Rocket tracker & monitoring thing

[strud]

So after the great post by Drew on rocket tracking using APRS etc, I realised that with devices like the new Yaesu FT3Dr a nice all in one solution (nearly) is possible (phone or similar still used for wireless GUI to configure system and get live view).

So I made up a PCBA design incorporating the following:

- GPS receiver (Titan2) with integrated patch antenna
- SA818 1W walkie talkie radio module (2m and 70cm versions available)
- ESP32 devkit module as brains with Wifi and BLE transceivers
- DTMF decoder
- 4 channel output module with continuity monitoring
- 4 independent voltage monitoring channels (eg for battery monitoring)

This supports the following user stories:
- When the rocket is on the pad
- I want to know the voltage of all my batteries
- I want to know if all my charges have continuity
- I want to remotely enable/disable devices/functions

When the rocket is in the air
- I want to know my rocket's location
- I want to know if my charges have fired
- I want to send remote commands to my rocket

When the rocket is on the ground
- I want to see the results of the flight immediately & wirelessly
- I want to disarm/turn off devices wirelessly

So the location function will be implemented using APRS and hence a nice combo HT will show you this information directly
The same HT can be used to send the DTMF commands.

The ESP32 will implement a WiFi AP and serve Webpage(s) enabling the GUI function from a phone, laptop, tablet etc without the need for any apps.

The first prototype will be with the 2m (144MHz) radio variant to maximise range. This is a 1W module, but 2W versions with same footprint are available so if more power is required this is an option.

Here are the board design pics:







Code will be developed using Arduino IDE and happy to share once it's up and running.

Going to buy some blank boards now from PCBway.

[strud]

Got the boards yesterday and put one together (minus radio and buzzer) last night and this evening.

Topside - GPS module topleft (Titan2), below GPS module is DTMF status leds (from left DTMF valid, bit3, bit2, bit1, bit0, arm status)

To the right of these is the missing buzzer, then to the right of that radio TX and RX status Leds.

Below all of that is the ESP32 Devkit module



Backside - (top left) Radio ant SMA, with LPF (160MHz cutoff), (next below) Missing SA818 radio module (to be installed once other items are debugged further), (centre) DTMF decoder (bottom) dual ch N fets for outputs



Close up of status Leds




Close up of LPF, 5th order 160Mhz




One issue that caused me some grief is that the doco for the ESP32 board lists the 2nd pin from the bottom on the left as CMD, however on the board and in some documentation this looks like GND..... so my board had this pin grounded and the ESP module was basically continously rebooting until I worked this out.......

Will crank on the firmware for a bit now before I then install the radio and play with it.

[strud]

Spent some time over the weekend resolving a few issues with the board/pin mapping conflicts with the ESP32. It mostly was caused by the odd minutiae of the ESP32 that I am now mostly understanding but obviously was not fully aware of before I sent the boards off to be made.....

Anyway, there is only 1 cut track and 2 wires...

Anyhow, on the firmware front I made a bit of progress tonight.

Have 4 tasks running across the 2 cores on the ESP32, DTMF state machine, GPS parsing, Webserver + WAP and APRS (empty shell at the moment).

- GPS parsing running (NMEA coming in at 9600)
- Web-page server with super basic page showing GPS info working
- Wireless Access Point working

Basic demo was this unit outside facing the sky, with me inside connected to WAP with my iPhone showing the basic webpage using no other infrastructure ie not running through the household router etc.

WAP shown as "RocTrak_WAP"




Basic webpage screenshot off my phone. Super basic at this stage....




I have to say, these guys have fantastic learning/training materials for the ESP32, definitely worth checking them out:

https://randomnerdtutorials.com/

[Voyager]

Very nice development Strud! I hope to see that in action.
I agree about the randomnerd site, it's been very useful for my smaller ESP8266-based hybrid remote sensing and launch control setup. I should actually move to the ESP32 module for its extra I/O.

[OverTheTop]

Nice progress.

Anyway, there is only 1 cut track and 2 wires...

That's a good outcome for a first revision PCA.

[strud]

Got the radio module and DTMF decode working now.

Basic DTMF state machine working, allowing a basic arming and command mechanism. Example command of call back with tone shown in pics below.








I had some issues with the serial interface between the ESP32 and the SA818 radio. The doco for this radio is pretty poor, so a bit of 'try and iterate' was needed to get it going.

In the end I did get it running at 140.000 MHz Tx & Rx, 1W output with reliable detection of DTMF signals.

[air.command]

Very nice work on that Craig! It's been really interesting following this project. What kind of a range do you expect to get in the end when it is in the airframe?

[strud]

Hi AirCommand

It's a fun one for me too, since it incorporates a bunch of interesting functionality.

The radio within the rocket running at 1W and 2m should be capable of pretty decent range, how far exactly I'm not sure (only testing will really tell).

The antenna on the ground will be very important, more so for reception than transmission since it is much easier to run higher power Tx on the ground than in the rocket.

So with a pretty large margin for error, I think that a minimum of 10km with the vehicle in the air and a good antenna on the ground should be possible. I will do some actual range testing soon, but this will be just between hilltops so not as good as when the vehicle is up in the air.

If more range is needed (probably will be) more power is probably the only option for this form of communication. Other transmission schemes like LoRA are probably best to stretch the range right out without having to go up too much in Tx power.

As for this project, an easy upgrade from 1 to 2W Tx power is possible, since the 2W module has the same footprint. However, the 1W module is pulling about 750mA on transmit, so I expect the 2W version to pull at least 1.5A so battery energy will need to be considered carefully. The APRS transmissions are much longer in duration to a digital packet radio and hence use a LOT more energy for the same overall result.

I'm going the analog APRS approach with this device because it is more easily made use of by people with existing equipment. I already have a system that utilises a 1W digital packet radio so this is something completely different

[OverTheTop]

Nice work strud.

Increasing Tx power on the bird will not gain you much extra range without significant power increase. You need a 6dB increase in power to double your range. A 3dB increase (double power) will increase your range by 41%. You are fare more likely to improve your link by a better ground antenna, and that doesn't cost any mass on the rocket. You also get into the realm of having EMC issues on the rocket as Tx power goes up. This can usually be mitigated, but dealing with the aggressor rather than the victim is usually the easiest way to reduce problems (ie turn the power down!)

[strud]

Good points OTT, totally agree.

Not sure where the sweet spot is for Tx power on the 'bird' but I suspect over 5W might start to get difficult with induced currents in other devices although this can be mitigated with filters and shielding to some degree.

Something I'd like to work on once the current work load dissipates is a ground antenna system that contains the high gain directional antennae mounted on an auto tracking 2 axis actuator that simply points to the known or estimated location of the vehicle.

So many project opportunities.... if only work wasn't in the way

[OverTheTop]

Something I'd like to work on once the current work load dissipates is a ground antenna system that contains the high gain directional antennae mounted on an auto tracking 2 axis actuator that simply points to the known or estimated location of the vehicle.

That's something I have thought about doing too. Would work good on top of the Jeep. Not enough time .

[SpaceManMat]

Great project Strud

Does the TX have an adjustable power output? Was wondering if you could “throttle” the power based on the signal strength or even launch detect. Basically while sitting on the ground, potentially waiting a significant amount of time, you don’t want to use up all your battery. Once you launch you want to go to a higher power setting.

[strud]

Hi Mat

The radio has 2 power levels, 0.5 and 1W and I could use the uC to select this as you suggest.

When I iterate the board (will need to) can see if there is a spare digital out I can use for that since the current draw is MUCH lower ie significantly less than half.

[strud]

Have RocTrak board talking to the Smart Power disconnect board.

Debug out showing 3 channels (3 lithium batteries connected, Ch1 powering RocTrak board)

------------------------------------------------------------------------
Read start:
Voltage (mV) = 4011.230 3669.922 3948.242
Vsense (mV) = 0.175 0.000 0.000
Current (mA) = 17.548 0.000 0.000
Raw Power (HEX) = E6730 0 0
Power (mW) = 0.070 0.000 0.000
Energy (mWh) = 23.486 0.020 0.019


Read start:
Voltage (mV) = 3997.070 3667.969 3952.148
Vsense (mV) = 1.038 0.000 0.000
Current (mA) = 103.760 0.000 0.000
Raw Power (HEX) = 54EAC0 0 0
Power (mW) = 0.415 0.000 0.000
Energy (mWh) = 23.564 0.020 0.019


Read start:
Voltage (mV) = 3992.188 3668.457 3948.730
Vsense (mV) = 1.045 0.000 0.000
Current (mA) = 104.523 0.000 0.000
Raw Power (HEX) = 557530 0 0
Power (mW) = 0.417 0.000 0.000
Energy (mWh) = 23.673 0.021 0.019
------------------------------------------------------------------------

Updated web page



Formatting and number of significant figures definitely needs a tuneup, but happy it's working.

[drew]

Fantastic work mate!