Voltage step-down for sensing rising pulses


#1

I have an anemometer that runs on a 5V input, which I generate from a boost converter, and returns a pulsed signal from an optical chopper in the anemometer. I need to step down this pulsed signal from 5V to 3.3V for the Mesh devices so I’m wondering if logic-shifting MOSFETs (e.g. a BSS138) are suitable for this or if something like a simple voltage divider is better. The fastest pulses are ~10-15ms apart. Thanks for your feedback.


#2

@LloydChristmas, a simple voltage divider will work. I suggest keeping the resistor values relatively low so as to not affect rise time on the digital input pin. You could, for example, use an upper resistor of 4.7K (connecting to the 5v signal) and a lower 8.2K resistor (to GND).