Building an altimeter & download data

[rxsid]

Hi all,

I just purchased an altimeter from apogee. It's an Alt15k/WD made by Perfect Flight
What I'd like to find out, is if anyone has ever tried to build an altimeter similar to this one. Especially the download the data to a PC part.

Does anyone have a parts list, schematics for building such an altimeter? I'd like to have a few of these on hand (as would my sons), but we would rather build something like this ourselfs to not only try and save some money but also to have the challenge and fun in building our own electronics.

Any links or info?

Thanks!

 

[slackdaddy]

There are kits,
And I have seen schematics/plans on the net.

Do a "rocketry altimeter" google search, you'll find it in the results.


Slack

 

[blackjack2564]

Pico used to sell one for around 35-40 , don't know if they still do

 

[MarkM]

Transolve markets a barosensor that can essentially do what you want. Unfortunately, a brief check of their website indicates they out of stock due to unavailability. You might check with them to see when/if they will be available.

Transolve also makes an altimeter kit, but this is more complex than a simple altitude reporting altimeter; it can fire ejection charges and is more designed for High power models.

 

[falingtrea]

The difficult part about building your own is that you need to write code for the microcontroller. Any kit you would buy would have a pre-programmed microcontroller so you are only saving money by assembling the board.

 

[Guy Smith]

Try looking at Circuit Cellar. Issue #98 for September 1998 had an article on a recording altimeter with code and download capability. It was an accelerometer based system with a record rate of 1000 sps. Change the accelerometer out for a barometric sensor, reduce the sample rate to maybe 16Hz or whatever you think appropriate and then figure out the voltage to pressure conversion for your setup. Use a spreadsheet to plug in your raw values from the download and then convert to altitude. Note figuring out the conversion, i.e. calibrate the system is the hard part. This is what you are really paying for. Do a search for the article on www.circuitcellar.com.

Guy

 

[bobkrech]

Originally posted by Guy Smith
Try looking at Circuit Cellar. Issue #98 for September 1998 had an article on a recording altimeter with code and download capability. It was an accelerometer based system with a record rate of 1000 sps. Change the accelerometer out for a barometric sensor, reduce the sample rate to maybe 16Hz or whatever you think appropriate and then figure out the voltage to pressure conversion for your setup. Use a spreadsheet to plug in your raw values from the download and then convert to altitude. Note figuring out the conversion, i.e. calibrate the system is the hard part. This is what you are really paying for. Do a search for the article on www.circuitcellar.com.

Guy

https://www.circuitcellar.com/library/print/0998/Consi98/index.htm is the address for the article.

As Guy stated, locating the parts are easy. It's really easy to simply set up an off the shelf microcontroller up to collect the data so you can download it after the flight and determine the altitude. The generic motorola 4100 absolute pressure sensor is use in <90% of the rocket computers. The time is really in developing the code and the lift-off detection algorythm and a beep out read out.

Dave Schultz really knows his stuff. Here's a good start for a rocketry based unit.

https://home.earthlink.net/~david.schultz/altproject/alt.html

Here's a online wireless altimeter project using a 4100 pressure sensor with code for RC airplane applications.

https://www.electronic-engineering.ch/microchip/projects/alti/alti.html

https://www.electronic-engineering....or.pdf#search="motorola 4100 pressure sensor"

Here's another.

https://home.arcor.de/d_meissner/d_logg2_engl.htm

Bob Krech

 

[WillCarney]

If you had bought the MAWD you could have also got the
download adapter for it. Your altimeter does not adapt to
download the data.

The P6K from Transolve is a good kit but does not have a down
load capability. They do have instructions/parts list but the kit
is OS now. The MAWD by Perfect Flight has more features.

If memory serves me right there are a few plans out there but
few to none with download data capability in them.

William

 

[UhClem]

Now that Bob has mentioned me, I thought I should say a few things.

The hardware design, as others have mentioned, is by far the easiest part.

The first altimeter I built used the Roctronics hardware design for no better reason than it existed, met my requirements, and most important at the time, I could buy the circuit cards.

If I were to do it again, I would roll my own circuit card using either ExpressPCB or the gEDA tools. I would also ditch the separate ADC chip and use a microcontroller with a built-in 10 bit ADC.

Since the software is the hardest part of the project, pick a microcontroller architecture that you are comfortable with. If you prefer writing in a high level language such as C, pick a microcontroller that is a good fit (this knocks out the PICs).

You can find the Rocktronics hardware stuff at: https://www.pmcserv.com/Roctronics/

You can download all of the software I wrote for this hardware from my web pages. The code is hiding in the 2004 R&D pages. The flight software is 100% assembly language but is hopefully well enough commented that you can get the idea of what is going on even if you don't speak PIC. It will download data to the PC but there is nothing easy about it. I don't do GUI and I was able to use existing tools to get the job done. Note that the software isn't finished. It did what I wanted it to but it is not something I would use in a day-to-day altimeter.

My design that Bob pointed out has a firing circuit that is much more complicated than average and it doesn't have the ability to download data to a PC. The goal is to store data on a removeable flash memory card, currently I am fixated on the Transflash/micro-SD cards.

 

[teflonrocketry1]

JBGizmo has plans for a model rocket altimeter at:

https://www.jbgizmo.com/page27.htm

I built a few JBGizmo kits (tracking transmitters), they were straight forward to assemble, and they worked great the first time I powered them up!

Bruce S. Levison, NAR #69055

 

[bcdlr]

Originally posted by teflonrocketry1
JBGizmo has plans for a model rocket altimeter at:

https://www.jbgizmo.com/page27.htm

I built a few JBGizmo kits (tracking transmitters), they were straight forward to assemble, and they worked great the first time I powered them up!

Bruce S. Levison, NAR #69055

I built one of Jerry's altimeters. It seems to work fine but haven't flown it yet.

If you contat FAR circuit boards you can get a board for it. I had him make a master for it.

 

[rxsid]

perhaps one of the things i find interesting is the opinion most seem to have that the coding of the software program is the most difficult part. i believe that would be my strong point as code for a living. mostly higher level stuff, but can get through machine code if need be. for me, the most difficult part is the reading and understanding the schematics since I don't have much of an electrical background...as well as knowing what parts to buy (would become apparent i would think once i can read/understand schematics). i guess that's why i was looking for a sort of 'laundry list' for parts.

one thing i'd like to point out is that

Your altimeter does not adapt to download the data.

that isn't true. i've used the Alt15k/WD three times now and downloaded the data very easily, using their "PC Connect data transfer kits." Not to mention the fact that on my last flight the Alt15k literally blew out of my payload section and fell ~520 feet (as best I can calculate from the data) into a cow pasture. I found it beeping out the apogee of my superbird on an Apogee D10-5 at 910 feet. Turns out the 5 second delay was way too long for that heavy bird coupled with the fact that the nose cone wasn't secure enough. I was pretty amazed at that little altimeter.

awesome info guys....thanks!

 

[Guy Smith]

The beep code was easy, I got that in one try. The serial protocol took about 3 days. The SCI eeprom interface took about a week. The 8-bit a/d code took less than a day. Now converting it to 10-bit and 12-bit a/d code that took weeks (mostly stipid stuff on my part, however, the docs from Microchip leave much to be desired). Being an old analog person, I found that designing a filter on the front end prior to entry into the a/d pin and providing the approriate bypass caps eliminated the need for a fancy digital filter to post process the data. The hard part is calibrating the data with a known reference. I picked up an ISO standard altimeter acurate to 1meter, built my own pressure chamber and took a fair number of measurements at different 'altitudes' then plotted the linear line to determine the pressure to voltage ratio (actually the a/d measured value). Then armed with the 1976 Atmospheric Standard and excel I calculated the conversion from measured pressure to altitude. So you can see that the code can easy or hard depending on your perspective.

 

[rxsid]

that's for sure...thanks for the info about your experience Guy!

 

[rxsid]

ok folks...one more newbie question if you don't mind. I'm looking at the BASIC Stamp 2 Module, and I see where one can connect that to a 'work board' or testing board...but what about when your ready to use it in practice? I would assume that a PCB board would need to be used, but which one and how to get the diagram on the board?

Thanks again!

 

[Philosophico]

Can I make an observation -


With the amount of skills on this board it should be relatively simple to combine forces to produce a "TRF Altimeter".

Discount to TRF members etc.

Not only a good advertisement for the TRF website but a useful learning project for members and, it would seem, filling a market need.

 

[jderimig]

Originally posted by Philosophico
Can I make an observation -


With the amount of skills on this board it should be relatively simple to combine forces to produce a "TRF Altimeter".

Discount to TRF members etc.

Not only a good advertisement for the TRF website but a useful learning project for members and, it would seem, filling a market need.

We have done exactly this for our club.

https://www.marsclub.org/new1/Member_Pages/JD_s/MARS_Altimeter/mars_altimeter.html

The link to the schematic is broken but it will be fixed soon. One thing to note, this activity is useful to learn and have a project but not to save money. In our unit the parts cost is about $45 (the most expensive parts are the baro sensor, pcb and the terminals).

I go this route because I enjoy experimenting and tweaking the code (not to save money).

 

[Philosophico]

Thats brilliant.


How did everyone get involved?

Did everyone contribute to the design & build, or was this done by the more technically minded people and everyone else contributed the later flight data etc?

Is this now available as a "project" that new members can follow to build and understand an altimeter?



Sorry for the questions but I'm interested in using projects like these with my students.

Apologies for thread-jacking too!

 

[jderimig]

It started out as a personal project of mine and I offered to the club as it got matured.

We plan to projectize it in time for winter construction season. If there is enough interest we may do a altimeter building during a winter meeting where members can build the unit under the watchful eye of more experienced 'technicians'. Then test at the meeting and wait till spring to fly it.

If you are interested in more info feel free to email or pm me. I'd be more than happy to share designs, code or parts...

 

[rxsid]

Interesting. Indeed (as I've come to know more) the chances of 'saving money' when doing these so called homegrown projects are a bit slim it seems. I would like to learn more about rocketry electronics projects because i like to learn and i like to tinker around with technical stuff.

It seems to me, from my research anyway, that most of the altimeter/electronics projects that I've been able to find are rather dated (aside from this MARS altimeter). With the most recent stuff being in the 2001 range at best. Are there any newer, more updated projects out there? Complete with parts lists? jderimig...will a parts list be posted along with fixing the schematics?

For other projects, links would be great, as most search engine searches return hundreds, if not thousands of results...many of which aren't useful (IMHO).

Also, I'm still not able to find the answer as to....OK, I've got this design I want to build, and have the parts...but what about the actual board it goes on? Is there some 'common' stock that people use? 2 layer, 4 layer? Solder mounts, no solder mounts, etc. For example, can the board that the MARS alt is built on...be purchased ready to have the components connected? Or is that custom built and not readily available?

Thanks again for your help/suggestions.

 

[jderimig]

The schematic is now posted.

As far as the board to use, the KISS principle applies. 2-layer is usually good enough for the level of complexity that most altimeters have (low). If you are doing your own design then you will be using a custom pcb or a protoboard.

If you want to build the MARS altimeter, then I can supply a PCB board for you.

 

[rxsid]

thanks for posting the schematics jderimig! Looks like a great project.

b.t.w. there is no download to a p.c. capability on that altimeter...right? is the alt beeped out?

 

[jderimig]

Yes the alt is beeped out (as well as continuity and battery voltage status).

There are three auxillary I/O pins that are brought out to the 6 pin header. We were planning to use the ICSPCLK and ICSPDATA lines to double as an RS232 port.

Being a barebones unit there isn't additional memory storage on board other that what is resident on the PIC microcontroller. In the next firmware release we are adding the capability to log the first 20seconds flight data after launch. This should be enough to cover the boost through apogee of most modest HPR flights.