Analog Target Indicator for VLF

[Nandor]

Does somebody have some scope pictures from the VDI module of the Whites 6000 di pro? Would be nice to see the signals from the filters and sample and hold stage.
Gurdal have you made this circuit you posted? Im having trouble calibrating it. The differential op amp output is only spikes and the detection distance is really low. At least it can make difference between iron and copper.

regards

[gurdal]

Does somebody have some scope pictures from the VDI module of the Whites 6000 di pro? Would be nice to see the signals from the filters and sample and hold stage.
Gurdal have you made this circuit you posted? Im having trouble calibrating it. The differential op amp output is only spikes and the detection distance is really low. At least it can make difference between iron and copper.

regards

hello my master;
I found it while researching on the forums.
I didn't test,
is an excerpt.
Yours truly

Gurdal

[Nandor]

You are very king Gurdal, for me you are the master!

all the best

[Nandor]

Found this on MD4u.ru
It is a the reverse engineered version of the Whites lcd VDI for Classsis and IDX detectors I think. First the lay file and than the parts placement pictures, the pcb looks a bit complicated to make at home.

[Nandor]

This is the version I made, it was posted by Gurdal some pictures of the pcb.
I had to change some components that were not available for me, like 330pF cap changed to 470pF and CD4016 changed to CD4066. It even works a bit with BF245, as i said it does not make difference between colored metals just iron and non magnetic metals. Still need some time to make it work properly, experimenting with IDX PRO.

[Nandor]

For the indicator I use an old voltmeters needle.

[Op04]

This is the version I made, it was posted by Gurdal some pictures of the pcb.
I had to change some components that were not available for me, like 330pF cap changed to 470pF and CD4016 changed to CD4066. It even works a bit with BF245, as i said it does not make difference between colored metals just iron and non magnetic metals. Still need some time to make it work properly, experimenting with IDX PRO.

Dear Nandor, thanks for bring this, a very good thread, as I need non programmed or simple vdi. I've build countless guitar fx and bypass system long time ago, I don't know the behavior on this vdi scheme, please let us know if you change to 4016 will it make a difference? Since CD4066 & 4016 slightly different as mentioned here, http://www.dedalofx.com.ar/bioroids/...4016vs4066.php

[Nandor]

Hi

I have read the same topic after I made the pcb, there should be difference. I only have CD4066 and BF245 transistors and it works with both of them.
About working, IDX signals with concentric coils are much cleaner and have better signals. TGSL does not really likes it also because of the high frequence of 14.5kHz low conductors have better response. I think it's better to make it for IDX with good frequency response to silver and a bit lower for nickel and modern coins.
The truth is that my projects is stuck, I can't progress further with it. My version cant take difference between silver and alu foil or nickel but it has now problem with iron.
The needle gets a small voltage from the start set with potentiometer so if iron is detected it swings left and stays there if non metalic object is detected it swings right.
Please if you have any ideas to improve it post here, I see great potential in this circuit manly for IDX.

regards.

[Op04]

Hi

I have read the same topic after I made the pcb, there should be difference. I only have CD4066 and BF245 transistors and it works with both of them.
About working, IDX signals with concentric coils are much cleaner and have better signals. TGSL does not really likes it also because of the high frequence of 14.5kHz low conductors have better response. I think it's better to make it for IDX with good frequency response to silver and a bit lower for nickel and modern coins.
The truth is that my projects is stuck, I can't progress further with it. My version cant take difference between silver and alu foil or nickel but it has now problem with iron.
The needle gets a small voltage from the start set with potentiometer so if iron is detected it swings left and stays there if non metalic object is detected it swings right.
Please if you have any ideas to improve it post here, I see great potential in this circuit manly for IDX.

regards.

Your explained so well since the 1st page, food for my brain. Honesty I don't really understand the schematic / whats's going on there. There is no further / enough information from Gurdal version the real capabilities it can achieved, maybe it only can separate ferro / non ferro. I'm in process build lobo, next I will use 3 led VDI while Redram on md4u done good with IDX vdi. I believe you can do more for this project, if you have 1.2nf you can put series with 470pf to get closer 330pf. I hope this analog vdi can do as good as the digital version.

[Nandor]

Well as far as I could understand the first two parts are X/Y filters with clipping for the differential amplifier DA4. Than there is a VDI gain stage to set a start voltage level for the needle, just a few millivolts so the needle is a bit higher than 0, like 1 from 0-10 that's how I centered it. The next stage should make a square wave from the Geb channels signals to drive the sample and hold circuit with CD4016 or CD4066 and DA8. I have took some measurements from a Whites 6000 Di pro sl detector and the wave forms are pretty much the same I have on my pcb the only difference was in the filters output, while the IDX has waves the 6000 Di pro has more smooth DC voltage so it's more precise of measuring the phase difference and amplitude changes between the channels. You should see spikes and square waves with your scope. 3 Led VDI is nice but in sunshine you cant really see them as well as a needle.

regards

[Nandor]

Here are some VDI test from the Whites 6000 with picture of Indicator attached.

Coins VDI number 0-100

1 Byzantine Bronze coins 65-80
1 Silver Mark 1939(silver) 70
1 Hungarian Korona(silver) 58
1 Kreuzer (copper) 58
1 As-Roman (bronze) 58
10 Kreuzer (small silver) 35
3 Poltorak (small silver) 26
1 Follis-Roman (bronze) 22

You can clearly see that small hammered coins are in the junk scale. Modern coins are between 20-60 aprox.

[Op04]

....measuring the phase difference and amplitude changes between the channels. You should see spikes and square waves with your scope. 3 Led VDI is nice but in sunshine you cant really see them as well as a needle.
regards

Dear Nandor,

Respectively a big thanks for above explanations. Perhaps, I will use VU leds to replaces LED to be more visible, by now all I need is Non/Ferro separation hints.

Here are some VDI test from the Whites 6000 with picture of Indicator attached.

Coins VDI number 0-100

1 Byzantine Bronze coins 65-80
1 Silver Mark 1939(silver) 70
1 Hungarian Korona(silver) 58
1 Kreuzer (copper) 58
1 As-Roman (bronze) 58
10 Kreuzer (small silver) 35
3 Poltorak (small silver) 26
1 Follis-Roman (bronze) 22

You can clearly see that small hammered coins are in the junk scale. Modern coins are between 20-60 aprox.

Many thanks for provide this data. For white's needle meter, do you know the exact value for this meter?

Regards,

Taufik

[Nandor]

Hi Taufik

Ferrous and Non ferrous indication is not that hard, if you look at the pictures I have shared, you can see that Iron gets better response in Geb channel and also makes a phase difference between Geb and Disc channel signal amplitude. This is why it gets discriminated, because of the phase shift. When a non magnetic metal is detected there is no phase difference so the comparator senses both signals and opens up. If you make this VDI pcb it will have a negative output voltage for iron and positive output voltage for non magnetic metals because the differential amplifier.
I should try to put a Red and a Green diode in paralell reverse position maybe it should work, like Red for Iron and Green for non ferrous. I want to make some more experiments as soon as possible .
The Indicator if I remember well has only 60 ohm resistance, should have measured more precisely. I did not wanted to damage something so just measured with multimeter, scope.
The machine is from 1995 and works splendid, good old White's quality!

best regards

[Nandor]

Made a little experiment with a Led soldered in place of the Meter. When iron is detected the Red Led turns on, when non ferrous is detected it remains dark . Not a Nobel price invention but works just great, huge iron objects that brake the discrimination are indicated by this Red Led.
Still many work ahead.

[Op04]

Hi Taufik

Ferrous and Non ferrous indication is not that hard, if you look at the pictures I have shared, you can see that Iron gets better response in Geb channel and also makes a phase difference between Geb and Disc channel signal amplitude. This is why it gets discriminated, because of the phase shift. When a non magnetic metal is detected there is no phase difference so the comparator senses both signals and opens up. If you make this VDI pcb it will have a negative output voltage for iron and positive output voltage for non magnetic metals because the differential amplifier.
I should try to put a Red and a Green diode in paralell reverse position maybe it should work, like Red for Iron and Green for non ferrous. I want to make some more experiments as soon as possible .
The Indicator if I remember well has only 60 ohm resistance, should have measured more precisely. I did not wanted to damage something so just measured with multimeter, scope.
The machine is from 1995 and works splendid, good old White's quality!

best regards

Dear Nandor,

I finally got time. Thank you Sir, splendid explained. So before your last post I was thinking using optocoupler to drive another alarming indicator for non ferro, you also took time to get it work somehow, appreciably thanks for that. If I finished my lobo, if it working plan to put analog vdi. Please keep this thread update....many thanks
Regards