Prock-1 Info
page in progress as of Aug-6-2008. last updated Aug-17-2008
The Prock-1
The Prock-1 is my first attempt to build and fly a high altitude balloon. Go here for some back history on this. Now lets get to the good stuff.
System design
-Flight control system
For the flight controller I am using a Basic Stamp 2px microcontroller made by Parallax. I chose this chip due to its popularity and amount of information on the net. It has been a while since I have programmed or done any serious hardware designing so I wanted something that I could get help with easily. Plus it offered many features in both hardware and software capabilities. I will get more into that in the sensors section.
I have gone through many revisions of the circuit layout since I designed the first schematic. My first design was made before I bought any parts or read all the way through the part manuals. Read back through the blog and you can see some of my first designs and the mistakes I made.
I used ExpressPCB to design the layout. The current design is :
Here is the Expresspcb source file: prock1ver1_6.sch
As you can see the BS2px controls all parts of the system except the telemetry (radio and GPS.)
I will post source code for the system code as soon as I get it put together. Right now it is in chunks of code that I use for testing certain components one at a time. I will post the code chunks in the other sections where appropriate.
-Sensors
I am using a basic set of sensors used on balloons, temperature and pressure.
There are two temperature sensors, one inside the housing and one outside the housing. They are DS18B20’s from Maxim. The DS18B20 has a “1-Wire” interface that when used with the Basic Stamp is very easy to setup and use. The temperature is sent as a digital signal and easy to store in the flight data logger. Each DS18B20 has it’s own unique address which allows multiple “1-Wire” devices to ride the same bus.
To test the temperature sensors, I will put them in an area with another thermometer and make sure the readings are close. I will try to test to the colder extreme if possible. Stamp code to read 1-Wire device address. .bpx .txt Code to test temp sensors. .bpx .txt This code is still a little rough. I have not had a chance to finish commenting or clean the code.
For atmospheric pressure sensing I am using the ASDX015A24R from Honywell/SenSym. It will output a voltage that changes as the pressure outside changes. I will have to make sure that the payload housing is not completely sealed so that this sensor will work and to keep payload housing from exploding when ascending to high altitudes.
I am not sure how I will test the pressure sensor in advance. I will add further info when I get to that.
-Telemetry
I am still debating on what I am going to use for telemetry. I know I am going to use an OEM Garmin GPS-18 LVC or something equivalent. But I am not sure if I am going to use an Opentracker or a TinyTrak4. Right now I am leaning towards a TinyTrak4 because it will receive and decode packets to allow some remote controlling of operations in the payload. I still need to do some research and see if it will work for what I need.
-Video and still camera
For initial testing I am just going to the local pawn shop and pick up a twenty or so dollar digital camera. I will do the same for the video camera as well. Once the testing is done I will see what kind of budget I have at the time and get the best I can. Will be updated as I know more.
-Power system
After reading up on a few other launches, it looks like I will be using Lithium batteries because they preform better in the cold temps of the high atmosphere. Since the most of the flight control system is still in design stages I have not evaluated the power consumption of the electronics. When I get closer to this I will update.
-Balloon, parachute, and other flight pieces
<pending>
-Control panel
<pending>
System Testing
<pending>
Flight Planning
<pending>
Launch day activities
<pending>
Post flight analysis
<pending>
Flight media
<pending>
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