Microcontroller chart for the DIY

[HowardB]

Here are some microcontrollers that ought to be suitable for home made projects like altimeters etc.
Most support I2C, except for the pro mini, all seem to have USB. The adalogger ($21) has an on board micro USB holder, will run on 3.7V and has a built in charger. It is intriguing to say the least.
For larger projects, the new Raspberry Pi Zero is interesting. It's most of a whole Raspberry Pi with a fairly small footprint. It might be finicky about power supply.
Enjoy!

source	board	length	width	mass
adafruit	trinket	31	15.5	1.85
adafruit	trinket pro	38	18	2.6
adafruit	adalogger	51	23	12
arduino	uno	75	53.5	28
arduino	pro mini	33	18
arduino	micro	50	18	4.5
arduino	nano	44	18.5	5
raspberry pi	raspberry pi zero	65	31	9

 

[HowardB]

Dimensions are in MM, mass is in grams. Divide by 25.4 and 28 respectively to approximate inches and ounces. For barleycorns and grains you're on your own.

 

[cwbullet]

1 gram is 15.4 grains. It is a worthless conversion unless your are weight bullets.

 

[rharshberger]

1 gram is 15.4 grams. It is a worthless conversion unless your are weight bullets.

Typo right? 1 gram = 15.4 grains, why anyone would want to use grains outside reloading I have no idea as 1 pound= 7000grains, I still use grains instead of switching to grams for reloading because all my load recipes from almost 30 years of reloading are in grains and I am too lazy to convert them.

 

[cwbullet]

Sorry. I have to start using my bifocals.

 

[Jeffmhopkins]

You should add the Teensy boards

 

[ipostelnik]

You can build altimeter with BMP180 and ATtiny84 for under $5. Use on-chip EEPROM to store apogee of 10 flights and configuration. You can even get 1 channel to fire an igniter or ring a buzzer with that. In fact, your highest cost and heaviest component is likely to be the battery. For under $10 you can build a full dual-deployment logging altimeter using one of the pro-mini boards, BMP180, an I2C EEPROM and a few discrete components.

For the next iteration I want to play with ESP8266 modules that include WiFi and a 32-bit ARM processor. This would let me turn things on/off while rocket is on the pad, and also get data off the altimeter quickly.

 

[whiskeyBear326]

I am planning to do just this with a BeagleBone Black. Some will probably scream that it's overkill for this type of project, but you'll understand later on when I write something up on it.

My main concern about this project is the accuracy of the barometric sensors (like the BMP180). Does anyone know of any documentation that talks about good algorithms for detecting apogee without being subject to erroneous / outlier readings from the sensor?


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[whiskeyBear326]

I'm also planning to use a usb wifi dongle to make the board a wireless access point and host a web service from which the system can be armed / flight data viewed / etc.


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[Jeffmhopkins]

As far as barometric pressure algorithms I'm using a simple kalman filter, but I've even had success with a simple complementary filter (alt=(alt*.95+newAlt*.05)).

A little fiddling with your data and you can extrapolate velocity as well and implement your mach lock out.

A good explanation of the kalman filter is here: https://blog.tkjelectronics.dk/2012...ach-to-kalman-filter-and-how-to-implement-it/

My IMU (accelerometer, gyroscope, magnetometer) has integrated filter implementation, so I only worry about the pressure sensor.

 

[bdureau]

maybe you want to check my web site I have done some of it
https://rocket.payload.free.fr/

 

[UhClem]

A good explanation of the kalman filter is here: https://blog.tkjelectronics.dk/2012...ach-to-kalman-filter-and-how-to-implement-it/

As it turns out, that is not such a great explanation. It follows an old and wrong approach to the balancing bot problem. Something I have written about before. Not that it has done a lot of good.