I'm building a little project, where I'm about to try and send/receive a signal; from one piezo-disc to another piezo-disc.
Have one mounted on the bottom of an aquarium (the sender) and the other floating at the surface (the receiver).
Both piezo-elements are inside waterproof containers and the one at the bottom (the sender) has - for the moment - a plastic tube mounted on it's top.
The aquarium is filled with water (drinking water, so the salinity is low) and it's at room temperature.
Using a quite simple "knock-code" for the piezo-discs connected to the Arduinos; have two Arduinos, i.e., there are two completely separated systems.
GOAL (nr. 1): To get the receiver/piezo-disc at the surface to be able to pick up the (yet too faint) signals produced by the sender/piezo-disc at the bottom.
PROBLEM: Need to enhance/increase the sensitivity of the receiver, i.e., want to amplify the output-signal from the receiver. As it is now - unamplified - I can pick upp the signals if there is only approx. 2-3 cm between them, but want to be able to receive them from the bottom.
QUESTION: If I do amplify the output signal from the receiver with the help from a transistor/-s; how do I then make sure that the Arduino isn't damaged if the signal gets to strong? The receiver is connected to analog port A4 on the Arduino and I guess it's easy to damage the Arduino if ampilfied to much?