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UltraSonic Level Detection (H2O).

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Ayne

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I am making an UltraSonic Level detector for just experiment.
Using PIC for doing all the work

Now the problem is
UltraSonic transducers are not available in our local market. So i am planing to use Audio Tweeters for transmitter and receiver. At lower frquencies 16KHz.

What u say it will work or not???

Want to measure Level of water in a tank at home just for experiment.
 
A sonic approach seems like it's worth a try. It certainly eases the demands on the transducers. You might go lower in frequency and try the plastic coned speakers - as they'd be more tolerant of moisture.
 
Hi,
It should work OK, the original ASDIC ( SONAR) worked at audio frequencies.
You should try to find the resonant frequency of your transducers. Mount them facing each other at the sort of sange you want, connectone to an indicator of some sort ('scope is best but a multimeter on AC low voltage should be OK), connect the other to a signal generator and ajdjust the frequency for the highest received signal. Use this frequency for your design.

Robert G8RPI.
 
Being someone with above average hearing range and fidelity I would recommend just upping your frequency a few khz. 16khz is quiet painful to me. 18khz is in the annoyance area, our TV puts out a bit too much 18khz noise for me, but it's tollerable as long as their's noise (the TV volume itself) After listening to even a small 18khz clip at a loud volume I'll be able to notice the 18khz noise coming from my TV for upwards of half an hour. If you can just reach 20khz or maybe a little higher you're going to effectivly be outside the range of direct human hearing, though you may hear people complaining about hearing sounds in weird places from the odd heterodyning effect, but that's only within line of site, a level detector doesn't need a lot of power.
 
Since the wavelength is longer and a lower freq response means the speaker and/or mike is slower to respond, the resolution and offset accuracy may be very limited.
 
I think a human cannot listen above 14Khz.. It is in theory that Audible frequency range is 20Khz..
Whay u say???
 
Ayne said:
I think a human cannot listen above 14Khz.. It is in theory that Audible frequency range is 20Khz..
Whay u say???

20KHz is just an average, some people (particularly women and children) can hear above that. Only 14KHz would be well below average.
 
oops it means when i will run my circuit at 20Khz, all the women of my colony will come to my house with stick in their hands.
 
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My Software

Below is the Picture of software made by me for Sending data and receiving.

I made in VC#.

Rate this??
 

Attachments

  • MyLevelmasda.GIF
    MyLevelmasda.GIF
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hi Ayne,
Running at around 20kHz, it should send all the local dogs quite 'barking mad' after a few minutes of operation.

Some dog barking deterrents work around these frequencies

There's a guy in the UK, developing a sound system, I think its around 24kHz, that is used near shopping centres in the evening, to 'disturb' and drive away gangs of youths who sometimes gather in these areas.

It seems to work, so you may drive away all the young ladies!!

I expect you don't require continous water level monitoring, so you could just have a 1 Sec pulse burst every 10 minutes or so.

Regards
EricG

edit:
As Oznog points out, the overall resolution would be low at 20kHz.

G8RPI
When the lower frequencies are used a Sonar, the velocity of sound in seawater is around 1500m/sec compared to 330m/Sec
in air, so you get a 4.5 increase in 'apparent' resolution.
 
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The ultrasonic pulse commercially built units send out just sounds like a ticking sound a couple of times per second or so. They only send out a few cycles of the signal, that's why it sounds like a tick. They run at around 35-45 KHz (sometimes higher) and use the same transducer for transmit and receive. Here's a link to one: **broken link removed**
JB
 
Cheap tweeters don't make sound to 20kHz. Maybe up to 15kHz.

Tweeters are very fragile. Continuous power destroys them.
 
I don't know if it's any help?, but MANY, MANY years ago the magazine Practical Electronics (now called EPE) did a car 'radar' project, the idea being you could detect cars ahead in fog - I suppose a primative version of what the top of the range Mercedes do now?.

This was back before ultrasonic transducers, so they used a speaker as the transmitter, cutting the cone down till it was small, and then doping it to make it stiffer - this allowed the speaker to output ultrasonics. I seem to remember they used some kind of microphone as the receiver?.
 
You can buy special modules to do this.

But if you want to build your own then a simple piezo transducer will work. Those little copper disc ones have a sharp peak at around 30kHz and are very cheap.

The best way is to check be buying two and connecting one to a signal generator or even 555 astable and the other to a scope and tuning until the peak output is found, a frequency counter is useful to precisely measure the frequency.
 
I thought the Mercedes used real radar? Ultrasonics don't work so good at highway speeds. the power output would have to be huge.
 
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