Wiring an LED bar graph array?

[Matt Thorn]

I got hold of a nifty LED bar graph array identical to the one used in the Shaak Ti/Adi Gallia saber. Rather than just use it purely cosmetically, I'd like to have it actually light up when the saber is on. I know how to wire a simple LED accent light, but this one has 20 pins! Does anyone know how I might do this, assuming, for example, that I'm using a 4aaa battery pack with a Luxeon III and an Ultrasound 2.0? Obviously, I'm going to need a resistor, right? Here's a JPEG of the datasheet:

And here's a link to the original PDF file. The technical information is mostly Greek to me. And for those of you interested in buying it, here it is on mouser.com.
Finally, here's what it looks like on a fan-made replica of the saber hilt:

BTW, does any know who made this? I found the photo on the Lightsaber Archives here. It's beautiful, but I would have polished the brass part and protected it with a sealant. I suppose it's a matter of taste.
It would be extremely cool if I could wire it so that the bar graph reflected the amount of power the Ultrsound board is sending the Luxeon, but I'd be happy just have have all ten LEDs light up while the saber is on.

[Matt Thorn]

Nevermind! I figured it out for myself. It's tedious, but quite simple. It's literally an array of ten separate LEDs that just happen to be encased in the same shell, so you treat each individual LED as you would any accent light. So I just soldered 150 ohm resistors to each positive post, then connected all those resistors to the positive lead from the battery pack. The negative posts (hidden from view in this photo) are all connected together directly, and connected to the negative lead from the battery pack.

Is this cool or what?

Now I just have to find a way to jam this thing inside a hilt without causing any shorts. But I'm not even close to that stage yet.

BTW, if I place this array between the Ultrasound board and the Luxeon, the LEDs in the array will flicker and flash in unison with the Luxeon.

One more BTW: Lumex makes these in a variety of colors and styles.

[xwingband]

You can also switch to one resistor by putting them all in parallel. Just solder all the legs on each side together and it will act as one LED. That might help you fit things better.

It looks like a really nice soldering job though.

[Matt Thorn]

You can also switch to one resistor by putting them all in parallel. Just solder all the legs on each side together and it will act as one LED. That might help you fit things better.

It looks like a really nice soldering job though.

Thanks (for both the tip and the compliment). I tried getting more than one LED to light up using a single 150 ohm resistor, but had no luck, so I figured it couldn't be done--at least not with one 150 ohm resistor (and those are the only kind I have on hand). Would it take a different resistor to handle all ten LEDs? How many ohms would it have to be? I used the LED series/parallel array wizard, and it suggested this set-up:

The first thing that struck me about this diagram is that it shows the resistors on the negative side of the LEDs, rather than the positive side. What's up with that?

[JetSet]

This is ten levels of cool.

Think this will work with a mrfx board wired through the led to get power on and off flicker and stuff?

[neophyl]

The first thing that struck me about this diagram is that it shows the resistors on the negative side of the LEDs, rather than the positive side. What's up with that?

Its a circuit, it makes no difference what side the resistors are on. The total resistance stays the same.

[eastern57]

You calculate the resistance based on the total [required] current of all 10 LEDs. 10 LEDs x 25mA per segment = 250mA. With just a single 150ohm resistor, you were still only feeding 20mA to 10 LEDs (IOW 2mA per LED ). If you're going to power all at once, try a 10ohm 2W resistor.

[Sairon]

that is COOL, and the saber looks like one of do-clo's, but I could be wrong, and idt does look mhs doable.

[xwingband]

Well, what I would do is to run it in parallel with the LED. If you are using an ultrasound or other driver the resistor calculation is made a bit simpler.

(Main LED Voltage - LED bargraph voltage)/Amps = resistor value

I'd recommend 100mA (or .1A for the calculation) to the whole bargraph.

If you don't have a PSU to test the main LED just meter it once setup or take the average value from the specs.

[Matt Thorn]

This is ten levels of cool.

Think this will work with a mrfx board wired through the led to get power on and off flicker and stuff?

Someone with more electrical savvy than I should have no trouble transferring the "ramp-up/ramp-down" effect to the LED bar. That would be pretty sweet, particularly since that effect is lost when using a single LED like a Luxeon III.