Analog Target Indicator for VLF

[Nandor]

Thank you for the kind words Op04 .
It still needs a little noise reduction. I have started to make a TGSL pcb with the VDI incorporated on it with the same size 100x100mm. Those many cables are the noise sources.
Sensitivity is about 80% compared to the air depth of the search coil.
Well im pleased with it, noise reduction can wait till winter.

best regards

[Op04]

Sir Nandor, I see error on the V1.3 schematic pin no 4 (U2a) should be connected to V+ reverse with pin 11 ??

[Nandor]

Hello
You are right, it's my fault but the lay file is not affected! Never hurry with a work.
I hope you can do your project and post your results here. The sensibility of the circuit is pretty good and with the Disc pot set at 4 just a bit below foil discrimination works the best for me.

[Op04]

Ah..my bad. I've should've just sent you pm. It's not your fault, your pcb lay is very good, I mean you've gathered everything for us here, make it alive an give us scope measurement that was big job done, many many thanks for that Sir Nandor,, Umm since already proven this analog version is quite accurate, I try make my own PCB built-in instead extra board, that's when I found small error on the schematic. I will post my PCB later when I finished.

[Nandor]

Hello
Thank you for the kind words . I wish that this project was made ten years earlier when TGSL and IDX was very popular. Mr Gurdal is the the one I have to thank for the schematic and lay file.
The best would be 2 separate filters for the VDI circuit so it could work in all metal mode also. I was thinking about it and also 3 tone mode with comparators.
I have posted this in the IDX PRO topic

best regards

[Op04]

Hello
Thank you for the kind words . I wish that this project was made ten years earlier when TGSL and IDX was very popular. Mr Gurdal is the the one I have to thank for the schematic and lay file.
The best would be 2 separate filters for the VDI circuit so it could work in all metal mode also. I was thinking about it and also 3 tone mode with comparators.
I have posted this in the IDX PRO topic

best regards

Hello Sir,,,
You're welcome! You are Star here Sir Nandor you deserved it. You're right, but making VLF to get first real working is quite a struggle, so if one wants to build VDI they must have a good working made device with good discrimination & GB. Your idea is what we all want! The video is pleased that's enough, well for me... Anyway I just make a PCB couple hours ago but still need to check. Thanks again Sir for keep us update. Regards

[gurdal]

hello my master nandor is really nice. good luck

Hello
Thank you for the kind words . I wish that this project was made ten years earlier when TGSL and IDX was very popular. Mr Gurdal is the the one I have to thank for the schematic and lay file.
The best would be 2 separate filters for the VDI circuit so it could work in all metal mode also. I was thinking about it and also 3 tone mode with comparators.
I have posted this in the IDX PRO topic

best regards

[rolling rock]

It struck me a while back that what I would be needed for my project is Target ID VCO tone. SO, then I pulled out LTspice and tried to work up something using the el-cheapo AD633 analog multiplier. The data sheet has an application for an analog divider, so I gave it a try. Unfortunately, AD633 does not have a dedicated divisor input, so the multiplier is connected inside an op-amp's FB loop to implement division, and that seems to complicate the issue. I'm having trouble taming the LTspice output which seems to want to peg to one or the other supply rails instead of being "analog".

So, RC4200, RM4200, or NJM4200, may be the way to go - but they are kind of hard to find unless you want to try a Chinese clone. I may grab some and plug them into a breadboard to see if I can find some confidence to go farther. The fact that '4200 does have a dedicated divisor input should simplify things. '4200 has current output and inputs which is a little different, but we have the Toltek schematics to follow for a ready made "cookbook" solution.

[rolling rock]

Hmmm If just using the multiplier for vco control, I shouldn't really have to worry about calibration, either use the Toltec scheme, or else tap off x and y signals, sum them together, then divide y by the sum x+y, that way the result should always be one or less than one to keep from pegging the output. Maybe I won't breadboard, but instead tweak it in place after building the darn thing. Nothing critical, it's a noise maker, eh?

[Carl-NC]

A super-simple VCO is a 555 timer where pin 5 is used as the voltage control.

[rolling rock]

There is always the possibility that some of those NJM4200 on Ebay are the real thing and they are priced right for experimentation.
Everybody should take a look at the MAT02 datasheet, fig. 3. The '4200 is no longer so mysterious because what looks like transconductance amplifiers on the '4200 datasheet are now hugely simplified. LTspice and I could analyse the fig. 3 circuit over a couple beers and a bowl of Weedies.

So the RC4200 multiplier-divider isn't going to be so scary to work with but I would still like to know, where is the positive power supply?





time for another spam folder check ?

[rolling rock]

This is the schematic on which I was working on and I would like to try.

Could you please post the schematic you are working on without it being encapsulated in a RAR file?
RARs are not opening for me today for some reason.

[rolling rock]

A super-simple VCO is a 555 timer where pin 5 is used as the voltage control.

Thanks, Carl. That reminds me I should probably use that instead of the Goldbug style VCO I was planning on, but I have them both working with a multiplier output feeding them (on my laptop, anyway).

I know the OPs original intent was to gather ideas for a visual target ID. I would like to suggest instead, use VCO target ID, and reserve the meter for a depth indicator - (future endeavor maybe).
Anyway, after getting over the -missing- positive power supply, I think the RC4200 architecture is pretty slick. You set your own scale factor instead of having to settle for 1:10 as is common with most other multiplier ICs.

[dbanner]

A super-simple VCO is a 555 timer where pin 5 is used as the voltage control.

That's not what he's asking. Perhaps he's asking for your permission. Jedi master.

[Melbeta]

I looked at the patent, and that is how George Payne set up the Compass Electronics Coin Scanner and Coin Scanner Pro TID detectors.
Melbeta