can anyone advise on the above?

 

Fred_UK,

Are you simply looking for a signal that goes high for all frequencies within the 500 to 3000 Hertz band and is low for all other frqeuencies?

hgmjr

 

Fred_UK,

Are you simply looking for a signal that goes high for all frequencies within the 500 to 3000 Hertz band and is low for all other frqeuencies?

hgmjr

basically yes, im looking at a high pass then a low pass and another circuit with a couple of transistors to drive an led...

have you got any ideas there hgmjr?

thanks for your reply

 

I posted the Sallen and Key highpass and lowpass filters.
Then on another website I posted a rectifier and LED driver.
What more do you want?

 

My approach would not be quite as minimal and elegant as Audioguru's circuit. Just out of curiosity, is there something about the performance of Audioguru's circuit that falls short of your requirements?

hgmjr

 

My approach would not be quite as minimal and elegant as Audioguru's circuit. Just out of curiosity, is there something about the performance of Audioguru's circuit that falls short of your requirements?

hgmjr

no, not at all, i dont think there is one answer. i appricate everyones help im currently constructing gurus design, just need to work out the values first

 

no, not at all, i dont think there is one answer. i appricate everyones help im currently constructing gurus design, just need to work out the values first

That being the case then I will finish up on the approach I was considering and post it later today.

At least you will have several approaches from which to select the one that best fits your application.

hgmjr

 

im abit concerned about covering the full bandwidth whilse filtering out under 500hz, i would be happy with abit of a curve appearing, ive got the tones as wav files anyway so i should be able to test it ok...

thanks for everyones replys

 

I recommend you give this time to ferment and let other members weigh in on whether it will do the job or not.

There are a number of things to keep in mind if you decide to use this approach.

All 74HC123 are not created equal. In the device I used the datasheet defined pulse width as 0.45*R*C. Consult the datasheet for the 74HC123 that you use and adjust the series timing resistors as needed.

I will be happy to answer all questions.

Remember I warned that my approach was not minimal. It does however mean that you do not have to become an analog engineer to understand how it works.

hgmjr

 

Hello hgmjr,

For the input signal fred needs to make the signal square wave.
The upper part detects the lower border frequency, the lower part the higher border frequeqency (if I am correct).

Greetings,
Bertus

 

I recommend you give this time to ferment and let other members weight in on whether it will do the job or not.

There are a number of things to keep in mind if you decide to use this approach.

All 74HC123 are not created equal. In the device I used the datasheet defined pulse width as 0.45*R*C. Consult the datasheet for the 74HC123 that you use and adjust the series timing resistors as needed.

I will be happy to answer all questions.

Remember I warned that my approach was not minimal. It does however mean that you do not have to become an analog engineer to understand how it works.

hgmjr

thanks for your reply hgmjr

what do you think would be the difference between the two designs? would the bandwidth be similar with a peak in the middle or would the freqency response of your circuit be different?

thanks

 

Hello hgmjr,

For the input signal fred needs to make the signal square wave.
The upper part detects the lower border frequency, the lower part the higher border frequeqency (if I am correct).

Greetings,
Bertus

Greeting Bertus,

You are absolutely correct. The signal will need to be converted to a square wave. This would entail the introduction of gain and perhaps a comparator.

hgmjr

 

sorry!

im lost again, but i do know it start out as a sine wave, how would this effect the cirucit diagrams provided?

thanks
fred

 

thanks for your reply hgmjr

what do you think would be the difference between the two designs? would the bandwidth be similar with a peak in the middle or would the freqency response of your circuit be different?

thanks

One advantage of the retriggerable one-shot based design, is that it is a straightforward task to calibrate the two tone detectors for their respective frequency points.

Once calibrated for 500Hz, this filter would differentiate between an input frequency of 490Hz and 510Hz with the output remaining low for the former and high for the latter. In this respect, it would discriminate between these two frequencies similar to a high-pass analog filter of order 5 or higher. This same discriminatory performance would be repeated on the high end of the detection band.

It is worth pointing out that the second one-shot in each detector leg determines how long after the detection of a valid tone it takes for the output to respond.

The RC integrator is there to provide the second one-shot in the detector leg time to trigger before the output of the first one-shot is presented to the first NAND gate. This prevents any glitches that would occur due to the response delays associated with second one-shot.

hgmjr

 

sorry!

im lost again, but i do know it start out as a sine wave, how would this effect the cirucit diagrams provided?

thanks
fred

As I mentioned earlier, an opamp with gain will probably be needed to bring the signal up to a level that can then be fed to a comparator. The comparator would square up the signal and establish the 0V to 5V signal level needed by the HCMOS circuitry used in the tone detector.

hgmjr

 

Bertus

remember that inductive amplifier circuit you recommended, it's what provided this with the signal i presume that provides a sine wave output doesnt it?

 

Bertus

remember that inductive amplifier circuit you recommended, it's what provided this with the signal i presume that provides a sine wave output doesnt it?

also....

if it is a sine wave input does it need to be converted to square wave, if so do i need any additional components to the above circuit.

the input signal is abit noisey, i have already amplified it some what to be able to hear the tones. i hope this will be ok

 

Hello,

Here is the schematic again :

At the collector of the transistor will be a amplified signal. (run the circuit at 6 Volts as well the detector from hgmjr).
When you drive it through one of the 74hc14 ports you would have a squarewave as input to the detector from hgmjr.

Greetings,
Bertus

 

me AGAIN...

The above circuit that bertus found out for me a few weeks ago does work, you can clearly hear the audio tones, but only when i put it through a seconed amplifier (acutally it's one of those cheap sets of pc speakers, but it is amplifying it that bit more), is there a way i could change around the components on the circuit above to give greater amplification or should i just put it through a second amplifier and then into the freqency detection circuit?

and...

sorry i dont understand that last bit about square singal and the 74hc14 ports

everyone has been so helpful on this project,
thank you very much, im determined to get it working!!

 

Hello,

hgmjr has used 4 inverters from the 6 in the 74hc14, so there are two inverters left.
You can use one of them to "shape" the input signal for the detector circuit from hgmjr.

Greetings,
Bertus