TL12000

[Asanka Sanjeewa]

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 using only the VCO part of the CD4046 IC chip. Alternatively, you could use a LM566 VCO IC. But this is also quite hard to find and expensive. The VCO made from a 555 timer is really one of the cheapest options. Even Eric Foster, the metal detector guru from the UK, has used a 555 timer VCO circuit in his excellent detectors. So did Carl in his Hammerhead PI detector. There is actually nothing wrong with using a 555 timer IC as a VCO. It is easy and cost effective.

You are right GioMax, I looked into the details of the 4046 IC, it can be used to change the pitch of the tone rhythmically using the VCO. I think this may be used in some minelab metal detectors. But I like the clicking sound of the old geiger counter.You said that some polonese md also had this mode of discrimination. I personally tried some of them. But it didn't go well.I think this D type flip flops and sample and hold [ because LF328 can ultrahigh DC accuracy ] method is successful.This is the best part I see in this device.
He rejects large pieces of iron, brass, and some aluminum without any cost. I have seen this all the time.

[Detectorist#1]

The simplest VCO is the two transistors multi-vibrator known from maybe 100 years. Try to use it in simple MD designs.
Different possible schematics are attached.

[boilcoil]

Hi Asanka,
Now I saw the video, and I came up with a question (I'm not very good with detectors, so excuse me if I write some nonsense):

As far as I saw in the video, the ferro/nonferro algorithm is to reject all targets with a large time constant, considering them to be iron, i.e. any sample less than the reference value (invert preamp) will be considered iron.
But if you come across a large lump of gold, chance to just pass it is very hi.

[mazari]

hello everyone.
I am interested in making this device, but I do not know which version to use. I found this version proposed by haylaz0036( page:#15
11-05-2024, 02:25
ABU ZEID.TL12000..pdf (28.9 KB, 105 views)
I want to make it. Do you advise me to do that?thank you in advance

[haylaz0036]

I did it but couldn't get it to work

[haylaz0036]

Hi Asanka Sanjeewa

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

I just haven't tried this yet, I want to do it soon.

[Detectorist#1]

Do It, you have right to learn the things!

[haylaz0036]

Dear Asanka, I canceled the janper here, but the device works but does not detect it. And I canceled the delay potential meter and installed 210k.

[haylaz0036]

[haylaz0036]

The device was not stable, the ticking sound was constantly increasing, it would not stop. I found the best sensitive point and added the resistance, it was very nice, it was stable and very deep, but there was no separation, one last thing, the sound is very low. I want to make a Sar schematic, by the way, I could not find an LM709, I used TL081, I used TL072 instead of LM358, it was great.

[haylaz0036]

Pcb

[haylaz0036]

[GeoMax]

Dear Asanka, I canceled the janper here, but the device works but does not detect it. And I canceled the delay potential meter and installed 210k.

Why have you removed the jumper here?

[haylaz0036]

Dear Geomax jumper, I don't know, I took it off but put it back on. Now I'm doing Asanka's project, I'll do it when I find time.

[haylaz0036]

Dear Asanka, I assembled the device and started it, the sound is great, the performance is very very bad, the MOSFET is overheating, I did not change it, there is no MOSFET TRANSISTOR left, moreover, you say run it at 400mhz, the batteries will run out in 15-20 minutes in the field, the issue of separation is yes, it isolates iron type metals, the funny part is that it isolates under it. That's all I have to say, do not deviate from the original map, the only sound is weak, another problem