Download Aurora Monitor Build Instructions

Aurora Monitor Build Instructions
Version 1.0
Author: Jetty
Thing: 25528
License: Creative Commons - Attribution - Non Commercial - Share Alike
Disclaimer: Don’t blame me if you hurt yourself or bust something. You are responsible
for your own actions. If you don’t understand these instructions or are not aware of all
safety issues, obtain professional advice.
This document may already be out of date. To get the latest version, visit:
http://www.thingiverse.com/thing:25528
” The Science Bit ”
The Aurora Monitor uses the Wing Kp Prediction Model (http://www.swpc.noaa.gov/
wingkp/index.html) combined with solar wind data from the ACE Satellite which is
located at the L1 point (http://en.wikipedia.org/wiki/Lagrangian_point).
This is approximately 1 hour solar wind upstream of earth (depending on the speed of
the solar wind). When the solar wind hits the satellite, the speed and strength are
relayed to earth and the prediction is made for arrival time and strength based on the
current dynamics of the earth's magnetosphere and it's relative weakness.
This technique is highly accurate because when the satellite is hit, we know the CME
(http://en.wikipedia.org/wiki/Coronal_mass_ejection) that occurred 1-2 days earlier was
truly earth directed, and we can get an accurate read on it's strength and likelihood to
get through earths protective magnetosphere and produce the northern lights.
The accuracy of this approach when used correctly and then seeing an aurora on earth
at your location is around 95%.
Components
1. Arduino capable of Wifi (WiShield 1.0 and BlackWidow compatible) or Arduino
Ethernet (or Arduino with Ethernet Shield). The following Arduinos I’ve tested, so I
recommend these ones:
(http://www.robotshop.com/productinfo.aspx?pc=RB-Lin-40&lang=en-US)
(http://arduino.cc/en/Main/ArduinoBoardEthernet/)
2. 10mm RGB Led (Common Anode). I used this:
http://evilmadscience.com/productsmenu/partsmenu/329
Note: you can also use Common Cathode, in which case wire up the common to 0V
(instead of 5V) on the Arduino, and uncomment “LED_COMMON_ANODE”.
If you’re using another LED, somewhere in the 20ma-40ma range per color is best.
3. Resistors x 3. If you’re using the above LED, then 100 Ohm x 2, 150 Ohm (for the
red color). Otherwise, use the LED Resistor Calculation below to figure out the
values you need.
4. Miscellaneous parts. There are a few ways to crack an egg. I used a strip of header
pins, wire and heat shrink.
5. Some kind of power supply for your Arduino (or you can hook it up to a computer via
USB). 9V PSU is ideal, 12V is probably the upper limit because the voltage regulator
on an Arduino is small and it will heat up (even at 60ma). There is some venting in the
case to allow for this. If using a power supply it’s best to check the actual voltage, as
many power supplies are unregulated and can supply more voltage than specified.
LED Resistor Calculation
Larger LEDs tend to use more current and there's a limit to how much current the
Arduino can source. Pins are rated for 40ma max on newer Arduino's, however it's
generally considered safe to limit usage to 20ma per pin with a serial resistor.
The calculation for this resistor is (and you'll need 1 per color) is:
!
Resistor (Ohms) = (5Volt - LED Forward Voltage Drop (per color)) /
!
!
!
!
0.020 (Current Amps)
For example, if the forward voltage of the LED is 2.2V, then:
!
(5-2.2) / 0.020 = 140 Ohms
If you have any doubt about this calculation, a 220 Ohm resistor will work with any LED
that can handle 22ma or more.
RGB Led's can be Common Cathode or Common Anode, set the appropriate type in the
LED settings. Also, RGB led's have various spectrums, forward voltages etc., all of
which effect the color, you will likely need to tune the color table below for your LED.
Printing The Case
Inukshuk (the clear shape on the top):
I printed this in Clear Makerbot PLA , it should also work printed in natural/white ABS.
Avoid colored ABS as only certain colors will show through, although you can always
change the software to colors that work with the color you’re using.
The inukshuk was printed at 0% infill and with 3 shells. This provides the best “glow”
effect. Adding internal fill gradually diminishes the light transmission. If you have issues
printing the larger spans without support, you may be forced to print 1-2% fill.
After printing, use a file or carefully drill out the recessed hole, so that the LED can
transmit light through to the center of the object unobstructed.
The remainder of the parts can be printed as you would normally, I printed the Stand
Holder at 25% fill, and the Stand Top at 15% fill.
If you are using the Arduino Ethernet, you’ll want to print EthStandHolder.stl and
EthStandTop.stl. If you’re using Asynclabs Black Diamond Wifi, then you’ll want to print
WifiStandHolder.stl and WifiStandTop.stl.
For anything else, you may need to use OpenScad to change the dimensions in
Stand.scad.
Assembling the LED Lead
The RGB Led will have 4 leads, 1 will be Common Anode or Common Cathode, and the
others will be Red / Green and Blue.
Wire up the resistors to the Red / Green and Blue wires, and then wire from the
resistors to a 4 pin header. The header will plug into digital pins 6-3 on the Arduino. Pin
6 is Blue, Pin 5 is Green and Pin 3 is Red. (Pin 4 is unused). These are the PWM pins
on the Arduino, which are used to control the brightness of each color channel.
The common lead is wired to a single pin header, which is plugged into 5V on the
Arduino (Common Anode), or GND (Common Cathode).
Use heat shrink or electricians tape where appropriate to protect exposed connections /
wires. Be careful that the LED leads can’t short against each other.
Schematic for Common Anode LEDs:
Photos of the completed lead:
Software
Using the Arduino 1.0.1 IDE or higher is strongly recommended as the software was
written and tested with this version.
Download the software for your Aurora Monitor from here. Installation instructions are
contained in the attached README.
https://github.com/jetty840/AuroraMonitor.
You need to determine the Kp Index for your location. Note that most tables / charts
have incorrect values for locations that see less auroras. This is partly due to a
difference between alerting levels and actual levels at higher Kp’s.
Therefore I highly recommend Private Messaging me via the “Thing” with the latitude /
longitude (for a location within 70 miles of your real location). You should obtain the
latitude/longitude from here: http://itouchmap.com/latlong.html
I have a piece of software I wrote that will provide me the Kp Index you need to plug into
the Arduino software for TRIGGER_KP. For example, San Francisco is:
GeoLat:37.775N
GeoLon:-112.419W
CorrectedMagLat:45.1736N
CorrectedMagLon:48.4436W
GeoHemisphere:North
MagHemisphere:North
OverheadKpIndex:9.0
HorizonKpIndex:9.0
AlertOverheadKpIndex:7.0
AlertHorizonKpIndex:7.0
and the last value (AlertHorizonKpIndex) would be the value you would use. I’ll run your
Lat / Lon through the software and reply back.
The software will not work without configuration for your network, all settings that you
tune are at the top of the .ino file before the line:
// Global stuff - Shouldn't need to change anything past this point
The Wifi version supports WEP, WPA and WPA2 (static IP’s), the Ethernet Version
supports regular ethernet networks (with or without DHCP).
If you require twitter support (recommended for a detailed log of your aurora alerts),
and for getting updates if you’re out in the field viewing the aurora) then you also need
to setup ThingTweet. Instructions can be found at the top of the .ino file.
You’ll also need to setup your Timezone and Daylight savings settings to get accurate
times. To verify you have the correct timezone setup, all predictions should be for
around 30mins to 60mins into the future.
Finally, different RGB Led’s have different color spectrums. There’s an led color table
that begins with:
static const struct LedStatus PROGMEM ledStatuses[] =
You can alter the RGB values (the first 3 values) to adjust the colors. 255 = Full On,
and 0 = Full Off for a color channel. This is the same regardless of if you’re using
Common Anode / Common Cathode.
When the monitor first starts, it cycles through all the colors in this table, so you can
easily see if the colors are correct, adjust and power cycle to test your adjustment.
Of course, if you don’t like the colors used, or are color blind, you can change that table
to meet your needs as appropriate.
Changing Software
The software in particular took some time to get working correctly. The Arduino has
RAM limitations, and by the time a network stack is added, there’s not much left.
If you decide to alter the software, be aware that some things are done a certain way to
save memory, or processing. Also, buffers are reused and sized close to their limits
(again for memory reasons). Changing any of the structure or processing will need a
careful eye on buffer sizes and memory usage.
There is a memory usage indicator which can be enabled, but the Arduino doesn’t crash
when it runs out of memory, or warn you, it just runs erratically.
So if odd stuff happens and you changed the main software, then check memory and
for overflowed buffers first.
Assembly
Everything is a press fit, but you can use glue if required.
1. Push the inukshuk into the top of the stand.
2. Slide the Arduino into the holder.
3. Push the holder into the stand making sure it’s orientated so you can use the sockets.
Operation
When you power up the Aurora Monitor, the first thing it does is to cycle through the
colors in the various states. This takes about 30 seconds. The colors are:
Magenta, Magenta, Magenta, Yellow. White, Aurora Green, Aurora Green, Orange,
Aurora Red, Aurora Violet
After this it enters a Magenta slow flash prior to network startup, when the network has
started and it’s started to communicate with the Wing KP server, it enters a moderate
magenta flash.
Finally whilst it’s downloading data, it flashes a fast magenta.
After that first download, it enters normal operating mode and gets data every 14 mins,
until it’s sync’d up with Wing KP, at which point it updates every 15 mins.
The LED color indicates the various states (with a 30-60 min lead time). In normal
operation you can think of it like a traffic light, green, orange, red for increasing aurora
power and violet for “Read Your Newspaper By It !”:
Color
Meaning
Off with occasional Aurora
Green flash
Index is below threshold,
there’s no aurora you can
see.
Aurora Green with
occasional flash off
Index is at or above
threshold, it’s a storm. In
30-60 mins, the aurora
should be on the northern
horizon.
Orange with occasional
flash off
This is a moderate storm,
it’s should be visible
originating from overhead.
Aurora Red with
occasional flash off
This is a major storm, you
don’t want to miss this.
Color
Meaning
Aurora Violet
Extreme Storm.
Occasionally storms are so
strong that the aurora oval
may be pushed further
south than your location.
In these situations, your
best times for viewing will
be after dark and before
sunrise.
Flashing Yellow
No communications,
website or network could
be down. Will auto
recover when things return
to normal.
Flashing White
Wing KP returned a -1,
indicating it can’t make a
prediction. This happens
sometimes if parts of the
satellite are down, under
maintenance, or the
satellite has got a blast
from the aurora, knocking
out some of the systems
temporarily.
Twitter
Depending on your settings in the software, detailed information about the Kp index
prediction is sent to twitter:
Example: Aurora Prediction: Kp: 5.33(11:16) 4.67(14:16) MDT (earth 3.00) 100% Status:
Major Storm
5.33(11:16) = 1hr Predicted Kp Index 5.33 at 11:16(time)
4.67(14:16) = 4hr Predicted Kp Index 4.67 at 14:16(time)
earth 3.00 = Measured Kp Index on earth (last 3 hours)
100% = Amount of confidence in the prediction
Status: Major Storm = Interpretation for your location, equivalent to the LED colors
above
If you only want to see the status above your TRIGGER_KP, then there’s a setting in the
Twitter section of the settings in the .ino which can do that.
Aurora Viewing Tips
1. Look North, when an aurora is at the correct Kp Index for your location, it will follow
an arc on the Northern Horizon. When it's stronger than the Kp Index for your location,
it will originate from overhead.
2. Get away from light pollution. Only very strong aurora's are visible through light
pollution. Scout out a location where you can see 10 or more stars to the North
beforehand so you're ready.
3. Best time for Auroras are 12am - 3am for the Kp Index for your location. Outside of
these hours, the aurora will need to be stronger to see it. For example, a Kp 5 Aurora at
12am will need to be a Kp 6 Aurora at 8pm to see it. This is because the aurora forms a
donut over the earth centered on the “Magentic” North pole in Northern Canada. The
earth then rotates under this oval during the night.
4. Auroras are more frequent within 2-3 months around the Equinox. http://
en.wikipedia.org/wiki/Equinox However they can happen at any time of the year.
5. If it's cloudy, you won't see an Aurora, they occur typically >100km above the ground.
6. Take your smart phone with you and monitor your twitter feed, so you can go home
when the display is over. If you’re like me, an interruption to your shuteye better be
worth it, and if it’s over, then sleep sounds good. :-)
7. Watch out for wildlife at night and tell someone where you're going.
8. To take photos, use a 30second exposure on a tripod at maximum aperture. I always
try to make sure that I have a tree or building in the photo to give the aurora some
context.
Also, the Aurora is better photographed wide angle, it gives better
perspective and you don’t get “Star Trails”.
9. If it’s cold, keep a spare battery for your camera in your jacket pocket, there’s nothing
worse than having that perfect aurora and your battery dies.
10. If you’re using film to photograph, different films have different color biases, ability to
render aurora colors and reciprocity failure: (http://en.wikipedia.org/wiki/
Reciprocity_(photography)).
The best way is to experiment with different types.
There really is a lot of difference. Some pro films are good, some aren’t. Agfa is
generally bad for color (everything looks yellow). I’ve found Fuji to be one of the
better overall. Make sure you take it to a good developer (ask them to not cut the
negs, as they will often cut night shots in the wrong place). Store your film in a
fridge, it lasts longer and will give you an extra “stop” if it’s cold and will last long
past the expiry date.
11. Have an aurora kit ready to go, when you get an alert, often you’ll want to get on the
road to your viewing location fast. A thermos is also useful if it’s cold.
Reference
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