Introduction: PropVario, a DIY Variometer/Altimeter With Voice Output for RC Sailplanes

This instructables will show you how to build an inexpensive Vario, that could speak the altitude and
of course send various tones when changing the height of your sailplane.

Some features:

- voice and tone
- use your own (wave-)samples in your language
- wave-samples stored on sd-card
- switch via rc between altitude-voice/vario-tone/off
- automatic announcement of altitude in hundred meter steps
- audio frequency output, you could use your own radios,PMR,FRS,baby monitor or whatever
- the Microcontroller will automatically switch on the radio and "press" the TX-button
- uses 5 Volt from rc-receiver

Here's my first Video, voice output is in german yet, but i 'll upload English voice-samples

Step 1: What You Need

What you need:

- Parallax Propeller Microcontroller (-board)
   i use cluso's CpuBlade because it is the smallest and lightest board
- (Micro-)SD Card + Socket
- Pressure Sensor Modul MS5611 on Breakoutboard
- some caps and resistors, see schematic
- you could use a stripboard or my layout for a PCB
- for the radio link:
  i use a pair of PMR/FMR Walkie Talkie (15-20 $/Euro on Ebay)
  up to 5 km Distance
- Programmer FTDI USB-TTL ( e.g. those needed for Arduino)
- wave-samples and firmware, see next steps


Step 2: PCB or Stripboard

If you want to use a stripboard or the like here's the schematic diagram and you could skip the next step about the PCB.

When using my PCB here's a good making guide

Step 3: PCB

- PCB-Layout is a 1Bit-BMP
- Dimension: 51mm x 28mm
- best choice for SD-Socket is the micro-version, when using a "big" socket you have to assembly
with a little bit space between socket and pcb.
- solder pads for smd or wired caps and resistors, use bottom side for wired parts
- don't forget to connect the 3,3 V pad from sd-socket to 3,3 V regulator from the MS5611-board (see assembly/schematic)

Step 4: Programming the Vario and Prepare SD-card

If the hardware is finished we've to flash the Eeprom of the propeller microcontroller.
You'll need the propeller tool.
After installing start the tool, connect the FTDI programmer to usb and pcb, open the binary i added
and load it into the Eeprom.
The Propeller Tool is very easy to use, the com-ports will automatically scanned for a connected propeller microcontroller.

Now it is time to prepare the SD-card with the wav-samples.

- Format the card with FAT.
- All samples must be placed in the root folder
- I added english spoken sound samples, see zip file
- You can download good samples from here or here
- 8 bit or 16 bit up to 44,1khz needed
- when using you own samples rename in 1.wav, 2.wav ........ (see zip file)
- SD-card max. size 2GB !!!
- When using the pcb with a normal sd-socket instead of micro-sd-socket you need another firmware because
  another prop-pin for DI is used !

Step 5: Connecting Vario With Radio

Here's an example of how to connect the Vario to a cheap Walkie-Talkie i bought at ebay for 15$.

There are five connections to be done:

- 5V supply voltage to the battery contact from radio, also ground
- remove the electret microphone from the radio and connect the "hot pin" to mic from vario
- hot pins from the power- and ptt-button (radio) to vario-pins power and ptt
   (this is needed for automatically switch on the radio)

see also at the attached photo


Step 6: Final Details


- connect a free channel from you rc-receiver to the vario, use a fuse ( 0,5 A ) to avoid risk of shortcut,
the vario is powered by the rc-receiver !

- the rc-transmitter needs a 3-position switch:

Pos1 (off) : PropVario sends no information, radio-transmitter is off
Pos2(mid) : PropVario sends lower/higher tone when the plane is sinking/climbing
Pos3(on) : PropVario sends the actually altitude in meter

When powering the plane the vario turns on the radio and will welcome you with a spoken "ok".
Now you can test the vario-tone by raising the model in you hand.
Also the height response should be tested.

Maybe the rudder limits from your 3-position switch must be modified.

Pos1: 0-20%
Pos2: 21-79%
Pos3: 80-100%

i think the hundret-meter-steps can only be tested in the air :-) they will automatically spoken every hundret meters

Checkout if the use of the radio/frequency is allowed in your country, this is only a test-example for the downlink.

I'll hope you enjoy and feel free to ask your questions !!!


Cluso99 (author)2017-02-27

Congratulations Gelstronic. This is a great little project!

I now have a "lighter" board than my CpuBlade, called P8XBlade2 which has the microSD socket on-board. It's the same area, but is rectangular instead of square, and the pcb is only 1.0mm thick instead of the usual 1.6mm.

It also uses the cheaper USB-Serial CP2102 6-pin converter (<$1.50) rather than an FTDI board.

Further info on my website

Gelstronic (author)Cluso992017-02-28

Thank you Ray

Christian (from Germany:-)

tarales (author)2014-01-08

Can we make a FPV sailplane with ardupilot to program like find thermals in 3 kilometer radius to climb without what meter we find then fly what we need then if we want to climb it again push a button and climbs.
I have an idea like this
Using Ardupilot - minimOsd - Sailplane EP - extra Variometer sensors - speed sensor - Fpv Equipments - UhfLRS . But dont know how to start.

Gelstronic (author)2013-11-10

I added a second binary file for using a normal sd card instead of a micro sd.
This is only important when using my pcb.