Tubez
Posts: 7
Joined: Wed Oct 17, 2012 6:22 pm

RP for video and temp / pressure messuring

Wed Nov 28, 2012 12:30 pm

Hey!

I am a part of a group that wishes to send up a weather balloon into the stratosphere (goal is 115.000,0ft) where we are intresting in using the Respberry Pi for streaming a live video and recording of temperature and air pressure.

The members of the group have a usable knowledge within programming with C# and some Python.

The things that we want to Raspberry Pi to do is:
1: have a webcam and transmit the video back to the ground over a low frequency radio
2: messure and store temperature, pressure and maby radiations by using link: Radiation Sensor Board for Raspberry Pi and a sensor for pressure and temperature that the Raspberry Pi supports.

So the things that we are woundring about is:
1: Is it possible to use the Raspberry Pi for this?
2: What OS and what language is the best to do this whit?
3: What do we need to think about? Power use and so on?
4: What kind of equiptment are the best for this purposes?

I hope all of you good folks on this forum can help us get started :D

With best regards
- PST team.

khooke
Posts: 25
Joined: Sun Oct 07, 2012 6:38 am
Location: CA, USA
Contact: Website

Re: RP for video and temp / pressure messuring

Thu Nov 29, 2012 8:04 pm

An idea for the live video feed, but not necessarily using the Pi for the video capture - look into the equipment that's available for RC planes/helicopters for First Person Viewing (FPV). They already have hardware for wirelessly transmitting a live video feed - google for 'RC FPV' and you'll find plenty of resources. Some of the kits come with data loggers that superimpose heading, altitude, speed etc on the video that might also be of interest to you.

Another related idea, look on diydrones.com - there's an online community that have developed rc plane and helicopter auto-pilot systems for diy autonomous drones using Arduino boards and community developed software. Again, not directly related to what you're looking for, but there may be some parts or ideas that could be useful for you.

Tubez
Posts: 7
Joined: Wed Oct 17, 2012 6:22 pm

Re: RP for video and temp / pressure messuring

Fri Nov 30, 2012 12:13 pm

Well we are not intresting in piloting this thing, becouse for us to do that it will require a lot of power.

We are so far planing on using 2-3 GoPro3s for the main camera, but since there is no way for us to transfer the video from GoPro so are we thinking of using a Webcam with the RPi. And then transfer that feed with a low frequenzy radio inkluding the GPS signals. But found a site ( http://www.fpvpilot.com/ ) that had alot of good information, so are going to check it out! :)

do you have any idees for what OS and prog language we want to use? Are thinking of using Python as the main language?

Thx for your help so far.

ghans
Posts: 7877
Joined: Mon Dec 12, 2011 8:30 pm
Location: Germany

Re: RP for video and temp / pressure messuring

Fri Nov 30, 2012 12:29 pm

I do not know how you want to transmit digital video over
30 kilometers or more.
Perhaps 5 pictures per second would be achievable. Please test your webcam extensively
with the Pi beforehand . Or save yourself from all this trouble and buy a
proper Camera like khooke suggested.
Note that the Pi features hardware 1080p h.264 encoding (realtime) for free ,
but you need to be a versed C\C++ developer with a taste for obscure
multimedia APIs to use it.


ghans
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User avatar
daveake
Posts: 184
Joined: Thu Jul 12, 2012 12:07 am

Re: RP for video and temp / pressure messuring

Thu Dec 27, 2012 9:16 am

A few points ...

First, find out what power/frequency you can legally transmit in your country "from an airborne vehicle", and whether you need a licence to do so. In the UK for example we are severely limited by our laws, and we use 10mW UHF signals. That power is *not* enough to do a live video link (nowhere near). Even with higher powers, for live video you'll probably end up needing a steered dish on the ground.

A webcam will get you to about 10 frames per second, with the CPU doing the compression. A better option would be the Pi camera because that runs on the GPU.

For temperature, the DS18B20 works well and will connect to the Pi GPIO using the driver in Raspbian. Info on the web for how to do that. You can put that device on a wire tail to get it outside of the insulation to measure the external temperature.

For pressure, no cheap sensor will give you good results at < 1% atmosphere. You'll get more noise than signal. If you're only interested in the pressure gradient during the flight then a BMP085 will do that cheaply. It also measures temperature and connects to the Pi via i2c, again using drivers included in Raspbian.

You can write software in C or Python for reading sensors and transmitting data. Personally I almost always use C as I'm more familiar with it. For the video feed try ffmpeg. It can be rather temperamental - the "wrong" parameters and it just dies - but it does work. I use my own hacked version to overlay telemetry data onto the video feed, and that wasn't a pleasant job - ffmpeg is enormous and takes over 3 hours to compile on the Pi!

You didn't mention tracking. Ideally that will work throughout the flight (and a GSM tracker will *not*).

Send me a pm or email to daveake at gmail if you want more advice.

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