I had a goal to produce a flight computer that could be used for dual deploy and recording flight data but was cost effective.
I have made several variation for different purposes. My main device is set up to track flight data at around 25hz or 25 readings/second, as well as 3 output pyros. 2 for deployment charges and 1 set up for air starting a motor.
I also have built others for smaller rockets down to a BT55 tube that either only have one charge or only do data logging. If you want any additional information please let me know.
Step 1: Getting the Parts
For this you can mix and match from different places/parts to build the same thing. For the sensors I have codes for both the MS5611 and the BMP280. I also bought parts in bulk and from china to save on prices in the long run.
What 2 buy:
1x - Arduino mini - $3.20/each
1x - MS5611/MPU6050 Sensor - $10.85
1x - MicroSD Card Reader - $0.99
3x - 1n4001 Diode - $0.48/3-pack
3x - N-Channel MOSFET -$2.85/3-pack
3x - 10K resistors - $0.24/3-pack
1x - 150mAh 30c 3.7V Lipo - $3/each
4x - 2 Pin Terminal block - $0.76/4-pack
1x - PCB Prototype board 4X6 cm - $0.66/each
Total = $23.03/device (I was able to get cost down to $16.93/device)
Tools you will need:
Helping hand (useful for soldering but not necessary)
FTDI USB to TTL Serial Adapter (for programming arduino pro mini)
USB Mini cable
Hot Glue Gun (Optional)
Step 2: Putting the Pieces Together
Before you solder anything lay everything out on you pcb so you know where everything is going to fit. Make sure you leave space in at least 2 of the corners for screw holes(the one on the board were super tiny).
Also I labeled the 4 terminal blocks. S = switch / A = apogee / M = main / I = Ignition (air start)
Next I soldered the headers on the Sensor and the Arduino but I left the front 6 row off the arduino for programming. (I just hold it in place when programming) .
Now solder all of the components to the board and wire everything up as shown in the schematic(sorry not the best at making schematics).
For added security you can use a hot glue gun to insulate the exposed connections. Just don't cover the hole in the sensor.
(Picture of my final product coming soon)
Step 3: Program It
Hook up the arduino and use the arduino ide to add the program.
!! IMPORTANT !! Change the main deployment altitude in the code to what you would like it to be. (Will soon be updated to jumpers to change altitude)
While it is hooked up press F8 to open the serial monitor in the arduino IDE to make sure everything is wire correctly and functioning right.
You should see it go through the sensor checks and then start outputting the current alt.
Step 4: Launch It to Space
Place it in an ebay with proper holes for reading the pressure.
I would recommend flying it one to make sure the reading are right before adding any charges in it.
Step 5: Read Your Data
After you flight turn off your switch and then you can remove the SD card. The files have an extension of .AWD but the data is just CSV format. You can either load the data into excel and plot it to a graph or use the software I have made.
The software is only for windows and require .net 4.5 or higher.
You can download the software from here.
If you use Excel the data can be imported like a CSV file. It is formated as follows:
Altitude, Time, Acceleration reading, Main Fire, Apogee Detected
I am also working on an android app.
More picture and information to come.