[SOLVED] Ultrasonic sensor hc-sr04

[irfan ahmad]

hi engineers.........
what is minimum interval between two readings of this sensor
i want to read after 1ms every time.
will it work???????????????

 

[FvM]

What's your intended distance range? Consider sound velocity and find the minmum interval set by sensor physics. It might be that the sensor electronic sets an additional lower limit on the interval. 20 ms is said to work for this sensor. Smaller intervals may work for short distance, but can give erroneous readings, e.g. a far echo is faking a near one.

 

[shahbaz.ele]

Dear it can measure from 2cm (minimum) to 400cm (maximum).
its minimum time I measured is about 50 us.
its formula is

Distance = [delay time (s) x 340 (m/s)] / 2

 

[irfan ahmad]

Thanks everyone.
It is working well after 1 ms inter wall. without noise.

 

[shahbaz.ele]

have you written uc code for it.

 

[irfan ahmad]

T
his one
https://www.ccsinfo.com/content.php?page=compilers

 

[shahbaz.ele]

Thank you dear.

 

[irfan ahmad]

here is code and video link.
https://digilogelectronics.blogspot.com/

 

[shahbaz.ele]

Thank you once again.

 

[paulfjujo]

hello,

Dear it can measure from 2cm (minimum) to 400cm (maximum).

Did you really test it at 2cm ?

because on my device, i started with a minimum of 6cm , wich is over time for:
10µS for trigger pulse and waiting 200µS to the end of burst slave of 8 cycles à 40Khz (internal action made by the device)
so total of 210µS before testing echo..

Regarding what you said .. 2cm
i tried to reduce the delay between pulse trigger and Survey the echo feed back
When i reduce to much this delay, ie 50µS measures between 6 cm to 2cm are very erratic
and the measure can be reversed ( increase instead of decrease inside the gap 3 cm to 0 cm)

if i keep half of the delay of burst salve ,just after trigger start.. so 10µS +100µ=110µS
Measures are correct and stable from >= 30mm up to 3900 mm. (not tested above)

I think we can not reach very close measure as 2cm , because Receiver sensor recive in same time
the burst salve of pulses 40Khz of Emitter sensor..

I don't know if all sensor of this type have same behavior, but i know that
there is allways a dead band of measure with ultrasonic sensor.

could you confirm if you can reach 2cm with good measurement (linear and stable) ?

 

[irfan ahmad]

1. i have measured 2cm minimum .
2. my coding is different from datasheet.
3. it has resolution of 1cm .
4. measurement is started from pcb edge, not from ultrasonic sensor edge.
as shown in pic