Clarification Ultrasonic Sensors..!!!

Hi... i am working on a robotics project which involves obstacle detection... planned to use ultrasonic sensors.. purchased them too... i tested the transmitter and receiver circuit... the receiver side not workin... i am lukin for another transmitter and receiver circuit ... which will work for sure...
please reply as soon as possible... need to submit the project within 1 week...!!!

Please post the circuit that didn't work and we might be able to help you get it working.

i have posted the circuit i have used.. please do help..!!!

What do you mean it doesn't work?

Does the relay remain energised all the time or does it not energise when the transmitter is activated?

How do you know it's the reciever that's not working and not the transmitter?

What are you using for the speaker? Is it a piezo tweeter, 8hm: dynamic tweeter or a piezo transducer?

The reciever won't work with an 8hm: dynamic tweeter, it needs to be a piezo, unless you add DC blocking capacitor.

I don't see the point of having T1 and T2 as booster transistors then having R5 and R4 limit the current, you might as well drive it directly from the 555 and remove D1, D2, T1 and T2.

can u give me an alternate workin circuit... i am less experienced with the sensor parts....!!!!

Even if I had the circuit in front of me I still couldn't do that because I don't know what sort of sensor and transmitter you're using.

Can you please post pictures of them or catalogue numbers?

Hi, this is the circuit I have designed and it surely works.
**broken link removed**
The receiver circuit consists an OP-amp, LM567 (which is a frequency filter), and LM393 (comparator, to avoid false triggering) The circuit operation is very simple - send +5v on pin4 (send ultrasonic sound) for about 200us and start a timer, then wait for pin5 (receive ultrasonic sound) to become high, then stop and read the timer. Multiply the time by the speed of sound, then divide by 2 and here is the distance. The only posible problem is that you can't afford to supply +12V for the ultrasound transmitter there are 2 ways to solve that problem:
#1 Use 5v but the range of the transmitter will decrease dramatically
#2 Use MAX232 and from 5v you'll have around 16v (-8v and +8v)

I hope this will help u

My first thought is the lack of filtering on the receiver?.

It could be easily improved by limiting the frequency response of the two amplifier stages (by adding low pass and highpass filters).

The old LM358 dual opamp has dificulty amplifying frequencies over only 6kHz. It is not suitable for ultrasonic frequencies.

The old LM358 dual opamps are shown with positive feedback instead of negative feedback so they won't amplify anything anyway.

That's right, they'll act as comparators.

Ultrasonic you said?
Use the search function on this forum
Lot's of hits

One written by myself
Never the less, if it's for "normal environment" take a look at this site **broken link removed** you will find all you need on US systems with very clear explanation on transmitter, receiver detection, ...

Sorry to repeat myself

@Nigel Goodwin There is filtering - LM567, you should read first.
LM358 works perfectly in the circuit, the measurments are exactly as if they were in the book Test the circuit and let me know the results.

sv_shady said:

@Nigel Goodwin There is filtering - LM567, you should read first.

Click to expand...

No, the 567 is a tone detector, NOT a filter - by the simple addition of a few capacitors to filter the incoming signal performance would be enhanced. The 567 will only detect the one specific frequency (+/- ?%), but will be helped by not feeding it lots of rubbish.

And like Audioguru says, using a better opamp would help immensely as well.

sv_shady said:

LM358 works perfectly in the circuit, the measurments are exactly as if they were in the book

Click to expand...

The book is WRONG!
The old LM358 operates very poorly at ultrasonic frequencies. It is the first low-power opamp so it is very slow.
The circuit has its inputs connected backwards so it cannot amplify.

thank for ur ultrasonic curcuit,i think it is useful to me!

Hi All. This is my first post here. I have been having a heck of a time with what I thought would be a fairly simple task. Unfortunately, I don't know much at all about analog stuff, filters, etc. Days of head scratching and Google-ing have landed me here.
I am a little off-topic because I am not using a transducer, but everything else suits this thread. The threads I found about buried wires had no useful info.

I am trying to do a variation on the buried wire thing.
I found this circuit a while back and breadboarded it. In the wire I am using a 40 khz square signal originally generated by a spare PWM on a AVR micro.


**broken link removed**
I substituted an LM358 for the 348 pictured as well as the resistor and cap to set the freq of the 567.

I am using a telephone pickup coil for the sensor, although I'd like to be able to use an SMD inductor if possible.

It did not work at all, I now think the amp section is tuned for a freq other than 40khz. I read up some and modified it to a simple 2 stage amp, but with much too high amplification. Despite this, it worked well on the breadboard. I did a PCB for it and shrunk it down to about 19mm square.

It still picks up the wire, but now also scissors, pliers, nails, etc. I think it is picking up the internal signal from the 567.

Can anyone share a +5 volt circuit that will detect the wire loop, and just as important, not detect it when it is not near.

Is it possible to tell from the schematic if the op-amp is tuned for a certain frequency? I don't need to use 40khz, anything over 8khz should be fine.
If it matters, it will be used in a remote control car.

Any ideas are greatly appreciated. This is one part of a much larger project and I can't spend much more time on it alone with my limited knowledge in this area.

Thanks in advance,
Craig

AVR_Craig said:

I substituted an LM358 for the 348 pictured as well as the resistor and cap to set the freq of the 567.

Click to expand...

So why didn't you read Audioguru's post above which says the LM358 is useless at ultrasonic frequencies?.

AVR Craig's circuit is designed for the very odd biasing of an obsolete LM3900 quad "Norton" opamp.

Ordinary opamps are incorrectly biased with the (+) input connected to the +5V supply. So they cannot amplify anything.

The datasheet for the very old LM348 shows a minimum supply voltage of 10V and its response drops above only 2kHz.

The lousy old LM358 has a minimum supply voltage of 3V but it also must be biased correctly. It hardly has any output at a frequency as high as 40kHz.

The MC34071 single, MC34072 dual and MC34074 quad opamps have a minimum supply voltage of 3V and a bandwidth to 100kHz. They also must be biased correctly like all ordinary opamps.