Hi Tomas,

I noticed a very unstable voltage level on integrated Rx in RS und GTR.

It various up to 0.9V (e.g. 7.4v down to 6.5v under BEC load)

The separate logged BEC Voltage (HW or YGE) is absolutely stable.

I want to use the Rx Voltage for reference of proper BEC job vs. Buffer job ( Emergency Autorotation)

But with this unstable is Rx voltage it makes no sense to trigger a BEC alarm.

With external Jeti receivers connected with Spirit pro the logged Rx voltage is absolutely stable (same ESC‘s).

Best regards
Walter

Hi,

Nobody else noticed this my in point of view strange behavior?

@Tomas: It would be nice if you could give me a short feedback about this topic. Is it known by you and it is ok or not?

Best regards
Walter

Hello,
I see this only at the start up when the Buffer-Pack loads itself - my BEC-Voltage is setted to 7,0 V (and shows 7,03 V) and then you see till the Buffer-Pack is not fully loaded 6,93V but I think that's absolutely normal, 0,9V are maybe a little high - what du you see if you take an seperate battery too, drops the voltage also in this range ? Detouch the Buffer itself and see if you also have such voltage drops -

The BEC voltage is only controlled by the ESC and not from the Spirit side in my opinion - if there is an problem it results out of the BEC of the controller

this is a common topic with modern strong HV servos on a i.e. 700 heli.... i've checked it with oscilloscope too and the values shown by Spirit GTR are OK (you cant check the inside power rail, but it seems reasonable from outside results). i've seen similar values (a bit less extreme due to additional interal CAPs in the REX) when connecting a Rex3 with a single servo cable to a Spirit GT (do not connect BEC directly to REX to compare - it's not the same). my BEC was set to 8V btw.

it's mainly the resistance of the rather long BEC cabling (with fairly thin wire tbh) and the servo plugs - under load there is a slight (to important) voltage drop on the Spirit side where the high current occures (and backfeed from servos too) where the Esc at the same time correctly reports almost 0V drop. i've solved this by using much better BEC cabling for the HW Escs (i.e. Hacker/Powerbox 2x AWG21 + 1x AWG26, the ones from YGE have been much better in my case). after doing so and adding the CAPs the drop was down to around 0.3-0.5V max.

added 0.5V as the alarming threshold which is quickly reached after power disconnect i am fine...

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cheers
Michael

Hello,

your findings are not strange at all and what you can see as Rx voltage is real measurement. It is measured at same point as Servos.
The issue is developing mostly in RC servo connectors with pin header contact. The most connectors are rated for 3A continuous current. In peak it depends a lot on how contacts are holding firmly. Modern servos are drawing more and more current - note that 6V servos are much less demanding in reality but are also weaker.
To resolve the issue you need either to replace BEC connectors or add cables as close to servos as possible or add capacitor or similar change related to BEC.
In other words Spirit unit is showing much more relevant values than anything else.

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Spirit System developer

I noticed the same thing today with a GTR.

When I log/alarm on the "Voltage Rx" I constantly get warnings.
Running buffer pack so I don't think the ACTUAL voltage to the servos is a problem.

When I log/alarm on "S BEC Volt" the voltage looks stable. Set to 5.5v and never drops below 5.4

Not sure why the two values are different