Hi all!
Anybody tinkered with this sort of common ultrasonic sensor module before?
I'm just trying one out for the very first time today. Pretty good performance in general - after having downloaded some test code from the internet.
The test code that I downloaded uses 'PulseIn' function for measuring the 'high time' of the pulse on the 'echo' pin.
I now realise that the high-time of this pulse on the 'echo' pin is the "round-trip" time (between start of the transmitted ultrasonic pulse and the start of the received echo). I realise that the module conveniently does all the work for us.
But ------ I notice that when the ultrasonic sensor is pointed in a direction with no targets in its usual specified detection range, I get one of two possible results - either values around 16000 to 18000, or values of approximately 70000.
The values can just flick around between these two ranges. Or they may stabilise to 70000 if I move the sensor a tiny bit. Or may stablise towards the 16000 to 18000 range of values if I move the sensor a little bit more.
Some results are shown below for the case where the sensor wasn't being touched, and we get those particular values mentioned.
I also wrote new code (not based on the tutorial) which uses interrupt pins (pin 2 and pin 3) for timing the high-time of the 'echo' waveform. I saw the same results --- either in the 70000 region or in the 16000 region.
Has anybody else encountered the same thing? I even tried a second (same model) HC-SR04 module ..... just to make sure that it wasn't related to a single module.
I'm only just tinkering with this module. And interested to see if anyone has seen the same thing, and if that's expected - or unexpected behaviour? Thanks all!
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