Planning first flight for late September (hopefully!)

[Max Dymond]

Hey folks,

I'm looking to do a one-off flight in September and just wanted to document how it's going so far.

• I've had a very useful conversation with Steve about the feasibility of this, and I'm likely to be launching from Elsworth if this all comes together.
• I'm putting together a tracker from scratch - currently trying to link together some old Raspberry Pis, a GPS module (which I've gotten working) and some 433MHz LoRa Pi hats. I'm kinda hoping I can use Dave Akerman's Pi software on both ends - both the LoRa HAB gateway software and the Pi in the Sky software, even though it's just stuff I'm cobbling together.

It gives me a month and a half to put together the tracker and receiver, and worry frantically about aerials, balloons, helium, cameras - all the fun stuff!

Max

[David Akerman]

Do you have all the Pi bits you need?  I have plenty of stuff in boxes here.

Dave

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[John Laidler]

Best of luck with the project. I used a Pi Zero in the tracker, following Dave's excellent guide but I see no reason why you can't use a full sized Pi. I think the only changes you will need to make will be telling the software what pins to find the GPS on. The only design tips I can suggest are keep the GPS and the radio antenna as far away from each other as possible as you can get interference. I used a sideways facing camera although I think downward pointing ones are more popular.  I made a dreadful cut-your-ankles-off video of my launch which you can find below. This might also show why an assistant or two is useful.  If you don't have one I have a filling tube I can post you, it will fit into the neck of most of Steve's balloons I think. But let me know before the end of the month as I am on holiday after that.

https://youtu.be/Clx7ZhlAxxc

September isn't far off so if you haven't already I would put in for permission to launch as you need to give a minimum of 28 days notice. You don't have to choose a specific date but you can choose a range. For example, you could select 10 Sep to 2 Oct inclusive, which will include as many weekends as possible if that is a constraint. You can then tell them the exact date say 48 hours before launch if the weather forecast looks suitable.  You want very little wind for a first launch. I think you might get away with 24 hours notice but there has been a change of personnel at the CAA and we don't seem to have a lot of experience yet if things are the same.

The application is now done online at this site:

https://apply.caa.co.uk/CAAPortal/terms-and-conditions.htm?formCode=BAL

John

On Tue, 9 Aug 2022 at 10:15, Max Dymond <maxmak...@gmail.com> wrote:

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[David Akerman]

John, as he mentioned launching from Elsworth then Steve already has yearly permission and will just need to do the NOTAM request 2-3 days prior to the flight.

Dave

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[Steve]

:-)

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[John Laidler]

Thanks!  I didn't get the connection.   

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[Max Dymond]

> Do you have all the Pi bits you need?  I have plenty of stuff in boxes here.

Hi Dave! Your blog is amazingly informative, thanks for writing it.

The answer is "I don't know, but I'll happily take anything you're willing to loan". I currently have:

• A Raspberry Pi Zero (untested, from the front of MagPi a few years ago) and a Raspberry Pi 3B+ (tested)
• Two of these 433 MHz LoRa hats from PiHut: https://thepihut.com/products/sx1268-lora-hat-for-raspberry-pi-433mhz 
• A Neo 6M and a Neo 8M module which I've tested over UART and gotten NMEA information out of both.

I haven't dug into the LoRa hats yet but there is at least code available on https://www.waveshare.com/wiki/SX1268_433M_LoRa_HAT for me to dig into. I'm not tied to this though - I'd much prefer to use stuff that will definitely work with your software 😅

> Best of luck with the project

Thanks John! I'll check out your video. I haven't yet ventured into the "making my own antenna" side of things so I have that to look forward to!

[David Akerman]

Max,

Those LoRa boards use the SX1268 which is a completely different software interface to the older models that my code works with, so neither PITS nor the LoRa Gateway will work with them.  At some point I'll write the code for the 1268 but that's waaay down near the bottom of my to-do list!

You need boards with the SX1278.  Let me know if you get stuck.

Dave

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[Max Dymond]

Comms: The SX1268 demo code from Waveshare seems like it's working in one direction at least - unfortunately the least useful direction (WSL to Pi). Still, for ten minutes of fiddling I'm surprised how well it worked!

[Max Dymond]

Progress update: I've had the week off so I've been coding up the tracker. I now have the Pi sending UKHAS-format messages with live GPS data over my SX1268 LoRA hats. Next thing is to get the Pi capturing video periodically (which I've prototyped successfully) and then I have to test over range.

I think my best bet for testing over range is making an antenna from guides:payload_antenna [UKHAS Wiki], getting an antenna for the receiving end (any recommendations?) and popping to a (very) wide open space!

Also, is there any way to check whether the Hab network will be able to pick up my LoRA broadcasts?

[Kev Walton]

Good work Max, 

Regarding Rx antenna, the world is your oyster, anything from a rubber duck to a Diamond X 5000 mounted high on the chimney.  Something you can transmit through (for uplink / SSDV resend) is useful, especially if you have / get your amateur radio license.  Alternative approach is a Yagi to get directionality.

Re Checking the Hab Network - well if you receive in the same way the rest of us do, then that is a good start, a Lora Gateway - https://www.daveakerman.com/?p=1719 (You can strip board it, no need for a PCB if you don’t want to) is the main fixed install option.  Have a read here - https://www.daveakerman.com/?p=2828 for other options.  A TTGO is another good mobile option:  https://github.com/daveake/LoraBluetooth

Cheers

Kev

[Max Dymond]

I was hoping to not have to buy any more LoRa modules but I feel like it's an inevitability at this point. I have an Rpi Zero knocking about - I can get the Rpi Zero LoRa hat from Uputronics and try and get the Gateway software running on that. Bonus might be that I can run a Gateway after this project is over!

Thanks for the advice on antennas! Mostly I'm worried about chase antennas. I'll do a bit more research.

[Kevin Walton]

Chase antenna wise, a magmount antenna for the car, and maybe a small yagi if you want to maximise ability to find it - but IMHO the handheld yagi doesn't make a lot of sense with LoRa, you can either recieve the packets or not...

Where in the country are you?

Cheers
Kev

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[Steve]

For a chase antenna you can't beat a magmount IMO.  Cheapest commercial option is to buy a UHF taxi antenna and cut down to size for 433MHz.

    Steve

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[Max Dymond]

I'm West-Norfolk based, but I'll be launching from Elsworth.

[Mike Sharps]

Hi Max

You could just buy a hope-rfm9x 433mhz lora chip and make a tracker with the raspi zero. It is only a matter of half a dozen or so solder joints to hook up the SPI port and Dave provides a step by step instruction on one of his older blogs you will need to add a gps device to the serial line and a cam etc but it will then run the pits software as per standard installation. 

I found the blog I used to make one a cuople of years ago it works fine http://www.daveakerman.com/?p=2101 

You can build the same hardware to run a gateway as well just plug in keyboard and screen

Best of luck

Mike

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[Max Dymond]

Minor progress today - avoided one potential disaster by implementing GPS model switching based on altitude (based on me remembering that that's a problem 😂). I've configured it so that over 8500m the Pi will set the NEO8M module to AIRBORNE_1G mode; and under 7500m it'll set it back to PORTABLE mode. Hopefully that will allow GPS tracking up to 50km, and more accurate tracking under 7.5km. Numbers picked mostly out of a hat, though PORTABLE mode only works up to 12km.

[Mark Jessop]

Tracking on the ground in Airborne 1G mode is more than accurate enough, there's no need for the added complexity of switching modes throughout the flight.

73

Mark VK5QI

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[Max Dymond]

Ok! I'll comment that out then. 

Some more minor progress:

• I ran a Raspberry Pi (admittedly not the actual one I'll be using) off 6 AA batteries through a 5V UBEC until it died - according to the timestamps I got 5h 45m out of it (and this was with rechargeables, not Lithium AAs), so I'm quietly hopeful that this will power the tracker through the flight.
•  I made my first ever antenna today following the guide on the UKHAS wiki! The Pi appears to be able to send messages using it, so fingers crossed a long-range test will work. I might need something a little hardier than paper straws, though...

[Max Dymond]

As September draws ever closer, I'm starting to worry about other stuff.

• Considering getting a Drift Ghost XL camera as a primary/secondary camera - it's got a claimed 9 hour battery time, which seems decent. And it's 133g. FOV can be set to 90 degrees too.
• Trying to find a good source for Expanded or Extruded Polystyrene boxes - any better places than eBay I should be looking?
• GPS antenna - is something like https://www.amazon.co.uk/Active-Antenna-Connector-Navigation-Stereos/dp/B01BML4XMQ ok or should I be thinking a bit smaller? (The amount of cable is quite long with these, because they're meant for cars...)
• Still need to source an Rx antenna but I have the suggestions in this thread.

Once I have the payload box and can put everything in it, then I have to worry about helium, parachutes, balloons, and how to fill the balloon. Easy 😅

[David Akerman]

Re the Ghost XL camera, I've not tried it, but in general keep cameras away from the GPS antenna in case of interference.  Definitely test the assembled payload for this.

Re cases, Steve (Random Aerospace) sells them.  Also Hobbycraft have some small boxes but probably too small with a camera included.  That said you can glue 2 together for more space.  Remember to use UHU Por glue, or possibly hot melt (but don't let it get very hot as it'll just melt the foam).

That GPS antenna is fine, though it has a long cable.  I cut the cable to save weight, and replace the SMA plug.  Speaking of which, some models have an "RP-SMA" plug which has no pin and will not work.

Dave

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[John Laidler]

You can get small sheets of expanded polystyrene on places like Amazon and no doubt eBay. Using these you can build a payload container in layers. I've found the 20mm thick sheets best.

John

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[Geoff Mather]

I use the Ghost XL myself, not for a balloon flight however, it certainly has an excellent battery life and is certainly moisture proof.  Do test your device well, there are various reports of problems, I've not had any serious ones myself, but it has been known to change mode on its own a couple of times over the last 2 years I've been using it.

[Max Dymond]

So, after a week of waiting and an evening of convincing my Raspberry Pi Zero that it really does have access to the internet, I finally got the Hab Gateway installed and running on my Rpi Zero with the recommended LoRa 433MHz hat from Uputronics. And... I'm not receiving anything from my tracker on freq 433MHz 😥

I think my problem here might be not knowing how to translate the SX1268 parameters into whatever configuration settings I need on the Lora-Gateway software - I'd hope for at least "I got a message but I don't understand the format" from the gateway.

(For reference; I've configured the SX1268 with frequency 433 MHz, address 0 (???), air speed 2400; and I don't even know if it's possible for it to talk to the HopeRF chip but I'd hope it would be.)

Getting late for tonight; probably will bash my head against it a bit more tomorrow.

[David Akerman]

Can you set the bandwidth, spreading factor etc individually?

If so, use these settings:

Explicit mode, error coding 4:8, bandwidth 62.5kHz, Spreading factor 8.

And set the gateway to mode 2.

Mode 2 has a fairly high bandwidth which means that frequency offsets between transmitter and receiver won't be enough to stop it working.  Once it's working then a better mode for range can be used.

Dave

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[Max Dymond]

Looking at the datasheet (https://www.waveshare.net/w/upload/6/62/DS_SX1261-2_V1.1.pdf) I think the answer is maybe; It looks like there's a "SetModulationParams" function of the chip that would allow those settings to be made. I'll have to look into how I would actually call that.

[Max Dymond]

Did a bit more investigation into the Waveshare hats and I think I'm just going to bite the bullet and get a 434MHz hat from Uputronics. After that I expect I'll probably just be able to run the PiInTheSky software, which does render a whole lot of work moot 😞

(Basically I looked at what the Waveshare Python code was doing and it looks extremely close to https://www.manualslib.com/manual/1902714/Ebyte-E28-2g4t12s.html?page=12 which gives you configuration of only a handful of options, none of which are error coding, bandwidth or spreading factor)

[Max Dymond]

With loads of thanks to Dave for guidance, I managed to install PITS and get my Pi talking to the LoRa gateway! Success, though I lose the capability of video capture on the Pi (unless I hack the snapper into calling raspivid instead of raspistill).

So, my next question is I think one of weight. I need to:

1. calculate the weight of box + raspberry pi payload + battery pack + action camera + line + mounts + gps aerial + kitchen sink
2. calculate the right balloon, parachute, and quantity of helium for those bits using the Random Engineering calculators and predict.habhub.org to get to 35000Km (which seems by consensus to be a sensible "edge of space" target without the payload tending to end up in the sea, or France)
3. order those bits ASAP so I can start construction...

I feel like getting the LoRa broadcast working is a good milestone 😅

[Ben Z en de rest]

35000 km 👍 go go go for it !

Op wo 7 sep. 2022 23:22 schreef Max Dymond <maxmak...@gmail.com>:

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[Max Dymond]

Would just appreciate a double-check on my numbers before I go ordering stuff from Random Engineering please!

So:

• Totalling everything up my payload is going to be about 600g (including the parachute)
  • Camera    146.83
  • Pi and Hat    35.82
  • GPS module and cables    70.77
  • GPS antenna    36.85
  • RPI camera    8.84
  • 6xAA Lithium    90.77
  • Power pack and rectifier    28.38
  • Aerial    27.03
  • Camera mount    9.23
  • Payload box - 2.7l    90
• I think that means I should get:
  • a 1200g balloon (e.g.  Hwoyee HY-1200)
  • a 24" parachute (e.g. RocketMan 2ft)
  • 2.61 cu m of Helium (e.g. BalloonHelium.co.uk) 
    
  • 1.5mm braided nylon cord

which should get me to 35Km, for a flight time of roughly 2 hr 45m

Does that all sound plausible? Should I be buying anything special for getting the helium into the balloon?

[Kevin Walton]

Hi Max

For getting the Helium into the balloon most of us concoct something to step-up the pipe size.

There is an example here:

https://ukhas.org.uk/ideas:balloon_filler

And a other here:

https://ukhas.org.uk/guides:fill_tube

Or a picture of mine attached (I have only got a 10 bar regulator, hence the needle valve).

Cheers
Kev

[John Laidler]

I don't know the details of the components you are using but some of them seem very heavy. For example, a GPS antenna should only be a few grams, you can form one out of a couple of bits of copper wire, or buy one of the Uputronics GPS units which with the antenna on the chip weight next to nothing. Similarly, the annena for the radio only needs to be short length of copper wire.

Not sure what the power pack and rectifier do and an RPi will run perfectly well from 4 AA batteries. 

I think your biggest issue might be the cost of the He needed to fill a 1200g balloon. You will also need to factor in that in my experience those disposable containers don't always hold what they claim so you will need to order a few spares to make sure you have enough.

You might want to consider a first flight with a much smaller balloon, leaving out the heavy camera, to test the payload works as expected at altitude before you commit to the much larger balloon.

John

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[Kevin Walton]

Good advice John, I went 'all in' on my first flight many years ago, and it landed just off the coast of Kent in the Channel with all the equipment I had on board - sadly never recovered.

Smaller balloons - the 5 packs of 100g for example are a great option.

Cheers
Kev

[Max Dymond]

Thanks for all the responses, let me try and address them.

• Kev: thanks for the links for the balloon filler, I'll look into them.
• John+Kev:
  • My guiding principle behind most of my decisions here has been redundancy and known-good components wherever I can. 
  • I'm hoping to shave a little weight off here and there where I can, so the total could go down.
  • The second camera decision here is to make absolutely sure I'm going to get some images and video out of this flight, assuming recovery.
  • My GPS antenna was this SMA one from Amazon: https://www.amazon.co.uk/gp/product/B07ZBVFHBS . I didn't fancy making a GPS antenna and this one seemed fine. The module I have known-working is an SMA connector.
  • The power pack and UBEC feed the Pi a "known" 5V - I know the Pi is a little tolerant of higher voltages but I didn't want to let the blue smoke out. Also, by going with 9V-worth of batteries, the run-time of the Pi should be quite long, which means the buzzer I'm planning to add will also be running for a long time.
  • I don't really mind the cost of the balloon and helium.
  • I'd love to do a first flight if possible but time and spare weekends are unfortunately against me, so it's unlikely to work, logistically.

I think fundamentally I know that there's significant risks of failure here, but I'm happy to try anyway.

Thanks,

Max

[Max Dymond]

I just received a Raspberry Pi Zero W, which means that now I actually have a camera port to plug the camera into... (Raspberry Pi Zero, why no connectivity!!)

Thought it'd be nice to post a photo of everything connected together and working!

Got the piezo buzzer working this evening, so hopefully that's a bit of added detectability. With any luck the payload box comes tomorrow, so I can start construction proper.

I ordered a balloon, parachute and cord from RandomEngineering so hopefully that's going to be delivered in time.

I discussed with a few people on IRC about helium; I did send an email to Steve wondering if we'd be able to do hydrogen instead but no response. If I don't get anything soon I'll have to just go with helium instead because there's a bit of a lead time for fulfilling helium.

Getting closer!

[Kev Walton]

Hi

You can get Ethernet over USB on the Pi Zero, and then connection sharing to give it Internet.

A Google will show you how.

Cheers

Kev

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[Max Dymond]

Payload box has arrived - total weight without parachute is currently 448g (though I expect that to go up a bit). Still no response from Steve - probably going to have to pull the trigger on helium soon.

Wondering what the best way of mounting my action camera is going to be - do people mount inside and make a hole in the box? Or mount it on the outside?

[Kevin Walton]

I would go with a 'funnel' shaped hole, keeping the camera and battery in the warmth and protection of the Box, but allowing a full view to the outside world.

Camera might be fine outside, but why risk it if you don't need to?

Cheers
Kev

[John Underwood]

The only time I ever had a problem with a HAB camera was due to overheating within the insulated box. Remember that you don't have any significant convection up there so there is nowhere for the camera heat to go. I have never had a problem with a camera outside the box.

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[Max Dymond]

I went with a funnel hole, which appears to be working nicely. I put everything together this evening and currently the tracker is sitting in my freezer happily pinging away, sending me pictures of the inside of my freezer. I'm going to let it go until the batteries give out - I bought spare lithiums to test.

I'm going to sort out a helium booking now - then the only thing left is balloon, parachute, line and fill tube (the first three of which I'm hoping to receive in the very near future...)

[Max Dymond]

Ok:

• helium booked, picking it up Thursday
• Steve has responded and we're in sync about balloon, parachute and lines
• I did a range test this afternoon - as best I could - wandering around in a park in Nottingham; signal was pretty good but thwarted by trees (thankfully there are no trees to get in the way in the sky)

Not sure what more I can do on the planning front! There's still an open question of the thing I'm going to be photographing but I'm aiming to solve that early next week 😅 sorting out the mount for that shortly as well.