Analog Target Indicator for VLF

[Nandor]

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

all the best

[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]

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

[Nandor]

I have built the pcb. Worked on the first sturt up but it cant make huge difference between colored metals and silver. Ferrous and non ferrous separation is working good. It's difficult to calibrate, somebody some ideas on calibration?

[Nandor]

Looking at the schematic there are 2.2uF capacitors at the inputs, those must be polarized?

[Nandor]

Gurdal

Im really happy now, really! I havent made any progress with mine since 4 weeks almost, got stuck at a prototype working so so.
Thank you really much for this, as soon as I can, will make it.

best regards

[gurdal]

Hello to everyone,
Has anyone tested the circuit?

[Nandor]

I have seen Eduardos topic, its very interesting for me. I have read it many time over, just started to understand how it works basically,but its a very big circuit as big as my TGSL board, too large to fit in the controlbox of my detector.
After taking some measurements with my scope it's easy to understand how discrimination works and how target identification should be made, ground effect cancelation is also possible. It needs ground balance because the Disc channel reacts to ferrite and the it moves the needle on my prototype. I was thinking about a circuit to measure the maximum aplitude of the Geb channel and if it exceeds a treshold level it should cut the voltage for the needle drive. I have observed that the Geb channel reacts very little to non ferrous metals, but if I wave a big iron object over the coil and it brakes the discrimination circuit than the amplitude of the Geb channel is way bigger than the amplitude of the Disc channel and they are also in phase. This is why I would like to make this circuit, the places I detect are agricultural lands and there are many iron components and parts from different machines .

Thank you for you time dbanner, regards!

[dbanner]

Toltec uses the RC4200 analog multiplier chip, I like this solution as it cuts down on component needed to realize an analog vdi meter circuit. Stability ought to be excellent based on the datasheet.
There is however another chip, the Analog Devices AD534 analog multiplier/divider chip which is available and could possibly be the basis of a VDI meter circuit. I'm not sure.
Of course all this can be done using opamps and few components as is the case with the White's VDI circuit for the 5900/6000di. Notice on that particular circuit there's a dual transistor package no doubt to address errors due to temperature instability.
Here is the datasheet for the RC4200 and AD534.

[dbanner]

Have you seen this. You can make the White's 5900di VDI. Eduardo did give all details.

https://www.geotech1.com/forums/showthread.php?24888-Analog-VDI-meter-update-question&highlight=Analog+vdi

[Nandor]

I totally forget about Toltec ! Compass is really complicated, and never heard of Big Bud Pro. Thank you for the ideas, I have put it aside because of no progress. Been studying the discrimination of the TGSL to understand what to measure to get a proper arctangens with analog circuit. I have leared a lot, but still somethings are unclear.
Toltec has some special chip that makes this calculation if I remeber well anyways needs to be studied. Detecting with the Di pro 6000 SL is really cool and fun, I really like the VDI of it!

Digital is not my favorite, maybe the VDI of IDX Pro the original, because thats not with uPic. Eduardo shared a part of that schematic with the name of VDI LED and after he shared the original full schematic with LCD driver, thats also very interesting to study. It uses phase windows to compare the signal and that drives the specific part of the LCD.
Back to the basics

regards!

[dbanner]

Shouldn't it be a straightforward thing to add/ modify code to existing micro based VDI to instead drive an analog meter circuit.? A nice big analog meter to me is far better than a small 16x2. In the sunshine.

[dbanner]

I also have a schematic for a vco mod done with the Toltec by someone who posted a YouTube video. Seems to work very nice. If I remember correctly, there were two or maybe three distinct tones.

[dbanner]

Big bud pro schematic, coinscanner schematic, tesoro Toltec 100 schematic, are here on forum. Look to these for analog meter based VDI circuit different than White's. Especially the Toltec 100 which is easier to discern. The others are buried in the clutter of an overcrowded schematic drawing, not so easy to follow what's happening.
What about the CZ3/CZ5, didn't those have analog vdi metering circuits?

[Nandor]

I would be happy if you could share your drawings. Had some minor progress with this but not that much to be posted yet, been studying whites methods. Im stuck at iron signal overload and it still needs a circuit to detect phase difference.

regards