ultrasonic project

Thread Starter

yasir_66

Joined Jun 25, 2009
71
hi friends,
plz help me in troubleshooting a problem in my circuit.I made a ultrasonic transmitter & receiver project.I couldnt find SL100 & SK100 transistors so instead of these i used A684 & C1383 transistors.When i energize transmitter & receiver circuits,the relay on receiver circuit switch on instead of receiving transmitted signal by transmitter.Plz held me in analyzing whats wrong with & circuit.
here the diagrams.

click here to enlarge schematic
 

Wendy

Joined Mar 24, 2008
23,415
I think I recognize this design. The transmitter is brute simple, and sends a simple U/S tone. The receiver is similar to an AM receiver, and picks up sidebands. If anything moves in the area doppler will create sidebands, which triggers the relay.
 

Ron H

Joined Apr 14, 2005
7,063
The receiver will not work. The op amp output needs to be able to swing to the positive rail (vcc) to turn off the PNP. It can only go to about vcc-2V. Also, the input stage is biased into saturation, assuming you are using a piezoelectric transducer.

The transmitter does not need the transistors, diodes, R3, R4, and R5.

The receiver (if it was biased correctly) is just an amplifier and peak detector, followed by an op amp that is being used as a comparator. I don't see and sideband detection.

Where did you get this design?
 

Thread Starter

yasir_66

Joined Jun 25, 2009
71
if there is a equivalent of SL100 & SK100 so plz tell me.I thing these two transistors A684 & C1383 is not suitable for this circuit.plz tell me true & working equivalent for these transistors.
& also tell that how can i identify the terminals of u.sonic transducer.one terminal is shorted to metal surface of transducer is this a gnd?
 

Ron H

Joined Apr 14, 2005
7,063
if there is a equivalent of SL100 & SK100 so plz tell me.I thing these two transistors A684 & C1383 is not suitable for this circuit.plz tell me true & working equivalent for these transistors.
& also tell that how can i identify the terminals of u.sonic transducer.one terminal is shorted to metal surface of transducer is this a gnd?
You don't need transistors. A CMOS 555 might give you a little less power output than a bipolar 555. See attachment.

The receiver won't work.
 

Attachments

Ron H

Joined Apr 14, 2005
7,063
The transistors are used to drive an 8 ohm tweeter through a coupling capacitor. The transistors are not used to drive a piezo transducer.

The designer of the circuit does not know much about electronics.
The transmitter has 110 ohms (equivalent) in series with the transducer, which would not give much output into an 8 ohm tweeter, so I was assuming piezo.
 

Audioguru

Joined Dec 20, 2007
11,248
I think the original article said that the author tested the ultrasonic transmitter with a low power piezo earphone which might explain why the two 220 ohm resistors are there.
 

Thread Starter

yasir_66

Joined Jun 25, 2009
71
i think transmitter circuit issue has been solved.i just have to remove transistors & diode & connect transducer directly to 555.Now how my receiver circuit will work correctly & what replacement should i have to do?
 

Wendy

Joined Mar 24, 2008
23,415
Posted as a PM to me...

yasir_66 said:
Plz tell me why relay goes on on energizing receiver circuit instead of activated by transmitter?
Wookie says this best...

SgtWookie said:
General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.
To answer your question, if this is the same or similar to Popular Electronics circuit I mentioned earlier, the output speaker sets up an ultrasonic field, which the input speaker and circuit receives. Note the two diodes in front of the op amp, this is a AM detector. If something moves in this U/S field the U/S frequency is dopplered, which means frequencies slightly above and below the U/S carrier are formed, which means the diodes will have a very low frequency (around 1Hz, give or take, depending on the speed the object is moving) feed into the op amp. This will in turn trigger the relay activating an alarm.

In other words, it is a simple motion sensor.

I could also be wrong (but don't think I am).
 

Wendy

Joined Mar 24, 2008
23,415
To Bertus:

What you saw is what I got...

To Yasr 66:

One other point, you can safely drop the U/S frequency to just above audible. If you have teenagers, cats, or dogs expect complaints if you do this (since their hearing goes above ours), but the concept is not frequency sensitive. This might help the speakers work better.

With the Popular Electronics article the speakers were patio speakers, and were very well disguised as to their true purpose.
 
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