In the pulse type detectors PI (Pulse Induction) to assess the presence metal objects in the search area used is the phenomenon of occurrence of eddy surface currents in the metal object under the influence of external of the electromagnetic field.This is open hardware DIY project. A simplified block diagram of the pulse detector. SM Gold aqualine PI-Homemade metal detectors with double coils This is the legend of my legend Baracuda the Pulse induction.DIY Metal detector project with PIC12F1572 (or PIC12F1840) microcontroller.Fig. You can put a reverse-conduction bipolar transistor with a voltage K-E of at least 200V.Category Arduino Metal Detector. The transmitting node consists of a pulse generator on a KR1006V1 chip (an analog of NE555) and a powerful key on a KP505A field-effect transistor (an analog of IRF740, IRF840). The metal detector circuit consists of two main components: transmitting and receiving.Eriez signal processing circuitry is almost 100 in-house developed. PIC12F1840 still usable also.The sensor of a pulse induction type metal detector also commonly consists of a. This is strongly evident in magnetite hotrock conditions which will cause the VLF to overload but not impact on a PI.Ported to the PIC12F1572 at. Very much like other commercial PI detectors, which tend to have similar circuit designs.The pulse Induction metal detector is the best metal detector for finding gold in the WA Gold fields because PI Detectors do not respond to the iron mineralization commonly found in the WA Goldfields e.g.
Pulse Induction Metal Detector Circuit Generator On ABasic discrimination features. Non-ferrous result in lower tone than ferrous metals. Discrimination between different metals. So there is no manual tuning. Moving mode detecting, search algorithm automatically adapts to the coil parameters and detects as those change in time. Just use standard inductor or wind some turns of wire yourself and start detecting. Kicad project files (circuit and PCB Ver3.00): Kicad_project_filesQuick link to the PIC12F1840 datasheet: 41441B.pdfFirmware source code version 1.80: firmware180.zip HEX file for PIC: metaldetector_hex.zipThis circuit has been tested to work with different coils. Black and white version of the schematic (better for printing): metaldetector_bw.pdf Schematic pdf file here: metaldetector.pdf Reason I publish all details is that I want others also benefit from the hard work I have already done. NEW!I keep pursuing my original goal, to keep the schematic as simple as possible with as few components as possible, yet to have good sensitivity. In circuit programming (ICSP) connector for easy firmware uploading. ![]() I soon realised that all available circuits are not for me. Then searched web for DIY metal detectors. And of course found out that cheap ones are probably crap and better ones I can´t afford. Then I researched market for metal detectors. So logical step was to get a metal detector. Pulse Induction Metal Detector Circuit How To Build BuildIn principe it is inspired by commonly known pulse induction detectors. Technical description:I call this “Pulse oscillation decay” type detector or just " Pulse oscillation" detector. If you do not have programmer you can purchase preprogrammed microcontroller from my shop. I bought PICKIT3 because sadly i discovered that PIC12F1840 was not supported by my JDM and Parallel TAIT programmers. Surely we can do better nowadays - We can do it with one 8 pin PIC microcontroller and very few external components! I guess I make separate article about my sawmilling system some day.So here is, how to build build good metal detector for only microcontroller cost, all other components and coil wire can be obtained from electronics crap laying around everywhere, and if you want to program PIC yourself, you need some programmer device compatible with PIC12F1840. So why bother building some ancient design metal detector with several opamps and bunch of resistors and other components. Microcontroller just have to measure the decay time, to detect differences in oscillator circuit losses. Mainly there are constant resistive losses in oscillator circuit, and apart from that there are EDDY CURRENT losses in possible metal target. So all circuit must be well isolated to avoid electric shock! Oscillation is then of course decaying fast, because of losses, and because energy supply to the circuit is cut off. This oscillation is by the way relatively HIGH VOLTAGE. High current pulse is applied to the coil and after the pulse is cut off, oscillation occurs in a tank circuit formed by search coil and capacitor in parallel with it. In my detector circuit the coil is not dumped by dumping resistor as found in common pulse induction detectors. Free acid pro downloadMost logic level drive and 150V mosfets should work. Mosfet I use in latest working rig is IRLI630. Capacitor C1 is chosen so that voltage at the coil never exceeds about 150v, the MOSFETs rated voltage. So it is even possible to discriminate between targets with this method, and this function is included in latest firmware.Oscillation maximum voltage is also dependent of the C1 value. The ferromagnetic metal target objects decrease free oscillation frequency and non-magnetic metals increase oscillation frequency. And frequency also changes slightly depending of the target metal properties. Pulse duration is 140 microseconds. It is reasonable to choose 200V maximum voltage mosfet transistor, if supply voltage is 4,8V from 4 NiMH cells.In my design pulses occur at 2 millisecond intervals. Higher voltage mosfets have always larger on-state resistance which in turn limits maximum current for given supply voltage. Pulse Induction Metal Detector Circuit Series For PowerThe PIC internal features are configured in the way shown. At the same time, as pulses are very short, circuit average current consumption is very low – no need to carry huge batteries with you.Use ONLY 4 NiMH or NiCd cells to supply this circuit! There is no supply voltage limiting circuit and four Alkaline batteries voltage will be 6V, which is too high for PIC microcontroller!I repeat: This circuit is designed to use 4 NIMH cells(AA or AAA) in series for power supply.This is equivalent circuit about what is happening inside PIC12F1840. This makes pulse current as high as possible – more sensitivity. Coil Pulse current is limited only by MOSFET on-state resistance and search coil resistance. And this is our measurement. Program then activates Timer1 just after the coil pulse is ended and reads the value from the timer before starting the new pulse. This valuable function only lets the Timer1 to count when comparator output is high. Comparator output is internally connected to TIMER1 gate. So voltage reaching PIC input is always in the range of supply voltage. Schottky diodes D2 and D3 dump the excessive voltage to supply rails. This is why there is limiting circuit of R4,D2,D3. Gem perangWhen I started the project I used MPLAB IDE v8.83.Firmware pushes this little microcontroller to its limits regarding speed and takes full advantage of the PIC´s on-board peripherals. Firmware:PIC firmware is now written in assembler using MPLAB X environment. Oscillation center point is positive supply V+. Limited voltage waveform at Microcontroller input.Notice how upper part of the oscillation is almost completely limited out, and lower part is limited to negative supply V-. To be exact I also tried the circuit without the diodes D1 and D2 and it seemed to work well because of the PIC internalt protection diodes, but there is too few testing to reccommend that.Figure 4. Slight discrimination between different metals. Speaker is connected between two outputs because this creates sort of bridge circuit, voltage is doubled, sound is stronger, and signal do not have DC offset.PIC resources used:Interrupts, Interrupt-on-change, Sleep mode,DAC, Comparator, all Timers(Timer0,Timer1,Timer2). Much less than NiMH batteries self discharge anyway.Sound generator just uses timer2 to toggle speaker outputs. When circuit is turned off PIC is in sleep and current draw is virtually none. All functions are controlled only by one push button. Longer push on the button turns detector offSource code version 2.00 (for PIC12F1572) whole MPLAB X project: PIC_program_12F1572.X.zipFirmware source code version 1.80: firmware180. discriminating mode, less filtered than mode1 gradual beeping(distance indication), now with discrimination discriminating mode, standard on/off sound Double push on the button changes operating mode.There are 4 modes:
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