PI Audio

[ZOUjiarui]

Seems to be forgotten. I built a pi with a vco and sound amp added, not designed by me. It makes a buzzing sound like a ground balance, but it is a bit thicker. The depth is probably reduced by about 25%, but it excludes the red bricks and does not just bark like the white surf pi. I have not tested...

[Detectorist#1]

In my PI-MD project with IB coil, I also use VCO for high-low tone for Fe/non-Fe targets discrimination and different threshold stage, but I'm not sure for GB capabilities of my design until the field tests.

[eduardo1979]

The error has disappeared, as using a 4066 as a demodulator with its corresponding level translators worked perfectly. The VCO was also modified and replaced with a 4046. The Threshold stage was also modified. In any case, this is a project that can be further improved. For now, it detects a gold wedding...

[eduardo1979]

Hello everyone.
First of all, I congratulate Carl on this great project.
I've tried to add some fuel to the fire, as there is always room for improvement in any project.
Now the preamplifier is two-stage, using the OPA1612AID, the audio VCO is made with the famous 4046, the demodulators...

[eduardo1979]

Hi Carl.
I'm stuck and need your help.
I'm drawing the PCB for the Bipolar PI in SMD and I have a question regarding the 74HCT4316 as I see that it gives problems. Could I put a 74HCT4066 instead, making the corresponding modifications on the PCB on the power pins, since they are different?...

[Emersonpaz]

Excellent video Carl congratulations, it was very well explained, I believe that if the VCO with the 4046 two tones was integrated into the bipolar project it would be a great improvement, I made an adaptation to the Polish pi
https://youtu.be/RDV93ZdeGhk?si=ekkBRbZmtrbz_A20

[Carl-NC]

I have completed testing the Bipolar PI design and posted new firmware. I changed the timing to use 1 timer and is now all interrupt-driven, there are no polling delays. This gives the delay adjustments more resolution and more consistency.

Two things I don't like about the design. One...

[Mdtoday]

Here is a great little VCO circuit Mickstv posted back 2-3 years ago and I've had veroboard version for use on my bench for so long..it finally gave out so I decided to put it onto a PCB.
I added extra decoupling, changed Fet and added option for audio amp connection..all vanilla stuff.
...

[Carl-NC]

As I said before, I need a few days to thoroughly go through this. Apparently what happened is that I built a first PCB proto of the circuit (derived from the PI-GB circuit) and found some problems with it. I made corrections to the circuit but then forgot to transcribe those changes to the book schematic,...

[GeoMax]

Hi Asanka,

if you can't find a LM331 VCO IC, just use a CD4046 IC. The CD4046 is actually a PLL IC, but also has a nice VCO part. Of course, you need to further modify the TL12000. The CD4046 is a DIP16 IC, cheap and widely available. I have already seen some detector circuit modifications...

[GeoMax]

Hi ArchibaldSTM,

the question is where to start improving the TL12000 circuit.

I would start with the following circuit parts first.

1) Redesign the power supply circuit and relabel the power pins.
2) Redesign the front-end-receiver using a widely available...

[GeoMax]

Hello,

If you take a closer look at the circuit of the TL12000, you would see that it is almost identical to the circuit of the PI Polones. As far as I have seen, the PI Polones has no other design problems. The major difference between these two circuits is essentially just that the switching...

[Auto-Mation-Assist]

I have not had a chance to read everyone's latest comments carefully yet since I have been very busy laying out the circuit boards for my AGD24.1 version. The AGD24.1 version will have two back to back circuit boards. I have completed design of those boards and submitted them for manufacturing to my...

[GeoMax]

Your board looks like a modified PI Polones or Proscan schematic with an additional 4046 VCO circuit. The PI Polones or Proscan are almost the same circuit. They are all modifications of the original Sandbanks PI from 1979.

[Emersonpaz]

I see that the intention is to adapt a VCO to the Polish pi circuit and for that it is using the VCO of the 4046 but as you can see there are a lot of pins left it would not be more interesting to use a dedicated Ci with just VCO I would use the LM566.

[GeoMax]

What is the name of the detector? From the IC's it could be a mix out of PI Polones with VCO.

[Op04]

I would like to add. We still don't have PI project (analog one) that has ground balance in one package with less complexity (I know GS5 pain to build it) all scattered into many deep post painfull to dig and mix them all. Waltr use 3ch on HH2 but It's not analog, I wish someone could make this 3ch...

[ivconic]

Of course, with such "broad" things, one can never compile a precise wish list from the start.
I would add just one more suggestion.
That the same concept is developed in parallel both in the analog version and in the "digital" version, or. without and with the use of...

[GeoMax]

Hi Hesam_k69,

here some thoughts about your "great TL12000 device". I drew the schematic from several hand drawings last year to see whether it would be good to make a PCB out of it. But after drawing it, I saw that it is more or less only a simple PI. There are much better detector...

[Emersonpaz]

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

[moodz]

Thanks waltr ....

Attached is the source code ....

Theres stuff in there to do LCD / Serial and Rotary Encoder .... WIP.

The timing is set up for a 30us TX followed by a 30us RX. Why 30us ? ... because otherwise the TX fet will approach avalanche and the linear...

[Elliot]

Updated version of the TreasureLinx Mirage Pulse Induction Detector.
It's been about 40 years since I first started detecting. I also worked on making some detectors way back then - e.g. ETI 1500 and the Sandbank PI. I even used to review some early Minelab detectors for Miners Den in Victoria,...

[aulook]

Hello Guys. I have a delta pulse PI metal detector and have been using it for years. Its audio seems annoying to my ears. I want to modify it's audio stage by changing the 555 audio driver to cd4046 vco ic that will sound like the pulse star. Is this possible? Does anybody has the wiring diagram? Any...

[ivconic]

This could be used as nice audio vco for various projects, of course; suitable for PI detectors.
There are two versions of hex that i prepared; 0v to 5v at the input and 5v to 0v at the input.
Most of the diy PI's we have here on forum will be matched with second; the 5v to 0v at the input...

[6666]

I found this Surf PI mod in my collection of PI mods.

It gives the option of VCO audio, which could be handy if experimenting with TX PPS.

I dont know where it came from and there is no name on it, but could be useful....