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

[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.

[algan]

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

[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]

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

[pito]

you need to increase duty cycle

[kt315]

you need to increase duty cycle

algan:

[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

[pito]

increase C4,

[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.

[Xtrem]

try this

[pito]

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

[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.

[kt315]

try

[algan]

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.

Thanks, Carl, I'll work on the VCO, I think I'll try it and the circuit like this, I don't know if it will be correct, but if I put 100 k two trimmers on the red circle and see if at 32 hertz it will sound like 500 hertz, maybe I'll need wider pulses than these

[Carl-NC]

I assume that as the target signal strength increases, you want the frequency to increase and the duty cycle to move toward 50%. That will give an increase in both pitch and volume.