Analog Target Indicator for VLF

[Nandor]

Yes very good point! I soldered some caps in plus for the sample and hold and a 120oHm resistor in series with needle to slow it down. Have to check that hold and update circuit thanks for pointing it out.
One very important thing is the Meter itself, it has to be big enough for all the scale and 1.5 or 2 volts. Right now the little one I have is a bit short on range and alu foil gets a really little portion as nickle also.

best regards to you!

[dbanner]

Looks like it's working!! Perhaps you could try to include the meter hold and update circuit from White's 6000 patent. This might stop the meter needle from drifting after target has passed across the coil or at least the meter would hold the peak until the target crosses again. The meter moves sluggish, but perhaps it is due to it's construction.
Also, the log amplifiers, maybe they can be improved.
Nice, I like it.

[Nandor]

Im testing the one that Mr Gurdal shared. I know that disc pot affects VDI, was thinking about a switch for Disc and VDI select.
Finally after many trial and errors made some more progress today Im really happy now because it works much better now. just could not let it like that in the pcb's box my mind did not let me and "voila" with some logic thinking and some experimenting made this. It's still under progress.
Here is the test video with some coins and a pulltab, nickel-alu-silver.

https://www.youtube.com/watch?v=WcuZIPiQCn4

[dbanner]

I have been trying to make it work properly but after several weeks there is little progress with it. Im using my TGSL and without the proper positioning the Disc potentiometer it does not show alu foil only higher conductivity objects. Iron is still discriminated so it works some what and silver coins are at the maximum end sensibility.
The problem is that there is no middle range like pull tabs or nickle place on the needle only low and high. Have to make another pcb with other design and approach.

Which vdi circuit are you testing?
In the tgsl, the disc pot is at the phase shifters. So I think maybe it must be set at minimum discrimination and left alone, then tinker with the vdi circuit. If you change the position of the disc pot, it throws off the vdi calibration. With idx, it is different, because the discrimination pot is across the filters I think. In this case the x and y are extracted from each channel directly before the influence of the discrimination pot. So turning the disc pot doesn't affect the vdi calibration.

[Nandor]

I have been trying to make it work properly but after several weeks there is little progress with it. Im using my TGSL and without the proper positioning the Disc potentiometer it does not show alu foil only higher conductivity objects. Iron is still discriminated so it works some what and silver coins are at the maximum end sensibility.
The problem is that there is no middle range like pull tabs or nickle place on the needle only low and high. Have to make another pcb with other design and approach.

[Nandor]

Nice!
I have both schematics, the second I think is from Eduardo. The Whites patented schematic is very similar. It has phase windows and each has to be preset with potentiometer, thats how the ID series vdi works basically it's analog with LCD.
Toltec is very interesting it has separate channels for the RC4200, looks like one fixed and other for hot rock very interesting. There are RC4200 on eBay but they arent cheap and also transport taxes.

best ragards

[Op04]

I found old post around toltec it has analog vdi inside, so I'll be putting here it's a high class artwork by Merc, thanks to him for this.

[Op04]

Ok... Perhaps someday if I have time I will make PCB for that. I dig a little randomly in md4u got this scheme similar to Gurdal version I suppose, It's from vlaser, he did a lot efforts on that forum. I hope we can learn more..

[Nandor]

I have built the one that Gurdal shared, second page and post #27. It must be from a russian forum, you find the schematic and the lay file in the rar. Made some little modifications for my components thats all.

[Op04]

Im happy that somebody is interested in my project . I cant get bored of making detecting related electronics, made several TGSL and one IDX and pinpointers also. This is the one project that does not works yet.
Found another schematic on the russian forum, it has similar filters than the Whites 6000 Di pro has. Maybe that's the key of succes. Tesoro Toltec has VDI but also has separate filters for it!


Have fun with your project!

Dear Nandor,

Do you have lay file for this, Sir? Or perhaps I'm really helped if it ready to print for press n peel transfer if any. Thank you so very much

[Nandor]

It took me some time, but I finally did find the TID drawing, that I drew in the past, relative to the 1984 Compass X-80 Challenger. Now it shows the inputs, etc which were of the X-80, but John Earle was very good at this TID design, and he left Compass, went over to Whites Electronics and was the Chief Engineer at Whites. So it should give you the start of your TID drawing as it was an EARLY TID meter.

I am interest in seeing your final design, as I would like to use it on the Compass Coin Magnum which would fit with what you are trying to do.

Okay, was a problem as I am now using FireFox as my software between the server and this forum, and I now that the photo of the schematic I drew back in 2013 of the Compass X-80 new TID circuit, from the PCB inputs and outputs to the Compass TID meter, and all Nandor needs to do is figure it out. I cannot really explain the circuit, just drew it in the past...
Melbeta[ATTACH]54855[/ATTACH]

Thank you sir for sharing, I really appreciate it !
I try my best to make it as good as possible, cannot be that hard to do. I think the magic is in the sample and hold part of my pcb. Geb signal samples the differential output signal and the phase difference between these 2 signals gives a DC voltage spike. This is held by the capacitor and the voltage follower to drive the needle. IDX has better design for this but it should work with TGSL set on a proper discrimination level.

I have to study your desing, all the best

[Qiaozhi]

Ahhh. I give up. There is a fight between the forum and Firefox and I just cannot figure out how to make it work. I guess I am lucky it took the earlier schematic and transferred the schematic...
Melbeta

Click on the Go Advanced button, and then select Manage Attachments.
I'm also using Firefox, without any problems.

[Melbeta]

It took me some time, but I finally did find the TID drawing, that I drew in the past, relative to the 1984 Compass X-80 Challenger. Now it shows the inputs, etc which were of the X-80, but John Earle was very good at this TID design, and he left Compass, went over to Whites Electronics and was the Chief Engineer at Whites. So it should give you the start of your TID drawing as it was an EARLY TID meter.

I am interest in seeing your final design, as I would like to use it on the Compass Coin Magnum which would fit with what you are trying to do.

Okay, was a problem as I am now using FireFox as my software between the server and this forum, and I now that the photo of the schematic I drew back in 2013 of the Compass X-80 new TID circuit, from the PCB inputs and outputs to the Compass TID meter, and all Nandor needs to do is figure it out. I cannot really explain the circuit, just drew it in the past...
Melbeta[ATTACH]54855[/ATTACH]

Now in the year before, which was the earlier version, called the Compass X-70, version C, they had a meter which only shows GOOD or BAD target. I did that machine as well, and here is the schematic of that GOOD/BAD circuit, and from it, you can make one or the other, depending on whether you have a Meter with just a needle, or a TID meter. Now John Earle, had to make each meter target, FIT INTO the meter DISPLAY. And that is what the TID parts do, and the GOOD/BAD parts do, is make the U.S. Coins fit into the meter you use. Ahhh. I give up. There is a fight between the forum and Firefox and I just cannot figure out how to make it work. I guess I am lucky it took the earlier schematic and transferred the schematic...
Melbeta

[Melbeta]

Found that old drawing.......

It took me some time, but I finally did find the TID drawing, that I drew in the past, relative to the 1984 Compass X-80 Challenger. Now it shows the inputs, etc which were of the X-80, but John Earle was very good at this TID design, and he left Compass, went over to Whites Electronics and was the Chief Engineer at Whites. So it should give you the start of your TID drawing as it was an EARLY TID meter.

I am interest in seeing your final design, as I would like to use it on the Compass Coin Magnum which would fit with what you are trying to do.

Okay, was a problem as I am now using FireFox as my software between the server and this forum, and I now that the photo of the schematic I drew back in 2013 of the Compass X-80 new TID circuit, from the PCB inputs and outputs to the Compass TID meter, and all Nandor needs to do is figure it out. I cannot really explain the circuit, just drew it in the past...
Melbeta

[Nandor]

I have never built the Lobo, it was designed by Dave Johnson. I like the 7660, very nice opamp and if you use proper capacitors it has a great efficiency. Made several TGSL's with it and filtered the negative voltage with ferrite coil and a few capacitors, this way the output has low ripple.
Until then I try to make some more experiments

regards