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Forum Index : Microcontroller and PC projects : DIY ultrasonic range sensor

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Frank N. Furter
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Joined: 28/05/2012
Location: Germany
Posts: 987
Posted: 08:13am 01 Aug 2019
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Hi to all!

I try to build an ultrasonic rangefinder like the HC-SR04 (but with only one piezo for sending and receiving).
I found different circuits in the net (e.g. also from the HC-SR04 or also on transistor basis) but I can't see the reflections clearly on my oscilloscope.

When I measure with the oscilloscope at the input of the µC of the HC-SR04, I wonder that the part can measure distances at all! All I see is garbage - and every time it looks different!

Do any of you have any experience in this area?

Any help is appreciatet!

THANKS!

Frank
 
Solar Mike
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Joined: 08/02/2015
Location: New Zealand
Posts: 1173
Posted: 12:38pm 01 Aug 2019
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I remember building a range finder about 35 years ago, using a single 40 Khz transducer, after transmitting the single 40 Khz pulse the transducer was switched to a receiver via an op amp active BP filter tuned @40 Khz.

Today the dual transducers would probably work better, after sending a pulse on one, unblank the other for a time period, pass the signal through a filter, op-amp etc to get rid of the noise.

Post a link to the schematic you are using, its difficult trying to be clairvoyant.


Cheers
Mike
 
Frank N. Furter
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Joined: 28/05/2012
Location: Germany
Posts: 987
Posted: 08:21am 02 Aug 2019
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Hi Mike,

thanks for your response! I tried this circuit - page 3.
The signal after AD_WANDLER looks not bad but the sensitivity is not really good (slight tilting of the reflecting surface is already a problem)

After AD_WANDLER2 I get nothing back - just a constant fidgeting HIGH signal.

Then I tried to use the receiving stage of the HC-SR04.
I generated the pulses with my µC and tried to receive them with the oscilloscope on the line "signal" - I received non-reproducible garbage.

Frank
 
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