First, just about to do the experiment and see whether there will be enough work and performance , but it turned out quite decent for my meager experience of the device . Was based scheme impulsnika Tracker-PI, thrown brains, its program for Arduino , the scheme drew in Proteus, the sensor is made planar (in this scheme , ischtochnik here) . All other files , see the end of the article .
The characteristics were as follows ( tested on what it was )
10 kopecks . USSR - 12-15 cm
2 kopecks . royal ( 2 cm diameter copper) - 17-22 cm
Cartridge World German - 25-30 cm
Tin ( both from condensed milk ) - 45 cm
Old CD- drive - 60-70 cm
Furthermore aborted controller, the circuit has remained unchanged, except for the divider for voltage measurement. Measures by the way, is not entirely accurate, probably due to the setting of the ADC Arduino for the maximum frequency. With adjustment problems special was not, instead of R25, first put trimmer that you suggest, they lined the ledge on the waveform (the waveform will cast later, disassemble lazy) to measure the resistance of the tuning - has been exactly 400 ohm, made with the same nominal value of an ordinary resistor - IMHO safer . Inadvertently burned a couple of times and chip stabilizer 5V
Include the device without the coil is not necessary - of R7 will smoke . R1 set 0.25W - with a pulse frequency of 140-160 Hz is not heated (if heated - so any frequency is too high , or the impulse is wider than it should be ) . So it is not necessary to connect the detector to the switching power supply - will not work ( and even chips Pohorje )
As a display used by the Chinese in 1602 with buttons . If this is not present, the function of the survey will need to redo buttons ( function must return the same values in the sketch ) . Buttons need all three . That, incidentally , himself a sketch :
Everywhere uses the direct entry to the port in order to save precious time - the team "PORTD = B00001110;" 0.2mks executed order. AnalogRead performed slightly less than 20 microseconds - for a long time, but the ADC MEGA 328 16mks will digitize the signal can not, therefore, 20 - not so much for him. From saving time do not use the post to certain pins and write the entire port, in this regard, in the same pins that are used display also get zero, no glitches is not caused, and therefore left. The function are essential SendPulse can play around with the change of the guard interval in the range of 8-15 microseconds - will change the sensitivity better or worse. Yes, if you experiment with sketch note
that the house can obtain an increase in sensitivity , and decrease in the sensitivity , or vice versa. If someone will change something in the sketch - follow the main loop execution time . The stock is about 1000 microseconds - this is not enough , but the function are essential to display and various arithmetic eats whole time milliseconds .
If you tried to do PCB layout thicker track ( it was my first LUT ) :
Operation:
maxControl - number of measurements before checking for the presence of metal in the area of the device. In principle, this value - the only thing with which you can experiment after launch. If you decrease the value to 5 or 2 - a great influence on the result will provide electromagnetic interference (in the settlements, for example) and properties of the soil in finding small items. If you increase to 15 - good sensitivity is observed in terms of interference, but the field is much weaker. Then decide on the circumstances. I left 10 At the start pulse is sent to a couple of hundred, are measured by the average, maximum and minimum readings for a few seconds a message appears with these figures.
If the numbers in the range of 700-900 - it should work. If 1024 shows everywhere - so that it is not connected, or a problem in the coil. The sensor must be filled with epoxy, or in contact with drops of dew or rain sensor device will behave inappropriately. The button with the code "1" is used for tuning. They picked up the device, press
tuning, wait 2 seconds - the procedure can work. When auto-tuning sensitivity to small objects could be worse somewhere centimeter - twice, so if you are looking for a coin in the ground every little trash and debris, use the manual override buttons - the lower the value on the display, the higher the sensitivity.
In the diagram above the overall wiring diagram (unit without display and buttons - it just stuck in the Arduino) Carefully powered Arduino - I gave 12V at the vin, or as an option - you can make a power connector and insert it into the Arduino. The battery is connected gel 12V 800mA. According to estimates should last for 6 hours (consumption of about 150 mA). The module itself is exactly the detector consumes 100mA - if you get a lot more or less - you need to look for errors. The resistor in the tweeter picked at random, thought much about 20 Ohm - took what lying around the house. In principle, all of which can be forgotten - added ..
Archive the project to Proteus, a sketch for Arduino and PDF for the loot.
It becomes clear how it all works.
As I wrote at the beginning - I did not experience much the scheme is being finalized. Who has an oscilloscope, look for small variations of the power supply line during a pulse, as well as during the chime. This is necessary as that to stabilize, give an increase in sensitivity. The new version will be asking to get out of Arduino controller, and insert in the well, or directly to flash programmer - as you like, or similar devices in the network enough, was designed from the ground up once the program. The oscilloscope is desirable to adjust, otherwise we will have to adjust at random.
As for the field trials - with an instrument was unearthed many different and mostly rusty sensitivity in our area has to underestimate, because the whole earth is littered with shrapnel and shell fragments from the First World. Before that, only the Chinese used MD-3010II (to beat). Impulsnik certainly be convenient at times. There was a flaw in the search during the dew - when the sensor get wet squeaked constantly, but a thorough insulation fix it. Yes, any metal detector on the beats in a radius of ten meters from the included impulsnika goes mad and beeps constantly)).
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