ultrasonic transmitter

[azam.jan]

hi i am going to do my fyp on ultrasonic radar, and now want to draw my ultrasonic transmitter circuit using lm741 op amp. plz someone give me some link
thnx.

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[vinoth8051]

Hi,
Configure 741 op amp in Astable Multivibrator mode. preferrably around 30khz. This would give you series of square pulses. Interface Ultrasonic Transducer at output.

Hope this helps...

 

[FvM]

A 741 won't be able to generate a 30 kHz square wave. It's more a triangle wave form. Do you know why?

 

[vinoth8051]

May be because of slewrate... Dear FvM correct me if i am wrong

 

[FvM]

May be because of slewrate

Yes, 741 is a bad ultrasonic driver for this reason. Most transducers need 40 kHz drive.

 

[kak111]

Here is something to start...................

**broken link removed**

http://circuitos.cl.tripod.com/schem/r72.gif

**broken link removed**

Circuit explanation for the ultrasonic detection unit(1)
- look part : Ultrasonic sensor drive circuit ,
simple , add cmos logic oscillator
and if needed you can add transistor output stage.

KAK

 

[mister_rf]

You can find a similar project here:
**broken link removed**

Also a possible option for an ultrasonic Transmitter is based on a 4011 quad 2-input NAND gate.


You can also use a 555-type circuit, transmission control will be enable using the pin 4 (RESET).
**broken link removed**

 

[FvM]

Referring to the 555 transmitter cicruit, I don't see a reasonable purpose for the transistor output stage. You can achieve the same result with less current consumption by connecting the transducer to the 555 output directly. For pulsed operation, an enable input to the 555 would be used in addition.

 

[betwixt]

The output stage might be able to give a bit more 'kick' to the pulses but not wired the way it's shown. I would lose the two diodes and bypass the R5 with a capacitor. A capacitor across the supply would be advisable too. Check Vcb of the transistors will handle the voltage. Incidentally, some versions of 555 are only rated to produce as little as 2mA output current so a booster stage may be essential.

Brian.

 

[FvM]

Unless a special low power CMOS type is specified, I would assume a standard 555. It can easily drive a standard 40 kHz ultrasonic transducer. The only effect achieved with a pair of emitter followers is further reducing the output voltage.