Electronics gurus: How/Where to build/buy a small colored light setup (LED)

So I bought this fountain from Chinatown the other day. You’ve probably seem the style before. It’s a big fat buddha sitting down. There’s a spinning ball on his lap (being spun/propelled by the water coming up through the pump). One of the really cool things about this fountain was that the spinning ball (being crystal/glass) is lit up from underneath and actually changes colors.

Well approximately 15 seconds after taking it out of the box and turning it on, the lighting thing stops working. Let’s just say I was less than suprised. Anyway, upon dismantling it, I found that it is basically 3 different colored LEDs, attached to a wire running into the black box (power transformer thingy or whatever). The other end of the black box is the 2 pronged wall plug.

After all that, here’s the question:

How difficult would it be to build such a thing? I’m not totally clueless, but I don’t really know all that much about wiring electronics. But I think the basic RadShack parts I’d need are:

  1. A power cord that goes into the wall
  2. Some kind of transformer (is that the right word?) changing the 120V from the wall to something more appropriate.
  3. Some kind of circuitboard, logic dealy, etc. to control the cycling of lights (colors)
  4. 3 or 4 different color LEDs

(possivly 1 & 2 might be the same part)

Sound too difficult? Out of my league? Of course I’d be willing to buy something like this pre-made if available. Anyone know where to get one?

Lets say I just wanted only a single LED ( 1 color). How much easier would that be to put together?

I just want to light up my Buddha’s ball!

;j

Rather than worry about building a power supply, just pick up a plug-in wall transformer at Radio Shack. 4.5 VDC @ 300 mA (or higher) should do nicely. Then you’ll want to select current limiting resistors for each LED. Use the formula (V[sub]source[/sub] - V[sub]LED forward[/sub]) / I[LED]. For a typical red LED with a forward voltage drop of 2 V and a maximum forward current of 20 mA (we’ll use 10 mA for safety), it would be (4.5 - 2) / .010 = 250 Ohms. Then just wire them up to your power supply in parallel.

You know, Q.E.D., I was so sure that you would be the first to respond with a spot-on answer, I considered addressing it directly to you. Of course that would just be rude.

Appreciate the answer, though. Doing as you suggest shouldn’t be a problem. Any suggestions on how I might rig a simple color switching device? That is, cycle from one LED to another.
Of course, the original setup was meant to fade from one to the other, but I can cope.
___________________________________________________-
BTW, Q.E.D., love your sig! You might like the BBC’s Blackadder Quote Generator.
Baldrick, does it have to be this way? Our valued friendship ending with me cutting you up into strips and telling the prince that you walked over a very sharp cattle grid in an extremely heavy hat?

I personally would probably drive the LEDs from a PIC microcontroller. It has very few parts (you’ll need the micro, a crystal, and probably some transistors or a driver chip of some sort to supply enough current for the LEDs), is cheap, and you can do really neat things with timing, fades, and whatever you want.

Requires some soldering skill to make the thing in the first place, a PIC programmer, and software skills to write the control program.

I’ll second the PIC series of programmable microcontrollers. It’s a bit of money initially, since you need the programmer, but you can can get kits to build one fairly cheaply, and they come with software. You’ll need a serial port cable to connect it to your PC. The programming language is easy to learn. I’d suggest you spend a bit of extra money and get the reprogrammable PICs so you can alter your program while you experiment with it.

schematic of a simple 555 timer based oscilater, change the resistor values to vary the flash rate

If you’re not wildly interested in doing it yourself, you can buy commercial units. Try http://colorkinetics.com/products/consumer/details/index.htm?prd_id=86. At about $20.00 (here, for example, http://www.gadgets4sure.com/product.asp?ProductID=13301&DepartmentID=640), it’s barely worth trying to roll your own.

Using a microcontroller (e.g. a PIC) would be the best approach from a hardware reliability and component cost point of view. It’s also a very “clean” approach. But then again, you have to buy a chip programmer, compiler, etc. And then you have to write a program in Assembly Language, or Basic, or whatever.

If part of your goal is to learn how to do all that stuff, fine; go the PIC route. But if you just want to get something working in a relatively quick fashion and without doing any programming, I would suggest using a decade counter such as the 4017, along with a 555 timer.

Check out the 10-channel LED sequencer here:

http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm

As described in the accompanying text, it can be easily configured to sequence three LEDs instead of 10. I would replace the 1 uF cap with a 100 uF cap. And then I would replace the 47K fixed resistor with a fixed resistor and potentiometer in series. For starters, try using a 1K fixed resistor in series with a 100K potentiometer. That will give you a frequency range of 7 Hz to 0.072 Hz. The potentiometer should be wired in “two wire configuration,” where one end terminal is tied to the wiper. And with frequencies this low, you’ll probably want to use a CMOS 555. And finally, note that they decided to use a common 120 ohm resistor for all the LEDs. Because you would be using different color LEDs, you’ll probably want to use a separate dropping resistor for each LED. That way, you can “tweak” the value of each resistor so that they’re all about the same brightless.

Here’s some more good info on the 4017:

http://www.doctronics.co.uk/4017.htm

You can get LEDs that flash automatically every few seconds, about two seconds on - two seconds off. This has the added (dis-?)advantage that the light change will appear more-or-less random after a while, when they get completely out of phase.

By far the simplest solution - unless you go with finagles solution and buy something ready-made.
A PIC would be so much more interresting though.