Ultrasonic sensors questions

Other Hardware Sensors
1

Hi

Simple Ultrasonic sensors use the trigger pin every 60ms to trigger a measurement, and to my understanding, once the waves were sent out, the echo signal goes high, until it gets back the wave.

  1. I wonder what if there is nothing to reflect the ultrasonic wave back?
    Will the ECHO signal remains high, or is it being reset after a certain amount of time, before the trigger goes up again?

  2. All examples I have seen, were using the CPU power of the arduino as the trigger. I wonder why is that. Wouldn't it be better to use the built-in timer as a wave pulse generator, and use the CPU only to determine the distance from the length of the echo input pin? this can be don't using interrupt when ECHO signal goes high (start) and go low (end).

2

Since you do not specify I will assume that you are writing about a HCSR-04 type range finder and using the pulseIn function to get the duration of the echo.

If you are using the pulseIn function to get the ping travel time the function will time out after the default 1 second unless you set the timeout parameter in the pulseIn function.

I really do not understand question #2.

Post the code that you are using and a schematic so that we don't have to assume so much.
Read the forum guidelines to see how to properly post code.
Use the IDE autoformat tool (ctrl-t or Tools, Auto format) before posting code in code tags.

3

You mean the 10us trigger pulse, consisting of

digitalWrite (triggerPin, HIGH);
delayMicroseconds (10);
digitalWrite (triggerPin, LOW);

All that CPU power?

4

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