If you use Telemetry and voltage warning on your Taranis TX, you might notice the frequent false alarms due to voltage fluctuation, e.g. sudden drop in voltage due to punch-outs. In this tutorial we will show you how to set up Logical switches to make a more reliable voltage alarm.

For beginners, we recommend you to take a look at this guide on how to setup a simple voltage alarm to gain a basic understanding how this work.

Also check out this list for more awesome Taranis hacks and tricks.

Disclaimer: There are million ways to achieve the same thing, this might or might not be the best or most efficient way, but it works great for me. Please let me know in the comment if you have different ideas.

Why set up voltage alarm on the Taranis?

There are many ways to monitor your battery voltage, such as using OSD and voltage alarm buzzer. But my favourite way is to use the Taranis for low voltage warning.

You can make a low voltage alarm easily in the Taranis using simple logical switches, but the amount of false alarms can be both annoying and confusing.

So in this article I will show you how I setup a more reliable and sophisticated low voltage alarm.

Requirements

Make sure Telemetry is working, it will allow the RX to send all the flight information including battery voltage to the Taranis (tutorial: how to setup SmartPort)

And I strongly recommend updating your Taranis firmware to the latest version, because logical switches might work slightly differently in the old version (tutorial: how to update Taranis to OpenTX 2.2)

Step 1 – Setting up Logical Switches

Logical switches are just virtual switches, they can be activated when certain conditions are met.

We can use these switches to create audio and visual feedback both on the Taranis and on your quad. For example, to play a warning, or read out the battery voltage :)

On your Taranis, go to the page “Logical Switches” by pressing the [MENU] button once, and press the [PAGE] button to skip to the next page.

The following screenshot shows the logical switches on my Taranis.

They might look a bit daunting, but they are actually quite simple! i will explain the purpose of each of these Logical Switches.

Logical Switch Conditions Info L01 a<x VFAS 14V L02 This is our primary logical function, it will activate when VFAS (our battery voltage) gets below 14V and when L02 is on (you can set it to any voltage you want, 14V is a good value for 4S LiPo batteries) L02 a>x VFAS 0 L03 This switch is used to avoid false alarms when we are just powering on the Taranis TX. When Smart Port is initiating, VFAS will read 0V. This switch is only on when L03 is on. L03 a>x RSSI 0dB This switch is also used to avoid false alarms, when Telemetry connection is lost. L04 Edge L01 [4.0:<<] Battery voltage on our mini quad can jump up and down a lot, and the edge switch is there to prevent false alarms caused by voltage fluctuation.

It will only activate when L01 has been activated more than 4 seconds, i.e. it will only turn on when voltage is below 14V for 4 seconds or longer. The switch will not activate when L01 suddenly deactivates before the 4-second is reached, i.e. voltage is recovered above 14V. L05 a>x VFAS 14V This switch is used by the next switch, it simply checks if the battery voltage is recovered above our threshold voltage L06 Stcky L04 L05 L07 This is the switch we will use in our Special Function.

The Sticky switch activates when the first parameter is activated (L04) and it turns off when the second parameter is on (L05). This switch stays on or off until the one of the parameters changes state, thus the name “sticky switch”. L07 Timer 6.0 0,1 Without this timer switch, the voltage warning will only trigger once, if that’s what you want you can simply remove this switch. Using this timer switch, the warning can every 6 seconds (you can change to whatever duration you prefer). Beware this switch is added to the “AND” function of L06.

To summarize what we have so far… L06 is only activated when the voltage drops below 14V for more than 4 seconds (L04), and L06 is disabled when the voltage rises above 14V (voltage sag recovers or new LiPo attached). The timer switch will ensure the warning is triggered every 6 seconds.

Step 2 – Setting up the warning

There are more than 1 way to inform yourself of low voltage, you can choose to:

Play an audio track, that says “Warning, voltage is getting low, please land ASAP” or something like that :)

Or simply read out the voltage

I personally prefer to just know the actual battery voltage, so in the next page, “Special Functions”, assign L06 to a function, and select “Play Value” and “VFAS”.

That’s all! Now the Taranis will keep telling you your battery voltage every 6 seconds when it’s below 14V, most importantly you should get the minimum amount of false alarm.

If you have any questions, feedback or improvements to this script feel free to share them in the comments.

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