'KROT2-XM' (mole), new project Xmega32

[smity]

Here's a new project. All tested and everything works perfectly. Just take a soldering iron and do ... The software is open, without limitation, FREE!



author website http://radiodom.ucoz.ru/index/selekt...t2_m_quot/0-17

In the archives of the printed circuit board.


Video of the device ...

Who does not understand the Russian language, use a translator.

[smity]

Promo clip ..... Advertising for a good mood!

[WM6]

Something fresh. Expecting one more uC PI but this is uC VLF/IB.

Do you know where in circuit this signal is taken?

[smity]

This picture shows the interference (noise) ... This happens near the included computers, near the energy-saving lamps, a powerful home appliance ...

[Tepco]

My modified version of older KROT design based on Atmega8 chip, display sized PCB, standard parts, more on this later...

[kt315]

only reminder old project Krot-M here in this thread http://www.geotech1.com/forums/showt...highlight=krot

[Tepco]

Or in original version, here:


http://radiodom.ucoz.ru/index/selekt...ot_m_quot/0-14


Tested only to V.10 software, simplest detector ever, actually works just fine. Few mod's added, to fix phase adjustment, with completely improvised 8in coil get 23-24cm on 1E coin, with high threshold and strong signal, definite VDI indication, outdoor and on low threshold can be claimed at 28-30cm. Ground compensation works fine, excellent recovery speed (digital filters), complete “all included” package, nice.

[WM6]

IB/DD coil data:



Coil data for working frequency 8 to 9 kHz, coil diameter 25-27 cm (10"-11"):
TX number od turns ~45 wire diameter CuL 0.4-0.5mm capacitor С1=0.3uF
RX number of turns ~200 wire diameter 0.15-0.22mm capacitor С0=0.022uF or С0=0*
Frequency offset between TX and RX tank is about 1,5kHz Ftx>Frx
* "Крот-2" is working well with non-resonant RX tank where C0=0

[WM6]

KROT PCB

[smity]

WM6, рlease write a little more about the work of your modifications Mole-1. In the relevant subject. Why did you decide to use a transistor assembly in the transmitter? Instead TC4421 can be put IRF7105? The variable resistor for adjusting the phase you installed on the printed circuit board, or carried on the instrument panel? And so, the device is great. I have done in the author's version, was pleased with the work.

[WM6]

WM6, рlease write a little more about the work of your modifications Mole-1.

Hi smity. Probably yuor post is related to post #5 from Tepco. I didn't build Mole-1.

[smity]

Then, I apologize. Tepco redirecting your question.

[Tepco]

Sorry, I was unable to respond earlier, probably everyone here noticed my posting pattern, series of posts and some silence for week, sometime month, will be offline for some time again, so this is bit longer post.


This KROT design is probably best DIY project so far, extremely simple, low part count, easy to assemble and adjust using only DMM and detector itself, just one physical adjustment (phase), and still provide nice performance, equal or even better than entry level commercial machines. Soon when I get more time, I will post detailed how-to instructions ,and details in separate post. I have to admit, this project is on my workbench since august last year, but still not finished, not due to my laziness. Also it is not on my priority list now, i'm working on one promising Pi design, but long winter days coming so will be plenty of time for all this. In meantime, few comments may help.


I changed few things in Krot hardware. First, TX stage is different, based on TC4421 gate driver chip. Result of precise design, components used must exactly mach content of my nearest junkbox, I just had some 4421 at hand, used for some commercial units and decided to use it in detector. Original design with 34119 audio chip is inefficient, processor output is square wave, then low pass filtering it and amplifying with linear amplifier is not good idea. With this, resonant TX circuit is directly driven by low impedance square wave source. Solution in Quasar, using IRF7105 is better, having low Rds resistance, but more parts needed and 7105 is not locally available, also wont fit into display sized board without SMD, this is single component solution. On 4421 resistance is around 2R, but good enough, in series resonant circuit, only resistive component (coil and driver) remain. Powered with 5V this circuit typically produce some 50-60Vpp on coil (depending on coil type and frequency) somewhat distorted sine wave voltage, but no problem with that, current is sinusoidal. Normally detector needs 20mA for backlight, less than 10mA for everything else, rest is TX drive, so with total consumption of around 100-120mA this is relatively high power TX. I tried number of different coils, ready made DD halves, at different frequencies, this what is proposed, also similar to Quasar coil seems to be about optimal. Bit higher TX power, high transformer ratio coil and higher RX gain will not hurt, considering detector is bit “deaf” on RX side, about good combination. Everything is very flexible, even with some overclockig (24MHz quartz) works at 19.6 kHz. Additional 22-33pF capacitors on Xtal are not needed, circuit will reliably start with internal chip capacitance. Also, TX capacitor is recommended to be 100V or higher, so larger raster is provided on PCB.


Another change is with MCP 602, dual amplifier. One half is standard RX amp, another is used as a comparator, for phase shift adjustment. In original version, single amplifier is used, and phase shift is achieved with RC network from output to ADC input. This is nice if you need to add some small shift, but if you need few degrees less, software must be set for 45 deg less, and almost 45 deg added, changing amplitude on ADC input. Instead of this, I added comparator for phase adjustment and RX amp goes directly to ADC, low impedance source, more correct. In this version, MCP 602 must be used, dual amps like LM833 or 5532 wont work. Also I made single amp board version, will post if I find file, similar to original, without comparator. In this version, ordinary amp can be used, no need for rail to rail amp, 5534 will swing enough powered by single 5V. Actually, overload indication is activated at some 1.5Vpp on ADC input. Phase adjustment is fixed, works like “foil zero” on VDI, phase is initially adjusted in software in 0\45\90\135 deg step to hit right “quadrant” and fine adjusted with phase control to get zero foil, negative (but not flipping over to +) for ferrite, positive for colored metal. Please check twice everything on PCB, I never made schematic of this, boards are manually routed from prototype, I don’t have working hardware at hand right now, just posted file from backup. So if there is some mistake, it is not intentional, I will repost complete files and pictures of working machine as soon as possible.

[Tepco]

Forgot to mention, regulator marked 05 must be low drop type, from any manufacturer, in TO220 case. This is intended to be powered from 7.2V, like two cell phone batteries, ordinary 7805 will just barely hold regulation.

[smity]

For Tepсo. PCB has bugs. The generator output must be in the controller pin 15 (rather than the pin 16). So as not installed capacitors near the quartz.