FrSKY Variometer sensor

This is a barometric pressure sensor which provides telemetry for vertical speed changes and altitude. These values are very useful for RC glider pilots looking for thermal lift. Cost about A$33 (Feb 2015)

The telemetry can be presented in a few different ways.

1. As beeps of varying pitch to indicate whether the glider is rising or sinking. Higher pitch beeps for rising or lift and lower pitch beeps when it's sinking.

2. As spoken altitude values. My preferred method.

3. As on-screen numbers. Not so good because you have to look away from the glider to see the screen.

4. As an altitude graph in OpenTX companion on your computer. (If SD card logging is enabled on the Taranis)

This video explains how to connect and setup the vario with a Taranis Plus running OpenTX 2.0, and with OpenTX companion on an iMac.

FrSKY Telemetry sensors

One of the most exciting functions of the Taranis X9D is telemetry. 

As well transmitting signals to the onboard receiver, the Taranis can receive data sent back from sensors on the plane. That data can be recorded on the SD card for later viewing, or presented live on the screen or even as spoken values and audio prompts.

In the next series of posts I will explain the functions of each sensor and how to get them working.

Here are four of the FrSKY telemetry sensors with the X8R receiver. 40A current sensor. LiPo voltage sensor. Variometer sensor. GPS sensor.

Each sensor is supplied with a female to female servo lead to connect it to the S-Port on the receiver. A second set of S-Port pins allows more than one sensor to be connected to the receiver at a time. You simply connect one sensor to the next in line.

Once correctly connected to a powered receiver the red LED on the sensor will change from fast flashing to slow flashing. That may take a few more minutes with the GPS.

At this stage the sensor is transmitting telemetry data but you can't see it anywhere. You need to go to the Special Functions screen for the current model to activate telemetry recording and sounds, or the Telemetry setup page for on-screen displays.

Activating SD logs

In the Special Functions screen select a switch (e.g. SG-), select "SD Logs" from the list of available functions, select how often telemetry data points are recorded (e.g. every 1.0s) Now whenever the SG switch is in the middle position telemetry data is recording onto the SD card.

SD logs include all the available telemetry data. RSSI (signal strength) and the position of every stick, knob and switch on the Taranis are recorded without any sensors required. With the appropriate sensors connected data like speed, position, altitude, distance, current, power usage and voltage are recorded. It's a mass of fascinating information to look at after your flight using OpenTX companion. If you're in to graphs you will love SD logs. 

Here are a few examples of what is available via OpenTX companion on your PC. 

I will go into more detail with each sensor in following posts.

Signal strength

Flight battery voltage

Current draw 

Telemetry display screens

To view the data in real time you need to go to the Telemetry setup page for your current model, scroll down to Screen 1 and select the values to be displayed. You can choose Bars for bar graphs or Nums for numbers on the screen.

In this example I have selected RSSI, Current and Timer 1 to be displayed on Screen1 of the telemetry screens. The 40A current sensor would be required in this case.

Here's how it looks on the live telemetry screen. Of course numbers greater than zero would appear if the plane was powered up and flying.

Spoken telemetry

The most useful way to present live telemetry is via sound or voice. Dependng on which sensors are connected the lovely lady in my Taranis can tell me such things as the altitude of my glider or how many mAH have been consumed, no need to look at the screen at all. 

To activate audio telemetry go to Special Functions, select a switch, select PlayValue, select which value to play and select how often to repeat.

In this example the Taranis will tell me the Consumed Power (Cnsp) in mAH every 10 seconds when the SC switch is down. (As long as the 40A current sensor is connected)

This is only scratching the surface of what is possible with the Taranis and OpenTX. 

There are logical switches to play with and LUA scripting as well. LUA scripts are like little programs that you can run on your transmitter. They can add functions like the Model Setup Wizard or extra graphical telemetry screens. There are hundreds of scripts available for download on the OpenTX forums. The possibilities are endless.

FrSKY X8R and X4R receiver connections

The latest receivers for the Taranis are the X series. They are  telemetry, S-Port and S-Bus capable.

I don't really understand S-Bus at this stage, it has something to do with connecting another receiver for more channels or many S-Bus servos into one plug.

However I do use the S-Port for connecting telemetry modules. On the X8R the S-Port is a servo style connector - easy. But on the X4R the S-Port is a different 4 pin socket. A 4 pin plug with 4 bare ended wires is supplied so you need to make up your own servo style plug.

This video shows what I'm talking about

Taranis X9D vs Turnigy 9X battery plugs

Many RC pilots will upgrade from a Turnigy 9X transmitter to a Taranis X9D. It's a logical progression especially if both are running OpenTX firmware.

It is tempting to take the 9X battery and plug it into the Taranis, but it won't work. The plugs are the same but the wiring is different.


This photo compares the two plugs and wiring.

FrSKY Taranis and OPENTX 2.0

This is the FrSKY X9D TARANIS plus

It's a 16 channel transmitter that uses OpenTX open-source firmware. It has telemetry, sound, haptic (vibration) feedback and lua scripting capability. Telemetry logs are recorded on a micro SD card when activated.

For about A$250 this is a stunning transmitter. It must be one of the most programmable and adaptable transmitters currently available.

All the parts are easily replaceable and readily available from places like Banggood, Hobby King International and BoltRC in Australia.

There are no in-depth manuals for the Taranis or openTX but there are lots of online resources like OpenTX University, YouTube, and RCGroups.

I thought it would be a good idea to record the tweaks, mods and programming revelations as I progress. Mostly so that I don't forget them but also to share with like minded RC pilots.

Replacing the LCD

I cracked the LCD screen by dropping the Taranis onto a hard floor. It was in a backpack at the time but not a padded one. The Taranis still worked fine but not the screen. This video shows how to replace the screen. Very easy, no soldering, plug and play. New LCD bought from BoltRC in Perth for A$33 plus postage. Note that this video is for the Taranis plus. The original Taranis uses a different LCD. Some websites say that fine soldering is required but that refers to the backlight not the LCD.

Switching the switches

For DLG launching I like a momentary switch on the top left of the transmitter. Launch mode requires a brief blip of "up elevator" to rotate the DLG skywards, but my right hand is launching the glider, hence the need for a momentary switch on the left. 

As supplied the Taranis has a momentary switch on the top right and a 2 position switch on the top left.  Swapping them could not be easier. Both switches have their leads plugged. So you just need to open the back of the transmitter, unplug the leads from the switches, undo the retaining nuts and swap the SF and SH switches. Plug back in, replace the back and it's done.

Phoenix 2000 sloper mods

The 2m Hobby King Phoenix 2000 was designed to be a motor thermal glider, but it works very well as a motor-less slope soarer.

Soren from Denmark, speedsterDEN on YouTube, has some amazing videos of sloping and dynamic soaring with this very cheap glider.


Slope soaring is fairly rough on foam gliders due to the rough and often uncontrolled landings.

The Phoenix has a tough plastic fuselage which is perfect for the job. However the wing and tail need some strengthening mods to help keep it in one piece.

My flap control horns pulled through the foam after a few flights so I added ID card plastic reinforcing to spread the load.

The wing is supplied with bolts and plastic caps to secure to the fuselage. These tore through the thin foam around the rear mounting bolt after a few rough slope landings. I decided to change to a rubber band tie-down mounting method for more durability. The wings were glued and taped together permanently.







I drilled 5mm holes in the fuselage to fit the CF tie-down rods. No reinforcing in this area is needed. The rods are held in place with hot glue.

Here is the wing securely held in place with rubber bands.

Below are videos explaining these mods and showing some flights.

Sloping along the sand

Sloping from the dune