OpenTX - Application Note 19
Voltage Sensor – FLVSS
Set up a FLVSS Voltage Sensor for an X6R or X8R Receiver.
FLVSS means ‘FRSky LiPo battery Voltage Sensor with Smart port’. The FLVSS is connected to the X6R or X8R via their smart ports. The receiver automatically takes data from the FLVSS and transmits it continuously with any other telemetry values to the Taranis.
The total voltage and single cell voltages are displayed on the reverse side of the FLVSS when it is plugged in to the charge lead of the battery.
Taranis Set Up
The telemetry data sent to the Taranis includes the total battery voltage and each cell voltage. The total battery voltage is parameter ‘Cells’ and the lowest cell voltage is parameter ‘Cell’.
On one of the main telemetry display screens, each cell voltage is displayed in the column down the right side. (A1 is the receiver power supply voltage, showing the current value and the minimum and maximum values beside it. This is measured by the X6R or X8R and not by the FLVSS.)
On the Taranis Telemetry configuration screen number two, the variables ‘Cell’ and ‘Cells’ are set up as horizontal bar graphs. The ‘Cell’ bar graph is chosen to have a range of 3.70V to 4.20V. The ‘Cells’ bar graph is chosen to have a range of 14.8V to 16.8V.
Telemetry display screen two shows the bar graphs like this with the variable value next to each bar.
Low Voltage Alarms
Four alarm types are required. Each alarm uses a logical switch to compare voltages and a special function to announce the alarm. These are the messages and file names.
To create the audio files, see Application Note 4.
Logical switches for lowest cell voltage alarm are as follows
Logical switches for the 3S battery voltage alarms are as follows.
Alternatively, logical switches for the 4S battery voltage alarms are as follows.
Note that the voltages have to be less than the reference for more than six seconds before the logical switch becomes true. This is to prevent short term high battery loads from causing alarms.
Special functions use these logical switches to play the alarm tracks as follows.
Test the alarms by flying until a low battery or low cell alarm is announced. Land and check the battery. Adjust the reference voltages if necessary.
Logging and Viewing Telemetry Data
Refer to Application Note 8 – GPS Sensor for details on recording telemetry data in a log file and viewing it using OpenTX Companion.