Penumbra: Code

Coding the sundial has been a challenge throughout this project.  Though I have basic knowledge in C++ from my undergraduate in Mechanical Engineering, I have had to adapt substantial amounts of code to get the sundial working as it should.  During the last module, I successfully managed to write a code for the sun progression during the day, and programmed the moon to rise and set at specific times for the week that it was on display.  For this prototype, my aim was to get the clock fully working, so that it calculates sun- and moon- rise and set itself based on the latitude and longitude of its position and its time zone.  I quickly found out that there is a code library for calculating sunrise and sunset times that I can easily call into my code, but moonrise and moonset require calculating from first principles.  Thankfully, someone else has worked out the maths, and all I need to do is combine it into one programme and then write the code to get my LEDs to respond.

Essentially, the programme in my sundial has four features; sunrise and set (1) , moonrise and set (2), change colour depending on the time of day (3)  (red at sunset, yellow/white at noon etc.) and, position the LEDs to cast a shadow for the time (i.e. 180° from normal clock hands).  This equates to a fairly large amount of code, and so mistake finding can be challenging.  Thankfully there is time before the exhibition begins to watch the clock and fix any errors that might occur.

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1. Modelled from: Dawn Dusk Timer for LED lighting strips by Tom Loos
[https://forum.pjrc.com/threads/25084-Astronomical-code-based-Sunrise-Sunset-simulator-questions]
Using: TimeLord astronomical library by Michael Rice [http://swfltek.com/]
Using: Astronomical Night Lamp project code by Paulo Oliveira. [http://www.paulorenato.com]

2. Modelled from: Moon in my Room Code by “Slackmasterstan”
[https://github.com/slackmasterstan/Moon-in-my-room/blob/master/Moon.ino]

3. Modelled from: ds1307 RGB led day night cycle by Mccluskey1181
[http://forum.arduino.cc/index.php?topic=240832.0]

Penumbra: Building the surround

Making the casing for the sundial was challenging. From a practical sense, it had to be made from steel as it was strong enough to support the limestone and could be welded into place.  It also had to house the LEDs at a suitable height from the face, and have room at the back for storing the circuit board.  I started off with a simple design of three annular circles (each waterjet cut) that would have a metal collar wrapped around them and be welded into place. 

Quickly I realised that the back needed to be removable in case of emergency wiring issues.  This added extra considerations as the back could be screwed on but would need some form of block to screw into on the back of the middle plate.  After consulting with the metalwork technician, Rachael Baker, we decided that the cleanest way to do this was to drill three holes in the mid plate and weld a tapped and threaded steel dowel on to them cutting a shoulder joint at one end so it sat within the plate.  This kept it flush on the limestone side, and also meant that it could support the back plate as the dowel acted as a spacer. 


From an assembly point of view, the casing was quite difficult to put together.  Because the rim is bent around the outside of the plates, the plates need to be stacked to the correct spacing with wood and then the front plate welded on, and the collar welded down the side to hold the circular form.  The issue then is how to get the mid plate out.  It needs to be removed to glue the limestone on before it can be welded into place as the limestone won’t fit through the hole in the front.  In the end we knocked it out with a hammer, glued the limestone face on, and hammered it back in with wooden spacers so it could be welded.  It’s not ideal in terms of assembly, but it worked. 

Welded surround, unpainted.

There is a 5mm shadow gap between the edge of the limestone face and the mid plate which meant that heat produced through welding wouldn’t cause any harm to the face.  It also allows for a small notch at the top dead centre of the sundial for the LED cabling to pass through.  This notch also aligns with the seam of the collar so the back can locate correctly.  The centre of the mid plate has a hole in it to reduce weight but also to help with locating the underside of the stone face during gluing so the 5mm gap is even all the way around.

Once the mid plate has been welded in to position, the sundial can be assembled and blocked for spray painting and the wiring.  I chose to spray paint the casing matt black as I had used scrap mild steel from the engineering workshop on the circular plates, meaning that the rim of the casing (made from bright steel) was a different colour.  The matt black colour also helps to emphasise the face of the sundial and the stark contrast does make it look more celestial.

Penumbra: Faces

Limestone tile (detail).

Having started this project during the last module, I had already developed a strong message that I wanted to convey and had some experience with the electronics behind the project, now I had to finalise the aesthetics of the piece and write some fully working code.

The overall form of the product had been decided while making the previous prototype, but for the final prototype I had the challenge of selecting materials that best communicated the meaning behind the product.

From the outset I knew that I wanted to use a natural materials in the sundial to echo an ancient celestial/shamanic style.  I considered a variety of natural materials in different combinations; a smooth, chalky white gypsum face with a rough cut slate gnomon; a pale lime mortar face poured around a knapped flint gnomon.  From the chalk-like faces, I progressed to limestone.  Much easier to source and work with, a limestone face also echoes the sentiment of the piece as it is thousands of years old, made of fossilised sea creatures.  The problem with limestone would be sourcing a thin slab at a reasonable price, and cutting it.  I had initially thought that this might be a job for a stone mason, until a friend of mine asked if I could use a floor tile. Finding a natural stone floor tile was easy enough – I went to Topps Tiles and picked the style I wanted – the problem would be processing it and ensuring continuity. 
  
Because natural stone tiles are mined from vast quarries before being split up into smaller units, the colour of the stone varies from tile to tile.  Having bought three tiles in two different varieties, I felt lucky that they all turned out to be on the lighter end of the spectrum.  When I was tile shopping I was struck by the quality of the natural stone; some looked like aerial views of barren deserts, their veins like paths in the sand, while others looked like planets, craters scattered across their faces.  Naturally, I chose the celestial ones, with one tile resembling the moon and the other the sun.

During waterjet cutting

Cutting the tiles was the next hurdle.  The tiles were 12mm thick and because I needed a perfect 35cm diameter circle, the only accurate way of doing this was by waterjet cutting.  The issue with waterjet cutting natural stone is that if the jet hits any inclusions or fault lines, the whole tile can split.  Thankfully the technicians in the School of Engineering were willing to give it a go, and with my fingers crossed I watched as my tiles were cut.  I only needed one to work out of the three (I bought two back-ups just in case but at £15 a tile, I was really hoping for the best), and amazingly, all three worked perfectly. 

Then it was just a matter of choosing my favourite one and making the case for it.

Penumbra: Theory

Visual render of Penumbra

Penumbra: noun. A shadow cast by a celestial body.

During my research it has become increasingly apparent that the more technologically advanced (and technology dependant) we become, the more linear our time becomes.  We move forward at an ever-increasing rate, chasing the next advancement, and leaving behind the natural world and it’s cyclic time – that of re-birth and renewal.  In his essay on products and their relationship to time, Stuart Walker hypothesises that time has two distinct progressions; secular time and sacred time. (Walker, 2004) Secular time relates to the everyday life of a person, it is linear and fleeting.  Sacred time is circular, it represents the changing of the seasons, the rotating of the earth, birth-life-death-renewal.  Our lives are dominated by the linear progression of time; we feel it slip through our fingers like grains of sand. 

The celestial bodies in particular have resonance in our ancient and modern religions, where the events in our lives are an echo of the lives that have gone before us, their cyclic motions visualising the repetition of what Mircea Eliade calls “Great Time” (Eliade, 1954) – the long now.
Penumbra is a conventional timepiece that reflects the cyclic nature of the world around us.  In our technology obsessed lives we need a reminder of the forces that define our days and nights – the sun and moon. 

The wall clock takes the form of a traditional sundial, where the sun and moon are represented by LEDs set into the frame of the clock.  As the sun moves throughout the day, the LED sun moves around the outside of the clock, casting a shadow onto the hour position.  As the sun rises and sets the LEDs change colour, simulating sunset.  During the night, the moon becomes the time keeper as it rotates around the clock.  The LED cycles are set to mimic the natural solar and lunar cycles over Manchester.  At this time of month, the moon rises early in the day, shines with the sun and sets at around midnight.  This natural progression is replicated in the clock, meaning that at certain times of year, the moon will eclipse the sun and the clock will cast no shadow.