[greggold]

A major development for RC control links for planes -ELRS- is becoming available with the Frsky Twin. However the new technology can also be used in Radiomaster, Taranis, QX7 and other radios, and its already in use for drones where ELRS has started to displace Crossfire.

Twin uses the leading open source protocols developed over many years for racing FPV to improve latency, telemetry, distance and signal quality.

Twin is a dual band system that Mawz says "using 1 FSK link (traditional 2.4G tech, same basic tech as ACCESS and TANDEM 2.4G and 1 LoRA link (same tech as ELRS, Tracer and Ghost on 2.4G, as well as all current 900MHz systems)".
(Mawz post #8 in https://www.rcgroups.com/forums/showthre...Lite-Radio)
Mawz post #22 says:
" That is really a sea change in the available RF performance for 2.4G systems and a major shot across the bows of the older solutions, especially for those of us flying in more challenging RF environments. And it's not one coming from the high-dollar brands, but rather two of the brands often looked down on as 'Budget' solutions and the hobbyist community itself."

Github provides a fuller explanation:
https://github.com/ExpressLRS/ExpressLRS says:
"ExpressLRS is an open source Radio Link for Radio Control applications. Designed to be the best FPV Racing link, it is based on the fantastic Semtech SX127x/SX1280 LoRa hardware combined with an Espressif or STM32 Processor. Using LoRa modulation as well as reduced packet size it achieves best in class range and latency. It achieves this using a highly optimized over-the-air packet structure, giving simultaneous range and latency advantages. It supports both 900 MHz and 2.4 GHz links, each with their own benefits. 900 MHz supports a maximum of 200 Hz packet rate, with higher penetration. 2.4 GHz supports a blistering fast 500 Hz on EdgeTX. With over 60 different hardware targets and 13 hardware manufacuturers, the choice of hardware is ever growing, with different hardware suited to different requirements."

For a good discussion of ELRS see Bardwell, including flashing ELRS onto a Radiomaster with a Frsky R9 Access module and a Frsky R9 access rx.
https://www.youtube.com/watch?v=-TGYy1psWgU
This module is available on Horusrc for $US55 and is compatible with various access Frsky radios including QX7 and Taranis. 

Bardwell says ELRS is a radio control link firmware that has the highest performance, longest range length, and lowest latency  compared to all the competition.

An ELRS module for Frsky Tandem txs is already available on Horusrc for US$70
https://www.horusrc.com/en/modules/dual-2-4ghz-module.
The only rx that currently works with this module (AFAIK) is the Frsky Vantac ELRS rx for US$ 13, but it is a drone rx with no PWM ports for servos. But other receivers and a Twin tx are in the pipeline. See below for rxs available now. I understand the current Frsky ETHOS firmware may require an update to run Twin.

[greggold]

The online experts I have learned to trust seem to agree that the firmware for airplane radio gear that we all use is obsolete. Maybe this is a factor in the interference problem some of us have experienced. I have decided to give ELRS firmware a try.

I have now paid 51 AUD to BETAFPV for 2 ELRS Micro Receivers - ELRS 2.4G V1.2, that have PWM ports for the servo plugs. This is the only ELRS rx I could find with PWM ports.

and
67 AUD to Fpvfaster for a BetaFPV ELRS Micro TX Module 2.4GHz. These prices include postage.

This module is stated to fit a Taranis X9d tx, which I have.

Assuming I can configure the ELRS, I plan to use the rxs in 2 small 80cm span 3d planes. The rxs only weigh 4 gm. Unfortunately each rx only has 4 PWM channels, but that is enough for these planes. It seems clear that soon many more ELRS txs and rxs will become available.

[greggold]

For a quick easy start in ELRS using a Taranis, see
https://www.youtube.com/watch?v=iir5wT_W28k
Notice: no downloads, no lua scripts, no complexity.

These are the 2 ELRS components used in the video
TX module:
https://www.fpvfaster.com.au/products/be...ghz?_pos=2&_sid=26bc0ae0e&_ss=r&variant=39686499565650

Receiver with 5 PWM ports:
https://betafpv.com/products/elrs-micro-receiver

These components are both available in Aust. drone shops, of which there must be about 100:
eg Fasterfpv; Fasterfpv (in Lidcombe) have sold out of the 500 mw betafpv module, but have the 1000 mw one shown in the vid still in stock for $20 more; the BetaFPV 1W ELRS Micro TX Module 2.4GHz BLACK × 1 costs AUD 85. Both modules are fine for line of sight applications where you may set the module power at 25 to 100 mw.

Drone Parts Garage (in Brisbane) sell the BetaFPV ELRS Micro 2.4GHz Receiver shown in the vid for AUD 20.50

To get a 7ch rx, I am investigating Matek rxs.

A Matek ELRS R24-P PWM Receiver 5ch I ordered will require me to microsolder the PWM sockets onto the pcb board.

I am crap at soldering, so I plan to try a professional service.

(a) https://surecando.com.au/

(b) There is a phone repair place 20m from the entrance to Chatswood railway station. I asked about microsoldering on pcb boards, he said they do it every wednesday when they have a technician come and work at their microsoldering station, which he showed me.

This 7ch PCM Matek rx will also require microsoldering on the pcb board.
"MATEK Mateksys ExpressLRS ELRS 2.4GHz ELRS-R24-V 7CH PWM Outputs Vario Receiver Suitable for RC FPV Gliders Fixed-Wings Drones" AUD 34 at Ali Express

[caffeine]

Dredging up an old thread here, but the soldering on the matek receivers is pretty straightforward with the right equipment. I did mine without an issue. I've got another 3 receivers on order and on those I'll hard wire in the battery sense points to appropriate JST-XH balance connectors for the telemetry to report flight battery voltage.

If anyone needs it done, and isn't comfortable doing it themselves, I can do it for you (at home or at work, have suitable soldering stations and associated equipment at both)

[caffeine]

Regarding ELRS and the interference problems being seen with DSM at the flying field, I did a non-scientific ad-hoc test today; I set my ELRS transmitter power to it's lowest setting of 10mW at 500Hz, and then walked as far away as I could (almost back to the gate)

The TX showed 5 bars of signal still, I could only get it drop to 4 bars by pointing the antenna directly towards the model. The model remained fully responsive.

[srl]

I see that ELRS only has 4 'stick' channels in its normal mode as it is for multi rotors with FC's.
Most of my larger planes have two channels for the wing.
It would still be great for 3D EPP planes.

srl

[caffeine]

I see that ELRS only has 4 'stick' channels in its normal mode as it is for multi rotors with FC's.
Most of my larger planes have two channels for the wing.
It would still be great for 3D EPP planes.

srl

As of revision 3 of the firmware they have a few more options:

8 channels full resolution, full rate (100Hz or 333Hz)
12 channels where 1-4 are full resolution, full rate, 6-13 are full resolution and half rate)
16 channel full resolution at half rate 

I use the 8ch full resolution mode at 100Hz (1-4 and 6-9 are full rate, ch5 is a 1 bit channel dedicated to arming)

[greggold]

I see that ELRS only has 4 'stick' channels in its normal mode as it is for multi rotors with FC's.
Most of my larger planes have two channels for the wing.
It would still be great for 3D EPP planes.

srl

As of revision 3 of the firmware they have a few more options:

8 channels full resolution, full rate (100Hz or 333Hz)
12 channels where 1-4 are full resolution, full rate, 6-13 are full resolution and half rate)
16 channel full resolution at half rate 

I use the 8ch full resolution mode at 100Hz (1-4 and 6-9 are full rate, ch5 is a 1 bit channel dedicated to arming)

I use ELRS for 3D foamies using a tx module in a RM T12 tx. I tried using 5 channels on my various rxs, but could not get it to work well, it only kind of worked with the 5th channel servo movements too coarse. So I resorted to a Y lead to connect the 2 aileron servos, and this solution is in my view perfect, ie its as good as having 5 fully proportional channels.

I have been flying with elrs for about 4 months now, and I am very impressed. In one brownout/crash I had,  I suspected signal loss, but on investigation I concluded the cause was  loss  of rx power. There are extensive discussions of the causes of signal loss on RCGroups, that occur with all brands of gear, and most experts agree the biggest cause is loss of rx power. A faulty esc, or even a faulty servo can lead to loss of voltage in the rx.

[srl]

I agree Greg that loss of rx power is a consern, using digital servos on a old or 3A BEC-ESC is on the limit, more so when you increase your battery cells past 3S.

srl

[greggold]

I agree Greg that loss of rx power is a consern, using digital servos on a old or 3A BEC-ESC is on the limit, more so when you  increase your battery cells past 3S.

srl

It puzzles me that redundant power supply units are on sale for giant scale RC planes, but appear unavailable for regular RC planes. If experts agree that most brownouts are related to rx voltage drop, why not install redundant power. I have some 30gm NIMH 1/3AA 350mah 4.8v packs that I used on small Halfbad planes when I flew slope at Maroubra. I plan to try plugging a pack into an empty PWM rx slot on my 3D foamies, so there are 2 power leads, one from the esc and one from the NIMH pack.

Does anyone see anything wrong with this idea? Might it work to keep the rx working in case power from the esc is somehow disrupted?

[caffeine]

I use ELRS for 3D foamies using a tx module in a RM T12 tx. I tried using 5 channels on my various rxs, but could not get it to work well, it only kind of worked with the 5th channel servo movements too coarse. So I resorted to a Y lead to connect the 2 aileron servos, and this solution is in my view perfect, ie its as good as having 5 fully proportional channels.

Channel 5 is fixed as a 1 bit (on or off) channel for arming. You can go to your receiver's config and set it to use ch 6 (i.e 1, 2, 3, 4, 6) and that's full resolution in 8ch mode

[greggold]

I use ELRS for 3D foamies using a tx module in a RM T12 tx. I tried using 5 channels on my various rxs, but could not get it to work well, it only kind of worked with the 5th channel servo movements too coarse. So I resorted to a Y lead to connect the 2 aileron servos, and this solution is in my view perfect, ie its as good as having 5 fully proportional channels.

Channel 5 is fixed as a 1 bit (on or off) channel for arming. You can go to your receiver's config and set it to use ch 6 (i.e 1, 2, 3, 4, 6) and that's full resolution in 8ch mode

I agree. However I like using elrs rxs that arrive with their PWM pins soldered in place, meaning you have 2 choices: betafpv or the radiomaster 5ch ER5A rx. I have several matek 6ch rxs which should work with the config step you describe above (John on Radio Control Vid reviews has now detailed this step with a matek 6ch rx, if I tried it now I expect I could get it to work) but I have not tried this step on a RM 5ch rx, and I do not wish to be the first person to try it. 
Even if it worked on the RM rx,  my preference is now the Y-lead solution for aileron servos. One expert reviewer (Mads) has taken off the case of the RM ER5A rx, examined the board and gives it full marks for quality. All my elrs rxs (RM, betafpv and matek) have performed very well. 

I am now very comfortable with the standard elrs procedures, configurator, flashing rxs etc, but I would not say its simple, with elrs in planes there is a feeling of going where no-one has gone before. For example, the elrs flashing procedure where the rx provides the elrs network initially would not work on my mac laptop. Eventually  I posted about this on github, and immediately someone told me the trick to solve it - but the trick is not written down anywhere!

[greggold]

I agree Greg that loss of rx power is a consern, using digital servos on a old or 3A BEC-ESC is on the limit, more so when you  increase your battery cells past 3S.

srl

It puzzles me that redundant power supply units are on sale for giant scale RC planes, but appear unavailable for regular RC planes. If experts agree that most brownouts are related to rx voltage drop, why not install redundant power. I have some 30gm NIMH 1/3AA 350mah 4.8v packs that I used on small Halfbad planes when I flew slope at Maroubra. I plan to try plugging a pack into an empty PWM rx slot on my 3D foamies, so there are 2 power leads, one from the esc and one from the NIMH pack.

Does anyone see anything wrong with this idea? Might it work to keep the rx working in case power from the esc is somehow disrupted?

I just found a RCVR review video that explains why my solution above will not work. If the 2 power supplies (the second is the redundant one) have a different voltage, the higher one will try to charge the lower and that is bad. You need to stop any reverse flow on the 2 power leads using a diode soldered into both the power leads.

The video sets out how to make a redundant power supply for any plane.

https://www.youtube.com/watch?v=yowcjweWkaQ
 
The exact diode in the video is:
SCHOTTKY diode
price for 1 diode $1.14
https://www.digikey.com.au/en/products/d...kAREAXQF8g

I am planning to try this for my larger planes. I will likely use a lipo for the redundant power, so it requires a standalone BEC.

A quick addendum: how is it possible that there is no plug and play redundant power supply solution? That you have to go buy the basic electronic components and solder them together. Brownouts/signal loss are a fact of rc life, and people routinely switch brands of radio or protocols, trying to achieve a better signal. Why has the major cause - rx power loss - been overlooked?

[caffeine]

Bear in mind that the diode will introduce a 0.6v (approximately) voltage drop.

Also, that diode has a maximum reverse voltage of 35V. Probably not a limit you're likely to run into unless you have a 10S or higher pack voltage.

Digi-Key will also be quite a lot in shipping compared to the cost of the part. You can pick up similar diodes off the shelf at jaycar

[caffeine]

You've inspired me to try to work out a solution for this now.

[caffeine]

I put together a simple circuit with a couple of diodes to see if it worked as I expect.

I used an off-the-shelf DC-DC converter to set the voltage of one battery to 5.5V, (green LED) and ran that through a diode to the output

I then passed the output of the BEC from an ESC (blue LED) through a diode to the output.

If either of the battery connections is present, the voltage will be present at the output (red LED).



If the DC-DC converter (green LED) is present but the ESC voltage (blue LED) is missing, the the output (red LED) remains on.



If the ESC BEC is off (blue LED) but the DC-DC convert voltage (green LED) is present, the output (red LED) will still be on:



If both of the battery connections are present, the voltage will be the higher of the 2 voltages (in my case 5.0V after the diode on the DC-DC converter)

While this works well, it does drop the voltage from the BEC in the ESC to about 4.5V, so it will be drawing current from the DC-DC converter most of the time.

You might be better off with an off-the-shelf dual input discrete BEC like this one:

https://www.3dextratime.eu/products/ztw-...uble-input

[caffeine]

I have a subscription to ChatGPT, so I asked it what a solution to this problem might be, and it suggested 2 alternatives. The first one was the same situation described above (and it also suggested using shottky diodes for their low forward voltage drop) however it also suggested a second solution using a special controller chip designed for this exact scenario!

https://www.digikey.com.au/en/product-hi...controller

I might order in a few of them and get a PCB made, it's an excellent solution to this problem.

[caffeine]

I see that the mode that we're interested in using would require two of these chips.

Turns out there's a chip which combines 2 in the one package.

https://www.digikey.com.au/en/products/d...BF/1620210

It's specifically designed for the scenario where you have 2 batteries of similar voltage connected. Instead of the situation in the diode model I put together, where whichever supply has a higher voltage will supply all the current, this chip will monitor the voltage of the primary supply, independent of the backup supply, and only switch over if the primary supply goes outside the desired voltage range (and will automatically switch back if the voltage recovers)

[srl]

For those looking for a new radio upgrade this is what Liam uses -

https://www.nextfpv.com.au/collections/r...ll-edition

It's the ELRS version and available at local and Chinese stores. The cheaper Radio master's appear to be fine too.

For the receiver -
https://www.fpvfaster.com.au/products/ma...rrency=AUD&variant=40211197362258&utm_medium=cpc&utm_source=google&utm_campaign=Google%20Shopping&gclid=CjwKCAjwrpOiBhBVEiwA_473dGMsuiUYtsrocstjwoMFAiRqgA31r4_Kgq4rO6tZYOGHnu1GpZ-f9BoCW9sQAvD_BwE

srl

[caffeine]

I bought my radio and (now 6) receivers from phaserfpv.com.au. (Out of stock)

They had 33 receivers in stock last night before I ordered my most recent 2, for $23 each.

The radio is out of stock in most places at the moment. A lot have the max version available which has CNC aluminium accents, leather side grips and a folding carry handle.

Bear in mind that the radio can be adjusted from mode 1 to 2 and vice versa without opening it up (using an included Allen key), so don't be concerned if you can't find your preferred mode.

[srl]

About to give Elrs a go.
More stuff to learn.

srl

[caffeine]

I'll be interested to see what you think of the R24-V receivers

[caffeine]

Stephen, now that you have ELRS setup at the 100Hz / 8 channel / Full Rate setting, you may notice that the receiver takes longer to bind (5 seconds or so). This is because the receiver starts at 1000Hz and cycles through the available rates, eventually arriving at the 100Hz rate and binding.

The newest ELRS lua script adds a new menu item called 'Other devices' (when bound to the receiver) and in that menu you can set the intial rate for the receiver. If you set that to the same 100Hz Full rate, your receiver will bind quickly again. You'll need to do this for each receiver you have.

See this video at 6:15 for a demo:

[srl]

Just this week I found out that the Ranger ELRS modules only work best in RadioMaster 4in1 TX’s and the Taranis 2019.
Other Frsky radios may require a mod.
By luck I’ve only been using my module in my newer 2019 9xd+.
https://www.expresslrs.org/hardware/x9d-...eshooting/

srl

[srl]

For mebers with a new RadioMaster-

[dfw]

My Elrs experience thus far:

Radiomaster TX16 mark II
Matek ELRS-R24-P6 ExpressLRS 2.4G PWM Receiver With Antenna Support 2~8S VBat Voltage Sense

Upgrading firmware via Wifi is pretty straight forward.
Edge TX software updates straight from your browser.

I had an issue with the Matek RX not binding automatically to TX, even after quadriple checking the binding phrase.

I used the Matek specific model no to compile the code for the RX. Matek's website does instruct you to use the Generic source for this receiver.
After recompiling / reflashing with the generic code (Version 3.3.0), binding works perfectly fine. so Check the recomended firmware source from the RX manufacturer, it might be different from the actual model number listed !

Once that was out of the way, setting up EdgeTX for basic configurations takes some playingd around, but once you get into it, it's actually pretty straight forward and very flexible to setup.

[caffeine]

Good stuff Dirk!

Have you setup model match? I didn't bother initially, but got myself in trouble when I had the wrong model selected in my radio without noticing (all the channels were the same controls, but the scaling and limits were different so I had a very challenging flight)

Now each of my planes has the same binding phrase, but a different model match number, so it will bind but refuse to control the aircraft if the model match is different. It also allows you to set different packet rates and telemetry ratios on a model-by-model basis.

[dfw]

yes, I've setup model match. 

The battery voltage input on the receiver is great, but also dangerous, mis-plugging the Vbatt into one of the servo output ports will likely cause damage. 
Matek provides enough extra pins to make the Batt input a RED one,  so it stands out: 
   

[caffeine]

Yes, the vbat is a little precarious.

I've addressed that by permanently soldering in a wire with a JST male connector on the end that plugs into my battery balance connector.

On the plus side (pun intended) my receiver and servos survived having the battery voltage put directly into the 5V connection. (An off-by-1 error when (foolishly) hot-plugging into a hard to reach receiver) but my ESC didn't

[srl]

Very much in line with what we have seen at our flying field , not good for DSM.
Radio master ELRS has come along at just the fight time.

srl

srl.