DIY Copper Style LED Painting Illuminator

Step 2 Choosing the right LEDs

As I said in the previous step, you'll definately want a warm white LED. But there are many different kinds of warm white LEDs out there. I will compare 4 different kinds of LEDs in this step.

The 4.8mm wide viewing angle LED. This LED has a wide viewing angle, which is great for this project, but it's not bright enough to properly light up a painting or a photograph.

The classic 5mm Ultrabright LED. This LED is bright, which is great for this project. The problem with this LED is that it has a narrow viewing angle, so it will not distrubute the light uniformly, so there is a risk of getting light "dots" on the painting or photograph, that you will be illuminating.

The wide viewing angle SuperFlux LED. This LED has a wide viewing angle like the 4.8mm LED has, but as with the 4.8mm LED, it is not bright enough for this project.

The 8mm "StrawHat" Ultrabright LED. This LED has a wide viewing angle, and unlike the SuperFlux and the 4.8mm LED, It's very bright. It's the perfect LED for this project. The only problem it has is that it heats up quickly, but that's not a big problem in this case, since the LEDs will be hanging in mid-air. I chose these LEDs for the Copper Style LED Painting Illuminator.

The pictures below shows all the four LEDs mentioned above. There are also a couple of pictures showing the difference between a cool and a warm white LED from the same manufacturer.

Comments

[Coodude26]

The setup for the light-adjusted switch seems a little overly complicated. Why nor just connect the photoresistor to the + supply and the collector of an ordinary NPN transistor? It would trigger when the photoresistor limits the current below the threshold of the transistor. I don't know if you said somewhere what voltage you were using, but you could still use a pot inbetween the photoresistor and the supply to make it less sensetive. Last thing, you might want to aim them a bit lower so the bottom is also illuminated. Also, I'm pretty sure they make photoTRANSistors. That would simplify the whole thing...

[Artificial Intelligence]

Yes. The light sensor could probably have been done in a simpler way, but the reason why I used an opamp is that has a "cleaner" way of switching over the circuit that you mentioned, because it is either on or off, whereas the simpler circuit will limit the power going to the base of the transistor too much, so you might not get the full brightness.

[Coodude26]

Don't transistors use digital logic? IE, above 5v = on, less than 5v = off?

[Artificial Intelligence]

Transistors are usually used to switch or amplify small signals. A single transistor doesn't measure the voltage, and switch a larger current if the base voltage is over a certain threshold. Some extra components are required in order to do that.

[Coodude26]

AAAGGHHH oh my gosh. why in the world can't I get a simple explanation of how a transistor works. my brother is an electrical engineer at U of I and he can't explain it to me. can you give me a simple rundown of how a transistor would be "triggered" or how it's switched or whatever and what that triggers or sets in motion? Pleeeeeeeeassseee?

[pfred2]

Maybe because your question is flawed? There have been several different kinds of transistors developed. They mostly all work differently from each other too. I've even heard tale told that some of them are quantum tunneling these days!

http://www.google.com/#hl=en&q=quantum+tunneling+transistor&aq=f&oq=&aqi=&fp=F2LdvTVQwLA

Me, I'm more the old fashioned bipolar type though :) Those work on PN junctions and migrating electrons and holes. Just wait until you're checking out characteristic curve traces of those puppies. Switching is pretty dull stuff. Yawn, I'm all about analog myself.

http://www.google.com/#hl=en&q=transistor+curve+tracer&aq=f&oq=&aqi=g1&fp=F2LdvTVQwLA

Then there are different ways of using a transistor in a circuit.
One way:
http://en.wikipedia.org/wiki/Common_collector

Short answer to a screwy question though a small current controls a larger current flow.

[Artificial Intelligence]

I guess, it's one of those things that are hard to explain in a simple and understandable way. Try to google "how transistors work" and see what you get.