HOTT settings on Tx

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biblebrox
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HOTT settings on Tx

Post by biblebrox » Thu Oct 27, 2016 7:29 pm

Hi,
I just build an oXs for brushless RPM, current and voltage measurment on a ProMini. Installation went smooth I can also read the RPM on the transmitter. Unfortunately, I can not access the telemetry setup menu on my transmitter which should be available after the receiver menu if general is selected. I just checked with the same receiver and an original Graupner GAM: There I can access the menu.
Did I miss something? Can I set the # of poles of the motor in the oXs_config? Any setting that has to be changed in the Hott config files?
Any help would be great!
Cheers
Roland

mstrens
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Re: HOTT settings on Tx

Post by mstrens » Sat Oct 29, 2016 7:38 am

I do not know all details of Hott interface.
It could be that the transmitter can send parameters (and/or button keys press) to the original GAM sensor. This is not implemented in oXs.
oXs just send the data that have been defined in the config file whithout taking care of the transmitter.

The current version of oXs does not support the # of poles in the config (original code is for Frsky and this parameter is set up in the transmitter).
I can implement it in the next version.
Anyway, you can easily modify the code to get it already.
You have to modify one line in the file oXs_out_hott.cpp
In line 181 there is currently
TxHottData.gamMsg.rpm = RpmValue /10 ; //#22 RPM in 10 RPM steps. 300 = 3000rpm

You could change it in some thing like (where 12 is the #of poles ; replace 12 by your own value)
TxHottData.gamMsg.rpm = RpmValue * 6 / 12 ; //#22 RPM in 10 RPM steps. 300 = 3000rpm
In fact RpmValue is calculated by oXs in Hz. Tx expects a value in 1/10 of rotation per minute; So Hz have to be multiplied by 60 and divided by 10 (= multiplied by 6). I expect that there is have a pulse per pole; so you have also to divide also by the # of poles in order to get real rpm.

Can you test it and let me know if it is OK?

biblebrox
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Joined: Thu Oct 27, 2016 7:03 pm
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Re: HOTT settings on Tx

Post by biblebrox » Sat Oct 29, 2016 8:11 pm

Hi mstrens,

thanks for the quick reply.
I just gave it a try and in deed the value displayed on the transmitter changed with the settings I changed as you suggested. Unfortunately it is dark outside and I can not check the displayed value with my optical RPM measurement tool. I'll keep you updated.
For the RPM that will be fine to set the values in the arduino config file, but things like battery capacity and other alarm levels can not be set as they would also need to be set in the mentioned telemetry menu. So I will be able to display the used capacity but I will not get any alarm when the used capacity exeeds a defined value. So if there would be a communication towards the oXs, that would be of great value for HOTT users. In any case: Great work and thanks for your help.
Cheers
Roland

biblebrox
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Re: HOTT settings on Tx

Post by biblebrox » Sun Oct 30, 2016 7:38 pm

Hi,
I finished the measurements and found a factor of 12 between actual RPM and values shown on HOTT (using the /10 factor as mentioned by mstrens).
I know you have to devide the poles by 2 so I think the formula TxHottData.gamMsg.rpm = RpmValue * 6 /(#poles/2) should do the job.
The values I receive are reasonble now.
Cheers
Roland

pritt500
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Re: HOTT settings on Tx

Post by pritt500 » Sun Jun 18, 2017 9:02 am

Hi Roland,
I would like to use a RPM sensor for brushless motors with my OXS for Hott, too. Could you give me some Information which sensor you used and how you connected it to the motor and the sensor?
Thanks in advance,
Thomas

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