Taranis + OpenTX. How do I measure up to 600A to telemetry?

[Danielsson]

Hi everyone!

I'm currently involved in a project where I'm controlling a large scale rc tank. It's propelled by two 5000W brushless DC motors. The ESCs are rated at 48V and peak at 300A each, which pulls a total of 600A from the battery pack in certain scenarios.

I would like to measure the amperage and send this back to the Taranis so that I can program battery warnings etc. when I've used up a certain amount of Ah.

I'm also interested in being able to see the lowest cell voltage and use that as a variable, but is that possible on my battery pack? I'm using 16x 3.2v LiFeYPO4 40Ah cells to create a 51.2V pack. Any ideas if that would be possible?

Thanks in advance!

[jhsa]

I think your biggest problem is to find a sensor that reads over 600A
Frsky certainly doesn't have one, so your best bet is to find a suitable sensor and ask the guys if they would support it in openXSensor project..

[Kilrah]

This is a bit (far) beyond what's usually used in RC...

You'll likely have to design your own sensor indeed.

Envoyé de mon SM-G900F en utilisant Tapatalk

[Danielsson]

Thanks for replying!

I've googled a bit and found this sensor:

LEM HAS 200-S

It measures up to +-600A and outputs, at +600A, 4V. The FrSky FAS-100, what voltage does that output at 100A? I'm guessing I'd need some kind of scaling in the OpenTX firmware. I'm guessing the FAS-100 sends back the data as PPM? So I'd need to convert my 0-4V to PPM.

[jhsa]

No, you need to build a openXsensor.. Do a little search here on the forum. I can't find the link at the moment..
you will need an arduino pro mini 5V 16Mhz. Load the openXsensor code on itbut before you need to insert the specs of your sensor in the config.h file.. I use the allegro ACS758 unidirectional (reads only positive current) 50A and 100A versions.. 600A is a bit too much for my little planes.. I guess I could fly myself

João

[MikeB]

You could try using the FrSky 150A sensor. This is of the 'clamp' type so doesn't put anything in the wiring.
If you make a cable up that splits your power line into 4 equal wires so they current share, then you could put one of these through the 150 Amp sensor. You would just be reading a quarter of the actual current.

I have ersky9x firmware available for the Taranis, and this includes some "Scalers" that can take any telemetry value and scale it to your required value.

Mike.

[jhsa]

Clever workaround
But the wires should be exactly the same lenght and diameter, right?

I wonder if it would work with the normal allegro sensors too..

João

[Danielsson]

Just after I posted that one I read up on OpenXSensor, I am amazed at the things that come out of the open source community. OpenXsensor seems to be exactly what I need, can't understand how I've missed it! From what I can understand it has been updated to now support SPort (since my X8R receiver doesn't have serial)?

I forgot to add the datasheet in my previous post: https://www1.elfa.se/data1/wwwroot/asse ... ng_tds.pdf

Yes I saw the spreadsheet to calculate the scaling/parameters to openxsensor, I'll have a look at the datasheet and try to work that out, didn't look terribly difficult !

MikeB: The thought had crossed my mind, but I didn't know if opentx supported that kind of scaling. You say that you have the correct scaling feature in ersky9x, are they available in opentx as well? I had hoped to use Opentx, but honestly I don't really know what difference there is between opentx and ersky9x. Isn't opentx supposed to be like the "one universal firmware to rule them all (or most)"?

Really very big thanks you guys, I really appreciate it.

[MikeB]

er9x came first, open9x was forked from it.
Then the SKY board upgrade came along so I created ersky9x (from er9x) for it. open9x then added support for the SKY board.
Then along came the Taranis, also with an ARM processor, so open9x (openTx) was modified for that. Since I did a lot of the low level device drivers for that, I made ersky9x run on that.
Since both openTx and ersky9x came from the same starting point, they have a lot in common, but also have some differences, and there is transfer of code between the two.
The Taranis ships with a version of openTx. The new 9XR-PRO ships with ersky9x (with the bootloader I wrote for it, the SKY board and the Taranis).
Some people prefer one, some the other. Some just use whatever was shipped and don't upgrade the firmware.

openTx has recently added LUA that may well allow the same sort of Scaling I have in ersky9x.
If you get the bootloader installed, it is quite easy to swap between openTx and ersky9x and try them both out to see which you prefer.

Mike.

[Helle]

Hy,

measure 600A with pulsing DC:

Take a RMS industrie current clamp instrument with 0 to 10 V output
then the voltage into a A2
measurement error about 3-5% is normal

Honeywell solid stat sensor linear current sensor AC DC
CLSA2xx Serie
CLSA2EL

http://www.produktinfo.conrad.com/daten ... SLA1CH.pdf
Helle

[Kilrah]

The LEM sensor with openXsensor configured corretly seems like the perfect solution.