TL12000

[GeoMax]

Hi Asanka Sanjeewa

have you made this PCB? If not, do you know who did it?

[Asanka Sanjeewa]

Hi GeoMax
The story is this, I first tried some circuits on the internet. I have posted some photos of those made before. But they have a common weakness. The circuit works but the iron rejection and VCO design is poor. But 4013B flip-flops and LF398 sample and hold ic design impressed me. Finally i made the circuit VCO and some changes. The yellow paper posted in that forum is all my handwriting and my modification. After preparing everything , i checked the place where test point is written on the paper [ LM358 opamp output line ] the circuit very accurately shows negative volt for iron object and positive volt for non ferrous metals. I made and sold 3 piece of these. They said [ buyers ] that is suitable for an environment with high mineral content with mountainous rocks. Photos were not take in a constructed circuit because of the risk of share. I will post a photo of one that was made and sold with this. If i make a new one again, i can put it.

[Asanka Sanjeewa]

Dear GeoMax
I respect Kt315, Qiaozhi, dfbowers and their service in this forum.I have also gained a lot of knowledge because of these gents. I decided to post this circuit as a respect for it. I have put everything without hiding anything, of course. I have to tried to explain in a simple way that even the least knowledgeable member can under stand without going into deep theories. But remember that this is a rejection based on the conductivity of the metal objects.But rejection is much better than other PI devices. Please be careful when you sold 20K multiturn potentiometer because change pinout than normal pot.meter.
There is nothing to question again. All information required for construction is provided without lack. It is your choice to believe or not. I have fulfilled my responsibility.
Have a nice day friend

[haylaz0036]

This is another scheme, LM331 is gone, NE555 is there, is the sound of Barbie strong now?....... I want to ask something, you say to run it at 400hz, if it runs at 400hz, yes, the depth increases, but the battery cannot withstand this and everything heats up, I want to ask something, the 7809 output and the 7915 output are connected to the 20k pot, they get very hot, what is the joke here?

[haylaz0036]

Dear Asanka Sanjeewa, is this better now? I don't understand how deep does it detect a single coin and does it separate the metals completely? Which country do you live in?

[Asanka Sanjeewa]

Hi haylaz0036
By asking such questions, I understand that you do not even have basic electronic knowledge. The Lm331 is replaced with a better volume, volume controllable VCO circuit. Who told the big lie that the whole circuit heats up when increasing to 400Hz frequency? It is a fault in your circuit.if your BU508A transistor get hot please put the heatzink.Positioning of variable resistor [20K] is correct. It controls the output of the LM 358 [integrator]. Also if your variable resister get hot to connect this way maybe wrong pin soldering. I have not tried coins. Men's wedding rings look 8 inches [ in the discrimination mod ]. I am from sri lanka [ south asia country]

[Emersonpaz]

Hi GeoMax
The story is this, I first tried some circuits on the internet. I have posted some photos of those made before. But they have a common weakness. The circuit works but the iron rejection and VCO design is poor. But 4013B flip-flops and LF398 sample and hold ic design impressed me. Finally i made the circuit VCO and some changes. The yellow paper posted in that forum is all my handwriting and my modification. After preparing everything , i checked the place where test point is written on the paper [ LM358 opamp output line ] the circuit very accurately shows negative volt for iron object and positive volt for non ferrous metals. I made and sold 3 piece of these. They said [ buyers ] that is suitable for an environment with high mineral content with mountainous rocks. Photos were not take in a constructed circuit because of the risk of share. I will post a photo of one that was made and sold with this. If i make a new one again, i can put it.

Thank you for sharing your knowledge, I was curious about how it works although I had already seen this detector on the Felezjoopi forum, it looks like a great project.

[haylaz0036]

Dear Asanka, yes, I am an amateur in electronics. I take lessons from valuable masters like you. Please do not be angry. I printed four different PCBs. They did not work or I could not do it. I do not know. Right now, I am thinking about making a PCB with your design. Yes, I have a TL12000 that works, but since I could not find an LM709, the depth is weak.

[GeoMax]

Thank you for sharing your knowledge, I was curious about how it works although I had already seen this detector on the Felezjoopi forum, it looks like a great project.

I also think that the project has potential. But the circuit has many design issues. Especially in the area of power supply, audio and front-end receiver circuit, internal controls for circuit adjustments, etc. or in other words, basically everywhere in the whole circuit. But it somehow works more or less. The only "highlight" in the TL12000 circuit is that it uses a dedicated Sample & Hold IC. In my opinion, the whole TL12000 circuit needs a "facelift". On the PCB that people just have, it's not obvious that this design has problems, but if you look at the whole schematic, you'll notice.

[Detectorist#1]

According my opinion, it is time to left TL12000 to R.I.P. Too many issues, too old parts, too hard settings for beginners in MD area.

[Detectorist#1]

In reality, the changes in the schematic made from Asanka are "facelift" but many issues rest in this MD.

[ArchibaldSTM]

I agree. They are making some kind of intrigue out of an old-school device. One talks, but doesn't tell the whole story. The other promises to post the correct files, but that's not true --- there is no schematic, the board is bad. More noise and no result. I have closed this project for myself. I will build something else. It's a pity that I spent so much time on this.

[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 FET has been replaced by the LF398 IC and the CD4093 by a CD4013. Whether the timing is replaced by a CD4093, CD40106, CD4013 or CD4538 etc. is irrelevant. You could also just remove this FET from the circuit of the PI Polones and use the LF398 instead and the TL12000 is ready. The "original" TL12000 of course still had a real VCO IC LM311.

[Detectorist#1]

Hi GeoMax,

Yes, you are right, the MD PI Polones and TL12000 have the same structure and the results have to be similar. The true is that both are "old fashion" projects with very limited possibilities.

[Detectorist#1]

Many of simple PI projects use differential integrator for first and second sample and NE5534 in first Rx stage. This have as the result (popular opinion) that PI MD needs at last 100mA current from 12V power supply because of high Tx frequency (also heatsink on Tx FET and heavy batteries). If we use two sample-hold circuits and two OpAmps instrumentation circuit with low noise OpAmp in first Rx stage - this allows reducing of the Tx frequency down to 100-120 Hz with good noise floor and power consumption of the simple PI MD will be reduced to 15-20mA from simple 9V battery. This is similar to the current consumption of the simple IB VLF detectors.