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 Post subject: Rocket Payload
PostPosted: Wed Nov 04, 2009 2:07 am 
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Master

Joined: Sun Oct 05, 2008 5:40 pm
Posts: 111
I am looking for a little critique on a current project. This is actually the second generation of a previous project found here
http://forums.parallax.com/forums/defau ... 1&m=372500

What I am looking for is a platform that can be used for actual launch and thus flight tested experimentation. With out the restrictions of the previous micro I now have room to add gps and sd.

I have only limited use with Eagle so any feedback or discussion about pcb layout would be great. I got lucky with the first project being my first pcb design and working :mrgreen: .


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File comment: Front
Board.png
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File comment: Schematic
schematic.png
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 Post subject: Re: Rocket Payload
PostPosted: Wed Nov 04, 2009 2:54 am 
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Master

Joined: Mon Aug 18, 2008 1:26 am
Posts: 799
Location: CA bay Area
Cool. Did you find Eagle easy to use for this design?
What are powering all this with? I see you have a battery also on the GPS unit. And three LEDs to power up? Are LEDs actually necessary?

An SD card? Micro, no doubt. Does this plug in and stick out the side of the main board? All the simplest SD card circuits for embedded ucontrollers I've seen used simple SPI protocols, but you don't have a serclk on your design in the schematic. And they were 3.3V, but you seem to be supplying 5V. Is this some addon serial-comms board you're using? Why not stay with the 32Kx8 SEEPROM you used before?

USB and Serial? Why both? They use power, both have to have a header for a plugin connector, add complexity and make for a larger board. Simplify. Pick one or the other. Do the Lassen COMs thru the Atom, if possible.

I must say this is quite ambitious. Is this a personal project or is Hangman Rocketry producing a product line here? If it's personal, please share this when done. Submit an article for the Projects section.

Have a nice project. Take Care.

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 Post subject: Re: Rocket Payload
PostPosted: Wed Nov 04, 2009 3:48 am 
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Master

Joined: Sun Oct 05, 2008 5:40 pm
Posts: 111
I think Eagle worked good due to the exelent tuturals on sparkfuns website(incomplet now).

Power is an issue I plan on using the big rc car battery. Even then I dont see a extreamly long run time. Currently fly a commercal telemetery package that runs with this battery and runs low in about 1 1/2 hours.

The sd is from Rouge robotics. Mounts on the back of the board. As for why sd I guess just another method.

I want to add multipule port because I have a Maxstream Xtend wireless module I plan on throwing in the mix. This leaves a few different possabilitys of interface. I left the Lassens second port open to allow the ability to take the micro out of the loop and have GPS sent straight to the transmitter.

The thought behind the layout is to have a means of testing and modification. To find what works well and what does not work so well. This board will serve as a lower performance test bed. It will see altitudes between 5 and 10K maybe mach 1.

Then the units will get split Atom and accel/baro (gyro?) will ride in the carbon fiber airframe. Since GPS will not work in the middle of a carbon tube. The nosecone has been made of S-glass wich allows the gps to work. The gps/transmitter will be controlled by a Nano maybee with an accel just to be able to compare the data between the 24m and the nano.

The project is personal and I plan on updating the progress.


This forum really needs a spell check


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 Post subject: Re: Rocket Payload
PostPosted: Wed Nov 04, 2009 5:43 am 
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Master

Joined: Mon Aug 18, 2008 1:26 am
Posts: 799
Location: CA bay Area
Well, and there you have it, folks, a labor of love and knowledge seeking.

Mike, there are any number of documentation programs on the web you can download, install and type your text into and run a spell checker from, if you don't have Word or some such yet. Try Google Docs, you don't even have to leave the web to do it!

Is this the SD card unit you're using: http://www.roguerobotics.com/products/electronics/ummc
Looks straightforward enough.
Have fun with all this.

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http://blog.basicmicro.com/
http://kjennejohn.wordpress.com/


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 Post subject: Re: Rocket Payload
PostPosted: Wed Nov 04, 2009 3:43 pm 
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Master

Joined: Tue Nov 21, 2006 5:34 pm
Posts: 662
MikeWhorley wrote:
This forum really needs a spell check

Yep, I know I can not spell very good :lol: . But I now have downloaded and install iespell, which works pretty well. Once installed you can right click in the text area and do a spell.

Kurt

P.S. - Your project looks like fun!


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 Post subject: Re: Rocket Payload
PostPosted: Wed Nov 04, 2009 6:48 pm 
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Guru

Joined: Mon Mar 02, 2009 4:35 pm
Posts: 53
The reason I switched from IE7 to Firefox, is because Firefox has a built in spell check; as you are typing it is checking the word. Now, if only it had a Thesaurus on a right click.

How expensive does rocketry get? I mean for some entry level hobby stuff.


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 Post subject: Re: Rocket Payload
PostPosted: Wed Nov 04, 2009 9:58 pm 
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Master

Joined: Mon Aug 18, 2008 1:26 am
Posts: 799
Location: CA bay Area
I looked into the cost of using those "free" design programs slaved to one board fabricator. I have a 7 x 9, 2-layer board with silkscreen and mask in mind. Make two, pay $300. Don't even ask about 4-layer. Expensive start for a "what-if" project.

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 Post subject: Re: Rocket Payload
PostPosted: Mon Nov 09, 2009 2:46 am 
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Joined: Sun Oct 05, 2008 5:40 pm
Posts: 111
I have been working with the analog sensors this weekend. Both the accel and baro readings are going to be logged. The accel will work during the up part of flight calculating velocity and altitude.

ADC resolution = Vref/counts or 5/1023 = .00488 volts or 4.88mv

So for the ADXL 70g accel this means 5.6 counts = 1 gee. Once gee is determined from counts (counts/5.6 = gee) it then can be converted by: gee*32.2 for ft/sec or gee*9.79 for m/sec. This now becomes acceleration.

To determin velocity = previous velocity + previous acceleration * timestep from this

altitude = previous alt + previous velocity * timestep+ .05* previous accel*timestep^2

When acceleration becomes negative the rockets motor burnt out and the accelrometer is seeing drag as a negative acceleration. Likewise when velocity < 0 the rocket has reached its peak or apogee.

Noiw I have a little confusion with the MPX 4115 baro. The baro has an output from .2 to 4.8 volts from 15 to 115KPa and 46 mv = 1KPa.

My notes have this for resolution but I don't think its right:

resolution = ADC count range / pressure range or 1023/(115 - 15KPa) = 10.3 counts per KPa

is this right?

The point of the accel and baro besides data logging are to recognize three events
1. motor cutoff
2. peak of flight or apogee
3. Altitude above launch for main parachute deployment ( usually between 1000 and 500 ft above launch altitude)

once these phases of flight can be recognized cicutry can be added to
1. ignite a second stage motor
2. deploy drouge chute at peak of flight
3. deploy Main in enough time to slow rocket before contact

Because of the change in pressure around the rocket during mach transition the baro wont work on the way up but seems to be the best choice for determing altitude on the way down.


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 Post subject: Re: Rocket Payload
PostPosted: Wed Dec 09, 2009 2:46 am 
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Joined: Sun Oct 05, 2008 5:40 pm
Posts: 111
I changed the schematic a little (removed some of the feature creep).

Boards are here now all I need is time.


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 Post subject: Re: Rocket Payload
PostPosted: Wed Dec 09, 2009 6:34 am 
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Joined: Mon Aug 18, 2008 1:26 am
Posts: 799
Location: CA bay Area
Very nice, Mike. Really professional looking. Must be one HellaBig rocket, though.
Happy Holidays!

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http://blog.basicmicro.com/
http://kjennejohn.wordpress.com/


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 Post subject: Re: Rocket Payload
PostPosted: Sun Dec 13, 2009 4:55 am 
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Joined: Sun Oct 05, 2008 5:40 pm
Posts: 111
I have finished assembling the board. I only ran into 2 issues
1. USB connecter not connected to ground
2. Analog sensors do not work with dioeds (issue yet to be determined)

Nothing major that could not be fixed. Now its time to bring it all togeter with the code.

The green rocket will be the work horse for this project. Altitude between 4000 to 7000 ft.


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test bed.JPG
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Backside.jpg
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 Post subject: Re: Rocket Payload
PostPosted: Sun Dec 13, 2009 6:13 am 
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Master

Joined: Mon Aug 18, 2008 1:26 am
Posts: 799
Location: CA bay Area
Outstanding assembly job.
Like I said: HellaBig Rocket.
How do you secure components to keep them from popping out of their respective sockets?
What kind of G's does this pull at take off?
Happy Holidays!

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http://kjennejohn.wordpress.com/


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 Post subject: Re: Rocket Payload
PostPosted: Sun Dec 13, 2009 5:57 pm 
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Master

Joined: Sun Oct 05, 2008 5:40 pm
Posts: 111
The only thing that has a socket is the Atom. The G force needed to pull it out would be rather large well above 50g. The first few flights will only see 7 to 15 G. The high altitude flights planned for summer will hit around 28 G at max.

If this does turn into an issue it could easily be solved with an epoxy conformal coating.


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 Post subject: Re: Rocket Payload
PostPosted: Mon Dec 14, 2009 3:40 am 
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Master

Joined: Sun Oct 05, 2008 5:40 pm
Posts: 111
Assembled the radio breakout boards (I will post more about these in the wireless section) and connected one to the 232 port of the flight computer and one to a terminal emmulator on the pc.

Ran a simple program:

main:

serout p5, i9600, ["TEst Test"]

pause 500

goto main

And it shows up on the pc :)

I then connected the radio to the expansion port of the flight computer and ran the same program but changed the pin to P11 (Exp_1). I also had to change a few jumpers on the radio board to configure it for TTL. Ran the program and again success :D

I have now tested each circut individually and have gotten them all to work. Now I will finalize a flow chat of what I want and start poking away.


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232.jpg
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radios.jpg
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radio board.jpg
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 Post subject: Re: Rocket Payload
PostPosted: Sun Dec 20, 2009 8:52 am 
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Joined: Mon Jul 17, 2000 6:00 pm
Posts: 155
Mike,

When your done can I create a write up of your project? We are creating a section on the main site for customer projects which we will select from the forums.

Also Eagle is a great program. We have an engineer who lives aboard working on several complex designs using Eagle. I was thinking about asking him to create some better tutorials.

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