A resistor and a few capacitors with the 16 Mhz crystal will get you started, But you really need to consider how you are going to power it and how you are going to get your code onto the chip.
The instructions allowed for the connection of a voltage regulator so I can connect a battery power source at a later stage. But to really get the chip configured for the time being I have connected a USB FTDI board, which allows direct programming of the chip just like it was a really Arduino UNO board.
Ensure you get all the cap values right as I was getting an out of sync error, which was caused by the wrong cap between the USB FTDI and the chip.
One I have completed all the code for my tracker I will remove the FTDI and connect a battery power source hopefully the final piece of the tracker puzzle. This will allow me to use my nano for other projects and leave the cheaper chip on the board.
Well, things are starting to heat up here in good old Sydney Town, both weather wise and in the shack. I’ve been playing with the 2nd tracker and attempting to get it transmitting some RTTY, and finally tonight after several nights of learning I finally have it working.
First of all I’m still using the FlexTrack code with a Radiometrix TX2EH but have modified the code slightly to work for my purpose. The code appears to use FSK for a 3v model whilst my transmitter is 5volts. For what ever reason I didn’t have any real success with it. I had to tune my radio to USB to hear any tones, and for some reason I was only getting a single tone.
I wanted to have the ability to decode using a handheld and my handheld doesn’t have SSB, so I looked into the AFSK option. Instead of varying the frequency of the transmitter I generate an audio tone and transmit that instead. Tested the receive with my Yaesu FT-857 and the frequency looks a little off from what I would expect, but this may just need some further tweaking of the code.
Consulting a AFSK tone table for RTTY on the KLOTH.NET website, I chose a 425 Hz shift and selected a 2295 Hz high tone and a 1870 Hz low tone. I then exchanged some lines of code that would normally cause the transmitter to frequency shift with the Arduino tone command. After some mucking around, I finally had some success and was able to successfully decode the RTTY
After setting the correct RTTY decode options in dl-fldigi a big smile came across my face as I was decoding the output from the tracker. The example screenshot is with the GPS disconnected, but with the GPS connected, the zero’s quickly filled with the GPS coordinates.
I’ve still got some tweaking to do, as I’m not happy with the transmitter, it seems unstable with frequency drift and you can tell from the waterfall image it is a little noisy. Hopefully I just need to tweak the code to get this right.
But at least I’ve managed to get it working, as I can now look at experimenting with other digital modes. I know RTTY is fairly old these days and other protocols do exist, but RTTY just seems simple and if it works from near space, then I’m happy. Happy to hear from anyone who can suggest any improvements.
Next I want to de-key the transmitter between transmissions so that a receiver can be used to receive commands from the ground. May have to look at a DTMF decoder or something.
My Totex – Kaymont 1500g balloon has arrived, so its getting closer to having the critical parts needed for launch.
I decided upon the Totex balloon after reading reports of other balloon launches having success with them but also because there are limited sources for weather style balloons down under. The 1500g should be suitable for my payload which is already at 1.2 Kg’s and hopefully reach a good altitude.
Connected my GPS up this evening to the Ublox U-center to confirm that everything was in working order. Changed the baud rate to 57600. (maybe someone can confirm if this is wise or not?) and yipee everything seems to be functioning.
I’ve read a a number of forums regarding the Ublox GPS and they advise to set the GPS into flight mode, of which I have done. I found this site useful to connect the GPS with U-center. Ublox GPS – U-center
Found some Arduino code on Git Hub for an RTTY based tracker based on Habduino, called Flextrack . It sounds as though it may work for my purpose if I want to use RTTY for the 2nd tracker. However I’m still awaiting the delivery of my UHF transmitter so only have the GPS working via the code so far.
Connected it all up to my Arduino Nano and I;m already getting the Flextrack GPS debug messages. So far so good..
The Ublox 7M seems to be working much better than the GPS in my primary tracker which is only a 6. Much faster in acquiring a fix.
Really need the transmitter to arrive so I can really start to get into the fun stuff.
There are many photo’s and videos around the internet showing the beauty and awe of near space. The sheer contrast of the earth below with a dark black emptiness of space above.
Being my first launch, I want to ensure that I too get to celebrate a successful mission. Nothing helps show others what can be achieved then some great photo’s or video.
However I certainly don’t want to place super expensive camera equipment with the risk of never recovering it into my first launch. So I have attempted to keep it relatively inexpensive but still with some good quality.
I have seen a lot of success with Go pros and also moded Canon camera’s. So I have gone down that path.
First up take a look at the CHDK Wiki who list several models of camera that can be modified to function to your requirements. They also provide all the instruction needed to complete the mod.
I purchased a cheap Canon IXY digital camera and just had to place some software on an SD card that when loaded by the camera allowed it to automatically start taking a sill shot every few seconds. The CHDK code allows for many other features as well.
I also acquired a SJCam SJ4000 as it looked like a cheap Go Pro alternative. It supports HD video and will also can take a still every 5 – 10 seconds. I haven’t decided yet, but may use this as the main still taking camera.
With the amount of Go Pros
heading into near space, I thought I may as well go the distance and risk it for some decent video footage. So I stalked Ebay for a 2nd hand Go Pro
Hero 2. This will be used to shoot constant video for the flight.
There are many things to consider to ensure I get some great photo’s and one of them is to ensure I have enough storage for the flight, so I have picked up a 32 GB SD card as this is supposedly the maximum for this camera.
I need to ensure I set the camera for a good quality shot, but I must not fill the card to quickly. I estimate I need to shoot for at least 2 hours. This also indicates that the battery must last the duration of the flight, so some battery expansion will be required.
Deciding on a parachute seemed a little harder than I first thought. It needs to be big enough to slow the payload decent so it can be recovered intact. At the same time if its to big the payload will drift a lot further on its decent and potentially take much longer to reach the ground.
To assist with the parachute decision most manufacturers provide a guide to the decent rate based on the weight of the payload. Some parachutes aim for a decent rate of around 5m/sec. Spherachutes lists it chutes based on the payload weight and other websites provide similar info.
For my project I went for a 48″ or 1.2 metre chute from Spherachutes.
This seemed to fit the estimated weight of my payload of which was still under construction so I hadn’t determined the final weight. Spherachutes charged a small additional fee to sew some straps at the top of the chute for the balloon to attach to.
The air temperature at higher altitudes tends to be below freezing, thus there is a risk that the batteries in the payload won’t operate effectively. Batteries in cold climates are know to have a higher resistance and will usually become flat very quickly.
I don’t want to risk the chance of my payload loosing power, as it will certainly result in a lost payload.
One solution is to choose batteries that function better in cold climates. According to battery university all batteries are impacted by the cold, however some handle it better than others. Certain NiCad and Lithium Ion Batteries can still operate at -40 Degrees C but at a reduced discharge.
So to attempt to keep the payload at a warmer battery friendly temperature, I am considering some air activated toe warmers, the type you place in your ski boots when in the snow.
These toe warmers can reach 40 Degrees C, so a couple of them should keep the payload warm when its -40 outside.
I still need to test this functionality to ensure it actually works, and that camera lenses won’t fog, but I;m feeling confident.