Arduino based VDI!

[dfbowers]

Howdy folks! I have not posted for a while but since the ground is frozen it's time to build and experiment! I have been making small improvements with my own experiments lately tying to find the optimum sampling window with software. I have read elsewhere that others sample both negative an positive but up until lately I have only sampled positive. In the past, I never really paid much attention to the negative part of the signal swing while watching lissajous patterns on my scope but lately I have. Target patterns behave much like a "rubberband" pulled negative on the x - y axis and then released as targets pass the coil. It's apparent that the negative portion can provide much more reliable slope readings. But.. The Arduinos that I have been using cannot take a negative sample window that I'm aware of. By inverting the signal between the IDX and Arduino it takes some the uncertainty out of sampling, particularly when targets get really close to the coil. Besides adding a few components, does anyone know how to do negative sampling with the Arduino?
Don..

[dbanner]

Full wave rectification?

[dbanner]

In principle?

[waltr]

Op-amp Inverter?

[Altra]

Use the circuit in the link below. It uses ac coupled differentiators to isolate the dc power supplies between the md and micro. It also creates a virtual ground at 2.5v for the arduino. The 10bit adc will read 511-512 for zero signal. Negative signal is < 511 and positive is greater than.

See post #132 by holyuser, just replace pic with arduino

http://www.geotech1.com/forums/showt...-PRO-VDI/page6

[Virdi_248]

I have a problem with the distance of detection and the module vdi.

For example, if I have the subdued screen I detect 1€ to 20cm. In the moment that I ignite the screen the detector detects 1 euro to 15cm. I am using a battery between 9,6 and 10v, 8 rechargeable batteries of 1.2v each one.

Is it possible that this is the problem?

A tension fall takes place on having ignited the screen and for it the distance of detection diminishes?

[homefire]

Sounds like the Batteries can't handle the load. Not a voltage issue, Amperage issue.

[Virdi_248]

Sounds like the Batteries can't handle the load. Not a voltage issue, Amperage issue.

Is it possible to arrange with 9 or 10 batteries of 1.2v?

Do I change the batteries into others of better quality?

That you suggest me

[CDI]

Is it possible to arrange with 9 or 10 batteries of 1.2v?

Do I change the batteries into others of better quality?

That you suggest me

Dude, there is no problem with your batteries, it's problem with Arduino code.
I had the same problem with distance.
I will upload tomorow my sketch for Whites IDX.

[Virdi_248]

ok

[dgm]

Hello everyone, I am going to the Gurus of this forum, because nobody is more interested in experimenting with the VDI software based on arduino, thread started by Mr. Dfbowers and Mr. Daren Mr. Onuba? Thanks to all of you for your commitment !!!

[CDI]

Can somebody little help about this codes, i want to attach small OLED i2c 128x64 display, but i have no luck to make it to work.

https://startingelectronics.org/tuto...connection.jpg

And here is my sketch file.

[Tibuck19]

VID vs Discrimination question I noticed my TGSL gets more depth on All Metal and loses about an inch, inch and a half on disc, Does a VID lose the same? meaning would I be better putting a VID on the TGSL and leaving it on all metal, and discrimination based on the numbers I would see vers the board disc ?? I know an inch does sound like much but I want to keep that inch, and I need some for of disc as the area which I belive to still have a lot of old silver coins is very trashy ( nails and old bottle lids mainly. )

[CDI]

VID vs Discrimination question I noticed my TGSL gets more depth on All Metal and loses about an inch, inch and a half on disc, Does a VID lose the same? meaning would I be better putting a VID on the TGSL and leaving it on all metal, and discrimination based on the numbers I would see vers the board disc ?? I know an inch does sound like much but I want to keep that inch, and I need some for of disc as the area which I belive to still have a lot of old silver coins is very trashy ( nails and old bottle lids mainly. )

Ofcourse will be better to run machine with zero disc.
I'm runing mine diy idx like that, but u need to modify code a little bit cause vdi numbers depend on disc pot how u set. Sensor value need to be changed, it is easy task.
With this setup every idx is monster.
I found this at nearly 20" in the Roman field.

[dgm]

Hi CDI, did you change the code to use zero discrimination? Can you publish it? Thank you!!