10-30-2009, 05:47 AM
I have a sine wave signal that varies from 1.5vp-p to 12vp-p. I have been running this right into a basic stamp input and measuring the frequency and it has always worked fine except when the voltage goes to low. What can I do to allow the basic stamp to see a sine wave with a voltage that low?
Phil Pilgrim (PhiPi)
10-30-2009, 03:02 PM
Here's a circuit that should help:
The diodes will clip the capacitively-coupled input to ±0.6V (i.e. 1.2V P-P). This is further capacitively-coupled to a resistive divider, which biases the Stamp input pin so that, without a signal present, the voltage on the pin is just slightly above or below the Stamp pin's logic threshold. That way, even very small signals will straddle the Stamp's logic threshold, resulting in logic transitions.