suggest me a circuit for a detector that has a good sound circuit

[kt315]

try

[Carl-NC]

try this

The speaker drive is not the problem. The problem is that the VCO duty cycle is not correct. algan, most likely you will need to experiment with the VCO and figure out what component values will make it work correctly.

[pito]

put 1uF or more and show what you see on oscilloscope, show what you have on pins 4,5 lm339

[Xtrem]

try this

[algan]

increase C4,

Hi, Pito. I tested your suggestion, I put 100 nF, but the sound became more hoarse and nothing changed in the distance, I still can't hear a clear signal, I'll return the old capacitor, the sound is more pleasant with it.

[pito]

increase C4,

[algan]

Where to make a correction to the scheme, please correct it and I will test your suggestion and tell you if there is a difference

[kt315]

you need to increase duty cycle

algan:

[pito]

you need to increase duty cycle

[algan]

These are the signals at the output of the LM339. The first, weakest sound is heard at about 30 hertz, then it increases as I get closer to the object, the sound increases as it goes closer to 520 hertz

[kt315]

i think your sch has fatal mistake and you never do it. this attempt of to release VCO is bad. the sch has not a modulation - you do not hear the sound. go standart way, not turn up your fantazy.

[algan]

Thank you colleagues for the advice, I will try your suggestions.

[eduardo1979]

Hi Algan. I think, according to the schematic you posted, the speaker isn't connected in the correct location. I would connect the speaker between the collector of transistor T4 and V-, and connect the emitter of T4 to B+. Resistor R18 could be connected in series with the speaker if necessary.

[Carl-NC]

You need to look at the signal at IC5a with an oscope, see if the modulation is changing sufficiently with signal strength. Personally, I don't like using PWM as the way to modulate volume as it also changes the timbre of the sound and can make faint targets harder to hear. I prefer a constant 50% square wave and then use the envelope of the detected signal to control the loudness.

[Altra]

It looks like they used the fisher 1265/66 audio as Eduardo suggested. The target signal modulates the audio pulse width as kt315 mentioned. This circuit is sensitive to over modulation. If the duty cycle goes over 50% it actually starts to mute the audio. I would monitor the output of the lm393 with an scope. Experiment with different values for R16 and P1.