HC-SR04 ultrasonic sensor ECHO voltage check

Hi,

I need to make sure that 3.3V goes from the ECHO pin to my ESP8266 instead of 5V. I tried a bunch of different resistor voltage divider combinations and check the voltage on the ECHO vs Ground.

No matter what i did, the multimeter would bounce around between zero and 5…

I also tried Analogread (voltage). It did the same thing.

Without compromising my ESP8226, how can I ensure that my voltage divider has brought the ECHO voltage from 5v to 3.3v (or close)?

I dont have an oscilloscope.

Thanks in advance!

As long as you power the sensor off 3.3V (make sure you have a version that is happy with 3.3V, not all are) you will never get more than 3.3V on the echo.

If you power it off 5V, use a voltage divider to bring down the voltage.