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I am using jsn-srf04t ranging sensor (25cm to 5m range) I want to know when it is going out of range(when under 25cm) The problem is when it goes under 25 cm, the sensor output sometimes goes to (90cm to 95cm or 100cm to 120cm) and this cause undetectability of that it is really out of range or not!

Is there any solution?

Sadra
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  • How come this is listed under STM32? – SamR Mar 20 '17 at 02:40
  • I am using both Arduino and stm32 controllers to do ranging with such sensor, on the other hand, most of the guys involved with controllers have some experience with ranging sensors. maybe someone saw that and have had a solution for me :) – Sadra Mar 20 '17 at 15:44
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    Can't really give you a solution, without seeing any codes, or schematics or your setup. But I wrote something down that may possibly help you. – SamR Mar 21 '17 at 02:02

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This question is not directly related, but I thought I post a suggestion/answer anyway.

SRF04's can detect the distances as small as 3 cms. Please measure the width of the output echo pulse using an oscilloscope. It can be from 100uS to 18mS and if there is no object within its range, the echo pulse is 36ms. If the measured pulse width from the oscilloscope is agreeing with what you say, then presumably the SRF04 is faulty, or there is a problem with its mounting etc. If the width of the pulse is measured in uS, then dividing by 58 will give you the distance in cm, or dividing by 148 will give the distance in inches. The SRF sensors can be triggered as fast as every 50mS, or 20 times each second. You should wait 50ms before the next trigger to ensure the ultrasonic "beep" has faded away and will not cause a false echo on the next ranging.

Otherwise, check your timer configuration. Ensure that it can measure a pulse in the order of hundreds of microseconds with at least a resolution of tens of microseconds.

If you are using this, then perhaps you are at the lowest possible level.

SamR
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