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Metal detector pirate scheme
I want to share with you the experience of creating a pulsed metal detector pirate with his own hands. On the scheme of the metal detector pirate accidentally came across on the Internet. All the details presented on the scheme are quite accessible, they can be found in almost any store of radio parts.

The conventional scheme of the metal detector pirate I broke into 4 main blocks.

The pulse generator assembled on the NE 555 timer on how to assemble the generator was said earlier: generator NE555;
Search coil node;
Two channel operating amplifiers on the K157UD2 chip;
Sonic frequency amplifier on transistor
List of radio parts to assemble a pirate

9-12 Volt

If you are a novice radio amateur then it is useful to know what is the marking of capacitors.
A pulse generator is needed to generate pulses of a given frequency. It is assembled on the NE 555 timer. The frequency is set by selecting C 1, C 2, R 2, R 3, changing the values of these elements can change the frequency of pulse generation, squirt ingesis and duration.

The timer-generated pulses arrive at the T 1 transistor, opening and closing it. It in turn is connected to the base of the field transistor T 2. R 4 resistor is needed to select the transistor’s “work point.”

The sound frequency amplifier is assembled on the BC 547 transistor, with a maximum current of the collector 0.1A. In the chain of the collector which is connected low-circuit speaker and resistance denomination 43 Om.

The scheme at first glance seems to be quite simple. But in the process of assembly I still had to sweat a lot. The scheme was first decided to collect on the assembly board and make sure it is healthy.

The first thing I did was assemble a sound frequency amplifier. In order to check the performance of the pulse generator and chips in the next stages of assembly.

The assembly began to be produced by blocks, first assembled a generator of pulses. The correctness of its assembly was checked by connecting the speaker through the transistor to the exit of the timer.

Then he started to connect the chip K157UD2. There’s nothing complicated about the no-two-amplification cascade and that’s it. You just have to be careful and don’t rush anywhere. The correctness of the assembly was similarly checked, touching the metal screwdriver to the entrance of the 3rd leg at the same time in the dynamics, there was a characteristic sound. Whoever ever assembled the amplifier will understand what it’s about.

The coil was made of copper wire with a diameter of 0.5mm, wrapping it on a jar having made 30 revolutions, then wrapped it with a fuma-tape. The wire connecting the coil and the metal detector board itself should be taken as thick and powerful as possible. I had a stranded network wire from the TV.

After connecting the remaining block with the transistor and coil, the voltage of 9B from the Chinese power supply was applied. In the dynamics there was a long-awaited crackling. He began to set up a metal detector until “clicks” appeared in the dynamics occasionally.

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To my surprise, the metal detector did not react to the metal, it did not “see” even the refrigerator! Reacted only to electronic equipment, but at the same time in the dynamics were heard not “clicks” and noises generated by electronics. Started checking the scheme, the transistor search coil IRF 740 very much warmed up. After checking it out with the tester, I was sure it was him. Resistance to the closed transistor was minimal. It turned out that during the assembly I made a gross mistake by mixing the legs of the transistor. As a result, we have a spoiled transistor and mood, as the nearest store of radio parts in a 40-minute drive by transport from home.

After replacing the transistor all at once worked and “cracked” properly. And the transistor stopped basking. On the forums about the assembly of this metal detector write that the food is better to bring closer to the coil, they say, so the “chuika” will grow. After having leaked the power wire, to my surprise, the sensitivity really increased. Not by much, about 1 centimeter, but still. Although I do not see in this logic, what difference, where to lead the power line? Maybe just the tension from the blocks has changed, the block then Chinese i have.

This is the story of assembling a metal detector “PIRAT” In the future I want to modernize it, making automatic adjustment and subtuning or any other functions with the help of a microcontroller. You can implement the adjustment by connecting instead of reostats, transistors and change their resistance by submitting a certain voltage to the base. If there are any other ideas or ready developments write in the comments, ask questions, together can do what.

Pike and editing

The scheme was collected on the finished board, as there were no tools at hand to make the original circuit board. In the end, here’s what happened:

The quality of rations is certainly not very, collected in a hurry. But it still works.