This is PIC16F73 base digital data capture unit with optional EMF reader. This data capture utility is design to work with most of the analog sensor inputs and by default it is equipped with EMF reader module. This unit use PIC16F73's internal 8bit ADC to capture the analog signals.

EMF reader unit in this schematic is useful to detect variations of EM field in environment and it is mainly build around UA741 operational amplifier and 12mH detector coil. Normally EMF meters are used to trace electric wires, find hidden transmitters, and diagnose electric wiring problems, etc.

This digital data capture unit can operate in two modes. In first mode it directly convert analog signal into digital data and transferred to host via serial interface. In second mode it display captured signal in 5 LED bar graph either slow or high speed capture modes.

In EMF reader unit detector coil must be within 12mH - 15mH range and it must also wind on air core former with diameter of 30mm or higher. During our testes we wind 32 S.W.G copper wires on 30mm Ø P.V.C former to construct this detector coil.

12.75mH detector coil used for EMF meter project
12.75mH detector coil used for EMF meter project

The supplied firmware for this project can be used with PIC16F73 and PIC16F737 microcontrollers and this system can use with PIC16F737 MCU with slight modifications. The firmware of this unit is developed using MikroC Pro for PIC compiler/IDE.

In this project package additional Windows native application is provided to record captured data into CSV files. This application requires Administrative privileges to execute, and use Visual Studio 2012 or higher version to compile this application.

In EMF reader unit UA741 can be directly replaced with TL081, TL071, MC33171 or LF351 operational amplifiers and out of those ICs we got very good results with LF351.

udatalogger-mobile-12mh.png
Sample reading from EMF detector when mobile phone is ringing

This unit is design to work with 5V 500mA power source and to get optimal EMF readings it is highly recommended to use battery with regulator to drive this system.

Project Related Downloads


Schematics, compiled software binaries and source codes of digital data capture unit.

References


PIC16F73 - 28pin 8-bit CMOS FLASH Microcontroller
PIC16F737 - 28Pin 8-Bit CMOS Flash Microcontroller with 10-Bit A/D and nanoWatt Technology
UA741 - Operational Amplifier
LF351 - Wide Bandwidth JFET Input Operational Amplifier
TL071 - Low Noise J-FET Single Operational Amplifier
TL081 - Wide Bandwidth JFET Input Operational Amplifier
MC33171 - Low Power Single Bipolar Opersional Amplifier
MAX232 - 5V Multichannel RS-232 Drivers/Receivers