Disdrometer to measure rain and hail, limit voltage

Projects General Guidance
1

Hi

I am wanting to create a simple circuit using a Piezo Electric element to generate a voltage when it detects that it is raining or hailing outside. This will be interfaced to an Arduino and PC at a later stage.

The piezo element can product a positive and negative voltage when it picks up a vibration so I am thinking of using a Schottky Diode to rectify the signal so I only get positive voltage values.

The next issue is I am unsure of the maximum voltage that could be induced in the piezo element especially if I amplify the output voltage a little bit. Sometimes hail is very very heavy and may produce a larger voltage than I am expecting.

So my question is:

I want a limit the voltage to a maximum of 5v so even if the piezo + amplifier produced 7v I just want to truncate it at 5v, but the voltage < 5v is left to be what ever it is.

in software c# it would be something like below but I am unsure of the terminology to use when searching and hence my post here.

int Value = (Value > 5 ? 5 : Value)

Any help appreciated.

Chris

2

Hi, you don't want to limit the output in software, if you are using an arduino to measure the piezo output, after the amplifier you need to limit the output to 5V before the arduino ADC input, the input has a limit of 5V.

What you need to add to the output of the amp is called a CLAMPING circuit, this can be as simple as a resistor and a zener diode.
Google 'voltage clamping circuit' and see what you get.

Tom.. :slight_smile:

3

TomGeorge:
What you need to add to the output of the amp is called a CLAMPING circuit, this can be as simple as a resistor and a zener diode.
Google 'voltage clamping circuit' and see what you get.

Thanks Tom

The clamping circuit is what I was after just not sure of its name.

Cheers

Chris