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HC-SR04 problems

Hi all,

About a year ago I bought a HC-SR04 ultrasonic sensor, when I got it I tested it using some code I found on the internet and everything worked fine. Now I finally need to use it, I've tested it again with several different pieces of code and none of them seem to work, all I am getting is a seemingly random number that doesn't change no matter what I put in front of the sensor! However I can still hear clicking, so surely the trig pin is working fine and the issue is the echo pin? Any other ideas what the problem could be?

Thanks :)