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Old Apr 09, 2015, 11:54 AM
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A failed attempt to put a variometer inside a X4R receiver

I want to share a failed experiment here. The idea was to put my self-developed TE variometer (aka RaptorSense) in a X4R receiver from FrSky. It didnít work well due to the interference problems.

It all started when I was trying to fit a X4R receiver and my variometer in a borrowed Elf. Elf is an ultra-light 1 meter DLG with a tiny fuselage. The variometer disappeared easily in a corner and managed to fit the receiver despite the relatively huge connectors.

Itís easy to open the X4R. At least one of the boards needs to be insulated in order to stack the electronics. It would be logical to insulate the smaller variometer but I have to keep it naked to be able to update the firmware. The firmware is still in development and the electric contacts to upload new versions are at the bottom of the board.
The three wires for the telemetry port are internally patched. The wires are kept a little longer in order to make it easy to upgrade the software. As far as I can see, the RaptorSense will not make this tiny receiver noticeable thicker, as it fits between the antenna connectors.

I was initially extremely pleased with the results. Unfortunately, the variometer readings became too noisy after putting the RaptorSense on the top of the receiver. Just too intimate I guess. Other way around, the receiver doesnít have any problem with it.

I don't know how it would behave with other telemetry receivers. Is this a specific X4R problem or a FrSky problem or is it generally not a good idea to put this kind of electronics so near to each other? Or, maybe is my electronics to sensitive for HF noise.

Itís a pity that it didnít work as expected. Any ideas how this can be solved? Maybe a metal sheet in-between or wrapping the boards in aluminum foil or Ö?

Cheers, Sinan
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Old Apr 09, 2015, 05:04 PM
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Hi all,
My first post here. Greetings. . .

Hi Sinan,
I see the pictures but I don't get this. I have couple of questions:
- I have 3 of these X4R receivers in use. I have also two of the frsky variometers (high precision). They will never fit in an Elf (nice dlg btw) en certainly not in a 4XR. The variometers are in fact bigger than the receiver. Where is this variometer from?
- Why do you want to put an TE variometer in an Elf? I hope that you are not going to fit a TEK tube or even better a Venturi probe in an Elf.

Thanks
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Old Apr 10, 2015, 03:21 AM
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Hi Thermalist,
Welkom here.

I am developing this variometer together with a friend, it is not a product from FrSky. It is much smaller and lighter than the existing variometers.

The aim was to build a fully functional TE variometer that you can fit everywhere in the plane. Ideally, it should be installed in the tail fin together with a pitot-static probe without worrying about shifting center of gravity and without plumbing the otherwise necessary long tubing. I have also produced some pitot-static probes from carbon to keep the weight down at the tail. A complete set, consisting of the variometer, the probe and a couple of centimeters tubing weights together less than 5 grams.

And, I was not planning to install a TEK or Venturi probe in an Elf . It would double the weight of the plane and quadruple the drag. Although itís designed as a TE variometer, I can configure to act as a simple uncompensated variometer. That is how it is installed in the Elf.

This variometer has two pressure sensors, normally to measure the static and total pressure in order to calculate the altitude, airspeed and total energy (hence a TE variometer) of the airplane. Best source for the static and total pressure is usually a pitot-static probe. The variometer will function equally well with a TEK probe but it cannot measure the airspeed anymore.

Sinan
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Old Apr 11, 2015, 07:00 PM
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I have done some additional experiments, unfortunately without success.

Following the comments at the Dutch modeling forum, I have wrapped the variometer in cooper foil and wired it to the ground (with and without extra capacitors). It seems to have some influence on the characteristics of the noise but itís still unacceptable.


Vario in upright position reduces the noise significantly but it is still there.


Back to the original setupÖ
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Old Apr 14, 2015, 09:11 AM
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Although I don't understand yet what this variometer precisely is/does, it looks as an intriguing device. How would you use it. Do you have more info about the specs and pricing.

Thanks
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Old Apr 14, 2015, 10:21 AM
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This variometer is not available (yet ) It is an old project but we are still busy developing it. The one on the pictures is the latest reincarnation with the newest Bosch BMP280 sensors.

We call it RaptorSense (formerly known as SuperVario). It consists of up to 5 pressure sensors and a processor in a tiny package (19 x 6 x 3 mm). It weighs less than 2 grams including the telemetry cable and the connector (naked 0.7 gram). When connected to a pitot-static probe, it can measure the following values:
- altitude
- airspeed
- total energy
- temperature
- the rate of change of the altitude (=simple uncompensated vario)
- the rate of change of the total energy (pure TE variometer).

RaptorSense differs from the other model variometers by being a pure TE variometer. It eliminates the misleading stick thermals and provides the airspeed for optimal flight performance.
It can communicate through the FrSky and Multiplex telemetry protocols. I am planning to support other protocols as well.

I should start a proper thread to introduce this project. Should I do it in the electronics sub-forum or is the ďSailplane TalkĒ sub-forum the right place to publish?

We are planning to introduce it as a product soon. Meanwhile we are busy testing, tweaking and calibrating it.
I hope this answers your questions.

Cheers, Sinan
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Last edited by PapaHotel; Apr 14, 2015 at 10:27 AM.
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Old Apr 16, 2015, 02:48 PM
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I am trying to create an overview of the available variometers at the Thermal sub forum. I am started to get obsessed to find the best variometer available. Do you mind to take a look and include the specs (resolution, lag, dimensions, Ö) of your variometer.

The best variometer thread

Thanks
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Old Apr 16, 2015, 05:44 PM
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Done
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