Thursday 14 November 2013

NERD-1 development prototype

The NERD-1 HAB development prototype has been coming on in leaps and bounds. The first stage was to take the breadboard transmitter layout and construct a veroboard 'shield'  the transmitter module plugs into some sockets and the addition of an enable control allows me to turn it off and on. What cannot be seen on the photo below is a dual-colour LED to indicate the fix status of the GPS.

Veroboard shield with transmitter fitted
I am still waiting for delivery of the uBlox GPS module/breakout board which is on a slow boat from China, but in the meantime I have purchased a number of other breakout boards (pictured below) to evaluate potential additions and to generally experiment.

Top-Bottom, SD Card module, RTC/EEPROM module and GY-80 IMU
These include a SD Card module, which will be used to log flight telemetry via the SPI interface. The board on the right is a Real Time Clock (RTC) including a button cell and some EEPROM memory accessed and controlled via the I2C/Wire interface. This really isn't needed but was literally a couple of £s.

The smaller board at the bottom is the really interesting one! It is a GY-80 IMU clone, containing a three-axis gyroscope, three-axis accelerometer, three-axis magnetic sensor and a temperature and pressure sensor, again all accessed simply via the I2C interface. Popular in aeronautical RC and personal UAV projects such as Quadcopters it seemed worthy of some experimentation.

All the devices were purchased from Etang Electronics on eBay and was impressed as it all arrived the day after ordering.

I am using the only proper serial port for the GPS data and  I wanted some method of getting debugging and instrumentation from the device during testing. I could have constructed a software serial port but I had an unused LCD character display so decided to connect it up (won't be included on a proper payload!)

It looks nice and is 'cool' however the backlight LEDs do draw an awful lot of current so have been disconnected since the picture was taken.

LCD Character display
At the moment the whole thing is a little messy, but is functional and sits in it's own foam lined box!

The prototype connected up (still no GPS module)
The software development has been pretty straightforward, I am no stranger to the use of I2C and SPI in my day job and there are plenty of software libraries and guides available. Once I have perfected the software and settled on the final design then I am planning on constructing a veroboard flight prototype with all the unnecessary parts removed.

I have also yet to investigate another transmitter unit I have purchased.  

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