# Lightweight Variometer

To anyone that is electronically talented ...

I'm looking for someone to help me on a personal project that I've spent some time cooking up. I fly remote-controlled gliders with a audio and video-downlink. The camera and microphone is on the glider, the signal is transmitted down to a ground-station and I can see &amp; hear from the glider's perspective on the ground. Into that glider, I'd like to put a Variometer which you would develop.

A Variometer is a device that signals altitude loss or gain through varying the frequency of an audio file. There is a great article at Wikipedia: [url removed, login to view] ... And here's a variometer in action: [url removed, login to view]

Variometers are used to signal thermals (air moving upwards) so the glider can climb without using valuable battery power.

What I need is a MEMS PCB or component which I could plug between the microphone that I'm using currently ([url removed, login to view];cPath=7_33&amp;products_id=113) and the data transmitter. The PCB should then mix the audio signal from the microphone with the Variometer signal and output both in the same format as the microphone. So there is one &quot;signal in&quot; from the microphone and one &quot;signal out&quot; along with a power connector (+ / -) and a power passthrough to the microphone.

The barometric sensor on the vario must have a sensitivity of at least 10cm and the reaction-time (= frequency change) must be &quot;instant&quot;. The sensor must only be able to signal altitude difference, not absolute altitude, but must work under &quot;normal&quot; conditions (0 - 40 deg C, 0 - 5000 meters above sea). Here are some of the features that I'm looking for:

* Minimize power consumption and space (smaller = better!), I have about 1cm vertically, 3cm x 3cm horizontally available.

* Works on a wide range of input power (3VDC - 15VDC)

* Sound output (frequency calculation) following the other varios. Ascending frequency when ascending, descending frequency when descending. Pulsating tone when gaining height (seen absolutely, &gt; 0m/s), constant tone when losing height (seen absolutely, &lt; 0m/s)

* Quiet when no climb/descent is noticed (between +[url removed, login to view] and [url removed, login to view])

* Adaptive frequency according to climb rate. E.g. the highest frequency will first be assigned to 3m/s climb. If the glider exceeds that, the gamut of frequencies will be remapped to the current climb rate, so that the pilot can still differentiate between 3m/s and 5m/s climb.

* NO electric noise. All the equipment on board will get into problems when equipment emits noise/magnetic fields/etc.

And here are some of the &quot;deviations&quot; that could be discussed, e.g. to reduce cost or to improve features:

* Instead of mixing the signal on a chip, a small speaker could be implemented to output the signal. In this case, the vario could just be glued to the microphone, and the mixing will be done automatically

* Absolute height could also be given each 100m or so. See above youtube video.

* Exchangeable audio file that gets altered in frequency

* Power pass through not on board but done by myself using cables

Please give me the price for a single test component, what features you could include, what you require from my part and estimated completion as well as per piece cost should I want a spare or one of my friends wants one after the initial order. I will not promise any big orders, so charge me full for the first one and make the consecutive ones cheaper.