RLDAQ project update

Hey,

Right now I’m working on Rocket Launcher Data Acquisition System. There are a few things left to do and the project will be fully finished. It has already undergone its first field test during CanSat competition and it has proven effective (well, there are a few things to correct, but nothing lethal).

The biggest issue was magnetometer not working due to its placement in main case with all the electronics nearby. It turned out that batteries influence magnetometer’s readings so much that it’s impossible to calibrate the offset/perturbations. The compass module had to be moved somewhere else. I had two options: launcher rail (accelerometer’s case) or weather station’s arm. I chose weather station as I was afraid that launcher rail may introduce magnetic field distortions (as batteries did).

Here’s a photo of 3D-printed case and render from Inventor:

compassCase_comp

I still have to print modified main case, build receiver module (‘prototype’ version was used so far) and the project will be done!

2015 summary and plans for 2016

2015 has come to an end so it’s time for a small summary 🙂

Previous year “milestones” (major projects/ events/ skills etc.):

  • 3D printer purchase: this device improved my manufacturing capability. Great decision.
  • Electric mountainboard: this project took a lot of time and effort. I learned new things about designing electronics (power systems, embedded systems), mechanical design and manufacturing (3D printing).
  • First job: in the end of March I started working at Invenco as Embedded Systems Engineer. Good opportunity to gain experience.
  • Highest grade average for 2014/2015 academic year (among people on my year), Dean’s Scholarschip.
  • Starting this blog and personal website (lukemeyer.me).

2015 was pretty fruitful for me, I hope that 2016 will be even better and I bet it will (provided no unexpected problems occur, eg. health issues) – my belief is that one’s life is dependent mainly on person’s actions and decisions.

My main goal for the next year is to be consistent and disciplined. Other goals that I want to achieve (thanks to the first one):

  • resume eboard project, hone the details and use it on daily basis
  • keep getting good grades at University
  • great summer – by going to some special place to gain even more experience and knowledge. I’ll keep that a secret for now. If everything goes allright there will be a post about it full of happiness 😀
  • switch from AVR architecture toward more advanced solutions (STM32, PIC32)
  • work: release project that we are currently working on
  • other projects: data acquisition system for Students Astronautical Association (Rocketry Section), AutoBlinds, DSP filter.
  • update website and blog regularly

I wish you all great 2016, cheers 🙂

Projects update

Hey guys,

I wanted to create a quick note on projects that I’m currently working on:

-digital low-pass filter – based on AVR microcontroller. This semester I’m taking Digital Signal Processing course and I asked the proffesor if I could make a project instead of writing an exam at the end of the semester. She agreed and that’s how this project begun. Right now I’m using ATmega328p @16MHZ with its internal ADC and an external DAC8571. For first tests I chose first order Butterworth filter designed with impulse invariant method. Communication with DAC is via I2C @ 400kHz, although I’ll may need to increase the bus speed (sending 16+2 bits to update the DAC takes 45us, which results in 22kHz update frequency, so in theory I should double the bus speed. In practice that speed should do as attenuation for 11kHz input signal is around 36dB).

Software is pretty simple: ADC is configured in Free Running Mode, triggered by Timer1 Compare Match B (Timer 1 runs in CTC mode @ 44kHz). ISR for interrupt generated on conversion finished calculates filter output. DAC is updated in main loop all the time – right now I use blocking while-loops, but I’ll probably switch to interrupt-driven control.

Now the most important thing: proof that it actually works. I assembled the test circuit on breadboard, hooked up audio output from my PC to circuit input and generated a few sine waves (maybe I’ll buy proper function generator someday). FFT on the output. Cut-off frequency is 200Hz.

f=50Hz (yellow signal is output):

NewFile0

f=200Hz (you can see slight attenuation, around 2.5dB):

NewFile1

f=400Hz (spot-on -6dB):

NewFile2

f=1600Hz (perfect -18dB, everything according to the plan: 1st order Butterworth filter has -6 dB/octave slope)

NewFile3

-second project I’m working on is electronics helping in setting up launch rail for rockets (I do it for Students Astronautical Association, Rocketry Section).

Quick spec:

-AVR based (again…)

-MPU6050 to measure rail angle

-HMC5883L – orientation

-BMP180 – pressure

-TMP102 – temperature

-NRF24L01 with amplifier – communication with base

-anemometer and wind vane – wind parameters measurement

-Li-Ion powered

I’ll create separate post on that project in near future (hopefully 😉 ).

Cheers!