Analog Voltage sensor for FrSky X8R Receivers

Quick Overview

The FrSKY X8R receiver is a great product but it is lacking an easy external voltage sensor. This interface allows you to easily monitor an external voltage source like the motor battery for an electric powered aircraft.
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Please note that this is a neat little product brought about by FrSky users, and is not a FrSky manufactured product.

This device can be used to report voltages via telemetry with the X8R receiver and the FrSky Taranis transmitter. It utilizes a small 8 pin microprocessor to sense a voltage via an analog to digital converter and a voltage divider circuit. This board has its own 3v3 power supply and is fully self contained. There is a blue power indicating LED that will light when connected to the s.port interface on the X8R receiver.


The Smart Port Voltage Sensor can be used to report external voltages via the X8R receiver’s telemetry. 

It utilizes a small 8-pin microprocessor to sense a voltage via an analog to digital converter and a voltage divider circuit. 

This board has its own 3.3v power supply and is fully self-contained. There is a blue power LED that will light when connected to the Smart Port interface on the X8R receiver.

Voltage Reporting Range:

0.0  - 18.2 Volts DC
(will support higher voltages, but will only report the ranges listed i.e. will report 18.2v until battery voltage drops below 18.2)

NOTE: DO NOT exceed 25 volts or you will damage the sensor.

X8R Smart Port Connection:

Use the servo extension cable to connect to the Smart Port connection on the X8R (not the SBUS connection). Please verify the pinout prior to connection with specific interest to matching the positive and negative wires. 

Serial to (S)ignal, Positive to +, Negative to -

Analog-in Connection:

Connect to the voltage source being monitored. Please maintain the correct polarity. One of the terminals is labeled Analog-In, this is where the + or positive terminal of the battery you are monitoring attaches. The other terminal is labeled GND, this is where the ground of the battery you are monitoring attaches. (See the following diagram.)

Voltage Sensor image

 Taranis Setup:

The Smart Port Voltage Sensor voltage will be read as Sensor Channel A2. 

On the Taranis Telemetry screen set the A2 channel range to 18.4 volts. Set the offset to 0 volts. Set the Low Alarm and the Critical Alarm Values to an appropriate setting for the battery type and size you are monitoring.

Questions? Need some help? Please visit the manufacturers blog on RC Groups at this link. (Click Here)

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Works well Review by MacCross
But it took some time to figure out that it needs D16 in Internal RF Mode (model Setup). (Posted on 6/19/15)
Exceptional sensor, exceptional value Review by Darknoise
I love this little sensor! It is small, easy to connect, works well with the X8R and X6R, and is fully compatible with all the Taranis B firmware versions I have tried. I prefer this sensor as it supports voltage without requiring connecting to the balance tap. I put one of these in everything I own. (Posted on 4/8/15)
Analog Voltage sensor for FrSky X8R Receivers Review by Eli
Works without flashing my x8r. I have to adjust my A2 channel range to 18.6v and offset to 00.7v to match my actual voltage readings. Only issue is the voltage is a bit jumpy +/- 00.06v no matter how I adjust (reason for 4 stars, otherwise its 5 star solid). There's gotta be a way to stabilize the readings. (Posted on 12/26/14)
As always great service Review by Matthew
Wayne has gone above and beyond so many times I cant begin to count em, Great Support, even for bone heads like me. Will always buy my FRSKY stuff from him!! (Posted on 12/20/14)
Excellent service and quality Review by Larry
Received the sensor in three days. Easy to install, and works very well. (Posted on 11/27/14)
Works great Review by David H
Just installed one in my yak 55 connected to a 4s battery. Is reporting correctly to Taranis based on comparison to my dvm. No reflashing or other stuff required as reported by others. Will install two more this week in other planes but this is going to be great. Weighs nothing. Delivered extremely fast. Aloft rocks! (Posted on 11/8/14)
Works as advertised. Review by David
Connected to the Smart Port of a FrSky X8R to monitor a 3s Lipo it worked perfectly out of the box. No re-flashing or other drama. (Posted on 5/17/14)
Good Product Review by DanFlys2Hi
How great is this voltage sensor! I have 2 of the older style and 2 of the newer one, and one of each has the High Resolution jumper on and they all work perfectly with 2S and 3S and without the jumper 4s works great. Works with common ground (analog in only) or wired with a separate common. Each way you wire it though (I.E. with or without jumper, and with or without common ground) all have different ranges on your A2 channel, but once range set, seems to work accurately up and down the voltage scale. Thanks. (Posted on 4/30/14)
Good product Review by Roland
Soldered pins, connected to s_port, connected battery source, and set up a2 in transmitter. Voila works like a charm. (Posted on 4/24/14)
Don't buy this unless you are ready and willing to reprogram it Review by John
First let me say , if and when you get it working , it's great! now for the bad.. if you have a newer X8R , this will not work until you reflash it.
to do this you will need to research , dig through countless pages in forums, buy more parts, and sharpen your soldering skills.

if you like to tinker and read forums till whee hours of the night , this product is for you.

if you expect it to work when you get it.. you will be disappointed.

I rated this product 1 star... not really for the product itself but for the overall experience it takes to get this working as intended (Posted on 3/28/14)
Battery voltage the easy way! Review by Dave
The device works perfectly and doesn't require fine tuning like the frsky divider!

It can be reprogrammed by you or many others to keep up with frsky changes and it now works with the x6r, too!

(Posted on 2/17/14)

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