z axis feed back for under a dollar? - variable capactive-> freq-> mic

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That specific chip I linked is actually 1MHz, I dont think a 2MHz chip exists.

The thing which worried me about the standard 555 is that I am not sure if the circuit config in the datasheet to produce a fixed 50% on/off will work. My client tried using a standard 555 and claimed it didn't work, but since it wasn't me doing it I have doubts about his claim.

Here is what I recommend with what you have:

Get the standard 555 circuit working with a more traditional 555 oscillator configuration.
I found this on youtube:
https://www.youtube.com/watch?v=stN-ZzHfiO4

I used a 22Meg resistor with 57pF from the 2mm glass. Let's assume you get 570pF, since the equation is linear youll want to be getting a resistor in there between 1 and 5Meg. If you have a variable 20 turn pot of 10 Meg it would be perfect as you could tune it to within audio range. Also, buy a few 200pF capacitors so that you can get it working first without fumbling with the salt water until it is ready.


Oh, and I forgot that not everyone has an oscilloscope! Maybe look for a 555 to speaker circuit like this:
http://www.eleccircuit.com/many-simp...ound-circuits/

OR buy an oscilloscope for $250 because the'yre awesome (probably go with the speaker for now).

Carefully cut your foil tape with a ruler and exacto-knife so that you get a more narrow even strip such that your kapton will overlap it.

You'll need to probably fold over one end of the foil tape because you can't solder to aluminum foil (don't try, you'll ruin the iron tip).

Then stick the foil tape to the inside wall of the top reservoir as vertical as you can. It isn't critical since you'll need to calibrate it anyways eventually and it will all still be linear. Make sure to have the folded tape part way above your water level.

You need to completely and reliably cover that foil tape with the kapton tape. No air bubbles! Line it all up and slowly press it on?

You will need to put one capacitor wire from the breadboard into the salt water (ground?). use a long wire, have it in close proximity to the foil tape but not too close (maybe tape it right beside with your kapton). The other wire of the capacitor you should clip on the foil. Try to keep the whole thing tight (make sure to protect against splashes from the water on the electronics).

Maybe before even adding the salt water, you could have another piece of clipped foil and cover the sensor to test it without the water.

Good luck!


Oh, and if you do overlap the tape, it needs to be perfectly even. I see more success in cutting the foil to be even.