RPM resolution?

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Endorphin
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First submission. GPS only openXsensor

Post by Endorphin »

kalle123 wrote: Fri May 22, 2020 8:53 am ....................................
working GPS oXs
.................................................
I am posting this one first. I will post all three separately, to reduce potential for confusion (on my part as well as for the reader).
You could also try the #define DEBUG thing with the NOT working baro + GPS oXs yourself.
.........................
I have no knowledge of how to start with that. I figure it will be better to wait for further information about that before (probably) compounding the problem and increasing resulting confusion/mis communication etc.

Supplementary information (may or may not be relevant):

Taranis X9D Plus on OpenTx version 2.2.3
Companion version: 2.2.3
Baro BN-180
Computer operating system: Linux Mint 19.3
Arduino IDE version: 1.8.12
Barometer reading at time of testing: 1009 kp.
Atmospheric temperature 18 deg. C
Google Earth coords for same location as test above: 30.24 S 152.56 E to the nearest minute.
Arduino nano clone board used. (ex Banggood).
Proper old fashioned lead solder used throught!

I sincerely hope I have provided sufficient information.
Please let me know if I have not.

I will do the BMP280 Vario only test tomorrow.

Jim.
Attachments
GPSdisplay.JPG
BMP280_GPS29042020.ini.tar.gz
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Last edited by Endorphin on Mon May 25, 2020 1:28 pm, edited 2 times in total.

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kalle123
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Re: RPM resolution?

Post by kalle123 »

BMP280_GPS29042020.ini.tar.gz
Jim, this is now your NOT WORKING BMP280 + GPS oXs ??

br KH
Endorphin
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Working GPS only.

Post by Endorphin »

kalle123 wrote: Sun May 24, 2020 6:23 am
BMP280_GPS29042020.ini.tar.gz
Jim, this is now your NOT WORKING BMP280 + GPS oXs ??

Karl,
Please read my post above.
I have quoted your words, exactly as you asked. The quote at the top of my post clearly indicated: "working GPS oXs".
Picture of the displayed coords attached.

Jim.
Last edited by Endorphin on Sun May 24, 2020 8:34 am, edited 1 time in total.
Endorphin
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Picture of GPS display in my Taranis X9D Plus

Post by Endorphin »

Please find picture attached of my working GPS.
I forgot to attach it to the post above. I have edited the post to include it.
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GPSdisplay.JPG
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kalle123
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Re: RPM resolution?

Post by kalle123 »

So PROBLEM SOLVED, at least for me ;)

cu KH

Endorphin
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Re: RPM resolution?

Post by Endorphin »

kalle123 wrote: Sun May 24, 2020 9:06 am So PROBLEM SOLVED, at least for me ;)
I will do the Vario / BMP280 openXsensor test tomorrow and take a video of it working.
Endorphin
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Video of Working openXsensor BMP280 Vario.

Post by Endorphin »

Karl,
Please note: this is a Working Vario.
I am using the same board, same sketch as the previous working GPS test. It's working, but not very sensitive. I am ordering a MS5611 to use instead of this BMP280 baro.

https://vimeo.com/422278590

Supplementary information (may or may not be relevant):

Taranis X9D Plus on OpenTx version 2.2.3
Companion version: 2.2.3
Computer operating system: Linux Mint 19.3
Arduino IDE version: 1.8.12
Barometer reading at time of testing: 1009 kp.
Atmospheric temperature 18 deg. C
Google Earth coords for same location as test above: 30.24 S 152.56 E to the nearest minute.
Arduino nano clone board used. (ex Banggood).
Proper old fashioned lead solder used throught!

I sincerely hope I have provided sufficient information.
Please let me know if I have not.
Endorphin
Posts: 167
Joined: Tue Jan 26, 2016 7:46 pm
Country: Australia

Success!

Post by Endorphin »

I now have both functions working on the same arduino nano board.
BN180 GPS and BMP280 baro Variometer.
Same sketch as I have been trying for weeks now, before this, without success.
The only thing I have done differently is to power the GPS sensor off 3.3 volts and not 5 volts, as previously.

Wow!
This has been a long haul.
Thanks to all, especially Karl.

Jim.
Endorphin
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Faulty FrSky D8R-11 Plus rx.

Post by Endorphin »

A short explanation for at least some of my travails in getting an openXsensor working.
I discovered that the receiver I was using to test it was faulty.
Very poor range and intermittent RSSI.

My apologies for no picking this up earlier.

Jim.
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gastolectric
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Re: RPM resolution?

Post by gastolectric »

Hi guys,

I've been moving house, career change etc the past few months - dusted off my gasser this weekend to find that my RPM sensor isn't playing ball...

When I run the engine on the ground I get perfect, sensible read outs on my Horus all the way through the rpm range but the moment she is airborne the readings are all over the place - tried turning the filter function off in the Horus setup but this understandably only made it worse. With the filter on it seems to give sensible readings up to about 90% throttle but when I punch to full throttle I lose rpm values and telemetry reports zero rpm

Anyone experienced this in the past and/or any suggestions

I'm taking the pickup directly from the Hal sensor line to the Rcexl ignition unit via a y-lead that feeds into an Arduino nano that also has a gps unit connected to it (this is an old Rcexl that doesn't have a separate tacho line out)

Cheers
Greg
mstrens
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Re: RPM resolution?

Post by mstrens »

You can try to filter the value on oXS side.

In the .ino file you currently have
sport_rpm.value = RpmValue ;

Change it to
//sport_rpm.value = RpmValue ;
sport_rpm.value += 0.1 * ( RpmValue - sport_rpm.value ) ;

You can then adapt the "0.1" parameter.
With 0.1, it means that the new value is the previous one + 10% of the difference with the new value.
Decreasing the parameter increases filtering.
Parameter = 1 means no filtering at all.
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gastolectric
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Re: RPM resolution?

Post by gastolectric »

mstrens wrote: Tue Oct 13, 2020 7:52 am You can try to filter the value on oXS side.
Thanks Michael,
I'll give this a go and let you know how I get on, though I'm also reminded wading back through this thread that because I'm only losing resolution above 90% throttle it may just be the rc filter that needs tweaking because I'm reaching the threshold where the filter loses efficiency and starts dumping noise...
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kalle123
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Re: RPM resolution?

Post by kalle123 »

gastolectric wrote: Mon Oct 12, 2020 9:06 pm When I run the engine on the ground I get perfect, sensible read outs on my Horus all the way through the rpm range but the moment she is airborne the readings are all over the place
That sounds strange. And when the plane is back on the ground, everything is fine again?

On the ground, did you move all servos?

br KH
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gastolectric
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Re: RPM resolution?

Post by gastolectric »

kalle123 wrote: Tue Oct 13, 2020 10:32 am
That sounds strange. And when the plane is back on the ground, everything is fine again?

On the ground, did you move all servos?

br KH
Admittedly on the last flight I turned off the filter function on the rpm telemetry output on my Horus so that would explain it being jumbled throughout the rev range. With the filter on it offers sensible data until I go beyond 90% throttle so I suspect the rc filter at this stage but will play with servos while on the ground to rule that out too

And yes land and run it up on the ground and no issue, can only think that in flight the engine is reaching a higher Max rpm and therefore going beyond the rc filter threshold where on the ground these rpms aren't coming into play.
Carbo
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Re: RPM resolution?

Post by Carbo »

A 100pF ceramic cap connected to (D)8 and GND solved a similar issue for me. Interference was presumably caused by RX telemetry. OpenTX filtering should not be neccessary imo.
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gastolectric
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Re: RPM resolution?

Post by gastolectric »

Carbo wrote: Wed Oct 14, 2020 8:10 am A 100pF ceramic cap connected to (D)8 and GND solved a similar issue for me. Interference was presumably caused by RX telemetry. OpenTX filtering should not be neccessary imo.
Awesome thanks Carbo
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gastolectric
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Re: RPM resolution?

Post by gastolectric »

Following a weekend of field testing I can report back that a combination of factors were involved:
  • I swapped out the 5K6 resistor in the rc filter for a 4K7 which extended the rev range (100nf cap)
  • I used mstens suggested formula adjustment above to curtail the data output starting with cutting back to a value of 0.1 (10%), but settled with 0.2 (20%) which offered slightly better resolution without having to use the filter feature on OpenTx - could possibly even have upped this further to 25-30%
**Change it to
//sport_rpm.value = RpmValue ;
sport_rpm.value += 0.1 * ( RpmValue - sport_rpm.value ) ;

Both these changes resulted in a stable readout throughout the rev range both on the ground and in the air - but the mystery remains - on the ground (and comparing with a tacho) the rev range readout was accurate from idle around 1800rpm to max throttle giving 7500rpm, but in the air the rev range shifted to around 2200 in a low throttle stall, to around 9500rpm gunning full throttle in a dive and a steady 9100 in straight and level flight.

So I swapped out the nano board for a FrSky rpm sensor from another plane and sent it back up for a few full throttle passes - low and behold it was also reporting 9000-9500rpm. So I've resolved to let it be, that this must be one sweeeeeetly tuned 30cc gasser

Though there was one comment from the pits worth considering : that the Hal sensor may be 'double sparking' in flight ie picking up a pulse as the magnet moves towards the sensor as well as when it moves past - though you'd expect this to double the read out - and given that we've chopped the data throughput to just 10% without any seeming change to max rpm in level flight - unless I really need to throttle it further to say 1% just to see if over an extended full throttle pass I'm still getting such high end rpms.

But having said all that, the FrSky sensor that was running in my 50cc bipe seemed to report a reliable max 7000rpm both on the ground and in the air, so back to thinking I'll just leave it be (both sensors behave alike on the ground and in the air in my Sbach) - and I really only need the sensor to report Zero rpm in the event of a dead stick with other planes in the air and not being able to hear it soon enough to head straight for the runway..

Thanks again for all the generous support on this forum.

Cheers
Greg
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Re: RPM resolution?

Post by mstrens »

thanks for the feedback.
marevalor
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Re: RPM resolution?

Post by marevalor »

Dear, a query, I am new to this and I just managed to create a sensor with a variometer that works perfectly for my gliders. But I want to create a RPM sensor for my gasoline engines (with CDI) but I have not found appropriate literature, (only for jeti https://www.rc-thoughts.com/jeti-cdi-sensor/) could you help me with the diagram for soldering and some tips for the program? , the engine is a DLE 20ra.

Thanks and greetings from Chile.
Endorphin
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Re: RPM resolution?

Post by Endorphin »

gastolectric wrote: Mon Oct 12, 2020 9:06 pm Hi guys,
...........................
When I run the engine on the ground I get perfect, sensible read outs on my Horus all the way through the rpm range but the moment she is airborne the readings are all over the place - tried turning the filter function off in the Horus setup but this understandably only made it worse. With the filter on it seems to give sensible readings up to about 90% throttle but when I punch to full throttle I lose rpm values and telemetry reports zero rpm

Anyone experienced this in the past and/or any suggestions
..............................
Greg
Hi Greg and others,

I found a slightly different problem with my RPM OpenXsensor using:

FrSky Taranis X9D Plus.
OpenTx 2.2.1
FrSky D8R series receiver.
Second dedicated hall sensor installed in an attempt to obtain a steady read out.
I tried powering it with a separate battery - no change.

The plane has not flown since my last post due to festival cancellations.

My RPM sensor would work, but the figures were all over the place to the extent it was not workable. I have been meaning to remove it, but now I have a few ideas to try to remedy the problem.
So, I will revisit the problem and try again.

Thanks for posting.

I will start with the 100 pf cap.

Jim.
Endorphin
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Re: RPM resolution?

Post by Endorphin »

gastolectric wrote: Sun Oct 18, 2020 8:30 am ....................................
  • I swapped out the 5K6 resistor in the rc filter for a 4K7 which extended the rev range (100nf cap)
  • .............................................

Greg,

I have no idea where these components are located, especially the cap that is, curiously, in brackets.
I know...............I should know...........but................I don't.

Can you explain with connections please?

Edit:
I found your description with pictures back at post #42 explaining where and how etc.
Please ignore my question above.

Jim.
Endorphin
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Filter cap

Post by Endorphin »

Carbo wrote: Wed Oct 14, 2020 8:10 am A 100pF ceramic cap connected to (D)8 and GND solved a similar issue for me. Interference was presumably caused by RX telemetry. OpenTX filtering should not be neccessary imo.
I finally got around to fitting a capacitor across D8 and GND on my OpenXsensor. Fixed my jittery telemetry problem.
Thanks,

Jim.
Endorphin
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Arduino max voltage in?

Post by Endorphin »

I plan to add LiPo voltage sensing to my existing openXsensor.
What is the maximum voltage limit into the arduino?
And what pin # is the output of the voltage divider connected to please?

I found this in the description. Recommended max 1.1 volt. The output of the voltage divider is connected to any of:
A0, A1, A2, A3, A6 or A7
Have I read this correctly?
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