PI Audio

[h9361]

Just to add a bit more info..
My VCA circuit while designed to be driven from PWM outputs of a dspic or similar, is versatile enough to be a standard variable amplitude single tone output by using a 555 , cmos osc etc as audio input and feeding the CV input with a conditioned 0-2v DC signal from your favourite integrator , filter and gain stage. I don't vary the Pulse width into audio input only frequency ..eg digitise front end signal after integrator and filters then pump the value out to the PWM. The CV input is set frequency but variable pulse width which is based on same digitised signal input but inverted and firmware filtering and threshold added to it

cheers
Mdtoday

I hope you see my post and guide me to use your schematic.
Thank you.

[h9361]

Thanks waltr.

Here is the processor controlled audio I generally use...has variable pitch variable level.
It works well too. It uses 2 pwm outputs from DsPic.

Spice circuit and screenshot attached.

[ATTACH]45389[/ATTACH]

cheers

Mdtoday

Hello
Dear Mdtoday.
Before everything, thank you for your sharing your information.
Dear sir, i built the Mickstv's schematic by your help and it works very nice. Now, i am going to use your schematic over my HHD and to compare it.
If i understand correctly, i want to use a 7555 timer (osc) as input for Audio_pwm and CV connects to TP5, is that true?
Is it possible to share me full schematic with threshold control?
I think i can connect final audio_out as input to lm386 (including volume), but i don't know how to add a threshold to your schematic.
Thank you.

[Nightryder]

I redrew the pcb with thicker tracks & more space between them to make it easier for home etching.

Credits and thanks goes to Emersonpaz of course. I highly recommend to visit his YouTube channel and check out the link he provided first.

I had to fix two mistakes which are shown in the pic attached with the corrected PCB.

[Nightryder]

I made the project from mickstv I'm using it on the Polish pi https://youtu.be/RDV93ZdeGhk

I redrew the pcb with thicker tracks & more space between them to make it easier for home etching.

Credits and thanks goes to Emersonpaz of course. I highly recommend to visit his YouTube channel and check out the link he provided first.

[h9361]

Looks ok, now go build it and try it out, build the power supply and audio amp first, make sure it works, then add Mickstv circuit, do it in stages, test each stage then move to next one. Dom44 did a through hole version, others have built that one too, he used an Lm386.
As Mickstv and others have said, the circuit works, so why not build as per the schematic posted first, give it a try then start changing things.
It is the best way to start, try not to complicate things, I’m sure you will do just fine.

Hello
Dear Mdtoday
I hope you are in a good health.
Before everything, thank you for your supporting and please forgive me for my questions.
My friend, as you know, i added the GB (based four Sampling) part to my HHD (attached general schematic). Then i added your Audio to it.
Both of them is working nice but i have a strange problem with audio. As you know, the audio works based on both pitch and volume level. For exp, if a target is closed to coil, both volume and frequency will be changed. Similarly, if target is far from coil, only its frequency will changed. My problem is in middle of the distance, exactly edge of called close distance. In this distance, my audio part produces a strange audio, like a noisy signal. It acts like a non-motion mode but its sound is a very very noisy, instead of a clear audio for closer targets. I think the audio part can't make a decision for doing both pitch and volume or only pitch changing. So, it compounds them incorrectly. For solving the problem, do you have any suggestion for the schematic? which part of the schematic should be edited? Remember that i have no problem with high and close distance, only middle distance is problem

[bernte_one]

follow way MET_DET\ProScan_Impulsowy Wykrywacz Metali\kret + modul

https://drive.google.com/file/d/1Czc...ew?usp=sharing

Hi KT315
can you renew this link?

[aymenrhouma]

I made the project from mickstv I'm using it on the Polish pi https://youtu.be/RDV93ZdeGhk

Can you share the diagram and upload it in Grbr or sprint layout

[Emersonpaz]

I made the project from mickstv I'm using it on the Polish pi https://youtu.be/RDV93ZdeGhk

[kt315]

follow way MET_DET\ProScan_Impulsowy Wykrywacz Metali\kret + modul

https://drive.google.com/file/d/1Czc...ew?usp=sharing

[scrungy_doolittle]

As you may know, the whites 6000 di figures out a target, by taking the log-rhythms of the two channels, and then subtracts them, resulting in an analog signal that gives the ID. I wonder if this circuitry would be capable of doing something similar.

[h9361]

No, it's not required IMO.
Has this problem just occurred, or has it always been there?
If it was stable and you have made changes then the problem appeared, then you need to back track
Board layout, faulty component, component choice, bad solder joints...
Please post a schematic and photo of your build, then we can see what you have and maybe we can help more.
You can still test most PI designs in house but you need to at least do it away from computers, tvs routers etc.
If you have a variable frequency TX and variable gain RX, then you have a better chance of reducing the noise problem.
I haven't been following your thread much so I'm not aware of all the experimenting you have done, so can't really comment much more.

cheers

Before everything, i must thank you for your guiding because the schematic is working nice.
Dear Mdtoday, i'm interesting to change the schematic for detecting target timing.
Suppose that i detected a target, so my audio has a action and then will go to its base tone (no changing frequency and level position).
If you see carefully, going from changing frequency/level position (detecting target) to no changing frequency/level position (no target) has a high speed! If you see audio of GPX, the speed is slow and soft! Do you think we can reach such soft audio like GPX? Do you have any suggestion to change and to test in circuit?
Thanks.

[Mdtoday]

Thanks for your answer.
I tested it more and more out of city, clear of any noise.
Do you think i should use a multiturn for THD pot?

No, it's not required IMO.
Has this problem just occurred, or has it always been there?
If it was stable and you have made changes then the problem appeared, then you need to back track
Board layout, faulty component, component choice, bad solder joints...
Please post a schematic and photo of your build, then we can see what you have and maybe we can help more.
You can still test most PI designs in house but you need to at least do it away from computers, tvs routers etc.
If you have a variable frequency TX and variable gain RX, then you have a better chance of reducing the noise problem.
I haven't been following your thread much so I'm not aware of all the experimenting you have done, so can't really comment much more.

cheers

[h9361]

Thanks for your answer.
I tested it more and more out of city, clear of any noise.
Do you think i should use a multiturn for THD pot?

[Mdtoday]

Hello
Dear Mdtoday.
I hope you are fine.
I have a question about Mickstv audio.
Is it possible to change THD pot smooth?
For exp, i change my THD pot from silence to audio, i have a noisy audio. So, i have to increase my THD pot to have a clear audio.
For a better understanding, consider THD pot of GPX, it is very very smooth. Do you have any suggestion for reaching such smooth THD?
Thanks.

Check your power supplies are well decoupled, although it is most likely external noise, possibly mains power, RF and the like. Also, don't forget to check the simple things like a bad potentiometer.
If it is constant motor boat type noise, as in the audio pitch and volume is hunting up and down, then you can try adjusting the TX frequency up and down a little by 1 or 2 Hertz to reduce that particular problem.
If it is higher frequency hash type noise, then you will need to reduce the circuit gain a little but note, this won't always fix the problem.
It's always troublesome to test a PI detector on the work bench given the usual array of EMI present in most homes.

cheers

[h9361]

Hello
Dear Mdtoday.
I hope you are fine.
I have a question about Mickstv audio.
Is it possible to change THD pot smooth?
For exp, i change my THD pot from silence to audio, i have a noisy audio. So, i have to increase my THD pot to have a clear audio.
For a better understanding, consider THD pot of GPX, it is very very smooth. Do you have any suggestion for reaching such smooth THD?
Thanks.