Festivalljus – LED, Lens, Heatsink Assembly

Assembly Spotlight With Chassi 3D 1
One of the hardest things with this project is to solve the problem with the heating. 9 pieces of 3W LED tends to get very hot, 27W that have to be transferred to the air.

LED 3DLED Inverted 3D
If I bend the pins on the led I can make the LED’s go through the PCB. An alternative is to use a lot of small via’s under the LED to transfer the heat to the underside. But I think a direct contact with the heatsink will be more effective.

Assembly PCB with LEDs 3D Without Lens
Assembly PCB with LEDs BottomAssembly PCB with LEDs 3DAssembly PCB with LEDs SideAssembly PCB with LEDs Top

Assembly PCB with LEDs 3D With Heatsink Fan
Assembly PCB with LEDs 3D With Heatsink LensesAssembly PCB with LEDs 3D With Heatsink Side
A CPU cooler should be sufficient enough to transfer the heat out to the air. I don’t know if the fan is necessary.

The whole assembly will look something like this:
Assembly Spotlight With Chassi 3D 2Assembly Spotlight With Chassi 3D 3Assembly Spotlight With Chassi 3D 4

Optics Specification

Festivalljus – Lighting

IMG_3889
Regarding the lighting, the last few months I’ve been researching different kind of LEDs and optics.
Our goal is to get really narrow spotlight, maybe 6-10 degrees, and it’s really hard to get a narrow beam like that.

There exists a few models of 5/10mm hole mounted LEDs with build in focusing-optics right into the housing (http://www.ebay.com/itm/310181790384). Those LEDs makes a narrow ~13degree beam which is nice, but the RGB-colors are separated.
When you build an array of small LEDs like this it’s working quite well, but it’s not a perfect spotlight as it casts RGB-shadows (like this http://www.lungstruck.com/wp-content/uploads/2013/06/IMG_1965.jpg).
IMG_1965
Another bad thing with smaller LEDs are that it’s hard to get bright enough. If I were to but in 192 5mm LEDs it would only give me 15W of LED power.

Another LED-type that I’ve looked into is big 50W LED-arrays (http://www.ebay.com/itm/380676009599) with complementing 78mm lenses.
These types of LED-arrays give out it’s own LED-pattern when focused narrow enough. You can solve this by adding a diffuser close to the LED-array.
But you would have to add two 78mm lenses to focus down the beam. The narrow beam is the best so far, really crisp and around 6 degrees.
The bad thing is that it weights to much for my small construction, and also it brings upp the cost per unit really much.
Another bad thing is that you’ll need active cooling, which also adds to the weight. I used an ordinary CPU-cooler for desktop-computers.

The latest LED-type I’ve tried is 3W Star High Power RGB (http://www.ebay.com/itm/160582419768).
Ontop of that I’ve placed a special lens called a Collimating lens. Collimating lenses are directing beams from different angles straight into a column of light, it’s best described by this picture (http://www.laserfocusworld.com/content/dam/lfw/print-articles/2012/06/1206LFWnews05web.gif).
1206LFWnews05web

The lens I tried also have a built in reflector (http://www.ebay.com/itm/390625279166).
This is the best solution for my project so far. I weighs almost nothing, gives me 50W of power in an array of 16 LEDs.
A negative thing about the collimating lens is the beam is much more fuzzy than the two above LED-types. It gives out a narrow beam, but there is a lot of light leaking through around the beam.

IMG_3867
IMG_3868_annotation

DIY Moving Head Spotlight PAR RGB-LED

There’s a small festival up in Uddevalla (Sweden) called Elinorspelen. It’s a non-profit festival with the goal to have fun and spread culture. Unfortunately the festival have a very low budget and can’t afford all the equipment that it needs, and lighting has especially been down-prioritized.

Two friends of mine, and I, decided to do something about it. We got together and started discuss what kind of stage light that would be possible to buy/make.

We all agreed on that moving head spotlights would probably the cheapest alternative that gave the most visual effect.

Research

We started out to search for cheap LED-diodes to make our own spotlight.
But after a day or so we quickly found out that to just build the a LED-array would cost as much as a commercial spotlight. For example this LED PAR 56 black 151 LEDs RGB 16W for 296SEK.
We soon gave up the idea of making our own LED spotlights.

But we found out that all the cheap LED-spotlights had a very wide beam angle, and we wanted a very narrow beam.

Making an RGB spotlight on a tight budget

We got back to the idea of making an spotlight ourselves. Picking out narrow 10-13° viewing angle LED’s from Ledz.com.

As I started to pick parts to the project, the list grew longer and the price were raised by big numbers.

I managed to find really cheap geared stepper motors from eBay for a really cheap price; 28BYJ-48 DC 12V, plus controller, for around 26SEK a piece. After some research it looked like that model i widely used in different DIY- and Arduino-projects.

After a few weeks of picking components forward and back I’ve come closer to a final budget on 450SEK per spotlight, and that excluding some material prices like polycarbonate. I suspect that the final price per unit will end up on 500SEK. That’s at least 3 times cheaper than any commercial light.

You can find the budget for the spotlights here (Google Drive).

Electronics

I’ve just a basic idea of what components the electrical design needs. Some micro-controller based up on the STM32 series should work well.
Some mosfets to drive the LED’s.
The LED’s should be connected in series to 12V, and have the same pinout as the popular LED-strips that are so widely available now. This should make the testing very easy.

Designing the chassis and mechanics

The designing process were making its way alongside with the budget, a design-change could radically change the budget.

I had a pretty basic idea how I wanted the final product to look like.


A LED-array soldered on to a PCB, the PCB should be mounted directly on an axis that were attached in a U-shaped arm.
The PCB would make the LED-array really lightweight and it should not be a problem for the geared stepper motor to move it.

I also thought of having the cabling layed inside the axis, so why not make the axis into a tube instead of a solid rod?

Moving the U-arm

But how would the U-arm move? I knew that a central shaft would be the focus in this problem. It should be able to move a pretty heavy weight, PCB + Stepper motor + alot of polycarbonate.

I also think that the moving head spotlight should be able to be mounted in several ways; placed on a flat surface shouldn’t be a problem. But be able to hang upside in a ceiling, or hanging from the side of a wall, that’s tough.
The center-axis mus be able to take on forces from many directions.
One thing was for sure, we needed alot of bearings.

With the bearings a shape took form, centered around the axis.

4 bearings are used on the center axis. 2 axial bearings to make it spin easy upside down and standing. And 2 bearings up and down to make the center-axis stiff and prevent it from leaning.

And around the bearings, the framework took place.

Somewhere here the pieces started to place them selves in the big puzzle, it was much easier to design now.

Around the framework we needed a casing to hold out dirt and to keep it pretty.
It’s hard to make a nice chassis by yourself, so  I started to look around for a cheap case designed for another purpose.

I found this cheap water bawl for dogs for around 17SEK. It’s about 200mm in diameter and should house the mechanics and the framework nicely.

Designing in CAD

It’s one thing to have you design in your head and on paper, but it’s hard to grasp if it will fit or not. It’s here CAD-design comes into the picture.
I started to draw the different parts needed. As I draw the parts I could easily adjust lengths of parts to fit each other. Make puzzle-slots for the different pieces in the U-arm.

I try to make an easy design that could easily be milled out in our CNC-machine. The most parts are made so they could be cut out in X-Y-axis. I’m also trying to make as long and narrow pieces as possible, because long pieces are easier to fit narrowly on to a big polycarbonate-sheet.

The last part of the CAD-design was to put it all together, attach bearings to the shaft, build the U-arm.

The first design is now complete. We’ll have to make several adjustments to the design in iterative steps.

But for now, I’m thinking it’s starting to look good!