Daniel Reetz, the founder of the DIY Book Scanner community, has recently started making videos of prototyping and shop tips. If you are tinkering with a book scanner (or any other project) in your home shop, these tips will come in handy. https://www.youtube.com/channel/UCn0gq8 ... g_8K1nfInQ

Let's talk about Lighting

All about lighting. LED, CFL, Halogen, Other? Questions and info about lighting go here.
hg1027

Re: Let's talk about Lighting

Post by hg1027 » 10 Mar 2011, 16:31

Thanks, that does generally make sense.

It looks like I need to buy 4 of these, one of these and then a power supply. I think I need 3.7v each, for 14.8 volts, and the LEDs draw a max of 1 amp each. From the LED supply site, the 24v 4 amp power supply is $85, which would be more than any other single piece of the whole scanner. I think I'm misunderstanding something here. There's an electronics surplus type shop near me, but I'd like to have an idea of the specs I need so I can avoid sounding like a total fool.

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Re: Let's talk about Lighting

Post by daniel_reetz » 10 Mar 2011, 16:39

You need only a 1amp (1.5 or 2 for safety) power supply because you'll be connecting them in series - and I'd recommend finding one in surplus or on eBay.

For what it's worth, you can buy premade lamps for $35 each, too - but they take at least three weeks to arrive and it's tough to find them with a US power connector. You want to buy the Neutral White version of this:

http://cgi.ebay.com/110VAC-10W-White-LE ... 588d053123

I bought mine from seller "xiongeddie". I recommend him as a seller but I am not recommending anything else here - dealing with Asian resellers is a bit of a risk, though one I've had very good luck with.

I have purchased almost every single 12V MR16 bulb available on eBay one-by-one and I will test them when I return to my normal life at the end of this month.

hg1027

Re: Let's talk about Lighting

Post by hg1027 » 10 Mar 2011, 16:50

Is that preferred over something like Ryan's build? I'd rather do it myself to learn something, and to make it all flat for transport.

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Re: Let's talk about Lighting

Post by Ryan_phx » 10 Mar 2011, 16:58

For what it's worth, my power supply was scavenged from an old laptop (another of Daniel's good ideas). I'm sure you can find one of those dirt cheap on eBay.

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Re: Let's talk about Lighting

Post by daniel_reetz » 10 Mar 2011, 21:21

I love that attitude and then think you should definitely follow Ryan's build and use an old laptop power supply (old Dell supplies go for just a couple bucks). You'll learn a lot about LED lighting and you can help Ryan and myself teach others here, too. It will be great and you will like the results - the lights are extremely bright and the resulting images are good.

Koyaanisqatsi

Re: Let's talk about Lighting

Post by Koyaanisqatsi » 11 Mar 2011, 04:54

Hello again. I haven't posted anything about CRI on my blog yet. But I have been doing a lot of experimentation to try and identify the best combination of LEDs to achieve better CRI. I've been active on the reef aquarium forums lately because the community is interested in improving the look of LEDs against their corals, and that's coming down to CRI too.

In general, CRI boils down to sections of a color wheel, or rather missing sections. If the light is weak in a section of the color wheel, that reduces your CRI and those colors will look muted or shifted under the light. White LEDs cover (roughly) the blue and yellow opposing sections. But they're weak in the red/cyan, and magenta/green sections. They do reach into orange and green a bit, which gives them as good of a CRI as they currently have. But they lack cyan and are weak in red.

Colored LEDs are so narrow-band, it requires many of them to create a smooth spectrum. For small packages it's difficult to fit that many different LEDs. So one of my goals is to design a "star" board that holds many LEDs of different colors in order to compose a high CRI white output. I'm also considering contacting the LED manufacturers to see if they would be interested in making LEDs with many dies in one emitter.

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Re: Let's talk about Lighting

Post by curious » 13 Mar 2011, 23:46

Anyone tried using fiber optic strands to redirect a flash? like this:
http://www.flickr.com/photos/fiberstrobe/5482345644/

hg1027

Re: Let's talk about Lighting

Post by hg1027 » 21 Mar 2011, 22:25

I got all the parts from LEDsupply for $70 (could have saved $20 if I'd been lucky at the surplus store), soldered it all up to test, and it's blinding. I'll have to cut the wires when i build the frame, but then it'll just be wire to wire connections, quick and easy.

Off:
Image

On:
Image

If you're at all comfortable with a soldering iron, this should not be overwhelming. I chose the LEDs because they're so small and I expect they'll run cooler than equivalent halogens/floods.

hg1027

Re: Let's talk about Lighting

Post by hg1027 » 28 Mar 2011, 09:00

With my current setup, pot turned all the way counterclockwise (minimum resistance, should be lowest light output I believe) the first third to half turn makes no light, then between about 75 and 100%, say, dazzling to blinding.

When I measure continuity across an LED, I get a faint light I can look at no trouble. I set up the pot so that clockwise increases resistance, using I think the left and center tabs, I'll check when I get home but definitely using center.

Am I doing something obviously wrong? Is there possibly a faulty link in my chain? Should I expect, with the parts I've mentioned from LED Supply and this radioshack pot to be able to get full 0-100%?

I'll check which tabs I'm using on the pot, and whether there is some voltage coming from the buckpuck when there is no light from the LEDs this evening, but anything else I should check would be appreciated.

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Re: Let's talk about Lighting

Post by daniel_reetz » 28 Mar 2011, 10:33

OK, well, nothing comes to mind immediately - you've followed the directions exactly. You should connect one side to the middle pin of the pot and one side to the left or right lug. Clockwise or counterclockwise really doesn't matter.

One way to test this is to try some resistors - 1k, 2k, 3k, 4k, and see if you get a result different than with the pot. AFAIK the pot is the only thing that could be wrong here... isn't your power supply way overrated for this task, too?

If I were you i'd try the other "side" of the pot and see if it works better.

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