Fas100 - wrong current measurement

[Dilbert]

Hi I have a problem with the fas100 (frsky with telemetry mod). I have connected it to the hub2.0 that route to the receiver data port. After installing the last open9x firmware the measured current shows about 40A instead of about 0A. The analog output have a value of 0.6v corresponding to 0A. I am not sure if it is an hardware problem or a bug in the latest version. I will perhaps try installing an older version of open9 x.

Has anyone encountered the same problem???

Ciao Stefano

[Dilbert]

I made further investigations. I have tryied with a FAS-40 and the reading on the 9x display is correct. The problem is related to the FAS-100. I assume is my new fas-100 that is not working correctly.

STefano

[RightRudder]

I made further investigations. I have tryied with a FAS-40 and the reading on the 9x display is correct. The problem is related to the FAS-100. I assume is my new fas-100 that is not working correctly.

STefano

I recently ordered FAS-100 but received FAS-40 labeled as FAS-100. The BATT and ESC positions are opposite with these so I reversed my connectors and voila the current is reading. But it is only a FAS-40. I complained to hobbyking and they just said thanks for letting us know. No credit, no offer to send me the correct part. No promise to inform recent customers to check their parts! BEWARE!

[Dilbert]

Thank you for info. I will check mine, but how can I find if it is a 40a instead of a 100a?

[Kilrah]

The FAS-100 is bigger and thicker. On the 40 the thickest part should pretty much be the cables. On the 100 there's a big fat component pretty much in the middle of the board, about 1cm thick.

[rainer]

I recently ordered FAS-100 but received FAS-40 labeled as FAS-100. The BATT and ESC positions are opposite with these so I reversed my connectors and voila the current is reading. But it is only a FAS-40. I complained to hobbyking and they just said thanks for letting us know. No credit, no offer to send me the correct part. No promise to inform recent customers to check their parts! BEWARE!

Did you pay via paypal, and if yes, is there still time to open a Paypal case?

[RightRudder]

So here is the official response from Eva at FrSky:

Dear Joe,
Thanks for your e-mail and support.

There is one batch of 120pcs FAS-100 provided to HobbyKing that with the same PCB size as FAS-40 but they are true FAS-100 and could measure 100A without problem. They have been well tested, but were put on the wrong label - the BAT and ESC positions should be opposite.

Sorry for the trouble and thank you again for your report and support.
Best regards!
FrSky Team

[jhsa]

hhmmmm, strange.. because the PCB says FAS-40. would be interesting to compare the components with a real 40A sensor and see if that is really true.. if it is equal and can really measure 100A, why bothering paying more for the 100A one?

Something doesn't smell good

João

[Kilrah]

Because of what he said in the other thread, while the "small" 100A version can measure 100A it introduces a big voltage drop the real FAS-100 doesn't.

[jhsa]

so, the other sensor is really a 100A sensor sold as a 40A, right?
or is it a 40A accurate sensor sold as an inaccurate 100A.

Or someone just messed the labels up and now has to invent an excuse to try to make it look right? This sounds more like it to me..

[RightRudder]

I think what happened is that now that FrSky have a superior product ie the FAS-100 they were having a hard time getting rid of stock on the older FAS-40. So they changed the shunt so that it could handle 100 amps safely and maybe adjusted the firmware to get the correct readings with the new shunt and then stuck FAS-100 labels on the last 120 units and sent them to hobbyking to unload on the unsuspecting public. The only flaw in this devilish plan was that they didn't account for the fact that the current flows in opposite directions in the two devices. So the FAS-100 label creates a problem. It's not a nice thing to do though even if they hadn't got caught with their pants down because at high amperage the shunt robs significant voltage that the motor is never going to get to use. Since there is no shunt on a real FAS-100 there is no voltage drop. It senses current by sensing the magnetic field generated by the current through a trace on the board rather than reading a voltage drop across a shunt. (A shunt is just a very low resistance in series with the current). I hope that makes it clear.

[Kilrah]

I think what happened is that now that FrSky have a superior product ie the FAS-100 they were having a hard time getting rid of stock on the older FAS-40.

Tha can't be, because the FAS-40 was released 6 months after the FAS-100