Setup Taranis to Read Out Voltage & Simple Voltage Alarm

by Oscar

In this tutorial I will show you how to setup a switch on the Taranis to simply read out the voltage of the battery on your quadcopter.

Some of the links on this page are affiliate links. I receive a commission (at no extra cost to you) if you make a purchase after clicking on one of these affiliate links. This helps support the free content for the community on this website. Please read our Affiliate Link Policy for more information.

If you don’t have OSD on your quad to tell you your battery voltage, it’s tremendously helpful to get the Taranis read it out for you because you can’t fly and look at the TX screen at the same time.

For more useful tips and tricks about using the Taranis, make sure to check out this guide :)

Requirement – Telemetry!

In order to allow the Taranis know the voltage of the battery on your quad, telemetry is required.

For X series receivers such as R-XSR, XSR and X4R-SB, you will first need to setup Smart Port.

You can check if telemetry is working correctly by going to the “Telemetry” page on the Taranis (press menu button once, and keep pressing page button until you get to that page).

Now plug in the battery in your quad, and VFAS should display the voltage of your battery. (VFAS basically just means your battery voltage)

Set up a switch to play voltage value

Go to the “Special Function” page on the Taranis (press menu button once, and keep pressing page button until you get to that page).

Add a new switch (any switch of your choice), and assign a “Play Value” function to it, and choose “VFAS” as the value.

In this example, I assigned SH switch to SF1, and when I flip the SH switch, the Taranis will play value VFAS. Simple as that.

A Simple Low Voltage Alarm

Do you want the Taranis to automatically remind you when voltage gets low? Here is how.

It involves using Logical Switch – a virtual switch, that can be activated when a condition is met.

We can create a logical switch (L1 in our example) to compare the the battery voltage (VFAS) to a value of your choice, say 14V for a 4S battery. If the battery voltage is lower than this value, then L1 is activated.

To make the Taranis read out the voltage when L1 is activated, we just need to create a Special Function and assign it to L1.

But whenever you power on the Taranis, it will always shout “0 Volts”, that can be annoying.

That’s because it takes a moment for Telemetry to work when the TX is powering on, and VFAS will read as 0 volt which triggers the logical switch.

To fix that, we need to add one more logical switch (L2) to do nothing when VFAS is 0 volt, and put L2 in the “AND” switch in L1. So L1 is only on when voltage is lower than 14V, and higher than 0V.

Another situation where we might get a false alarm is when telemetry connection is lost. To fix that, we need to put in another logical switch (L3 in our example) to say we only want to trigger L1 when RSSI is great than 0 (don’t forget to add L3 in the AND switch of L2)

In L1, next to AND switch (L2), we have Min Duration (3.5) which means how long the switch will remain on before switching off. In our example, voltage must be lower than 14V for at least 3.5 seconds to trigger the alarm.

The next parameter is Delay (0.2), which is the cool down time for the switch to be switched on again.

So in our example, the Taranis will repeat the voltage ever 3.7 seconds if voltage is below 14V.

A More Reliable Low Voltage Alarm

There is more than one way to skin a cat, and there are many more ways to make the low voltage alarm more reliable and accurate: Using Taranis logical switches to set up reliable voltage alarm

Leave a Comment

By using this form, you agree with the storage and handling of your data by this website. Note that all comments are held for moderation before appearing.


BALAJI PRASAD 19th April 2023 - 11:49 am

Thank you.

Enrico 18th November 2020 - 5:26 pm

Thanks Oscar! Do you know how can I set an haptic vibration as alarm? I tried {L1 Haptic “any number” 1} but I can feel the vibration when telemetry is lost. Cheers

Lucio 10th February 2020 - 5:56 pm

Hi, my taranis qx7s read and repeat the same value 14.4 every time, I set 14.5 . What s about ? Thanks

Renato 2nd October 2018 - 11:30 am

Hi, I have a Kopis 2. On Taranis qx7, on telemetry page there are between the sensors, 4 VFAS. Why this? Thank you

jimmi 20th August 2018 - 5:39 pm

will this still work if i am using a crossfire module

Arcright 19th August 2018 - 8:39 pm

Has anyone else had issues getting this or the more complex voltage alarm to work on a 6S quad . I appreciate this may be an issue with my Eachine stack but it appears that the voltage is to slow to reach the trigger point so that alarm sounds every time the lipo is plugged in with a value like 0.2volts .

Kellie Stapleton 19th July 2018 - 9:11 pm

have a Mantis 85: RSSI A1 and A2 display, but cannot get VFAS to show up. Hit discover sensors, nothing. armed quad hit discovered sensors, nothing. Have checked Betaflight and telemetry enabled.

Hayk S 8th March 2018 - 3:31 pm

Thanks for sharing this tutorial.