AllThumbs

AllThumbs

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We noted in our data that the amperage in flight was bouncing around a lot from + to - in about a 10 amp range (+7 to -3). After some searching online I called Vans. Gus said their RV-12 gives the same readings and the shunt is inline between master and load to produce the +60/-60 range limits that Dynon indicates in their install manual.

Searching the dynon forums and rotax forums it appears the output from the stator/regulator-rectifier combo on the rotax is pretty wild and wacky.

A call to dynon confirmed that they are seeing problems with this configuration and have tried some software things to smooth it out but there is no update on the way. In the meantime I'm assuming that some + amp readings, combined with about a 13.5 or better voltage, indicate the battery is charging.

-Neil
 
Current shunt

If the RV-12 is wired similar to this schematic by Bob Nuckolls,http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z16M.pdf and the shunt is between the main battery contactor and the main power bus, then the ammeter should never read negative. But without an electrical schematic of the RV-12, who knows how it is wired. Does the RV-12 have a 22,000mfd or similar capacitor as shown on Bob Nuckolls drawing? A large capacitor will help stabilize the alternator output. Ideally, the alternator should put out slightly more than 14 volts to charge the battery.
Joe
 
WE NEED A COMPLETE SCHEMATIC DIAGRAM

Yes, we are in dire need of a COMPLETE electrical schematic diagram. VAN's....PLEASE!!!

From my time working in the digital controls industry, if the output of the generator is noisy, a large electrolytic capacitor will certainly help.

The Dynon samples the voltage across the shunt x times per second, and then displays the current reading. If the sample occurs during a noise spike, the reading will not be true but a combination of the voltage across the shunt and the noise spike. (The noise spikes can be positive or negative). The positive noise spikes are most likely clamped to some maximum voltage.

Most likely, this is what is happening. When I replaced the switch panel (to correct a laboring trim servo) I did not notice a large electrolytic on the board. A 22,000uf capacitor would be obvious.

I DID notice the fluctuating current reading during my first flight.
 
MartySantic said:
Most likely, this is what is happening. When I replaced the switch panel (to correct a laboring trim servo) I did not notice a large electrolytic on the board. A 22,000uf capacitor would be obvious.
Click to expand...

It is plainly visible on the back side of the switch panel. It fits within a cutout in the aluminum rear coverplate.
 
Yes, yes, yes. The large electrolytic was in front of my face!!!

Scott, any idea why the amp reading bounces so much??
 
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