Building a GSM module for recovery

Hi guys,

I want to build a module with a SIM card that works the same as a tracking device. You can buy mini tracking devices but they include a GPS antenna. I already have an GPS antenna, so I do not need an extra one. I want to take an existing GPS tracker and strip the unnecessary components to reduce weight and redundancy, and make it suitable to connect to the gps antenna and power. I guess it need a capacitor to keep some power to send the GPS coordinates after a crash when the battery is out of power or disconnected.

Who can help me with this, because my understanding of electronics is not enough for this to make myself.
I think it is fun and maybe commercially interesting!

Presuming we’re talking about Navio drones (for recovery and why you don’t want an additional GPS antenna) isn’t this just a battery backup configuration? With a smaller second battery connected to some devices, the downed drone (even if the main battery failed) could power itself then, the GSM dongle and Navio without motors spinning but GPS active.

That’s probably better if you’re not an electronics boffin, because it’s achievable with some simple wiring a perhaps a couple of components soldered in the right places. Things like this are fully described on various parts of the forums and even here in the main documentation we have an easy way to hook-up secondary power sources, e.g. secondary battery to 5v BEC to a USB connector then to the RasPi power port.

Finally all we need is a fail-safe mechanism. Inside APM has various options but I’m not sure if the backup battery thing has been fully implemented. Better, and only possible with a full OS above APM, is a separate OS service which looks for either the failure of the APM process or maybe uses MAVLink to monitor other fail-safe conditions on the APM communication.

The problem looking for an external hardware solution is you’ll end-up with a load of work to get the GSM and GPS functionality. You could start with REACH I suppose, which has everything except the GSM. Maybe there is an Intel Edison module you can attach which will add GSM, or you can work-out how to share one GSM dongle between too systems. You’ll still have to work-out how to share the antenna or just use a micro antenna on the REACH as it’s not for flight that should be enough for tracking.

Ideally you need something like a mini child phone/panic tracker with a developer SDK (most likely a cheap Android device). I’m not aware of any specific models on the market but would bet with some research you could find a candidate or kick-starter with such a device. Or the same thing a different way, a GSM and GPS dongle with a proper processor and developer SDK.

Dear Tony,

Thank you for diving into my question.
I should have given an introduction to my question, I give it now:

  1. I am completely new to Navio and it’s GSM capabilities. Here and there I picked up signals that Navio has functionalities related to GSM, but I need to know what that is.
  2. My intention is long distance fpv flying with a quadcopter. Tx 433 Mhz and Vtx 1285 Mhz.
  3. it could be my quad crashes far away from home and someone finds it and takes it, with good intentions or bad intentions, away from the crash location wit battery empty or detached.
    Because I want to fly long distance, I want to reduce any weight possible, tha’s why I would like to remove the battery and GPS antenna from the tracking device

some GPS trackers hav an extra feature which is not essential for my puerpose, but ‘nice to have’: with an sms you can activate the microphone and listen to the sounds around the device.

A GPS tracker is an extra safety above my telemetry data, equipped with a sim card.
Making a module that sends an sms with geographic coordinates is simple. I just buy a mini GPS tracker and I am done!
I can program it to send me an sms every 2 minutes during flight and I can also send an extra sms to ask for the present location. It sends back google maps coordinates I can see immediately on my smartphone.

You suggestion to program an extra module is not what I want.
I want to use the processing power of Navio for this reason:

Because the Navio is controlling the plane, it can recognize events that should trigger the GSM module to send an sms. events could be:
low power
no power
free fall (the same one that triggers a parashute)
certain angles of the plane

DIFFERENT STRATEGY:

I could also just have incremental (energy economical) 3g/4g connection through a gsm module that sends telemetry data to a log file.
In that case the only challenge is to send some time after the battery dies.
The easy way is a small backup battery or a capacitor. The question is, which one of those is the most leightweight option and how small can that battery be?

There’s a guy here who is already playing around with a long distance drone project with GSM and a server on the internet as a fail-safe and way to send commands when the RC connection is lost, maybe that helps:

http://community.emlid.com/t/my-next-build?source_topic_id=636

I can run my Pi2+Navio all day long as a computer with a 2000mAh 3 cell battery. So if you just need a few hours of tracking I imagine a much smaller 2 cell battery with low C rating would do the job. To calculate that you’ll need help from somebody else and use some kind of battery calculator tool.

I just measured my development RasPi2-Navio+ for you, it’s drawing 0.22-0.43 amps (depending how busy it is), 4.9-6.55 watts, with an ESC as BEC, servo, RasPi camera and HDMI cable connected to an active monitor. That’s just a quick snapshot, actually out of interest I’ll try to do some extended tests another time as I’m interested in the same thing. I’m writing some software right now which interacts with each chip, and noted some of them have a “sleep” mode. Such a tracker/failsafe program should take advantage of these modes to maximize backup battery life. Maybe I can help there later, it’s an interesting idea for somebody to develop.

Good luck. If you need another power measurement with a specific configuration of standard hardware (I don’t have a GSM module) and software running I could do that for you.

If you have any cheap android handset…just have an app with “find my phone” type of app running…simple and easy solution. Throw an app on there like AirDroid and you can even activate the camera on the phone remotely so if someone happens to pick it up you can take video/pictures and feed them back to yourself over the 4G cellular connection.

It’s really only a matter of time until most serious drones have integrated 4G cellular capability off the shelf. You just buy the drone and pop a SIM and good to go. Think about it too…it might actually HELP with regulations because now the drone can be tied back to someone especially if is crashed badly. Today I think that’s main problem regulating non-LOS (it’s illigal) because you can crash it and very hard for authorities to track who did it if it was only RC connection. So many people fly non-LOS and there is a huge gaps here and many risks. At least with cellular connection you can have more range and also the tracking spoken about above that you want (for good or bad).

Hi derek,

It will be more difficult to take the interior of a Phone and build it into my quad than take a cheap GPS tracker.
Thank you for your thoughts anyway.

Guys, after some thinking, I changed my concept.

Here is the idea:
You can expand the controller with an telemetry kit. The telemetry kit exists of two identical transmitter/receiver units who communicate over 900 or 433 Mhz.
I want the telemetry be transmitted and received to and from available 3g networks and not over the 900Mhz or 433Mhz bband.
I guess 3G baudrate will be enough for telemetry data, but 4G is also ok. With that I can control my aircraft via the computer by updating the waypoints.

I found this guy who already made it for Pixhawk: https://www.youtube.com/watch?v=FErI0uHLdRE