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Ultrasonic transducer question

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aruna1

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Hi
I'm working on a ultrasonic transmitter and using transducer pair like in image I attached.

Currently I'm giving 9V (7809) to drive the transducer (TX) through a H-bridge.

My question is;
I have read in internet that these transmitter drums can operate voltages up to 20V and as the voltage increase the transmission distance increases.I don't have any datasheet on the module and it doesn't have any model number or reference.

**broken link removed**

So is it possible to use a charge pump system to boost 5V supply to 15V and use this 15V to drive the transducer? Since charge pumps cant deliver large current I wonder whether this is possible. But if it possible it will save me from making an inductor based boost converter.

If this is possible what is the maximum ultrasonic burst duration I can achieve with charge pump?

I wonder how they do it on ultrasonic range finder modules like SRF05, they work with 5V.


as I'm using 9V currently I was able to send ultrasonic signal to about 25m. but this is possible only If I'm transmitting continues 40KHz stream.
But if I send 40KHz burst , receiver sometimes failed to grab it even at distance of 8m and receiver is already using gain of 1360.

please note this system is not using the reflected ultrasonic signal. transmitter and receiver are in two different places and used to measure the distance between transmitter and receive.

I want to send a super power ultrasonic burst so my receiver wont miss it at 20m
 
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Since you don't know the current it might be better to use a boost regulator.
 
You don't even know if the no-name-brand transducers work at 40kHz.
You don't know what is the max allowed signal level for the transmitting transducer.

We haven't seen your H-bridge circuit so we don't know if it has any output level.
We haven't seen the schematic of your receiving preamp.
 
You don't even know if the no-name-brand transducers work at 40kHz.
You don't know what is the max allowed signal level for the transmitting transducer.

We haven't seen your H-bridge circuit so we don't know if it has any output level.
We haven't seen the schematic of your receiving preamp.

Hi
Cant help it. cant buy these kind of stuff with model numbers in sri lanka. sellers dont know these items by part numbers all they know these as ultrasonic transmitter-receiver pair.


for circuits
I have posted them below.
in receiver i have fed output of second op amp to LM567 tone decoder to detet 40kHz. its not indicated here as my multisim some how doesnt have 567 IC.
 

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Since you don't know the current it might be better to use a boost regulator.
but i have seen in some circuits (SRF04 for example) they use MAX232 to generate +12V/-12V to drive the transducer. in SRF05 they directly drive transducer with microcontroller pin without even using a transistors. so it is very much likely that they don't suck large current, but I have no idea.
**broken link removed**
 
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In your new receiver circuit you show Q5 and Q8 upside-down so they barely work. Their emitter-base junction probably breaks down.
Q5 and Q8 are PNP so their emitter should connect to the positive supply, not their collector.
Their output is the collector, not the emitter.

Next time, please learn a little about the simple basics of electronics before posting such a randomly-connected circuit.
 
In your new receiver circuit you show Q5 and Q8 upside-down so they barely work. Their emitter-base junction probably breaks down.
Q5 and Q8 are PNP so their emitter should connect to the positive supply, not their collector.
Their output is the collector, not the emitter.

Next time, please learn a little about the simple basics of electronics before posting such a randomly-connected circuit.

ah my bad
circuit is correct,but schematic is wrong. it draw it in a hurry to post here, its a mistake in drawing,,but actual circuit is correct

and I know this basic of PNP

I added the corrected circuit
 
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Rec circuit

Your receiver is not biased correctly. Maybe something like this would work better.

Also, There may not be enough voltage from your battery for the 7809 to regulate properly. It may need as much as 2.5 volts above the output. It's probably ok but no margin.

Audio G may have a better circuit.
 

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Your receiver is not biased correctly. Maybe something like this would work better.

Also, There may not be enough voltage from your battery for the 7809 to regulate properly. It may need as much as 2.5 volts above the output. It's probably ok but no margin.

Audio G may have a better circuit.

hmm
but shouldnt we use virtual ground when using dual supply opamps like TL082?
 
hmm
but shouldnt we use virtual ground when using dual supply opamps like TL082?

A virtual ground is needed when something draws or produces a fairly high current from or into the synthetic ground.
But the input of an opamp has a very small bias current and the TL072 and TL082 have Jfet inputs that have no current, so resistors are fine to make the half-the-supply reference voltage.

Any opamp works from a single supply when its input is biased at half-the-supply voltage and input, output and feedback to ground coupling capacitors are used.
 
@audioguru
I see, can you please explain why is it need to put coupling cap to the "feedback to ground" path?
and how to calculate this coupling capacitor values?
 
If you don't use a capacitor in series with the feedback resistor to ground so the opamp has a DC voltage gain of 1 then the opamp will amplify the DC voltage and its output will be saturated.

The standard formula for a coupling capacitor is 1 divided by (2 pi RC) where R is the resistance the capacitor feeds and C is the capacitor. one coupling circuit produces an output that is down -3db which is 0.707 times. Each coupling circuit drops the output -3dB so they all must have a lower cutoff frequency if you still want the circuit to pass low frequencies.
 

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