slaak
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- Jun 19, 2014
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I have been making my own Rocketry altimeters for a couple years now, but up until this point Ive kept pretty silent about it and only used them in low power rockets for data logging purposes. I decided at BALLS this last year that I was going to bite the bullet and put the time into developing a full-fledged altimeter to log data, control dual deployment, and upper stage ignition with tilt sensing.
I am a Mechanical Engineer by trade so I have only taken basic courses involving electrical engineering and programming (I have Ive dabbled in different programming projects over the years thought). Because of this there Ive made many many revisions of my altimeters over the past couple years. But after reading probably a dozen books on embedded circuit design, embedded programming, electrical devices, countless hours doing internet research, and some reverse engineering I am finally confident that I have a viable flight altimeter.
On to some technical details about the altimeter!
4 channel output, each should be able to sink enough current to light a second stage if desired.
Kalman filter incorporating pressure and acceleration data running aprox. 125Hz.
Currently logging at 20Hz which includes time, altitude, 3D acceleration, 3D gyro, and velocity. Still tuning the logging logic, but I will probably have it log at 50Hz during accent and 5 or 10hz during decent. I have a 16 megabyte flash memory module onboard so a it can log for a couple hours no problem.
SAMD21 running at 48MHz to do all the thinking.
MS5803-14 Pressure sensor running in 0.2mbar mode.
BMI055 IMU for +/- 16G accel and 2000 deg/s gyro.
AD22286 +/- 70G Analog accelerometer to feed the Kalman when above 16G.
Tilt lockout isnt implemented yet, but I will be putting that in the firmware at some point down the road.
Data is retrieved using a cheep FTDI dongle like the FTDI basic from sparkfun.
There is probably a bunch more to tell about this but I think thats all I have for now, I hope to stuff this thing in a rocket soon and I will post some data.
If there is any comments or questions type away! Anyways heres some pictures.
Top view.
The brains.
size comparison next to some commercial altimeters.
I am a Mechanical Engineer by trade so I have only taken basic courses involving electrical engineering and programming (I have Ive dabbled in different programming projects over the years thought). Because of this there Ive made many many revisions of my altimeters over the past couple years. But after reading probably a dozen books on embedded circuit design, embedded programming, electrical devices, countless hours doing internet research, and some reverse engineering I am finally confident that I have a viable flight altimeter.
On to some technical details about the altimeter!
4 channel output, each should be able to sink enough current to light a second stage if desired.
Kalman filter incorporating pressure and acceleration data running aprox. 125Hz.
Currently logging at 20Hz which includes time, altitude, 3D acceleration, 3D gyro, and velocity. Still tuning the logging logic, but I will probably have it log at 50Hz during accent and 5 or 10hz during decent. I have a 16 megabyte flash memory module onboard so a it can log for a couple hours no problem.
SAMD21 running at 48MHz to do all the thinking.
MS5803-14 Pressure sensor running in 0.2mbar mode.
BMI055 IMU for +/- 16G accel and 2000 deg/s gyro.
AD22286 +/- 70G Analog accelerometer to feed the Kalman when above 16G.
Tilt lockout isnt implemented yet, but I will be putting that in the firmware at some point down the road.
Data is retrieved using a cheep FTDI dongle like the FTDI basic from sparkfun.
There is probably a bunch more to tell about this but I think thats all I have for now, I hope to stuff this thing in a rocket soon and I will post some data.
If there is any comments or questions type away! Anyways heres some pictures.
Top view.
The brains.
size comparison next to some commercial altimeters.