organize the images from the cameras as they're being taken).
Here are my questions:
Does a Digital LED strip and an Addressable LED strip mean the same thing? Adafruit calls them Digital, but stores on Alibaba/ DH Gate etc call them Addressable. Also I don't care about PWM, I just need to turn them on and off.
Does anyone know of a good product that is an array of addressable LED pixels or strip that are just ultra bright white and not RGB? Or even ultra bright RGB might be cool, I've heard that RGB LEDs produce a more even spectrum of light than whites, but that could be BS. When I google this I'm never sure if the product is actually addressable.
Does anyone have any link/advice about driving 64+ ultra bright LEDs from a battery? I want to keep this thing portable but obviously I still need to cart around some batteries.
Also if anyone randomly knows where I can get my hand's on a light weight geo-dome kit about 1-2m diameter that would be awesome
#3) I've got this board available that was designed for controlling LED light strips. The TPIC6B595 can handle the 12V supply typically used for LED strips, and its high current capability is needed for the 20mA or so that Each 3-LED segment needs. http://www.crossroadsfencing.com/BobuinoRev17/
Hi there Mr CrossRoads! I saw this in another post and it looked good! I was actually about to ping you an email. So with this board I can basically wire max 96 individual LED right?
Yes, it will support individual LEDs as well. Will need a current limit resistor per LED, while LED strips typically have a resistor/3 LEDs built in.
If you get some white extra bright LEDs
you can blind yourself pretty good! Be careful about looking into it.
You can use 2-3 LEDs in series depending on what your battery voltage is.
3 x 3.6V = 10.8V, will work with 12V battery
4 x 3.6V = 14.4V - will not!
Does a Digital LED strip and an Addressable LED strip mean the same thing? Adafruit calls them Digital, but stores on Alibaba/ DH Gate etc call them Addressable. Also I don't care about PWM, I just need to turn them on and off.
I'm sure that is the same thing - they "chain" from one to the next using a digital protocol.
Rambutan2000:
2. Does anyone know of a good product that is an array of addressable LED pixels or strip that are just ultra bright white and not RGB? Or even ultra bright RGB might be cool, I've heard that RGB LEDs produce a more even spectrum of light than whites, but that could be BS.
Haven't come across any, but that does not mean they do not exist. Since the "addressable" ones use a particular chip, and that chip is designed especially for RGB use, plain white ones are less likely.
It would be BS. RGB LEDs produce three very pure and distinct colours which the eye merges. In terms of the spectra, the combination of phosphors used in the White LEDs would each have a much wider spectrum and - if it ever mattered which for vision it should not - combine to a more uniform overall spectrum.
Rambutan2000:
When I google this I'm never sure if the product is actually addressable.
You do have to be careful.
Rambutan2000:
3. Does anyone have any link/advice about driving 64+ ultra bright LEDs from a battery? I want to keep this thing portable but obviously I still need to cart around some batteries.
Yes - big battery! Presumably Li-Po rechargeable but you do have to be very careful charging them. The problem is matching the voltage; one cell is 3.7 V nominal, two makes 7.4, you want 5V even. A low drop-out switchmode regulator could probably do a good job of turning 7.4 into 5.
Rambutan2000:
Also if anyone randomly knows where I can get my hand's on a light weight geo-dome kit about 1-2m diameter that would be awesome.
It's called - as you should know by now - a "perimeter". My mate Karl, now pretty famous as Julius Sumner Miller's (intellectual) inheritor on the media, was working on one when we were back at Uni - but that was a long time ago.
Does a Digital LED strip and an Addressable LED strip mean the same thing? Adafruit calls them Digital, but stores on Alibaba/ DH Gate etc call them Addressable. Also I don't care about PWM, I just need to turn them on and off.
I think so.
Rambutan2000:
2. Does anyone know of a good product that is an array of addressable LED pixels or strip that are just ultra bright white and not RGB?
That's the same chip as in the LED strips (so the same drivers will work) but you can connect 3 white LEDs. If you use those the wiring will be much neater/simpler than using shift registers.
When you're working with 20mA LEDs brightness is usually solved by adding more LEDs. If you want high power LEDs (eg. 1W) you can still use the WS2811 boards but you need to add a transistor and some resistors for each LED.
Rambutan2000:
3. Does anyone have any link/advice about driving 64+ ultra bright LEDs from a battery? I want to keep this thing portable but obviously I still need to cart around some batteries.
Reading between the lines: I'm guessing you're not going to light them all up at the same time. If you're only lighting a few of the LEDs at once then batteries aren't a problem.
Paul__B:
It would be BS. RGB LEDs produce three very pure and distinct colours which the eye merges. In terms of the spectra, the combination of phosphors used in the White LEDs would each have a much wider spectrum and - if it ever mattered which for vision it should not - combine to a more uniform overall spectrum.
OK cool sounds good. I was looking into multispectral image capture where you capture images at different wavelength intervals but this would take a lot of setup + the extra data costs.
Paul__B:
Yes - big battery! Presumably Li-Po rechargeable but you do have to be very careful charging them. The problem is matching the voltage; one cell is 3.7 V nominal, two makes 7.4, you want 5V even. A low drop-out switchmode regulator could probably do a good job of turning 7.4 into 5.
Sweet! Thanks for that info, this will probably change my plans a bit. Those PCBs are cheap as well.
fungus:
Reading between the lines: I'm guessing you're not going to light them all up at the same time. If you're only lighting a few of the LEDs at once then batteries aren't a problem.
When I was considering LED strips of thought I could probably cluster multiple together to make a brigher light ie same as rendering a cirlce on a TV. But the caculations I need to do on the images needs a point light source. So V1 of this project will probably only have one lit at a time. Plus I have a mini LED projector (for structured light 3D reconstruction) in the mix as well I could use for ambient light if I needed it.
Question:
So, I've been looking up typical RGB LEDs which look like they have a forward current of ~20ma which is the same as the white LED above. Does anyone know if that's 20ma for the whole RGB device or per pin? IE is R + G + B = 20ma or R = G = B = 20ma and since they're in parallel that would be a total of 60ma.
OK so doing some research it seams that each sub LED in an RGB has it's own forward voltage and therefore current so I'm confident the above combo would work fine. Now I need to work out resister stuff...
Also FYI found this post about white light and RGB LEDs:
