Re: [Paparazzi-devel] battery voltage for rotorcrafts, changes for booz board users

[Felix Ruess]

Hi Bart,

This is the same now, regardless if fixedwing or rotorcraft and on
every board including Lisa.
In most cases you won't need to define VoltageOfAdc since the
DefaultVoltageOfAdc is already defined for each board, but you can use
it to calibrate it better or if you have different voltage divider
values.

Cheers, Felix

On Thu, Apr 28, 2011 at 10:52 AM, Bart Remes <address@hidden> wrote:
> Hi Felix,
>
> Is this only the case for rotor-craft use on booz board or also the case for
> rotor-craft use on lisaL?
>
> kind regards,
>  Bart Remes
>
> On Sat, Mar 26, 2011 at 10:11 PM, Felix Ruess <address@hidden> wrote:
>>
>> Hi all,
>>
>> since Antoine recently added support for the electrical subsystem for
>> rotorcrafts (replacing battery) we now have the same code there as for
>> fixedwings.
>> Hence we now also have battery voltage measurement for Lisa/L.
>>
>> For users of the booz board this means that you might have to set the
>> conversion factor from ADC measurements to Volts in your airframe
>> file.
>> This is set now with the VoltageOfAdc(adc) macro just as for
>> fixedwings, the formerly used BATTERY_SENS and BATTERY_OFFSET are not
>> used anymore.
>>
>> So far you probably had something like this in your airframe file:
>> <section name="BAT">
>>  <define name="BATTERY_SENS" value="0.246" integer="16" />
>> </section>
>> You need to change this to
>> <section name="BAT">
>>  <define name="VoltageOfAdc(adc)" value ="(0.0246*adc)"/>
>> </section>
>>
>> The default value VoltageOfAdc(adc) for the booz board is
>> (0.0183*adc), which should be correct if you have a recent revision
>> with R1=4,7kOhm and R2=1kOhm.
>> Depending on the revision of the booz board you have (mine is the
>> first revision like in the example above), you might have different
>> values for the two resistors making up the voltage divider.
>>
>> This factor can be computed like this:
>>     reference_voltage / adc_max_value * (R1 + R2)/R2
>> R1 and R2 make up the voltage divider to measure Vbat.
>> So for the current booz board revision we have
>>     3.3/1023 * 5.7/1 = 0.018387097
>>
>> Cheers, Felix
>>
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>
>
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