UHF radio control for submarines (openLRS, LoRa, FSK etc. on 458Mhz and 433Mhz )

Registration finally worked for me so I have been looking at a lot of the detail of Tim's methods including   a very interesting (and forward looking) lecture. (Thanks also to Tom for making the video.)

Just some notes about some joint trials with David J at Barrow today.

Some conclusions:

- We operated 2 sets of the 458Mhz gear together without significant interference.

- Dave was using the "as supplied" aerials and these were giving reception problems. We swapped the TX aerial for the one I bought from Flytron and used the shorter (175 mm active length) home made one (as in the photo) and this combination gave significantly better reception.




The photo shows the small 1/4 wave antenna I used today in my small Holland class sub and the half wave antenna I have used in the larger Charlie class with good reception. The numbers give the active length of the aerial (i.e the wire length in mm beyond any coaxial screening.)

It is worth pointing out that these aerial lengths are not optimised for the 458 frequency. I really need something like Tim's LCD monitor (on order) to measure RSSI more accurately before we can improve this much.

Another observation was that the lost model beacon transmits from a depth of 4 feet of water with a short range of about 100 feet. So it would be quite useful for lost model location. (As long as the radio battery holds out.) But it comes for "free" with the openLRS technology anyway. This range was achieved with the short 1/4 wave antenna shown in the photo. This aerial was giving control of the Holland class sub on the bottom at 4 feet without going into failsafe.

The 175mm is not what is shown on the photograph it would appear to measure 100mm?
The trials today showed no interference between the two sets, I was getting glitches, but range checks appeared to be ok, I wondered if the RF from the RX switched off, might reduce the problem, I also had 5 servo's coupled in with no serious interaction. It looks a good system.

Regards Dave J

You are right, David!

Sorry I must have made a measuring error.

But that it the one I used and it seemed to work OK. So use that one until we know better with proper signal strength measurement ( Step the dimension off from the photo- don't count the coax bit. Or use the 332mm one - I think I  measured that one OK?!

It is obviously a rugged system this!

David

30th April 2015.

I'm editing this post rather than put this in as a reply- A summary for those of you out there trying different aerials, my findings so far.

- Half wave, 332 mm long
- Quarter wave, 166mm long.

Both of these are giving good, useful ranges in models out on the pond.

I've just been trying the 166mm long in my Holland 1 and it is a neat aerial for small models. The range is all the way out to "which way round is the model pointing."

These trials are done without measured signal strength (I'm still waiting for the FLD-02 FrSky LCD from Hobbyking) but I'm listening to lost "packet beeps" with the Telemetry turned on.

Just a quick note on this - I'm trying to get subs in the water!

The FrSky LCD screen has arrived - very neat.

I have wired it up using the single transistor invertor (thanks for the guidance Tim) (I will put more wiring details on here when I get a chance.)

The panel seems to be working nicely for signal strength. The first observation seems to be that the TX aerial supplied is pretty good and about as good as the one I bought from Flytron.

The quarter wave RX antenna in the Holland seems to suffer short range - so more development work needed. (I'm puzzled because it worked well initially.)

Dave J reports that he has the 458Mhz setup working nicely in one of his subs.

Hobbyking continues to be a good supplier and please note that I am buying this stuff myself (no freebies!) Fortunately this openLRS stuff is very economically priced.

This technology on 458Mhz is getting to be fairly "mature" so I thought a bit of a summary of where we are would be useful. I have also been asked to give a "keep it simple guide" to someone wanting to start with it. So here goes:

Summary:

- We have now had two modellers using this system at a pond without any problems.

- A number of you reading this will have seen me using the gear all day at Bournville without any problems.

- I have connected up the FrSky LCD module and data hub and used it to monitor signal strength, temperature and battery voltage. I will publish a detailed connection guide shortly but my personal conclusions so far is that it is not as useful for submarines as it obviously is for aircraft. Of the two modules, the TX mounted signal strength LCD display is the most useful, certainly for helping setup aerials initially. I actually prefer to use the "lost model alarm" built into the openLRS software. I use a cheap Walkie Talkie to monitor this and once you hear the Close Encounter theme you are getting out of range!
I don't use the telemetry option because I find this causes mild servo jitter - I don't yet know a fix - interference presumably.

- I have used this gear in several ponds with several model subs and the range is perfectly adequate using the normal "as supplied" 433MHz aerials. By adequate range I mean as far out as you can see the model. Submerged range is also fine. (I think I was initially a little too concerned about making special aerials. Range gains are likely to be small.)

- The only model specific problem I have encountered has been with metal superstructure screening the aerial in my Russian Nordenfelt.


A simple get you going guide.

(I will just describe the basic steps. If you need more detail go back through this thread and Tim's excellent threads on SubCommittee and SubPirates. My setup is a plug in module on my Futaba 9C Tx.

(a) Purchase the Orange 9 channel RX and TX module from Hobbyking. You will also need a PC running a Chrome Browser, a USB cable and a 3.3volt "Dongle". (Read back in this thread for the ordering info.)

(b) When you get this try it "straight out of the box" and it should work. (Don't use it for very long because you will be transmitting continuously on 433MHz which is illegal in the UK.) Try the spectrum analyzer function while plugged into your pc and see if you can pick up your car keys when you press them!

(c) Connect your PC up to the dongle and plug it into the pins on the TX module. (Make sure that the "DTR" pins line up. You will see this written on the back of the board. You will need to take the board out of the yellow plastic box. Most people cut a slot in the box to access the pins for later use.)

(d) Get the Chrome browser up and running, load up the "openLRSng" app. You will see a screen with various buttons including a Firmware Flasher  (bottom LHS)

(e) Click on Connect. You may need to click a few times before it says that you are connected (Top LHS). Then click on Firmware flasher. Select your module on the drop down box and then flash the firmware and the EEPROM. Unplug the dongle and connect up to the RX and repeat the process after selecting the correct RX. This has put the latest open LRS software into the RX and TX.

(f) Now to setup the profile/configuration in the TX and RX. (You only need to plug the dongle into the TX because the RX is configured by wireless) Plug the dongle into the TX module. (You don't need to power up the transmitter at this stage - the module is powered by the dongle.)
Click on connect and then on the TX Module button. A number of option boxes open up but fortunately you don't need to change much - frequency is the key one. Put a frequency between 458500 and 459500 kHz in the operating frequency box. (3rd box down on the LHS) Surface modellers are recommended to use the lower half of this band. I chose 458750.
- I suggest you select Telemetry - No - maybe try it later?

Click on Save to EEPROM (Bottom RHS) to finish.That is about it for the TX.

(g) Click on the RX module button and you will get a whirly wifi symbol. Power up your RX. A beep and the RX screen will come up.

Again not much to change. I've put a model location beacon frequency of 446043750 which transmits the Close Encounters Theme on channel 3 of a Walkie Talkie. I've set the Failsafe Delay and Beacon Deadtime delays to 10 seconds. (Yes it has Failsafe on all the channels. You press the Failsafe button on the back of the module to set them.)

Click on Save to EEPROM when you have done. Click on Disconnect.

(h) Now to do the Binding and you are away. Unplug the dongle. Switch the transmitter on while holding the Fail Safe Button. Release this Button when you get a single beep. You now get rapid beeps from the TX. Power up the RX and when the beeping stops, power off and then on at the TX. You will then find that the controls work on the model. Congratulations!

(i) You can try the whole process again until you feel relaxed about it. One of the nice things is that being open software you can access everything and it is in text files. If you look along the bottom of the configuration/profile  screen you can see various options including Restore Default  and Backup this Profile. It is worth Backing up the Profile when you are happy with it. You can inspect it easily because it is  text file. The profiles I use are shown below:


{"type":"TX_single_profile_backup","firmware_version":898,"configurator_version":"0.53","obj":[{"tx_config":{"rfm_type":0,"max_frequency":463000000,"flags":1342177280,"chmap":[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]},"bind_data":{"version":56,"serial_baudrate":115200,"rf_frequency":458750000,"rf_magic":2367824339,"rf_power":7,"rf_channel_spacing":5,"hopchannel":[65,54,75,25,71,57,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"modem_params":2,"flags":2}}]}

{"type":"RX_configuration_backup","firmware_version":898,"configurator_version":"0.53","obj":{"rx_type":1,"pinMapping":[33,0,1,2,3,4,5,6,7,38,38,36,37],"flags":2,"RSSIpwm":255,"beacon_frequency":446043750,"beacon_deadtime":0,"beacon_interval":20,"minsync":3000,"failsafe_delay":100,"ppmStopDelay":0,"pwmStopDelay":0}}

Hi all.

Thought that this may be of interest to the soldering iron brigade.

Its a Aircraft site (no engine reverse) and 2.4Ghz but no doubt a 458 module will substitute

http://www.singlechannel.co.uk/

ARCHIVE  tab

P16 and P 17 for schematic and Arduino C code

(can anyone add reverse and change arduino C to PIC assembler or basic??)

John

I promised to post details of how to use the telemetry options of openLRS with the FrSky Display screen and Telemetry Hub.

(John - I am not sure about converting C to Assembler because one reason to use C is that it stops it being specific to just one device. You may be able to do some conversion within the Microchip C compiler, but I haven't looked.)

The display screen mounts on your transmitter and  gives a wide set of options to give you data - most useful for aircraft, it has to be said.

The Telemetry hub goes at the receiver end and you can plug various sensors into it. It is designed to be used with an FrSky receiver but the clever openLRS community have included its use in their software.

First thing though is should you use the telemetry option?

Plus points:

- Signal strength data is very useful - it shows both the transmitter and receiver signal strength.

- Getting data back form the model sub is novel and could be useful e.g battery voltage for Lipos , or depth perhaps.

Minus points:

- I find the telemetry option gives servo jitter.
- The data hub and sensors contribute to the "cable jungle " in the close confines of model subs without adding that much to functionality. (I operate my subs more in "seat of pants" mode!)

Overall my conclusion is that I will only be using telemetry for setting aerials up or getting initial data from subs during development. For day to day sub operation I will just use the simple setup I outlined earlier in conjunction with a Walkie Talkie. The Walkie Talkie provides a useful signal strength indication and has potential for lost model detection. (I will always continue to use an audio Pinger.)

But here goes - the connection data for the telemetry modules:

First get your hardware. Copy of my order and what I paid at the time:

OrangeRx Open LRS 433MHz 9Ch Receiver 1  US$19.95   IN STOCK
FrSky FLD-02 Telemetry Display Screen 1  US$19.95   IN STOCK
OrangeRX Open LRS 433MHz Transmitter 100mW (compatible with Futaba radio) 1  US$19.99   IN STOCK

FrSky Battery Voltage Sensor - FrSky Telemetry System. 2  US$2.46   IN STOCK
FrSky FSH-01 Telemetry Sensor Hub 1  US$14.10   IN STOCK
FrSky TEMS-01 Telemetry Temperature Sensor 2  US$3.19   IN STOCK

FrSky FLD-02 Telemetry Display Screen 1  US$19.95   IN STOCK
OrangeRX Open LRS 433MHz Transmitter 100mW (compatible with Futaba radio) 1  US$19.99   IN STOCK

FrSky Battery Voltage Sensor - FrSky Telemetry System. 2  US$2.46   IN STOCK
FrSky FSH-01 Telemetry Sensor Hub 1  US$14.10   IN STOCK
FrSky TEMS-01 Telemetry Temperature Sensor 2  US$3.19   IN STOCK


You will also need to get out your soldering iron and get very few electronic components to assemble 2 simple little inverter circuits. One for the TX and one for the RX. Make it up in "dead bug" mode just soldering the component leads together as in the circuit diagram. The circuit diagram follows:




The diagram comes from the openLRS wiki (a very useful source of information:


https://github.com/openLRSng/openLRSngWiki/wiki

Tim S gives a lot of background on the telemetry, photos of the setup and the reason for needing the inverters on the SubPirates Forum.

You can use almost any small signal NPN transistor. (I used a BC548 because I had some handy.)

LCD Monitor on TX

I will now describe how to connect up the data monitor on the TX to the openLRS TX module. I refer to the labels on the circuit diagram.

-Connect the TX pin on the Orange module (This is the 2nd pin from the left, next to the DTR pin)  to the TX connection on the inverter.

-Connect the 3.3 v pin on the module (4th pin from the left ) to the +3v3 connection on the inverter.

-Connect the GND pin on the module (5th pin from the left) to the GND connection on the inverter.

- Connect the Smartport connection on the inverter to the TX pin on the Monitor. (2nd pin from Left)

- Connect +3v3 connection on inverter to +5v pin on monitor(3rd from Left)

- Connect GND connection on inverter to GND pin on monitor (4th from Left.)

Plug the module in, switch on the TX and the display should light up. Rotate and press the selector switch (opposite side to the plug pins) to go through the pages.

Sensor Hub  at RX

Next using the sensor hub. (You will need another inverter circuit.):

(In the latest edit I have included some later information from Tim S about battery voltage monitoring. Thanks Tim.)

The Hobbyking orange receiver connections are given here:

https://github.com/openLRSng/openLRSngWiki/wiki/Hardware-Guide

Connections to Orange RX pins next to the aerial. (DTR pin is next to aerial.)

- Connect GND pin (2nd pin from left) on the Orange RX to GND on the inverter.

-Connect 3.3v pin (3rd pin from left) on the Orange RX to +3v3 connection on the inverter.

- Connect RX pin on Orange RX (4th pin from left) (DTR is 6th pin from left) to SmartPort pin on inverter.

Connecting to sensor hub:

-Connect 2nd pin from the left on the Data connection of the Sensor Hub to TX connection on inverter.

- Connect 4th pin from the left (GND) on the Data Connection of the Sensor Module to GND on the invertor.

- Connect servo type cable from + - on sensor hub to any free servo connector on the RX.

Plug a sensor in (temperature is simplest) and you will see this come up on the LCD display. Hold the temperature sensor and you will see the temperature rise. Unless you are cold-blooded!

If you want to monitor battery voltage you will need a voltage divider network either home made or from FrSky. Connect the 0 to 3.3 voltage from this to either Port 10 (The SDA connection) or Port 11 (The SDL connection.) on the RX. (These connections are at the top LHS of the RX board. They don't have connectors fitted and so I soldered pins to Port 10 & 11 so that I could connect a trailing lead.)

The LCD display now gives you battery voltage. (Adjust the voltage divider in the LCD display software to get the right value.)

The next thing I intend to try is connecting an Orange TX module to any transmitter with a trainer plug. (I have a lot of old transmitters including ones for 35Mhz that could do with a new lease of life. I imagine you have too!)

Query?

3v3 seems to be used a lot with these 433/458 modules. Is this just a programming "enable" voltage or the main supply voltage?

Anyone got a link to the data sheets?

John

I think that it is the main supply voltage. (The voltage trend for microprocessors seems to be downward to reduce heating, perhaps?)

All this stuff seems to be based on WiFi and mobile phone technology. If you look on the boards you will see a little sub board which is the radio frequency side, I think. You may be able to get data on these sub-modules - I don't know I'm just a user!

Further research reveals some Technical info on the HobbyKing website and that the RX and both TX modules are fitted with voltage regulators (3v3 I assume)

for operating conditions:-
RX module requires 3v7 to 15v
Futaba TX and JR TX modules require 6v8 to 12v

So normal battery systems can be used for operation but NOT for setting up/programming where 3v3 MUST be used.

My order for rx / tx modules and other bits went in today.....


David - I think you did a double paste of your latest shopping list.
          ( or are you on commission for large orders? )


John

I understand your question better now - so you CAN feed more than 3.3v to the board supply.

And no I don't get commission or freebies.I have made quite a number of purchases 3 x RXs and 2 x TX modules to - date. Fortunately this Hobbyking Orange gear is low cost but seems reliable and well-made.

I have re-equipped my whole fleet and I don't intend to go back to 40Mhz. Just avoiding the dreaded peg board is reason enough for me!

David

guys,

the openlrs based rx and tx modules actually have multiple power rails. for the RX, that would be the traditional power feed via one of the servo pins. max voltage there is 6v, but there is also the bank of programming pins (DTR, tx, rx, vcc, gnd, etc) that is a direct VCC set of pins from the arduino. due to the fact that the RF module (on the RX and TX) is driven at 3.3v, VCC for the board has been set at 3.3v... any higher and you fry the RF module (hopeRF RFM22b or hopeRF RFM23BP).

same goes for the TX module, it has a set of pins that line up with pins on the transmitter and pins that are for programming. transmitter side can be as high as 12v, but programmer must be 3.3v

both set of programming pins (rx and tx) follow same pattern, the pattern used by a standard FTDI programmer. so, to program the rx and tx, it is easiest to use a 3.3v ftdi programmer to connect the devices to your pc.

David, join the club, i now have 9 receivers and 4 transmitter modules. i won't be going back to 75mhz unless absolutely mandatory.

1 of the receivers and two of the transmitter modules are special testing devices, but the rest will be used in submarines.

that does not include one transmitter module i accidentally destroyed. (blew out the RF module by turning it on without an antenna attached)

my final post for the moment... i don't know if i have noted it on my subpirates thread, but there is a "missing" pin on the OrangeRX receiver that needs to have a connector soldered to it to get the main motor battery voltage fed back thru the telemetry. I will need to take a look on my subpirates thread, and i will add it there if i need to.

for the electronically enlightened, it is port 10 or 11 - either can be used, on the OrangeRX module noted on this page of the OpenLRSng web wiki:

https://github.com/openLRSng/openLRSngWiki/wiki/Hardware-Guide

that 4 pin connector no longer comes soldered onto the pcb from the factory, so to use it, one must solder a connector into place. (or a wire directly to the individual pin)

Many thanks Tim for the info on voltages and a grim warning about not plugging an antenna in!

Also thank you for the information about the missing pin connection. This is probably why I couldn't get the battery voltage input working. (I used one of the analogue (temperature) inputs instead through the FrSky voltage divider board but you then don't get the correct scale and units on the display.)

The main problem I am having with telemetry is the pesky servo glitching! Whenever I switch in telemetry the servos start to buzz. Control of the sub is still OK but it is not good for servos or battery life.

Is this a problem with 433Mhz? (Perhaps flyers don't have this problem - more chance of interference in a subs packed interior?)

David

david, it is a problem associated with 433.... and telemetry... the problem is 3 things:

1) when you turn on telemetry, the receiver is now transmitting 50% of the time, so it is now the largest rf emitter inside the submarine. forget about capacitors on a brushless motor, this makes that look like the radar outline of a duck vs a b52

2) the "antenna" wire lengths needed to carry that signal out to the servos (as interference) is only 6".... about the same length as a servo wire.... in the 75mhz and 40mhz world, that length needs to be over a meter.

3) the antennas that all the systems ship with are monopole. they aren't grounded in any way (dipole), so they are less efficient and generate more noise.


it seems to vary from submarine to submarine. my skipjack and delta are completely un-affected, while my blueback suffers so badly that the servos actually twitch about an 1/8th of an inch.

in order to even make my blueback work, i had to wrap the servo wires around ferrite rings to kill the interference. something like this: http://www.ebay.com/itm/301198587261?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

i put one of those on every servo wire (including esc)

those are the exact ones i bought, and they dropped the interference to a point where the sub can now work. I assume that if you have room to install a proper dipole antenna, that would reduce the interference as well.

Many thanks for the information. I find it amusing that I have just been cheerfully removing all those ferrite rings only to have to put them all back!

(I used to use them a lot on 40Mhz gear in the "belief" that they cut down on servo glitches.)

Certainly one of the very nice things about this openLRS UHF equipment is the smooth response without glitches. So it is a shame that the telemetry introduces interference.

I wonder if a way out of this issue couldn't be done with a
modification to the openLRS software itself?

Would it be acceptable to have telemetry data less frequently? Perhaps only on demand?

If so a signal from the transmitter could be used to turn telemetry on briefly.

(There is already a similar feature in the lost model beacon part of the software. Pressing the walkie talkie transmit turns the beacon on. This works well.)

Some shots of  Dave J's excellent Type 9 operating on openLRS.


https://www.theassociationofmodelsubmariners.com/t1555-furness-mbc-regatta-barrow-june-2015#9567

Another pegboard heads for the skip! (Although my range problems with the Turkish Nordenfelt indicate that there are still some wrinkles which need to be ironed out.)

David

John Wrennall wrote:Query?

3v3 seems to be used a lot with these 433/458 modules. Is this just a programming "enable" voltage or the main supply voltage?

Anyone got a link to the data sheets?

John

It appears that today is not a day where my focus is at its best.... lets just say, i have answered the 3.3v question, as well as others.... but, for completeness, here are links to the data sheets.

the systems use the HopeRF rfm22b rf module for the 100mw setup, and the rfm23bp for the 1 watt setup, here are hopeRF's spec sheets:

http://www.hoperf.com/upload/rf/RFM22B.pdf
http://www.hoperf.com/upload/rf/RFM23BP.pdf

I just noticed that the OrangeRX 100mw futaba transmitter module on hobbyking.com is selling for $9.99

Good news about the reduced price for Orange modules.

It is rather important to us that they carry on selling and making them. We wouldn't want the market to dry up for us as it has with lower frequencies.

I have been doing some more antenna trials, mostly to solve the short range problem I've been having with just one model. (The Turkish Nordenfelt)

I re-configured the telemetry option to help with this displaying on the LCD screen.(Tim's suggestion to include some ferrite rings does reduce the servo tremor.)

I put in  a home made aerial (175mm) which was in water (insulated but sticking through a bulkhead into the free flooding area.

It worked as well as the previous aerial inside the WTC - but still gave about half "normal" range!

It is puzzling because I use the same WTC  with the Turkish Nordenfelt and get good range. The range seems to be specific to this one hull.

At the same time, I re-commissioned my Holland 1 with open LRS. This has a great big aluminium sealing ring, great big aluminium piston tank  and a brushless motor. You would probably expect range problems with such  a packed small model  but it worked fine over 100's of feet - until you couldn't see it to control it!

So all together rather puzzling but I will carry on the experiments with the Turkish Nordenfelt.

Hello David,
                   I have been following this thread with some interest because although I have several Futaba M6 Tx and Rx outfits on 27meg which should last my sub modelling time, progress is slow, I always feel it's a good idea to have a plan B handy, government being as it is. With regard to your problem with just one particular model led me to wonder have you used any carbon  fibre or aluminium filler powder in the construction which presumably is grp? Or even metalised finish or primer?

               Trevor

I have a friend who built a sub with carbon fiber, guess what does not go through it? Yes, radio signal.

Thanks all!

No, the hull is fairly standard grp using polyester resin. Halfords plastic spray primer and satin black topcoat.

My budget didn't stretch to carbon fibre, Tom! I don't think any of those paints contain metal and we did a range test in air which was fine (screening would have affected this, I think.) The problems seem to start when the model is in water.

The model has long brass control rods and a brass prop shaft (all about 500mm long)

I initially thought that the problem was the extensive metal superstructure but I have replaced it all with ABS (Plasticard)

Next thing to try is swapping receivers (I'm told that Hobbyking stuff can have variable quality control.) or could it be some diffraction phenomenon (the shape of the water over the WTC??)

Overall it doesn't mean a problem for openLRS, plenty of subs with no problems. It just makes its use more interesting!

(This sub will be going to Norwich "as-is" in any case.)

David

is there any chance the water is getting to the antenna wire core? If you swap thar RX to another boat that has the antenna in the wet does it work. I guess I am saying does it follow the antenna, RX, or boat.