If your metal detector is not working well. The resistor parallel to the coil MUST have a resistance of approximately 330 Ohms, you can change it to a few tens of Ohms and check whether it works worse or better. The 1000 uF capacitor that is on the supply, it is better to place it closer to the terminals supply TL072, and the other at 470 uF is closer to the terminals of the generator coil.These are the two main reasons why the device will not work well. This should be done if there is a constant buzz or something else when you turn on the power.
I built it and it doesnt work. I mean that I made a mistake somewhere but I dont know where. My detector works only on for example my laptop but when the laptop is turn on. It means that it detects only things which are powered by electricity. Can you tell me where I have a mistake?
I have a lot of questions about this. Where did you connect the function generator and what is the input? Where did you connect the coil? Please help me ASAP
@@Kositsyn83 Thanks for your reply. Without any dection or pulse, the current still is approx 1 amp. My oscillopscope shows a neat pulse on the IRF gate. Without the coil connected I also see a nice pulse on the 220Ohm resistor. The coil is 20cm in diameter and has 30 turns (0.5 mm) giving a resistance of 2.6 ohms. Maybe thes figures helps to explain what is going wrong.
Can you please specify inductance of coils or gauge of wire used ? I have problem with receiving response. I can see same 100V spike on my oscilloscope, however when i place something like swissknife on it nothing changed. I tested with coils 2.5 mH, 200 uh (SWG19) and 4mH (SWG40). R1 and R2 values so i got different frequencies. Do you have some data-set for R7 values to change of response time. (I used 300 instead of 330)
@@Kositsyn83 Thanks for fast response, I will try mentioned changes. My coil (2.5 mh ) is wound around plastic cylinder. No special winding. (Was used in different type of detector as TX coil. I just wanted to try it in pulse detector.) Is there need for special winding ? If so can you refer to it by name so I can find it on google ?
@@Kositsyn83 OK, I tried some changes and i did figured it out. I used 100K potentiometer as R1 and R2. Then 2x 1K potentiometers on R7 and R8. By trial and error I found way to see best ratios for each coil. My initial problems were coil didn't recovered fully after reset and pulse was too short.
