Frequency Hopping experiments on the NRF24 & full tx/rx

Any old or new electronic projects on the go
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jmp_blackfoot
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Joined: 24 Feb 2018, 23:53

Re: Frequency hopping experiments on the NRF24 - & full tx/rx

Post by jmp_blackfoot »

Phil_G wrote: 26 Dec 2024, 10:13 Brrrrr ! :D
There will be doughnuts and coffee. ;)
jmp_blackfoot
Posts: 24
Joined: 24 Feb 2018, 23:53

Re: Frequency hopping experiments on the NRF24 - & full tx/rx

Post by jmp_blackfoot »

Finished two receivers with NanoRF boards (Micro USB version) and end connectors for a tight installation.
First I removed the USB connector and the reset button.
IMG_8326.JPG
Then I prepared the connector.
4 channel connector.jpg
Finally, I wired the negative and positive busses and fitted the lot in the holes left when removing the USB connector.
4 channel NanoRF.jpg
The decoupling 100µF+100nF capacitors fit where the reset button used to be. The big 5V LEDs are all I had, still the receivers weigh less than 5.5 gram each.
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Phil_G
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Re: Frequency hopping experiments on the NRF24 - & full tx/rx

Post by Phil_G »

Very neat. Dont forget to post photos of your 'Freeze Fly' Jean-Marie :D
jmp_blackfoot
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Joined: 24 Feb 2018, 23:53

Re: Frequency hopping experiments on the NRF24 - & full tx/rx

Post by jmp_blackfoot »

The Freeze Fly was not as frozen as the forecast promised. The temperature was all of +3°C and the wind only about 12 mph. A dozen flyers showed up, most of them with foam ready-to-fly toys. I flew my faithful ruder-only Windmill (https://outerzone.co.uk/plan_details.asp?ID=13903) with the just finished NRF system in a metal box Futaba 2 channel transmitter. All went well (as expected) and during the following chat session around the donuts and coffee, I got one member quite interested in Mode-zero and the NRF system. Thanks again to you, Phil, for this great start to my 2025 flying season.
Attachments
IMG_8335.JPG
IMG_20250101_090350999_HDR.jpg
IMG_20250101_091145446_HDR.jpg
IMG_20250101_091213587_HDR.jpg
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Phil_G
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Re: Frequency hopping experiments on the NRF24 - & full tx/rx

Post by Phil_G »

The more the merrier Jean-Marie. It would be particularly nice to see more oldies taking up single-channel again. Even 1+1 :D
Looks to be a great facility you have there, if we had a similar set-up at our club the yobs would immediately destroy it. Our reinforced steel cabin has been broken into 4 times, 2 ride-on mowers stolen (or is it 3?), we cant even keep a solar panel hidden on the roof for more than a few days. The UK is in a sorry state and it seems to be getting worse :(
I'd not seen the 'Windmill' before and reading up on Outerzone it looked quite scary - 5lb, 0.45cu in engine, rudder only :D ....but then I saw yours was 2/3 scale, much more manageable! Looks very 'Ken Willardy' I think. Its a great shame we dont have the competitions we used to, comps used to push development quickly - look at Fossie's 'Phase' gliders :D
Cheers & thanks for the report!
Phil
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Shaun
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Location: West Yorkshire

Re: Frequency hopping experiments on the NRF24 - & full tx/rx

Post by Shaun »

Remember the s/c Lightening I did Phil? .That was originally designed for a 5cc / 0.29 cu in glo motor and a sequential esc. :shock:

Image
jmp_blackfoot
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Joined: 24 Feb 2018, 23:53

Re: Frequency Hopping experiments on the NRF24 & full tx/rx

Post by jmp_blackfoot »

Now, for something completely different:
I do not know if the following will be of any use or even interest to anyone, although it may give some ideas to convert say a Staveley or Flight Link system using the original servos, but I am really having fun doing it.
In 1987(!) I built a few servos with an analog amplifier of my own design, see attached pdf, which I'll have to fly one day just to prove they work.
Having the opportunity now to play with the NRF FHSS system, I realised the receiver could drive these servos directly.
The modified receiver sketch for a three analog servo system is attached. Changes are identified on lines 44-45 and 261-262. The idea is to shorten the frame time down to 4 ms and the output pulses so they vary between 100 and 1100 µs, with 600 µs being neutral. The former requires a modified Servo.h library file, see attached ("ServoA3ch.pdf" should be renamed "Servo.h" before use), while the second is done on lines 261-262 of the the receiver sketch. Channel 4 is output as a fixed 600 µs pulse and channels 1, 2 and 3 are the control output pulses. The analog signal is extracted by subtracting the fixed channel 4 pulse from each control output. This is accomplished by connecting the channel 4 output to the center tap (0V) line of the servo battery and the channel 1 to 3 outputs to the analog input of their relative servo so that the fixed 600 µs channel 4 appears as a negative pulse, while the control channel pulse is a positive pulse, the averaged voltage being the resulting input signal to the servo as shown on the attached oscilloscope pictures. The receiver requires its own battery, see attached photo (the external 180k/100nF RC has now been moved back inside the servo). The above generates a +/- 0.4V control voltage to the servo with the 3.3V Pro Mini version of the receiver, which suits my servos and seemed to have been more or less the standard in the 1960's, see attached Accutrol ad. With a NanoRF version and 5V, the control voltage would increase to +/- 0.6V or the frame time could be increased to 6 ms..
Four channels with a 6ms frame time or even two channels with a 3 ms frame time will also work.
The transmitter sketch needs not be altered.
Attachments
Accutrol servo.jpg
JMP_analog_ servo.pdf
(329.38 KiB) Downloaded 33 times
ServoA3ch.pdf
(5.27 KiB) Downloaded 31 times
AnalogWiring.jpg
IMG_8345.JPG
IMG_8346.JPG
receiver_analog_3ch_250110.ino
(11.14 KiB) Downloaded 28 times
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