Part 2 - My Stumbling First Steps with an Arduino Mini Pro

[DBK]

In this Thread:

<Broken link removed>

I started to record my first impressions of constructing something using an Arduino Mini Pro, a tiny little processing board which weighs just 2g.

I've soldered a few wires and other bits and bobs to it since then.

The thing in the foreground is the GPS chip which is far too big but it is fine for a prototype. The little thing just beyond the Arduino is the LoRa radio transceiver. The copper wire is the antenna which given this is supposed to operate at 868 MHz is quite short. The red and black wires in the bottom left go to the battery box containing three AA batteries.

So I turned it on - and nothing seemed to happen! Not surprising really given my complete lack of knowledge of what I was doing.

The device is using a system called The Things Network which operates in specific frequency bands according to the part of the world you are. Europe is 868 MHz as already mentioned and it wasn't issuing a squawk on this frequency.

Then a minor breakthrough, I checked the US frequencies and this is what I saw:

The purple "flying saucers" in the bottom half of the display are packets of data it was transmitting. They are broadcast on several different frequencies chosen at random by the code.

So it was working, but speaking with an American accent around 904 MHz.

It has now been sorted thanks to a huge amount of help from an online friend who really does understand all this. . And the answer wasn't corrections to the code but the need to use a very specific version of a library when compiling it and to do the compiling on a specific (earlier) version of the IDE. I would never have thought this was how to solve this issue - and the other issues overcome I won't mention because they are too tedious to relate. One of the problems is if you use the latest versions of everything the resulting compiled code is too big to fit within the board's memory.

This is just the first step, but it is a positive step. I'll start work tomorrow on decoding what the device is saying to me. It is saying something sensible as I can see the latitude and longitude in the packets of data but it needs a bit more tinkering to become useful.

 

[Spriddler]

What is it / What is supposed to do / what are you expecting it to do?
Genuinely interested in and have been following your techy boys' toys balloon exploits but I've no idea what this widget is apart from it having a GPS module.

(Using the link in your OP I get 'Page not found'............)

 

[DBK]

What is it / What is supposed to do / what are you expecting it to do?
Genuinely interested in and have been following your techy boys' toys balloon exploits but I've no idea what this widget is apart from it having a GPS module.

(Using the link in your OP I get 'Page not found'............)

Sorry, should have explained that. I'm trying to make a very lightweight tracker I can hang below a tiny balloon. It won't have batteries but use solar power. The ideal is to get everything below 10g but if I can be under 12g I'll be happy. Some folk have got it down to an astonishing 6g. The photo below may not be very clear as the solar panels are hiding the rest of the electronics but the total weight of radio, GPS, controller and solar panels is under 7g. Some of these have flown around the world more than once although the guy who made this one "only" got as far as Japan. My aims are much more limited, reaching mainland Europe will be a success.

 

[Jane And Rog]

Very cool, watching with interest.

 

[Spriddler]

Ta. Is that the sort of tracker thing they attach to birds and animals?
Why is the weight so critical? Is it to enable it to be carried by the smallest possible balloon requiring less Helium or could you have a heavier module and just use a larger balloon to carry it?
I guess having solar charged batteries to keep it working overnight would add far too much weight.
Fascinating.

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[Just smiffy]

To boldly go....

 

[DBK]

Ta. Is that the sort of tracker thing they attach to birds and animals?
Why is the weight so critical? Is it to enable it to be carried by the smallest possible balloon requiring less Helium or could you have a heavier module and just use a larger balloon to carry it?
I guess having solar charged batteries to keep it working overnight would add far too much weight.
Fascinating.

The trackers they fit to migrating birds are a bit different I think. One I read about just sent out a single ping a few times a day. Orbiting satellites picked this up and by comparing the time difference could work out where the bird was. A bit like GPS in reverse. The idea was this used very little power so it could last for some time on a very small battery.

And yes, the idea is by keeping the weight down you can use a much smaller balloon, say 36" across but importantly it isn't a latex balloon but one made from a material which doesn't stretch. The idea is this means the balloon will rise to a certain altitude but no higher as the balloon won't expand any more. It then becomes a "floater" and can in theory stay up indefinitely and drift wherever the wind takes it.

There are a lot of things which can go wrong!

 

[Spriddler]

........ it isn't a latex balloon but one made from a material which doesn't stretch.

I imagine a stretchy material could be restricted to max size within a mesh bag - but that would just add more weight I suppose. Inflated Cows' guts were good enough for Zeppelins ....................
It's all fascinating stuff to ponder and beats trying to exercise the brain finding a solution for a slow emptying m/h sink.
There's more fun when things go wrong.

 

[DBK]

Significant progress today.

It is often remarked there is a great community here on MHF of folk willing to help others and of course this is true. But there are other places where the same applies.

This morning's progress came from advice on the The Things Network (TTN) Forum the end result of which was by lunchtime my tracker was producing readable data of its GPS position. But I needed to put this position data on the high altitude balloon map.

A Dutchman has written some software which acts as a bridge between the TTN network and the world of balloons. I managed to install this on a Raspberry Pi but I was stumped when it came to configuring it.

At this point we are going to step back several decades into the realm of Internet Relay Chat (IRC) which was a sort of fore-runner to well, forums!

Using an IRC channel I had some serious assistance from the said Dutchman this evening and finally got it working. In my defence the problems I was having highlighted a bug in the software which Bertrik (the Dutchman) rapidly fixed.

And the result late this evening is my tracker, "ttnwiv2n" now appears as a balloon.

Except it isn't actually a balloon yet, that will follow, it looks more like a tangle of wires attached to a battery on the windowsill of my shed.

But it is talking via radio to a gadget nearby which in turn transmits the data by WiFi to my home router and then onto a TTN server somewhere in mainland Europe.

There it would be lost except the Raspberry Pi (mentioned earlier!) in another room is scanning the TTN servers for news of my "balloon". When it finds some it converts it into "balloon-speak" and uploads it to the balloon server which displays it on the map shown above.

Mind boggling.

But over to me now. With the software now sorted (fingers crossed) it is now a physical construction project and very much down to me.

 

[Insider]

Complete nerd here and projects like this where the learning is more important than the end result are the reason for getting out of bed - used an Arduino board to make make a wireless button box on a steering wheel for Sim racer - bluetooth - not LoRa
Anyway it struck me that you could have a really beautiful backup solution here for vehicle tracking. Power is not going to be an issue here, without doing the maths even a small 1AHr battery should last months if just obtaining & transmitting location data once/twice a day. End result is that if someone steals your vehicle and puts a GPS etc blocker on it and parks it up for a few months(no idea about this side of the business) you still get to track it once the GPS blockers are removed. If 2G/VHF is being blocked then no problems - unlikely that LoRa is high on the list of campervan thieves just yet!!

Someone please tell me I'm an idiot as I feel a winter project might be in order once I run the numbers

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[DBK]

Complete nerd here and projects like this where the learning is more important than the end result are the reason for getting out of bed - used an Arduino board to make make a wireless button box on a steering wheel for Sim racer - bluetooth - not LoRa
Anyway it struck me that you could have a really beautiful backup solution here for vehicle tracking. Power is not going to be an issue here, without doing the maths even a small 1AHr battery should last months if just obtaining & transmitting location data once/twice a day. End result is that if someone steals your vehicle and puts a GPS etc blocker on it and parks it up for a few months(no idea about this side of the business) you still get to track it once the GPS blockers are removed. If 2G/VHF is being blocked then no problems - unlikely that LoRa is high on the list of campervan thieves just yet!!

Someone please tell me I'm an idiot as I feel a winter project might be in order once I run the numbers

It's certainly possible but run from a tiny solar panel on the roof might be another option. At the moment the GPS is powered up all the time but I'm sure the design could be altered so it only turned it on for a short while and after a delay to allow it to get a fix then turned it off after transmitting the location data.
The other aspect is it would need a new website created with its own map.

 

[Insider]

It's certainly possible but run from a tiny solar panel on the roof might be another option. At the moment the GPS is powered up all the time but I'm sure the design could be altered so it only turned it on for a short while and after a delay to allow it to get a fix then turned it off after transmitting the location data.
The other aspect is it would need a new website created with its own map.

I glibly said power isn't going to be an issue but essentially it pivots around power. I will be looking at this in more detail but you only need to have the system wake once a day, get a fix and transmit. You don't need GPS on constantly and more importantly you don't need it lying in wait to pick up a signal. I have a cheap as chips GPS tracker using a SIM. It has a 5AHr battery and lasts close to 2 months - it's main power consumption is listening for an SMS so it can respond. I have everything else turned off, GPRS, movement detection both by acceleration and movement out of a zone, etc because everything comes at a power price. GPS modules are very low power and LoRa is very low power. All you need is a cron job running to wake up the required bits of code and off you go. One of the strengths to me is having a modular box that you can hide - no wires.

On the receiving side - have a look at NodeRed - https://nodered.org/ I'm not a programmer but when I have play with stuff the odd time this is the stuff of dreams. Throw it on a Pi and you can do lots of things with it - think of it as a techy version of IFTTT.

 

[DBK]

I glibly said power isn't going to be an issue but essentially it pivots around power. I will be looking at this in more detail but you only need to have the system wake once a day, get a fix and transmit. You don't need GPS on constantly and more importantly you don't need it lying in wait to pick up a signal. I have a cheap as chips GPS tracker using a SIM. It has a 5AHr battery and lasts close to 2 months - it's main power consumption is listening for an SMS so it can respond. I have everything else turned off, GPRS, movement detection both by acceleration and movement out of a zone, etc because everything comes at a power price. GPS modules are very low power and LoRa is very low power. All you need is a cron job running to wake up the required bits of code and off you go. One of the strengths to me is having a modular box that you can hide - no wires.

On the receiving side - have a look at NodeRed - https://nodered.org/ I'm not a programmer but when I have play with stuff the odd time this is the stuff of dreams. Throw it on a Pi and you can do lots of things with it - think of it as a techy version of IFTTT.

TTN devices in sleep mode can consume just a few micro-amps if properly designed. My device is transmitting every 30 seconds but I'm probably going to slow that down a bit. I took it for a drive through Plymouth today and three TTN gateways (or RECEIVERS) picked it up and captured the location data. But I'm not sure this system would be suitable for ground based tracking as there are too few gateways in the UK. It will work from a balloon because the height vastly improves the range. A balloon using a TTN tracker recently took off near Ipswich and its signals were picked up as far away as Northern Ireland as well as down here in the south west - but it did go very high.

 

[DBK]

A quick update. I've built a second tracker but this time using a much smaller and lighter GPS module.

At under 7g it is lighter than even I'd hoped and I can save another quarter of a gram when I replace the current heavy copper antenna with some much thinner wire when it arrives from eBay in a few days.

But the heavy antenna does have a use, I can stick it in a block of foam to support the tracker and point the GPS at the sky.

The next task is to build an array of solar panels to replace the current battery box. I'm going to try 6 panels first which will give 3 volts which should be enough but I may have to go to 7 or 8. The problem is each panels weighs 0.5g so I want to use as few as possible. I will also need to build some sort of structure to hold everything together and supports the solar panels. I've bought some thin balsa strip and will use that I think in an effort to reduce the amount of plastic.

Biggest threat to this project is going to be the lack of sun to test it.

 

[DBK]

Today's update is I've built the solar panel array and (amazingly) it is working! To maintain the MH connection I've put it all behind the windscreen of the van as it is too breezy outside.

And here it is on the map. Solar powered.

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[jwells]

Can you let us have more tech information please i.e. components, where you get your project information from!
Really interested in the gps/tracking, and pressure/altitude sensors(and time management!!!!!!)

 

[DBK]

Can you let us have more tech information please i.e. components, where you get your project information from!
Really interested in the gps/tracking, and pressure/altitude sensors(and time management!!!!!!)

The design is all from this link:

LoRaWan GPS tracker - The Things Network

This LoRaWan GPS tracker uses the TTN Cayenne integration and shows your movements on a map in your Cayenne dashboard. …

www.thethingsnetwork.org

It just does position without any further environmental data.

A small balloon was launched today which is currently probably somewhere over Denmark based on the ground stations picking up its signals but it has suffered a technical glitch and says it is still over the English Channel. The technological details can be found on this page below - it uses a custom made circuit board which isn't something I've considered yet. I haven't looked in detail at this page yet as I've only just found it but this design uses very different components to mine and can measure environmental stuff. The author does admit the page needs cleaning up so it may be confusing.

GitHub - ImperialSpaceSociety/picotracker-Lora: This is the code base and hardware design files for the Lora pico tracker to be flown around the world

This is the code base and hardware design files for the Lora pico tracker to be flown around the world - ImperialSpaceSociety/picotracker-Lora

github.com

This is a screen shot of the Imperial College balloon taken a few seconds ago. It shows it near the UK but it is being detected from Denmark so that is probably where it is. The temperature reports also way out. The helium would be liquid at that temperature.

 

[DBK]

It's suddenly woken up. There must be big smiles somewhere.

 

[DBK]

Things have moved on after several frustrating setbacks due to my clumsiness.

But after all that I managed to make a payload under 10g*. A change from 26AWG wire to 30AWG saved a whole gram.

The one above has a wonky solar panel because I broke the original (clumsiness!) and replacing it using a soldering iron upset the expanded polystyrene somewhat. So I built a new one and that didn't work all that well either but third time lucky the solar array seems to be working as expected. What a difference an array makes. I've now added some fishing line to it and here it is suspended below the MH rear view mirror.

And in close-up:

And it is now working, when the sun shines it wakes up and sends a GPS location report which appears on the map.

The next stage was to look at the balloons, and plural it will be because at 10g I really need two to be able to get above the worst of the weather. The balloons I'm using are the 36" clear party balloons bought from AliExpress for about 50p each.

They can be used "out of the box" but their performance can be improved by stretching them first. This is the rig I'm using. A cheap aquarium pump and an equally cheap digital manometer. The Silver Screen windscreen cover is an optional extra.

The rig takes up to a couple of hours to reach pressure (should have bought a bigger aquarium pump!) but taking things gently is no hardship. It is nerve-wracking and I was wearing ear defenders when near it as the pressure built up. The envelope of the balloon becomes very tense - like the proverbial drum skin.

The critical pressure is 0.6 psi. Much above this, even 0.61 or 0.62 and it is likely to fail.

Did I mention this was a tense time? I need to calibrate the manometer I think so will rig up a U shaped water manometer this week. But it must be working. After holding pressure for 24 hours the deflated balloon was about 2" wider than an unstretched one which may not seem much but volume increases with the cube of the diameter so this is getting on for almost an extra 20% in volume, which is significant.

The plan, when weather conditions are right, is to launch it with the aim of visiting as much of Europe as possible as the radio system only works in Europe.

If I had launched this morning it is conceivable the balloon might has followed this bizarre path. The idea is the balloon will rise to a certain altitude and then stay there. This is possible because the balloon, unlike a latex one, will stop expanding at a certain point and thus stop ascending. The minimum altitude I need is 7,000m but 9,000m or even higher would be safer.

Just over 111 years ago Louis Blériot made the first crossing of the Channel by an aircraft. If I can do the same in the opposite direction and just get over into France I will count that as a major success. Anything beyond that will be a big bonus.

* 10g is not much to brag about. A balloon was launched this morning from Romania with a 3.5g payload. Suspended below a very high tech and expensive balloon it is a serious attempt at circumnavigating the World. I'll be happy with Brittany.

 

[Spriddler]

Fascinating.
Your previous balloon kept rising and expanding until it burst. How do you prevent this one doing the same in order that it will continue its tour? Does it vent off gas with increasing altitude?
If the balloon doesn't burst what will be the cause of the end of the tour? Presumably it will continue to transmit data 'for ever' powered by the solar array (until it passes behind the moon).

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[DBK]

Fascinating.
Your previous balloon kept rising and expanding until it burst. How do you prevent this one doing the same in order that it will continue its tour? Does it vent off gas with increasing altitude?
If the balloon doesn't burst what will be the cause of the end of the tour? Presumably it will continue to transmit data 'for ever' powered by the solar array (until it passes behind the moon).

The phrase used is it is a "super pressure" balloon. With a latex balloon the pressure inside the balloon is only very fractionally above atmospheric. With a "super pressure" balloon the gas will expand as the balloon rises but there will come a point when the fairly stiff material it is made out of stops expanding and resists the pressure of the gas. I'm testing these to 0.6 psi and as long as the pressure inside remains below that, which it should if I get my calculations correct and don't overfill the balloon the whole thing should rise to an altitude when it reaches neutral buoyancy and stops going up because the balloon won't expand any further. The internal pressure of the gas isn't enough to either burst the balloon or cause it to expand further. If you can get it right these balloons can last for months and go around the world umpteen times.