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Mattnuke

Mattnuke's Big Kaly project (Kaladrax Bones)

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That would be the case with conventional bulbs, but not really with LEDs. As long as the source voltage is enough that each LED in the string sees it's Vf then it'll put out its rated light.

 

Actually, putting them in parallel could create more of an dimming issue, since the battery output voltage will drop as more current is drawn.

 

Runelord: 9v batteries contain about 400-600 mah of energy, so at 30 mA (series) draw that's about 13-20 hrs of evil unlife for your Kaly. AAs are about 2700 mah each, but you'd need 2 batteries in series to get the 3v needed to drive 1 LED. Additional LEDs would have to be added in parallel because of the low source voltage, so running 4 LEDs (parallel) would draw 120 mA total. You'd get about 22 hrs of unlife from two AA cells. Not a big difference.

 

The biggest benefit to using AAs is that if you only needed, say, 2 or 3 LEDs then that would not be a problem because of the parallel arrangement. If you go 9v then you pretty much need to use 4 of those LEDs or else a power-robbing resistor to take the place of the unused bulbs.

Edited by High Priest of Syrinx
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The more I'm looking at it, the more I'm thinking two separate strings of 4 LEDs might be my best choice.

 

What I'm not sure of is if I want more than one color. Yellow and green seem to have the same voltage requirements, while blue seems to draw slightly more.

 

I'll stop on the way home from work tomorrow to get the rest of what I need and try to get some in-progress pictures.

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We discussed this awhile back, and I still think electroluminescent wire is the lighting I'll use when I get around to this. Still, love the work so far and LEDs should work fine - expecially for 'point-source' applications : )

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That would be the case with conventional bulbs, but not really with LEDs. As long as the source voltage is enough that each LED in the string sees it's Vf then it'll put out its rated light.

 

Actually, putting them in parallel could create more of an dimming issue, since the battery output voltage will drop as more current is drawn.

 

Runelord: 9v batteries contain about 400-600 mah of energy, so at 30 mA (series) draw that's about 13-20 hrs of evil unlife for your Kaly. AAs are about 2700 mah each, but you'd need 2 batteries in series to get the 3v needed to drive 1 LED. Additional LEDs would have to be added in parallel because of the low source voltage, so running 4 LEDs (parallel) would draw 120 mA total. You'd get about 22 hrs of unlife from two AA cells. Not a big difference.

 

The biggest benefit to using AAs is that if you only needed, say, 2 or 3 LEDs then that would not be a problem because of the parallel arrangement. If you go 9v then you pretty much need to use 4 of those LEDs or else a power-robbing resistor to take the place of the unused bulbs.

Did not know that about LEDs. I teach high school physics, and we build circuits as part of our electricity unit, but we use regular lamps and bulbs (it's what we have).

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For me, the benefit of using 2 AA's over the 9V is that when your Kaly goes flat, you're more likely to have spare AA's (or be able to steal them from a random battery powered device) than finding a spare 9V lying around. It would be rather embarrassing talking up your Kaly mod then realising you forgot to turn him off last night and flattened the batteries :unsure:

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Here I am, waiting for the dremel to charge, so I thought it might be a good time for some updates.

 

I had a pretty busy week, so over all most of this is some experimentation from this morning. I toyed around with what would be easiest vs. what would look best for running wires through Kaly's neck. At first, I was going to leave the LED loose in her mouth with the leads tucked up inside her neck, then run some green stuff down them to clean it up. In theory, this would be really easy. In practice, I decided it would look awful.

 

Cutting her neck further by hand was out of question, mostly because I am running out of room to get tools in there! However, I want a groove in her neck that I can hide the wires in and then sculpt over to make the neck bones sit flush again.

So, I decided to try my dremel tool with a round cutting head. It works like a charm (when charged!), but adds cleanup time to the evolution. The bonesium frays when cut with a high speed tool, so after each vertebrae has its groove cut, I need to go back and smooth it out with my long blade on my x-acto.

 

As far as the LED in her head, my solution was to make a recessed lip in my previously drilled neck hole so I could seat the LED on it.

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I completed more work on the first circuit (why stop at one?). Of note, I found this page helpful to check my math and make sure everything seems right: http://led.linear1.org/led.wiz

 

I've decided to use three LEDs in each loop. Each will have one blue LED (3.4V) and two green LEDs (2.1V each). This gives me a total of 7.6V on my 9V circuit. I'll use a low value resister (68 ohms) on each circuit to drop the voltage and keep my LEDs as bright and as cool as possible. The last part is something I read about on an electrical hobby board where the poster was using LEDs for power supply indication. I don't expect any of my LEDs would get hot enough to damage the bones, but paint can do funny things when exposed to heat (cracking / discoloring)

 

Putting everything together is pretty easy. I started out by soldering each of the leads on the blue LED to a 22 gauge wire. Then, to keep from shorting out anything once assembled, I used electrical tape to insulate my leads and soldered joints.

 

I widened the hole in her neck wide enough to slip my LED and wires down. I fed my wires down to her chest cavity and the reattached her neck. From here, it was easy to mix up a big batch of green stuff so I could hide the wires. It ended up looking something like this (note, the floral wire in her mouth is an armeture for her tounge):

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Kaly got a break over night, so her green stuff could cure.

 

Next up, I need to wire those two green LEDs up in her chest cavity.

Remember that LEDs only work when installed in the correct direction. The longer lead needs to be attached to the positive leg of your circuit, or it just won't work. Even knowing this, I tend to second guess myself when I'm actually getting ready to put them together, so I always test the LED prior to soldering it in.

 

A picture of my test rig is below. I have looped the leads on a 270 ohm resistor, to use for testing, because if you test an LED right on a 9v, it's only going to light up once, then be useless forever after.

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So I solder in my two green LEDs wrap everything in electrical tape (again, we don't want any shorts here!). And now it's time to test everything:

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Looks fantastic! The green is a little hard to see in the pics, but the blue looks awesome.

 

Some heat shrink tubing on your solder connections will give you a cleaner finish over electrical tape, will hold up better, and could probably be painted if you wanted.

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