I want to over complicate my HAB because I feel like everyone else has done the same thing, so obviously I want mine to be different, and more challenges makes could make the whole project more fun!
For me to consider my project a 100% success, it must meet these requirements:
- Arduino based
- Must transmit GPS coordinates at all times, even once the payload has landed
- Live first person video
- Transmit GPS using APRS
- The parachute cannot be inline with the balloon and payload, it has to eject from within the payload
- Waterproof and shockproof
I've already bought a GPS module (http://www.parallax.com/product/28501) but after reading online, I realized it will only work up to 18,000 meters which is about 60,000 feet. That GPS module uses the SIRF chipset, which is very common so when picking out a GPS module for a HAB, make sure it's not that. It's still a fun GPS module though and maybe I'll make another little project out of it or something. The data sheet for the PMB-688 can be found at http://www.parallax.com/sites/default/files/downloads/28501-PMB-688-v0.1.pdf.
In order to transmit the GPS coordinates via APRS you need to transmit it on 144.390MHz in order for local digipeters to pick it up on the APRS network. The transmitter I will likely use is the HX1 radio module (http://ava.upuaut.net/store/index.php?route=product/product&path=71_63&product_id=78), which has plenty of support with the Arduino online. What's great with using APRS is that you can track the balloon in real time online at aprs.fi, and you can search by call sign, and HAB's usually have a -11 at the end of the call sign.
A problem I read with other HAB's is that once they land on the ground, it get's really hard for them to be found, because if it lands in the woods or a hilly terrain it could be hard for the GPS signal to get out to the digipeters. A way for me to make my chances easier to overcome this problem is to somehow detect the orientation of the payload on the ground, reorient if I need too, then extend an antenna as high as possible to make better contact. A mini mars rover would be cool too...
I'm still not sure how I'm going to make the parachute pop out of the payload, but to disconnect the cord that connect the payload to the balloon, I think I'm going to have the cable somehow attached to a resistor and use a relay to short a battery over it to cause it to overheat and break causing the cable to become disconnected.
As for FPV, I found out with a GoPro you can record video and output video at the same time to a video transmitter. Which is perfect for what I need. I found a helpful video explaining what to do here: http://www.youtube.com/watch?v=UKMQhWZtNRg.
That's really all I've thought of so far, hopefully I can get something built during Christmas break, but mostly I'm excited for the video footage!
Here's a whole bunch of links I've bookmarked that I find really helpful:
- HAB IRC channel: http://webchat.freenode.net/?channels=highaltitude
- Beginners guide: http://www.ukhas.org.uk/
- TinyGPS library for Arduino: http://arduiniana.org/libraries/tinygps/
Hopefully my next update won't be too far away!
And ignore any spelling or grammar mistakes... it's like 4:30 in the morning.