Introduction: Winter Sports Black Box
This is a black box built specifically for winter sports. It is a complete overhaul of my original design.
This black box has a stronger crush proof case, internal temperature controlled heater, and an external temperature and humidity sensor. As well as the 3 axis GPS location, barometric altitude, and 3 axis tilt and acceleration found in the aeronautical version: https://www.instructables.com/id/Black-Box/
In this project the temperature sensors, humidity sensor, carbon heat tape, and foam board were all leftovers from other projects.
I am currently testing this Black Box, but here is footage of the testing of a similar model (without temperature or humidity sensors, a heater, external battery, or reinforced case)
For this intractable you will require:
- A strong container (ribbing is a good sign)
- A temperature sensor (salvaged mine off of an old printer)
- A temperature and humidity sensor (also salvaged off of an old printer)
- Carbon heat tape
- MOSFET (salvaged off of an old printer)
- male and female jumper wires
- Scrap wire
- Goal Zero or another external USB Power source
- LinkIt USB cable
- GPS Antenna
- Grove 9-axis sensor
- microSD card
- paperbacked foam board
A huge thank you to Instructables, AutoDesk, MediaTek, and Penolopy Bulnick for sending me the Link It One used in this instructable.
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Step 1: Mounting Boards
The first step is build a stable base to mount all of the components to. I used paper backed foam board left over from an architectural model but plastic board will also work. Avoid highly flammable materials such as cardboard or balsa for the heater side. (Just in case something malfunctions).
I pressed the lid of my case into the foam to create an impression then cut it out with a utility knife. I made the pieces of foam fit tight enough to friction fit into the two halves of the container.
Step 2: Heater
The heater is made using carbon heat tape. Since the heater is not essential for the operation of the data logger, I used a 9volt battery to power it, so even once the heater runs out of juice the data logger will continue to function. The MOSFET is placed on the "cold" or neutral side of the heater. The left in is the hot pin, right is the completion, central is the data link to the LinkIt which MUST be connected to a PWM (pulse width modulated) port (i.e. digital pin 9). For temperature control I used an analog signal thermometer, 3.3 volt hot grounded to analog pin 0.
I HIGHLY recommend testing the heater throughly before adding your other components, also ensure that in the event of receiving null or a zero value from analog pin 0 the heater shuts off. If this failsafe if not implemented a loose wire could literally lead it a meltdown.
Step 3: Wiring
The exterior thermometer and humidity sensor require a 5 volt power supply and grounding to the LinkIt board and have seperate data return lines. The temperature and humidity are returned as analog signals to analog pins 1 and 2. The 9-axis sensor is connected to the grove port on the LinkItOne and the GPS antenna and battery are connected to their corresponding ports.
The Start/Stop switch is added between two of the digital pins and an LED is added between a digital pin and the ground pin.
Step 4: Component Layout
Lay out all of the components neatly onto the foam board and trace the components as well as marking any screw holes. Then make pilot holes in the foam using a pin.
Step 5: Mounting
Select screws that will pass through the component without penetrating all of the way through the foam. I have found that the best place to find small screws for mounting components is electronics, I salvaged most of my screws off of old printers. For components without screw holes I used rubberized mesh, as it will not conduct electricity, and screwed the mesh down the the foam.
This rigid mounting will prevent false sensor readings due to movement of the components.
Step 6: External Wiring
You will need to cut an access port to pass wires into and out of the Black Box. I cut two slits in either side of the lock tab.
Make sure to test that the mediate will run off of your external USB power source before you hit the trails of slopes.
Step 7: Coding
To read any of the data from the 9-axis sensor you will need to get the libraries from the git hub repository here:
Some general notes for setting up the sensors are:
The default I2C address is 0x68 Each of the value types (gyroscope, accelerometer, and magnetometer) are transmitted as their own 16bit integers
To find the vector of each value use the 3 dimensional pythagorean theorem to find the modules (m = (x^2 + y^2 + z^2)^1/2)
Things to keep in mind:
Barometric altitude will need to be calibrated in post (leave it raw), check the local airport weather (ATIS) for calibration values or find a known altitude during your trip (mountain top or chalet while skiing or skidooing).
GPS altitude is inaccurate an average of GPS and Barometric is advisable if calibration is unknown Magnetometer data can be skewed by electronics (the cellphone in your other pocket) and ore deposits (especially in the mountains) so it is best to rely on the GPS hearing while moving.
This sensor array is for informational purposes only and as you may note in the video at the start of the video is not always highly accurate I will post a full source code file for this project on my website Just4FunMedia.TK under the "Apps" tab once I finish working out the bugs.
Currently these bugs are inaccurate sensor data, randomly crashing, and corrupted text files. I believe this is due to inefficient coding and the large amount of data gathered during an activity.
I am currently working to find a balance in sensor update rate between quality and reliability, as I believe that my log rate is causing my errors.
Step 8: Use
I have found the best way to carry the tracker is in a small backpack, in a jacket pocket, or in the back of a skidoo or similar trunk. For the temperature and humidity sensor data to be reliable, the sensor must be exposed, headphone and camelback ports in backpacks and jackets work great for this. :-)
The temperature and humidity sensors take some time to acclimatize (minutes) so initial data is not reliable.
Be careful how the external battery is positioned. If the USB cable becomes unplugged the Black Box will stop logging data.
If you have any suggestions for improvement, questions, or photos of you own projects make sure to comment below.
Have a great day! :-)