- 1 What?
- 2 Progress
- 3 Inspiration
- 4 Things to display
- 5 BOM
- 6 Stretch goals
- 7 Artist impressions
The space is in serious lack of a clock.
September 18, 2014
The clock is finished!
It turned out that the weather updates were still buggy but that is fixed now.
We do need to think about a good place to put it up. It is now hanging left of the 3d printer because there was network and power there but at least the cables need a bit of tidying up. An enclosure for the electronics is also still on the wish list.
September 6, 2014
We are now a lot of softwarebugs further and I'm happy to announce that the arduino firmware is finally done. The clock is now capable of showing the time. Updating the time over NTP and displaying the local shower precipitation as scraped from buienalarm.nl. The most annoying bug that I had to fix was that the millis() was running behind because the neopixel does some stuff in noInterrupt() mode which makes the arduino millis() code miss some interrupts. I solved the issue by using Timer1 instead and patching some of the Time.h library functions to use that instead of millis(). What is still to be done?
- refine and reprint the 3d model. There is a small mistake in the model which shows on the front as an ugly area. Also, the circumference seems to be slightly to big for the end pixels to have the same distance as all the other pixels.
- Solder the wires in a shorter fashing such that the fit inside the 3d printed shape (a.t.m. the clock looks like its guts are spilling out)
august 7, 2014
I have soldered the 5M white usb cable between the controller and the ledstrip. This means that the controller and the powersupply can be placed somewhere on the ground while the clock is on the wall. I had two concerns: one being the influence of a long cable on the delicate 800Hz self timed signal. The second being the thickness of wires inside the usb-cable that I repurposed. It was made for a maximum of 500mA while the clock can theoretically draw up to 3500mA. Both turn out to be no problem after all. Even at five minutes to 12 (largest number of leds on concurrently) the cable doesn't get warm or anything.
august 1, 2014
Major progress today. Arduino code (for fetching the time over ntp and showing it on the leds) is finished. Weather-apis require more work. I also reduced the wire-spagetti by soldering a conversion board that wires the arduino to the ethernet module. Finished up the 3d designs for the clock and started work on the designs for a case(really a requirement; the 230V screw terminals on the power supply are now only covered by a piece of tape:s).
These pictures show the entire setup now. No more cable spaghetti! Note that the leds are on 10% brightness now because I was being blinded by the leds all the time ;)
juli 28, 2014
Back from holidays. Most stuff has been delivered now. Just gave the ENC28J60 ethernet module a testdrive and it 'just works'! Who would have believed that?
I also updated the 3d model to better fit the exact dimensions of the ledstrip. Started the arduino code for the actual clock but I still have to test the ledstrip. It is a delicate part and it's late not so better do that next time...
juli 12, 2014
Everything ordered in eBay:)
juli 10, 2014
Budget accpted by the board!
- original post on hack-a-day
- an inwards shining led clock. looks good but probably hard to make
- article on hack-a-day about efficiently controlling these leds
Things to display
- primarily the time
Many other things are imaginable:
- 60 minute rain forecast (http://buienalarm.nl/app/forecast.php?type=json&x=366&y=429)
- wifi bandwidth usage [Thanks Spliet]
- add your wishes here...
Also: we have to consider how to switch between functions. It could just alternate but then the reader has to know what statistic is shown in which color. It would be really cool if it was voice activated but that requires more hardware...
This is the minimum for a simple clock:
|Digital Leds||50cm for a 16cm diameter, ws2811 with 144 leds/m||ebay||20.88||15.34|
|controller||arduino pro mini||ebay||2.54||1.87|
|power supply||the leds are 35Watts/meter so we need at least 17.5 watts(=3.5A @5V)||ebay||6.99||5.13|
|cable||abuse a usb cable because we have exactly 4 strands to power||ebay||3.25||2.39|
72 led addressable led string like this (or similar).
For simple tasks an arduino pro mini might be enough, but to display cool statistics requires something network attached. Maybe someone has a sugestion for a very small usb arm dev board with ethernet/wifi?
The leds draw 35Watts per meter. so for 50cm they will draw 17.5 watts when the leds are full on. At 5V this means we will need a power supply that can handle 3.5A. This is quite a lot and we may need something like this:  (Note: 3.5A is peek current if all leds are full white. In the case of the clock some leds will be off altogether or only one of the colors will be on. Nevertheless it would be bad design not to account for the maximum current)
A digital timer to keep track of time accurately and also when the clock is off. (it should be off when the space is closed to save power)
A nice looking cable is required to power the ledstrip. My idea is to put all electronics externally somewhere on the floor/ceiling. The ledstrips have exactly 4 wires so we can abuse a white usb cable for maximum stylishness.
Small supplies like connectors and a power supply for the controller are excluded from the BOM because I think we have them lying around in space.
3D printed parts
The ring that holds the leds will be 3d printed. Furthermore I intend to design a small housing for the controller and the power supply.
internet capable controller +€22,-
To display anything more interesting than the time we will need a small internet-capable controller. For instance a RPi or a beaglebone. Suggestions for cheaper controllers are welcome... wifi or ethernet is the minimum requirement.
After discussion with FooBar and effractur on IRC I have a few options:
- a secondary arduino with an ethernet shield could do the trick. memory and cpu will be maxed out at times:)
- A lauchpad might be perfect. This one does wifi and costs only $30. Not sure but maybe this one can be tricked into controlling the ledstip directly... saving one arduino.
- The randomkey might be an option but I don't have enough details yet to know if it can do wifi/ethernet and how much it would cost.
- [gl-inet.com] sells dd-wrt devices with wifi and usb. The usb could communicate with the arduino. Still a pricy $30. Advantage, it runs linux;)
- A Rpi(€35,-) +SD(€7.50) +adapter(have in space?) costs about €42.50. This is expensive, does not do wifi yet, and does not replace the arduino because the rpi cannot get the timing for the ws2812 apparently.
- the same discussion for the beaglebone
It would be cool to replace the leds by lasers. We could mount them outwards or inwards. Alignment will be an issues that will require a few test-prints but I think we can make this work.
This does mean you only get one color. Laser modules in other colors than red are unfortunately hard to find on ebay. link to cheap laser modules. 60 of those costs $54.60, subtract the costs of the ledstring and the power supply(because lasers probably don't need that) and this costs $26.73 extra.
I'm not yet clear on this one but I think we could display the hours on randomdata-green, minutes as a blue dot and seconds as a red dot(temporarily switching the green led of if they coincide).