A Low-Cost DIY Speech Synthesis Sailplane Variometer

I'm Andy Smith and I fly sailplanes at the Cotswold Gliding Club in the UK. I've been using XCSoar and LK8000 since they were first released. My current system uses a Kobo Aura 2, KRT2 radio and Cotswold Vario connected via a Manhatten MTT 4-way usb hub. I will post info and updates on this open-source project on this blog

The vario has a 5611 pressure transducer, ADXL345 accelerometer, X25 stepper motor, Arduino Uno ATmega328P and LM386 audio amplifier. These are all breakout boards from ebay and they are connected by soldering to a pcb
I designed it for our club because the available commercial varios have lots of features which are difficult for pilots to use in the air. It has only a simple volume control because that was the most common complaint from pilots, they need a manual to turn existing varios up! It beeps when you are in lift and burps when the sink is more than 4kts. If you are cruising it's silent, these numbers can be changed easily in the open-source software. I've been using it in my Ventus 2cxt for a couple of years and I find it does the job. I fly block speeds and just speed up when I hear burps and slow down when I hit lift. The accelerometer gives early indication of lift and allows the sink indicated when pulling G to be eliminated. The gain can be adjusted in the software as it can be slightly different for each installation. The vario has both Kalman and first-order damping.
Having an Arduino allows access to the huge library of open source software so I've added speech synthesis. This makes an LK8000/Kobo system attractive as it lacks sound. Airspace announcements in LK8000 are very helpful.
I fly in the Cotswold hills in the UK at the Cotswold Gliding Club, so its called the Cotswold Club vario. Its open source and the 3d files for the front and back panels are available.
Here's the link for the video https://www.youtube.com/watch?v=LTBqkI74g3Y&feature=youtu.be

Here's the BOM Micro Audio Amplifier Module Board Mono AMP Module HIFI DIY LM386 DC 5V-12V X25.168 X27.168 Instrument Cluster Stepper Motor Gauge 8ohm 8#937; 16W Audio Speaker Stereo Woofer Trumpet Horn Loudspeaker 40mm LM2940CT-12 LM2940CT 12V TO-220 Voltage Regulator RJ45 Network Ethernet 8P 8C Female Socket Connector 8Pin PCB Mount Arduino Nano ATmega328P V3.0 with CH340G 5V 16M compatible + Headers PCB files available Stainless Bulkhead Fitting Barb Hose Tube Connector GY-63 Mini Size MS5611 High-Resolution Digital Pressure Transducer 470 microFarad electrolytic capacitor, >20v 16/09/2019 I've reduced the component count and eliminated the Easydriver board. This makes the unit much smaller and simplifies the case design. The system now also announces Flarm alerts  21/02/20 I've added another video of Flarm announcements when connected to a T-beam SoftRF. A new pcb is being designed to allow the breakout boards to be fitted into sockets rather than soldered directly to the pcb. https://www.youtube.com/watch?v=oU0J3tjPbks 25/07/20 The Cotswold Vario project has progressed. There is now a fully functional Vario/Speed Director available incorporating the Teensy 3.2 processor. The system retains the speech functionality developed to supplement Kobo sytems and is now multi-tasking so that audio and speech functions are maintained simultaneously with the vario stepper motor indication. It is designed to be very simple to operate, a middle push button cycles through the menu options with the top button increasing the menu value and the bottom decreasing. It contains XCSoar polars and the following can be configured: Glider type, MacReady, Kalman time constant, Cruise airspeed trip, Thermal airspeed trip, Speed to fly audio deadband, Bugs, Ballast. In cruise mode the vario displays airmass movement (netto). Both basic vario and speed director share a common pcb and case and can be operated stand-alone. Video: ttps://www.youtube.com/watch?v=TLILrTkEUwQ. The audio is controlled by a simple potentiometer which can be mounted lower right or left       Update 02/09/20 Switching between cruise and climb is transparent as the audio beeps in cruise mode when detecting an airmass greater than the MacReady setting. Setting the "Kalman" time constant to 800 is about right for cruise. Its still fast enough to enable you to reject a pull-up and initial turn well before the Winter, where I often have to turn nearly 180 to know if the thermal is good enough. Flarm warning announcements at 30 sec intervals are helpful when sharing a thermal, the height and distance info helps you concentrate on climbing rather than looking for the other glider all the time. The vario beeps still sound in the backgound while the announcements are made and the needle response rate is normal.  Three Speed Director Units