Can the Basic Stamp process an AC input signal?

Syd

Hi Everyone,
From the basic stamp FAQ, it appears that there are some techniques to accept input analog signals. I am currently attempting to use the basic stamp to determine the frequency of an AC input signal. Does the basic stamp provide any mechanism to handle AC (analog) input signals? Or must I convert the analog signal to digital and then input this signal to the basic stamp? Thanks.

Cheers!
Syd

Phil Pilgrim (PhiPi)

What's the peak-to-peak voltage of the signal?

-Phil

Syd

10V perhaps? Is there a particular "peak-to-peak" voltage that the basic stamp accepts (BTW, the basic stamp model is BS2pe)? In any case, I can always use a voltage divider to reduce the voltage.

Tracy Allen

A circuit that turns the AC into a square wave could do the trick to extract the frequency. With 10 V amplitude, there is plenty to drive a transistor across its 0.6V threshold. In the following, the value of R1 could be anywhere from 10kΩ to 50kΩ. The transistor a 2N3904. The capacitor is optional, and is a small value like 100pF to 0.001 µF and it helps if there is noise riding on the AC waveform.

Phil Pilgrim (PhiPi)

Here's the circuit I had in mind, before I saw Tracy's (which uses fewer components):



The diodes act as clamps, and the voltage divider biases the cap at the Stamp's logic threshold (1.4V).

I think I like Tracy's circuit better.

-Phil

Syd

Thanks a million! I will give it a try and report back.