Please note that this is a very old post and probably contains out-of-date information.

Just got back from a pretty intense three week session redeveloping and installing a second showing of Most Blue Skies at the Nikolaj in Copenhagen. Our piece was part of the Rethink show. It was nice to be back in Copenhagen, such a calm place compared to my new home in London. The Nikolaj had rented us a flat in Sydhavn for most of our stay. We also had access to the Spaceframe and a room in Christiania so plenty of options as crunchtime approaches...

Our main aim with this install was to produce, one way or another, a much more impressive sky blue colour than we achieve in Korea. In Korea, we used a CYMK stage lamp, the "Sea Changer" which Josh had a hellish time trying to target for accurate colour representation. So, this time we decided to use an LED based light, plus diffuser, to create our slab of blue. The question was weather to use an existing commercial panel (an EvenLED, lent to us by Martin) or to build our own. Even though it's a very nice product, the EvenLED only has 16 RGB LED triplets and we were worried that it just wouldn't be particularly bright in the gallery.

In the end we decided to attempt to build our own panel but with the same dimensions as the EvenLED so if we failed to finish in time or something catastrophic happened, we could fall back on the Martin panel. The choice of LEDs was the next step. We had about €2000 in the budget that we could allocate to LEDs. These LEDs are surface mounted but you can buy them pre-mounted onto a "star" - a sort of star-shaped aluminium heat-sink. We decided to lay the LEDs out in a 9 by 9 grid wiring each row serially - we wouldn't be able to control each LED individually but we would be able to control each row independently and produce a gradient of colour - something we were keen to experiment with. We chose the Luxeon Rebel RGB "Endor" triplets, next to which we would add a Cree royal blue LED to boost the range of blue's we could produce.

So we would need 81 of each plus a few spares. One lessons, that we never seem to learn, is that unless you only need a handful of a particular component (like 10) then you may it incredible difficult to source what you need at short notice. Suppliers of most components don't seem to keep anywhere near what a newcomer might consider reasonable stocks on hand. We ordering 50 or 60 from a German company but ended up just overnighting the whole lot from a US supplier and returning the German shipment.

The next step was figuring out how to control the LEDs. We have some experience with the DMX lighting protocol which we used for the Sea Changer in Korea. It's a pretty unsatisfying system and DMX hardware is just insanely overpriced for what you get but with heavy time constraints we decided to stick with what we know. We now know that all the cool kids build their DMX controllers on Arduino boards (we know for next time) but we ended up having to spend around 400 sterling for a horrible plasticy ARTNET Node which is just a simple ethernet to DMX bridge. We still needed DMX based LED controllers. We found a really nice product - the eldoLED POWERdrive.

These LEDs produce a lot of heat! Josh wired one of the Luxeons up to an eldoLED with no extra heatsinking and all the wires desoldered themselves within a minute or so. So we figured we needed some serious heat-sinking. No problem - we'll just build the entire panel as a giant heat-sink :-)

Then came the soldering. A lot of soldering... You really don't want an underpowered soldering iron when soldering onto a massive heat sink. And electronics shops get annoyed if you keep pestering them for "something a bit more powerful" so arm yourself well.

We decided to bolt the power supplies and controllers onto the back of the panel. The position of the bolts was the one thing we didn't really design or plan before getting the drills out. This resulted in quite a few unplanned "ventilation holes". The lesson we learned - plan absolutely everything with your 3D CAD program as the things you think you can improvise will end up taking up a unexpectedly long time.

The first time we powered up the light in the gallery, we tripped the fuse for the entire ground floor. We got our own dedicated circuit but it kept on tripping. In the end we divided the nine power supplies into three sets of three so we could spread the load over several fuses. We didn't really anticipate the large draw of power as the power supplies switched on. We were surprised to have problems as the LEDs only come to about 800 watts. The guys at the gallery did a great job building the box to mount the panel in:

I made a lot of changes to the software to make it easy for us to throw together a lot of machines dedicated to doing sky colour calculations. The film school donated a lot of old machines to us, and a very dedicated man from the school helped us a lot by wiping the hard drives (rather than destroying them) saving us a lot of hassle finding new drives. I had a very boring couple of hours installing Centos linux on all of these machines:

I experimented with Capistrano to automate some tasks over all the machines. I had some success but sort of lost track with it as we ran short of time.

Eventually we did finish on time. With the usual after-opening few days of tweaking and tying up loose ends. We found that LogMeIn is useful for getting back into machines left in strange places (for monitoring and diagnostics). Next time, we'll try to get hold of an Axis webcam and leave it in the gallery. I have some more photos from the trip here.

Here's a short screen capture of the giant map warming up - it shows current calculations across the world and updates live with data streaming in from the old machines (you may have to full screen to see anything). You can just about tell it's North and South America: