Open Source Flight Controller/Altimeter

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konkers

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I've been working on an open source flight controller/altimeter. I just had a successful data collection flight and thought I'd seek input here. Have a look at https://oss.tekno.us/flightcon/ and let me know you opinions/suggestions.


Here's pics of the first board rev.

top-sm.jpg

bot-sm.jpg


Thanks,
Erik
 
Couple of questions; How big is this altimeter? Ballpark figure on the price?
 
Originally posted by Rocketmaniac
Couple of questions; How big is this altimeter? Ballpark figure on the price?

The current board is just shy of 4" x 1". The next rev will have different (hopefully smaller) dimensions. As for price, I'm guessing somewhere between $100 and $150.

-Erik
 
Good work. The first questions that come to mind...

An accelerometer is used for apogee detection correct?

What are the options on the pyro triggers/timing?

Oh, and flight memory/time?

Sampling rate options?

Graphing interface/software on PC?

-Tim
 
Originally posted by dixontj93060
Good work. The first questions that come to mind...

An accelerometer is used for apogee detection correct?

Yes. There's a baro there too.


What are the options on the pyro triggers/timing?

The current software handles apogee and AGL triggers. The possibilities are limitless because the software is open source. I expect to have apogee, agl, launch, burnout, and landing triggers all with settable delays.


Oh, and flight memory/time?

Right now it logs to a microSD card which gives you practically unlimited storage. This is really nice because the flight log is stored as a tab delimited text file on the card which you can import into Excel or any other program that supports it.

The next rev will have the option of on board memory (probably 1-2MB) for hi-G flights where the SD slot may not hold up.


Sampling rate options?

Right now the sample rate is really slow. I'm switching ADCs in the new rev that will give ~1KHz combined sample rate at 16bits per channel.


Graphing interface/software on PC?

This is in the very early stages. Right now it has a rudimentary calibration UI. The software is based on the QT toolkit and will working under Windows, Mac OSX, and Linux.

-Erik
 
Originally posted by rbazinet
Are you going to sell this in kit form or built units...or both???

I'm planning on selling built units. The skill level required to solder these boards is pretty high.

When are you going to have the new rev ready with higher sampling rates?
[/B]

I hope to have the first few within a month so I can verify the design. A month or so after that (assuming all goes well) I'm planning on doing a beta run. This run would be aimed at developers more that users as the software will still be in flux.

-Erik
 
Sounds good the hardware looks great. I am planning on grabbing the source and taking a look at it. I have some ideas for implementation I would like in the software.

Thanks.

-Rob
 
Originally posted by rbazinet
Sounds good the hardware looks great. I am planning on grabbing the source and taking a look at it. I have some ideas for implementation I would like in the software.

Cool. One of my design goals for the software is to make it modular enough for people to experiment with new ways of doing things.

-Erik
 
Erik,

Thanks for the answers. Sounds promising.

Although I have a degree in computer science and engineering and began my career as a software engineer, I don't have enough free time now to commit to beta development (although I would love to).

Keep us posted on your progress.

-Tim
 
I know it would take a major board-revision... but I'd like to see a fourth pyro channel available.

(Multiple airstarts, anyone...? :D )
 
Is this the same altimeter project that was talked up at the Florida WinterNationals this past January?
 
Originally posted by LFLekx
I know it would take a major board-revision... but I'd like to see a fourth pyro channel available.

(Multiple airstarts, anyone...? :D )

I'll take that under consideration for the next rev.

-Erik
 
Originally posted by TWRackers
Is this the same altimeter project that was talked up at the Florida WinterNationals this past January?

I don't believe so. I'd be interested in hearing about other open altimeter projects.

-Erik
 
If you are considering more pyro's ... how about 5 total.

I have several rockets that want this profile:
1 = Airstart
2 = Apogee
3 = Apogee + 1sec (backup)
4 = Main Chute @ Low-Altitude
5 = Main Chute backup

But four outputs would be nice and fit most applications:

Single-Altimeter, dual deploy
1 = Apogee
2 = Apogee backup
3 = Mains
4 = Mains Backup

Staging:
1 = Stage Seperation (at Booster burn-out)
2 = Sustainer Ignition - delayed from seperation
3 = Apogee
4 = Main Chute


The ultimate sustainer altimeter would have 6:
1 = Stage Seperation (at Booster burn-out)
2 = Sustainer Ignition - delayed from seperation
3 = Apogee
4 = Apogee backup
5 = Main Chute at low altitude
6 = Main Backup


Just my wishlist.......................IMHO of course
FredA
 
Originally posted by freda
If you are considering more pyro's ... how about 5 total.

I have several rockets that want this profile:
1 = Airstart
2 = Apogee
3 = Apogee + 1sec (backup)
4 = Main Chute @ Low-Altitude
5 = Main Chute backup

But four outputs would be nice and fit most applications:

Single-Altimeter, dual deploy
1 = Apogee
2 = Apogee backup
3 = Mains
4 = Mains Backup

Staging:
1 = Stage Seperation (at Booster burn-out)
2 = Sustainer Ignition - delayed from seperation
3 = Apogee
4 = Main Chute


The ultimate sustainer altimeter would have 6:
1 = Stage Seperation (at Booster burn-out)
2 = Sustainer Ignition - delayed from seperation
3 = Apogee
4 = Apogee backup
5 = Main Chute at low altitude
6 = Main Backup


Just my wishlist.......................IMHO of course
FredA

you might be able to do that with add on boards if he can alter the software. Create a board the when the main board tells it its apogee the add on does the apogee. Then the it tiema 1+ backup. You could do that for all of them. Just need some programming. I agree that a 6 pyro altimeter would be beast!! :D

Ben
 
Originally posted by konkers
I'll take that under consideration for the next rev.

-Erik

I would also vote for 4 pyros to support airstart and staging applications. I think this is all you need as long as they are programmable, i.e., I don't believe in using primary and backup signals off the same electronics, I would just buy a second altimeter.

-Tim
 
Originally posted by ben
you might be able to do that with add on boards if he can alter the software. Create a board the when the main board tells it its apogee the add on does the apogee. Then the it tiema 1+ backup. You could do that for all of them. Just need some programming. I agree that a 6 pyro altimeter would be beast!!

I was thinking of including and add-on connector in the next rev. Maybe the solution would be to have 3 pyros on the main altimeter board and offer an expansion board with another 3.

Would that meet peoples needs?

-Erik
 
Originally posted by konkers
I was thinking of including and add-on connector in the next rev. Maybe the solution would be to have 3 pyros on the main altimeter board and offer an expansion board with another 3.

Would that meet peoples needs?

-Erik


How would you mount the expansion board? Piggyback the main board? I'd hate to see it take up more space, ie require a longer or wider ebay.

A lot of pyro outputs really sound interesting. I've been thinking starting a HPR 2-stage rocket for a while now. This altimeter might be the answer to the electronics issues.
 
Originally posted by Rocketmaniac
How would you mount the expansion board? Piggyback the main board? I'd hate to see it take up more space, ie require a longer or wider ebay.

A lot of pyro outputs really sound interesting. I've been thinking starting a HPR 2-stage rocket for a while now. This altimeter might be the answer to the electronics issues.

I expect the add-on connector would be on the end (lengthwise) much like the RDAS. Having the extra 3 pyros on an add-on board would not add much extra length rather than having them on board (just the size of the connector, a 1/4" or so.) Having them separate makes the main board smaller for the people who do not need all 6.

-Erik
 
May i suggest some kind of generic external interface? Something like GPIOs, UART, I2C or CAN. This could be quite useful, especially in an open source altimeter, as it allows the user to modify the firmware to support extended features like igniter boards, telemetry, GPS, external sensors and so on. Most of these interfaces can be provided with virtually zero effort.

I haven’t found the time for a detailed look into the source code, but there is at least one detail, that I would change. Your launch detection may fail when flying hybrids. Some of them tend to oscillate quite a lot, making it possible to reset the variable “advance” multiple times per second so that it doesn’t reach the threshold. You could calculate the average acceleration during the last 0.5s or so, to detect launch without this problem. If you’re interested, I’ll post some lines of code to illustrate a simple way to accomplish this.

EDIT: Forgot the most important part: Cool Project!

Reinhard
 
I love the idea of open source rocket electronics. Thanks for creating this! A few thoughts...

For me, keeping the card small is more important than tons of pyro channels. 3 on the main board would be nice. I like the daughtercard idea for adding more.

I like having the large capacitance across the pyro circuit since I tend to use smaller batteries and ematches; the ematches like the big burst of high current that capacitors provide. On the other hand, more recent "hot coil" igniters require steady current over a longer duration. I see in your notes that you're planning to move the capacitors to the VCC_5-0 line and using the battery alone for firing current. I wish you could offer both capacitor options, perhaps via a jumper. The latch time can be controlled in software. That way, both the "small battery, e-match" folks and the "hot coil" folks would be happy.

Having both the accelerometer and the pressure sensor is great. That can really enhance reliability.

I'm glad you have a beeper on the "To Do" list. I prefer audible signals over LEDs. It takes too much time to disassemble the alt. bay after every flight.

Looking forward to trying one of these out!

Jim
 
Originally posted by konkers
let me know you opinions/suggestions.

I looked through all the altimeter files on that site, but didn't find any files from the board layout program. Just pictures. Not even a gerber file.
 
Originally posted by Reinhard
May i suggest some kind of generic external interface? Something like GPIOs, UART, I2C or CAN. This could be quite useful, especially in an open source altimeter, as it allows the user to modify the firmware to support extended features like igniter boards, telemetry, GPS, external sensors and so on. Most of these interfaces can be provided with virtually zero effort.

My plan is to have I2C, SPI (with 2 slave selects) and a few GPIOs.


I haven’t found the time for a detailed look into the source code, but there is at least one detail, that I would change. Your launch detection may fail when flying hybrids. Some of them tend to oscillate quite a lot, making it possible to reset the variable “advance” multiple times per second so that it doesn’t reach the threshold. You could calculate the average acceleration during the last 0.5s or so, to detect launch without this problem. If you’re interested, I’ll post some lines of code to illustrate a simple way to accomplish this.

Thanks for the input. The flight algorithm is in the very early stages. The new board will have a much higher sample rate on the Accelerometer (~500Hz) which should let us do some digital filtering.


EDIT: Forgot the most important part: Cool Project!

Thanks!

-Erik
 
Originally posted by QuickBurst
What is the firing current?
What is the latch time?

7A max current through the FETs. Latch time will be configurable.

-Erik
 
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