Star Trek into Darkness: Klingon heavy disruptor [electronic help needed!]

kialna · Oct 3, 2014

Hello!

So I've been working on the cannon used in STID for my cosplay. I'm nearing the end of basic construction.

And here's what I have so far.

Now what I want, is something I can't figure out entirely. What I want is a big glowing light on the inside of the barrel, which pulses with the flick of a switch. I kind of understand I'll have to code it with either an arduino (which I have one) or with a dimmer. However, I have no idea how to even start with it. I'm very bad with electricity in theory. (I also have a lot of trouble calculating things due to dyscalculia...) but when I have to get it done, I'm good enough to get it working. And as my projects get better, I want to do more complex electronics too. But I just want to make it look like I'll actually fire with a bit of a fade in and a fade out.

The green LED on the side isn't really hard to do. In the actual prop it flashes, but for me it's not necessary to have that flashing. On stage I just want to have it working.

So basically: HELP ME BECAUSE I DON'T KNOW HOW TO WRAP MY HEAD AROUND IT

kialna · Oct 4, 2014

BUMP!

So without an arduino I managed to get this done, which is good for the side.
However,

WITH an arduino, I've been trying hard at the fade code. And I got that working. More or less. But it needs to go ONLY When I press a button. Please help! I have a deadline.

Harada357 · Oct 4, 2014

Sweet !

nomuse · Oct 4, 2014

I can look at your code.

A caution first -- what kind of LED? Arduino's outputs can only handle 20ma (60 at a pinch) which means a couple ultra-brites are okay, but a Cree is right out. You need a transistor to switch the larger loads.

Here's a bit of pseudo-code:

#define buttonpin = 4 //a valid I/O pin
#define ledpin = 2 //a valid PWM pin
int led = 0;
int toggle = 0;

pushed = digitalRead(button);
if (pushed == LOW)
{
if (toggle == 0)
{
led ++
if (led == 255)
{
toggle = 1;
}
}
if (toggle == 1)
{
led --;
if (led == 0)
{
toggle = 0;
}
}
analogWrite(ledpin, led)
delay(20);
else
{
analogWrite(ledpin, 0)
toggle = 0;
led = 0;
}

I haven't had my morning coffee yet so I might have messed that up!

kialna · Oct 4, 2014

I don't know yet.
I thought of something like this, but I'm entirely uncertain about it. I may just have to make a home-made grid.

I have some transistors though. Not sure if they are the ones necessary. Due to dyscalculia I failed electronics badly (calculating etc)
I have some BC 547B M3 E transistors, and two BC 557B KD E transistors available.

Here are some LED's I have. I was planning using the green ones (as seen in that video clip) which is the transparant big one. I need to buy a new one because I broke off one of the legs on accident... But those are NOT RELATED To the arduino. For the BIG LIGHT Which is the actual problem, I'm not sure which ones to use. I could go for a bunch of the smaller ones, but in yellow.

Also displayed is my arduino micro. Which is necessary because it has a different amount of pins than the normal arduino.

kialna · Oct 4, 2014

Another word of meeeeeeee..

When the con is over I will build a new barrel because damn the thing grates on me. But I do not have the time to create a new one atm.

nomuse · Oct 4, 2014

Hrm. That first thing (the LED cluster) lists at 60ma but it is also a 12-volt thing. So you'd need a driver regardless. The transistors you list are a high-voltage NPN and a "small signal" PNP. Better choices for switching LEDs off an Arduino are N-channel MOSFETs, or Power Darlingtons. I've been using the latter -- the old standby TIP120 -- but I'm trying to wean myself from it!

The Arduino's power regulator can handle 12v, so if you have the space you could run off a 12V battery pack. With that, and one nice switching transistor (Adafruit has a beefy N-channel MOSFET that plays well with Arduino and goes for about $2. Not sure what shipping is like for you), you can run pretty much any "automotive" LED fixture. If you browse any of the online catalogs or eBay, about half the LED clusters and so forth there are 12v devices too.

Alternatively, stormtroopers and saber builders are making a lot of use out of super-power LEDs; the most common (and cheap) ones are 1-3 watts, and can be purchased on a little star-shaped heat sink (extra heat sink recommended.) You can drive them the same way -- I put two in a costume last year with those same TIP120's running them, and had full fade control from my Arduino. If you want to get really crazy, though, there's constant-current drivers -- a little more oomph, and more consistent over a range of battery charge.

If you want to look at those things, try using "LED on star" as search terms on eBay. You'll probably see Chinese suppliers on page one of your search results.

kialna · Oct 4, 2014

This looks like a good one?

Edit: I've ordered a 3 pack of the darlington's and a star LED. Thing. I hope the latter will be here on time. Usually things arrive pretty fast but you will always see....

nomuse · Oct 4, 2014

Whoah.

That's a THIRTY WATT Cree. Besides being overkill (is there such a thing?) it will task pretty much everything. And need a hefty heatsink to make it through more than a second or two at full power.

Look for more like 1 watt. Those are the most common.

Also check your color. I don't know what color you are aiming for, but the majority of these will give a color temp in Kelvin. This one, for instance, lists 3,000K. That's roughly sunlight in color. You can get a pretty good idea of the color by looking at any one of the available on-line color temperature charts. Many of them read out in nm (nanometers), others are in Kelvin, converting is easy.

vidman · Oct 4, 2014

I was thinking more in the line of a 3 watt 3000k-3500k (yellow to sunlight yellow) single die rebel led on a 20-22mm star mount, only uses 3 to 3.2vf and can handle up to 1000ma giving about 130 to 150 lumen, a 1/4 to 3/8th inch copper or aluminum heatsink will suffice and can be run on a single 18650 Li-Ion cell and can be found for under $6 and purchased from a USA vender vs Hong Kong,,keeping the money in our economy . Just a suggestion .

http://www.ledsupply.com/leds/luxeon-rebel-endor-star-1-up-warm-white-high-power-led

kialna · Oct 5, 2014

I didn't buy the one I linked though. I'll check which one I got.

Sent from my iPhone using Tapatalk

nomuse · Oct 5, 2014

What he said. You pay over twice as much but you get better quality control, plus you skip that slow boat from China. Which can be slow indeed.

OP's in the Netherlands, tho. No idea what's the best supplier there.

kialna · Oct 5, 2014

I had bought this one, but I'll see if I can order the other one too for a reasonable price.

Hot Cree XML-T5 Warm white 4000K 10W LED Emitter Bead mounted on 20mm Star PCB

I looked at that other one. Looks nice and all, except shipping for a $4 item and $40 dollars of shipping is a bit much. ~~I haven't seen these in the Netherlands anywhere and so far not even conrad (a biiiig supplier with all kinds of niche productes) hasn't got them.~~ So far. I'll look around.

I found this one.
CREE 61001627 HighPower LED Warmwit 1 W, 2 W 67 lm 115 ° 3.4 V 350 mA[/h]3.4V and 350Ma, seems a bit like the one vidman linked above?

vidman · Oct 5, 2014

Looking at the specs for the Cree XML-T5 Warm white is what you are looking for at 220+ lumen at 700 ma vs 67 at 350 which up pumped to 700 ma will only give you 45 % of what the Cree XML-T5 Warm white will give and can still run off of a 3.7v 18650 Li Ion battery should last for many blasts

I was making lightsabers a few years back, look at the star wars threads to get a better idea of the different leds and what they are using

here is the calculated requirements;

http://led.linear1.org/1led.wiz?VS=3.7;VF=3.2;ID=700

kialna · Oct 5, 2014

the problem is, there's not much more available. Majority of the time, the LED will be off. It only needs a pulse/blast when I push the button, so I'd expect the strain to be not very high.

(also, I have trouble understanding half of the terms used. I'm really sorry about that. >___>)

nomuse · Oct 5, 2014

kialna said:
the problem is, there's not much more available. Majority of the time, the LED will be off. It only needs a pulse/blast when I push the button, so I'd expect the strain to be not very high.

(also, I have trouble understanding half of the terms used. I'm really sorry about that. >___>)

Heh. It is a lot to digest at first. And, yeah, engineering is infinitely deep -- you could be off calculating thermal transfer and non-linear resistance changes for days if you wanted to. But for all intents and purposes, just getting the watts in the ballpark, having a sense for what the different colors look like in practical situations, knowing the ballpark forward voltage and being over it (but not too far over), and you can run an LED with a battery and a resistor. And there's on-line calculators in profusion for the resistor.

I'm not real sure I understand all the behaviors you are programming in. Earlier you were talking about a "breathing" pulse. Now, you can wire the Cree right to a button for a simple trigger flash. Advantage in going through software is that you can program so it always emits a pulse of a certain length no matter how you press the trigger.

(And if you get really fancy, program so it fades rather than turns off at the end of the programmed shot.)

kialna · Oct 5, 2014

Well yes. It's supposed to look like a powerblast. I press the button, the LED goes full power and then fades out. That's the idea. And it seems harder than I thought it'd be. :')

vidman · Oct 5, 2014

Hello again,
If all you are looking to accomplish is a full power blast with a 1to 2 second power/cool down phase you will not need a heatsink, the star the led is mounted on will suffice.

Can you program the arduino to do a fast voltage or amperage drop after the full power blast? , if so then again the advice from my previous post stands.

Try the programming on a regular led to see if it will work and then we can go from there in helping you out further.

Just a heads up, I do not have experience with the arduino so I can not help you with programming it sorry

.

nomuse · Oct 5, 2014

One blast is nice...it even includes the switch debouncing (oops -- more terminology!)

#define button = 2
#define cree = 3
int pressed = 0;

void setup(){
pinmode(cree, OUTPUT);
pinmode(button, INPUT);
analogWrite(cree, 0);
}

void loop(){
pressed = digitalRead(button);
if (button){
pressed = 0;
analogWrite(cree, 255);
delay(40);
for (i = 255; i > 0; i --){
analogWrite(cree, i)
}
}

Not checked for syntax or other errors. Select a PWM pin for your hardware for the analog write. The delays are my estimates. For a slower fall, add a delayMicroseconds in there. For a faster fall, decrement by more than 1 with i = i - 4; or similar.

Oh, right. One more bit of advanced stuff. A linear fade will show little perceptible change for about the first half of the fade, then drop rapidly to nothing. To get a taped fade, you can either do more complicated math in the i values, or you can use a "gamma" look-up table (I realize is not a gamma correction, but people seem to understand when I describe it that way.) Not going to type that in here 'cause that's a big array that stores 255 values that are "stacked" towards one end to produce a more even fade profile. Probably overkill for your application anyhow.

propmaster2000 · Oct 6, 2014

Something you have to consider on creating the final "look" of the light blast in real time, live, is that you are trying to replicate an effect that was done by CGI.
Will you want the LED light to be visible slightly from the sides as well as directly in front?
A diffuser may be needed to create the "full on coverage of the barrel".
An ultra bright LED will have a "hot spot" from it's origin. You may want a more "even light" across the opening by diffusion.
How large is the opening of the barrel?
Does the blast start out dim and then rapidly go to full on, then a slow fade to off?
Would the blast need to "expand from center" (starting with a small point of light) to then have several rings of light turn on in sequence
until fully lit, very rapidly?

EDIT:
The multiple rings of white LEDs (3 to 4) don't have to be made from several high current STARs.
The rings can be made from edge lit LED strips.
http://www.ledlightsworld.com/side-view-flexible-led-light-strip-18-leds-p-133.html

One ring inside the other and fired one after another, in sequence until the final "blast"
from the center located "STAR LED".

Star Trek into Darkness: Klingon heavy disruptor [electronic help needed!]

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