My Deus Ex: Human Revolution-inspired candelabra project

seanspotatobusiness

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I have started a project to imitate the candelabra featured in the computer game Deus Ex: Human Revolution. The candelabra looks like this: http://imgur.com/a/BUQ8D#1

I'm having some trouble implementing my project, specifically with the diffusion of light. See below for a bad representation of my plan.

I'm using frosted 38mm diameter acrylic tubes and my original plan was to insert a metal tube holding a strip of 5050 RGB LEDs. However, despite the frosting and even addition of light diffusion "gel" (plastic sheet) inside the tube, points of light are clearly visible. One possible (long-shot) solution I read was to insert clear beads in the space between the LEDs and the outer tube, which may or may not diffract the light sufficiently.

Alternatively, I could use an RGB power LED such as the one here but the viewing angle is quite wide and I'd suppose I would need an optic which I am unable to locate for this LED.

The wiring will not be hidden but will be braided and decorative so that it doesn't look out of place.

qmHA0.jpg

Click to enlarge:
 

rock_007

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Interesting project, first of all to say, you want to imitate the candelabra in a computer game, seems interesting. Try to get some help from the internet if you can regarding the query. There is no display of image on link 2 i.; the (one here) link. Try to find an optic for your project if available on the Internet.:)
 

blasterman

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The issues you are dealing with are the same ones DIY light saber makers have to deal with. More specifically, the issue with LEDs killing the illusion of a diffuse rod because of hot spots. A suggestion to approach the problem from that angle first. I know a lot of those guys have solved it.
 

RoGuE_StreaK

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As per blasterman's reply, but not just DIY; the cheap Hasbro lightsabers use a white polyethylene foam tube as a diffuser, and I know others have used this method. Not sure where you can find this as I've never looked for it, but white rod polyethylene foam (ie. no hollow in the middle) can be found in many hardware stores as foam sealant strips for doors etc. DIY NERF people use it to make their own foam darts.

Here's a look at the lightsaber thing on Park Sabers: http://www.parksabers.com/Blade_Anatomy.html
 

seanspotatobusiness

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Hi. Thanks for all the replies. Regarding the foam tubes, I see the Hasbro design uses multiple small LEDs. I'll keep this as an option but since I would like to be able to change and tune the colour, I want to use RGB LEDs and it would be such a chore to solder so many leads. I imagine that the foam severely attenuates the luminosity of the LEDs as well?

There are many DIY light sabres which use power LEDs and collimator lenses so I think I'm going to attempt this route next. Can anyone suggest good value suppliers to the United Kingdom (I'll see if I can find any on this forum)?

I should also say that I'm hoping to use one of these controllers, designed for LED strip lights, to power the LEDs. I'm pretty sure that for most RGB power LEDs, I can wire three in series and connect directly to the controller, as though it was an LED strip.

KDLki.jpg
 
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RoGuE_StreaK

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Maybe you could use a tight-angle TIR (total internal reflection optic, think of them as kinda part reflector part lens), I got some bits shipped from LED Rise and they came from Romania, so kinda local for you and I believe it would be free shipping.
You haven't said how long or thick the tube is, from the 38mm OD I'd guess from the pics it's maybe 250mm long? Shouldn't be as much issue with fade-out along the length for you if you use base illumination.

Not sure about the controller, generally around here anything refered to as a "power" LED is considered to be more reliant on a constant current rather than a constant voltage, but that's probably going a bit overboard for your application. Find out what the Vf (forward voltage) of the LED is (or should roughly be), how much current (roughly) is required, then feed that into an LED calculator and grab a resistor to match the results. Your source driver is 12V, so for example if your LED Vf is 3.5V and current is 350mA, you'd need a resistor to suit a voltage drop of 10.5V (3x LEDs) and 350mA, with a supply of 12V (that one looks like it can do up to 2A, so that's fine); resistor for such a case would be 1Watt 4.7Ohm.

http://led.linear1.org/1led.wiz/
 

seanspotatobusiness

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Hi Rogue. Thanks for your advice; I really appreciate it.

The tube is 38 mm outside diameter, 35 mm inside diameter and 300 mm length. Indeed you're right; I won't want as tight an angle of collimation as those making light sabres. Any idea what angle I should try first? My guess is 25 degrees.

Regarding the resistors, the main (only?) reason I want to wire it up in series (I guess I will need separate cathodes/anodes for blue/green and red for that to be possible) is to avoid heavy energy loses in resistors. One watt per colour per LED comes to 9 W of wasted energy and problematic heat! If I can get them in series, I think I'll only need to drop 2.5 V with 350 mA for blue and green and maybe 1 V for red. I expect that I may use these (I've ordered one to test).

I will need to investigate the above pictured controller. I only measured the voltage when it was disconnected - I don't know whether it regulates current or voltage.
 

RoGuE_StreaK

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Actually I don't know if those controllers would regulate anything, pretty sure they'd just PWM each line. It says input/ouput: 12V. Also make sure you take note of whether it's "common cathode" or "common anode", this will dictate which pins you need to tye together. Come to think of, you NEED common cathode if you are dealing with a "power LED", as these only have one cathode and three anodes, whereas the 5050s have indiviual cathodes and anodes for each colour, and can be set up either way.

Honestly with the distance you are dealing with, I'd just say "experiment"! Get some power LEDs and put them at the base, see how well or badly the light shapes. You could then try something like a ping-pong ball as a diffuser, experiment sanding it in various places to maybe diffuse it more or thin it down to allow more light through... yes you are drastically losing light rather than trying to reshape it, but I think if you have a bright enough source it won't matter a damn at such short distances. You could spend forever trying to model the beam patterns, calculating to the inverse-square law, etc.

[EDIT] Ah just checked your LED link, those ones have individual cathodes, so ignore my comment about power LEDs
 
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Gunner12

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What about electroluminescent stuff? You could try wrapping white electroluminescent panel around something, or a few white electroluminescent wires in a white plastic tube. This will decrease the hotspots of LED and will not require a TIR optic or a diffusing tube. If your TIR and diffuse tube is not matched well, you could end up with one end of the tube being brighter then the other.

White uelectroluminescent is pink when unpowered though, so that might not work for your project, and I don't know hot bright they are and if they are useable for actual lighting.

Best of luck with your project!
 

AnAppleSnail

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White uelectroluminescent is pink when unpowered though, so that might not work for your project, and I don't know hot bright they are and if they are useable for actual lighting.
!

Rarely useful for useful light beyond indicator lines.

I suggest: Get 3 RGB strips in a triangular prism, put white foam around them, and call it a candlestick. You'll need all your usual controller-type stuff hidden, but this conceals the wires inside the light diffuser. White foam passes a fair amount of light, especially if you get the kind without TiO added to whiten it.
 

seanspotatobusiness

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Hi. I did consider electroluminescent stuff but both the light output, lack of colour customisation and the expense led me to ultimately choose LEDs. I think electroluminescent panels would look pretty sweet nonetheless.

AppleSnail, I'm not sure what you mean re: the triangular prism... would the LEDs be facing into the prism or away from it? Are they inside it or out?
 

AnAppleSnail

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Hi. I did consider electroluminescent stuff but both the light output, lack of colour customisation and the expense led me to ultimately choose LEDs. I think electroluminescent panels would look pretty sweet nonetheless.

AppleSnail, I'm not sure what you mean re: the triangular prism... would the LEDs be facing into the prism or away from it? Are they inside it or out?

My (white) LED strip lights are about 8mm wide. Imagine cutting a bar from triangular stock with 8mm faces. Glue the LED strips to the sides this bar (Which serves as a heat spreader) and stab this into the center of your foam 'candle' shapes. Attach wires in secret and you're halfway there.

ikdwH.png

Crude drawing of RGB LED strip being applied to one face of a triangular metal bar stock.
 

seanspotatobusiness

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Hey Apple. Thanks for the schematic! Unfortunately, I don't think it will work for me. I've currently got an RGB strip wrapped around a metal tube. I wrapped some packaging foam (this sort of stuff) and the spots are still clearly visible. In fact, while the spots are dimmer, I'm not sure that the gaps between them are actually brighter (I've got half of the length with foam and half without). I'm going to use the tube/strip in some other application where I will have a larger distance for the light to diffuse.
 

RoGuE_StreaK

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Actually sean you haven't mentioned what the LED spacing is on the 5050 strips? I've seen plenty that have big gaps between them, no matter how you try to diffuse it you won't be able to overcome that, you need tight spacing to begin with.
If you do have the ones with large gaps, perhaps there could be a way of wrapping them so two strips cross each other diagonally in such a way as to fill the gaps in one with the LED of another...

As a side thought, to try to diffuse multiple spots, you'd want to place the diffuse material far enough away from the LED so that it is catching overlapping pools of light from the neighbouring LEDs, rather than having the diffuser hard up against the LED, which will just give you a diffused spot. Perhaps also you could experiment with adding a dollop of clear caulking silicone over each LED, it may possible act as a dome lense and give a larger angle of emission? (or it might do the complete opposite, hence "experiment")
 

seanspotatobusiness

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Okay, I'll try it next time I get my hands on some (will ask friends to save any Styrofoam they get) but I imagine it will severely attenuate the light.

The LEDs strip is the highest density I could find (120 per metre for RGB). Unfortunately, the circumference of the pole leads the LEDs to almost be in a line. There are four lines running up the pole. In retrospect, I could have avoided that by wrapping two separate strips up the pole and aligning them out-of-phase.

As well as the acrylic tubes already being frosted, I inserted a few layers of diffusing plastic sheet. There isn't enough space in the tubes for other items to not be pressed up against the LEDs. Although I will try the Styrofoam, I'm expecting I'll have to use the strips for something else and wait for the power LEDs to arrive. The strip I already adhered to a pole, I will use in a frosted vase of 10 cm diameter. I think the extra 3 cm all around will make a lot of difference, plus the glass is more heavily frosted.

Incidentally, I noticed that my aluminium pole got very (skin-damagingly) hot after about 15-20 minutes power. I will need to ensure that the pole is connected to some metal which can better dissipate heat to the environment.
 
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yliu

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Can't you just put high power emitters on the bottom of the frosted tubes, so it will be like a flashlight with a traffic wand?

Look up "Philips LivingColors", maybe you could also fit Red, Green and Blue colored dies on the bottom, then you could make all the colors you want and the tube should light fairly even.
 

seanspotatobusiness

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Hi Yliu. Indeed, that is the method I'm attempting now.

I'm stuck trying to solder the copper rod heatsink into place. I need a thermal connection between the LEDs and the candelabra and this is my solution:

FBMwQ.png


The problem is that I'm unable to melt the solder/keep the candelabra heated/heat the copper rod. I've tried using a regular soldering iron to maintain an elevated temperature combined with my soldering gun (which is only meant to be switched on 12 seconds in every minute). I also try using a mini blow torch (about the size of a large permanent marker pen) but the flame keeps going out, presumably because it's upside down and getting blown out by hot oxygen-depleted air).

Edit: forgot to say that 45, 30 and 15 degree collimators were not sufficiently tight enough. I have ordered 5 degree ones and expect them in a couple of weeks.
 
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yliu

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Maybe you can use the thermal glue or whatever it's called, it is used to glue the CPUs to their heat sink.

Good luck.
 

RoGuE_StreaK

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How are you attaching the LED to the copper rod?
Is the candelabra cup intended as an extended heatsink, or is the solder purely as an attachment method? Can you perhaps place the cup on a hotplate if soldering is a must? Or could you just drill through the cup and tap a screw into the copper?
 
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