FrSky voltage sensor problem

[sihinch]

Hi,

I have an FrSky voltage sensor, which is part of their telemetry system.  It can be used connected to the rx, and transmit signals back to a display, or standalone with the built in display.  Here is the unit:

http://www.alofthobbies.com/frsky-lipo-voltage-sensor-and-display.html

I have a problem - whenever I connect a lipo to it, it displays the first cell as 4.2V and all others at their correct voltage.  I have tried the unit with several different lipos, and not matter which lipo, or what the starting voltage of each cell is, the sensor always displays the first cell as 4.2V.

Can anyone help?

Thanks,S

[Papa]

Are you hooking it up to the correct pins?

You haven't reversed it?

Jack.

[Ededge2002]

I suspect hooking it up reversed would have fatal results.   But possibly plugging it in staggered over one pin might have an interesting one. Does it indicate the correct number of cells in each pack you plug in?

[sihinch]

It's definitely not reversed - I think that would blow it!

It shows the right number of cells.  I'm going to try moving it one over......

Thanks Guys!

[sihinch]

Nope! Not that.  What you see is the same lipo with:

1) HK Power analyser showing cell voltage
2) FrSky lipo analyser connected as per the manual
3) FrSky lipo analyser connected 1 cell over.

All other connections fail to get a display.  Weird!

[Bobmic]

Hi Simon,

It sounds quite strange, just out of curiosity what's the total voltage you see on the sensor?
As for moving the plug, depending which way you move the plug, the results is completely different.
As long as the first minus on the balance plug starts at the ground port of the sensor you should be good.
If you move the plug over (outside the sensor pins) you will sense one cell less but if you move it inward you loose the ground.
On the Quannum telemetry there is a diode on the connector so it will not work if you flip the connector and will not show the wrong voltage.
Is there any setup you can do for the sensor? Maybe there is a problem with the sensor.

Good luck
Bobby

[Bobmic]

Nope! Not that.  What you see is the same lipo with:

1) HK Power analyser showing cell voltage
2) FrSky lipo analyser connected as per the manual
3) FrSky lipo analyser connected 1 cell over.

All other connections fail to get a display.  Weird!

Just saw your photos, looks quite strange what happens when you connect a higher cell count battery?
...the one cell over is correct..

[sts41]

I'm on the same page as Bobby...Plug in a 2S and a 4S or larger, and see if the same cell is at 4.2...If the cell that is 4.2 moves up or down...then there is a wiring issue inside the unit...If the 4.2 stays at cell 3, then the number 3 sensing circuit is shot.... But, either way, I think you need a replacement unless you want to start troubleshooting the circuit....

If you do want to troubleshoot.....

Look for cold solder joints...Most common issue with China stuff, in this case the load resistor for circuit 3 sensor. You normally need VERY fine soldering iron to play in these circuits 

Steve