Calibrate Tx Battery voltage readout

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Fernandez
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20 Nov 2018 19:31 #71831 by Fernandez

Calibrate Tx Battery voltage readout was created by Fernandez

Is there a possibility to apply scale factor and offset, to calibrate the Vbat readout of the transmitter battery?
Devo7e 256 (U7E)

I use alternative power circuit with up/down regulator, radio is powered by 1s and charge via the usb port connected after the diodes. My readout is about 0.3v higher...

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FDR
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20 Nov 2018 21:58 #71832 by FDR

Replied by FDR on topic Calibrate Tx Battery voltage readout

As far as I remember scaling wouldn't be enough, because the voltage reading isn't linear enough. If you calibrate the upper end, it will differ on the lower end...

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Fernandez
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21 Nov 2018 05:32 #71833 by Fernandez

Replied by Fernandez on topic Calibrate Tx Battery voltage readout

Correct best there should be an: offset and a scale factor.

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FDR
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21 Nov 2018 19:28 #71836 by FDR

Replied by FDR on topic Calibrate Tx Battery voltage readout

AFAIK there is an offset already. The linearity is the problem, the offset is not enough...

In each target_defs.h you can find something like this:

/* Compute voltage from y = 0.003246x + 0.4208 */
#define VOLTAGE_NUMERATOR 324
#define VOLTAGE_OFFSET    421

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Fernandez
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22 Nov 2018 15:01 #71843 by Fernandez

Replied by Fernandez on topic Calibrate Tx Battery voltage readout

Need to hook up variable power supply to map it, I think in my case I am just offsetted higher as I powered without going true the inline DIODE, which is used inoriginal circuitry.

Thanks for the info FDR!

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Fernandez
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25 Nov 2018 22:07 #71891 by Fernandez

Replied by Fernandez on topic Calibrate Tx Battery voltage readout

I checked and my tx read approx 0.3V, too high offset, that matches as previously there was a series Diode in 7e, which I no longer use.

Is it possible to get those fields in the hardware.ini ? So possible to tune to get it right?

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Fernandez
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12 Jun 2019 22:08 #74522 by Fernandez

Replied by Fernandez on topic Calibrate Tx Battery voltage readout

old topic, but would it be possible to add the Vbat calibration values into tx.ini

I still like to calibrate my U7E, as I use modded battery / charging circuitry, I am 0.3Volts too high in readout because of diode removed....

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