Step #1: Acquire the Trackuino board.PrevNext
The Trackuino shield PCB is not currently being produced but you can have it made very inexpensively at one of the online PCB houses. As of the writing of this article, the 2.2 version of the Trackuino is the latest version and can be ordered from OSH Park.
Step #2: Order your parts.PrevNext
- Order your parts using the parts list in this article. It's important to take some care in ordering the tiny components. Here's a DigiKey basket with many of the small parts: http://www.digikey.com/short/9cbhj
- Take advantage of the "Customer Reference" column — you'll find that your parts arrive in bags labeled to match the references on the Trackuino board. This makes assembly much easier.
- Also consider ordering extras of some of the really tiny and inexpensive surface mount parts that are so easy to sneeze away.
Step #4: Solder the resistors.PrevNext
- You'll solder the components from shortest to tallest. Start with the SMD components: resistors R1, R2, and R3. Check your work with a meter.
- I find that it is easiest to first tack one side of the SMD component to the board by holding it down with a pick, then touch a cleaned and heavily tinned SMD tip to one end. You just need enough to tack it in place. Then solder the other pads. Finish with the pad that you tacked first.
- As with any soldering, you need to apply heat to both the component and the board. Surface mount is just smaller and quicker.
Step #5: Install the integrated circuits (IC's).PrevNext
- IC2 requires special attention; it has a tab that must be tacked to the board to dissipate heat. You'll need to get plenty of heat into the pad and the tab (I used an 800°F setting for this).
- You'll find that IC3, IC4, and IC5 are the trickiest to solder because the pins are very close together on the side that has 3 pins. Take your time and check your work with a meter. Make sure the center pin is not shorted to either of the outside pins.
Step #6: Install sensor U1 and the capacitors.PrevNext
- U1 is the internal temperature sensor and is the only TO-92 component on the board (there is another off-board temperature sensor). Be sure to orient it as indicated on the board.
- Capacitors C1 and C2 are polarized components. The long lead is the positive lead. Be sure to orient it as indicated on the board.
- Bend the leads just enough to hold the components in place. Then solder and clip the leads.
Step #7: Install the switch and headers.PrevNext
- Press the switch into the board; it will hold itself in place. Solder this in first, then remove the board from your vise.
- Insert all the headers into the board, then flip it over (this can be done with 2 hands but may require some strong words). Tack one pin on each header then flip the board over to make sure everything is straight. If something is a little off, flip the board back over and press down lightly while applying heat to the tacked pin on the affected header.
- Finish by soldering all the pins. Check your work.
Step #8: Install terminal blocks and SMA plug.PrevNext
- The SMA plug (X1) and terminal blocks (X2, X3, and X4) take quite a bit more solder than the other components. I keep a heavier-gauge solder on my bench for jobs like these.
- Tack one pin first, then check that they are properly aligned and flush. Then solder the rest.
Step #9: Install the transmitter and external temp sensor.PrevNext
- Make sure the transmitter's not flush, so that it can be bent into position after being soldered. Here you see the board with and without the transmitter. The board on the left is the one that flew in 2013 (and the other is the one built for this article).
- The external LM60 temperature sensor is attached to a screw terminal header on the Trackuino. Simply solder a different colored wire to each of the 3 legs of the sensor. About 12" of each wire will do. Make note of which leg each wire is attached to (Vs, Vout, and ground). Carefully insulate each leg with electrical tape, then tidy the sensor end of the wire with shrink wrap.
Step #10: Program your Arduino with Trackuino firmware.PrevNext
- Download the Trackuino code from https://code.google.com/p/trackuino/. We ran Trackuino v1.4, which required Arduino IDE version 23 to compile. Trackuino v1.5 is out and should compile with later versions of the Arduino IDE.
- IMPORTANT: When flashing the Arduino, remove the Venus GPS or the entire Trackuino shield. After flashing the firmware, you can plug it back in. The GPS and the host computer share the same serial port on the AVR chip, so they'll conflict when used together.
- Open the file config.h and update S_CALLSIGN to set it to your amateur radio call sign. Set S_CALLSIGN_ID to 11. You can also set the APRS_COMMENT to something relevant to your flight (we set ours to "GDRMS Balloon"). Unless you're working with more than one balloon, leave APRS_SLOT at 0. APRS_PERIOD defines how often you broadcast your packets. Don't set it any more frequent than once a minute (to be a polite ham). You can also fine- tune the buzzer frequency and on/off time, depending on the buzzer you're using.
- Upload the code to your Arduino but do not power up with the Venus GPS receiver attached.
Step #11: Install the Venus GPS receiver.PrevNext
- Disconnect power from the Arduino.
- Solder the 8 pin headers to the Venus GPS if you haven't already done so. Then simply insert it into the Trackuino board.
- Do not apply power yet.
Step #12: Ready for testing.PrevNext
- Before you can test your Trackuino, you need to connect the GPS antenna and a dummy load to your transmitter.
- Why does it need a dummy load? If you think of the transmitter as a boxer, then the dummy load is her punching bag (or opponent). Without the punching bag, the energy in her fists has nowhere to go and bad things might happen. Your transmitter needs somewhere to dissipate the energy it is generating — if it has nowhere to go, bad things might happen (which may include smoke).
- The 300W dummy load you see here was given to me by a ham friend of mine soon after I got my license. It is way overkill for this tiny transmitter from a power dissipation perspective (we only need about a 1W load), but it's just fine to use for this application.
Step #13: Bench-test your Trackuino.PrevNext
- Tune your receiver to 144.39MHz (or the APRS frequency used in your region). Even though your transmitter is feeding into a dummy load, there will be plenty of emissions for your receiver sitting right next to the radio.
- Once you apply power, no APRS signals will be transmitted until your GPS receiver determines its location. The Venus GPS will tell you that it has found its location by blinking its on-board red LED when it has a GPS fix. This often takes a minute or two, sometimes longer. It helps to have your GPS antenna outside. Normally they have long leads to make this easy.
- Now listen to your receiver and think back to the 80s. You should hear, about once a minute, some of those old-school modem sounds. This is Audio Frequency Shift Keying (AFSK), which is used by the Trackuino and APRS to encode the data that comprise our packets. Once you get this far, you are ready to decode them.
Step #14: Decode some packets.PrevNext
- Now let's decode the packets. First install the app APRSdroid (http://aprsdroid.org/) on an Android device that has audio input capabilities.
- Use an audio patch cord to connect your radio receiver to the Android device. The most likely candidate for your android device is a phone because you need audio input (like a microphone). For my set-up, I needed a mono audio cable and adapter to plug into the mic input of the Android phone.
- Launch the APRSdroid app and you'll see it decode and display the APRS packets transmitted by the Trackuino.
Step #15: Build an antenna for the Trackuino.PrevNext
- We built the simple quarter wave ground plane antenna described on the Trackuino site at: http://www.trackuino.org/2010/04/trash-digging-at-its-finest-111-swr-vhf.html and at http://ccarc.org/_misc/so-239_ant.html. We built ours from metal coat hangers and a panel-mount SO-239 connector. We tipped the antenna's radiator and 4 radials with wire nuts to make it less lethal.
- The antenna is very straightforward to build, but it's critical to get the length right. This is a great opportunity to get involved with your local ham radio club. You will need an SWR meter and someone experienced in how to use it.
- Be sure to build your antenna just a little longer than it should be. You'll tune it by cutting off tiny lengths of it until you minimize the reading from the SWR meter.
Step #16: Field-test your Trackuino system.PrevNext
- Now test the Trackuino with your antenna and you'll see your packets logged at aprs.fi.
- We first tested with an inexpensive, magnetic mount, 2M antenna on the roof of my car (I ran it going back and forth to work for weeks). I was a little worried that my signal was picked up at very few APRS stations but, as it turns out, that was just fine for this transmitter at ground level.
- I then moved on to use the coat hanger antenna that we built. I ran the system with this antenna back and forth to work for weeks to get an idea about battery life and consistency.
Step #17: Hack a Canon camera.PrevNext
- For our balloon we wanted the camera to take photos and videos automatically on a programmed schedule: a photo once every 5 seconds then a 30-second video once every 5 minutes.
- We chose a Canon Powershot A560 camera because it can be programmed in this way using the Canon Hack Development Kit (CHDK). A secondhand A560 (or similar) can be had for less than $50 on eBay. Be sure to check the CHDK website at http://chdk.wikia.com/wiki/CHDK for compatible models before you buy.
- Follow the user manual at the CHDK website to install CHDK on your Canon. Getting it working on your particular camera may be tricky, so start early, and practice with it long before launch day.
- A 10GB will hold hours of images and movies depending on the frequency settings.
Step #18: Build the helium fill rig.PrevNext
- All you need is a 12" length of 1" PVC pipe with an elbow and a fitting that can be attached to your helium supply. Use Teflon tape to seal all the pipe fittings between the gas bottle and the fill rig.
- Also note the water jug. It has been filled with just enough water so that when it starts lifting off the ground, our balloon has the correct amount of free lift. We need about 2 lbs of free lift as discussed above. Given that our payload is 2.2 lbs, that's 4.2 lbs of water. Be sure to weigh everything ahead of time.
Step #19: Build your enclosure.PrevNext
- We built our enclosure out of 2" foam panel insulation that we got for free through our local Freecycle group. We glued it together with Gorilla Glue, then added extra duct tape on launch day.
- We cut a hole in the side for the camera lens and secured the camera with cable ties. The Trackuino and battery pack were secured to a removable foam platform more cable ties. We mounted the buzzer on the outside and secured it with screws and Gorilla Glue. And we routed the external temperature sensor to the outside of the enclosure through a seam in the box, and let it simply dangle about 6" from the bottom of the enclosure.
- We also included one small hand warmer which kept the interior warm enough (always well above 30°F, even when the exterior temperature was as cold as –60°F). We didn't make our enclosure airtight, but we sealed it up quite well to keep it warm inside.
- Be sure to practice the final assembly and sealing of the capsule before flight day. Add a duct tape tab to your instrument platform to help with disassembly.
Step #20: Attach the parachute and balloon.PrevNext
- The Rocket Man parachute we used is lightweight, sturdy, and has only 4 shroud lines, so it's less likely to tangle with our prickly payload.
- This parachute has a loop at the top to attach to a length of rope, which is, in turn, attached to the balloon. We used about 4 feet of rope, to provide some distance between the balloon and the chute.
Step #21: Launch day!PrevNext
- Get to your launch site. Prepare and utilize a checklist, and have at least 3 people available to help, each with their own assignments (including one person to call the FAA about 15 minutes before launch).
- Lay everything out, power up and check all your systems — run an end-to-end test by decoding packets from the payload prior to launch. Don't forget to turn the camera on and start the CHDK program!
- Assemble, seal it up, and let it go!
- Then tune into your Trackuino with your receiver, and your wider network of aprs.fi watchers, to enjoy your own fantastic voyage.