How to make a metal detector: assembling a homemade metal detector at home with a detailed description

A small number of people believe that factory-made metal detecting devices are significantly superior to home-made devices, but this is a misconception. If you competently make a metal detector with your own hands and set it up, then it can outperform proprietary metal detectors. Which, in turn, will save a considerable amount of money. But in order to build a homemade product, you should know the principle of operation and design.

Operating principle

The device detects metal underground using the electromagnetic field generated by the transmitter coil. It begins to interact with the object (almost all metals are conductive), as a result of which an eddy current is formed, vibrating the radio waves of the metal detector coil. Shielding on a computer will pick up interference even from those metals that do not conduct electricity, but in the event that they have electromagnetic properties.

When the equipment begins to pick up interference, the data goes directly to the control unit. This part of the detector produces an audible signal indicating that a find has been found. The sound can be strong or weak. A strong signal indicates that the object is shallow, and a weak signal, on the contrary. There may be a coin at a distance of 50 cm, its signal will be weak. And with the same level of sound notification, large objects in the form of a helmet, weapons, and so on can lie at a depth of 100 cm. This factor must be taken into account.

Some expensive factory models display the received data on the monitor, it is very difficult to build them at home. The Pirate detector is the easiest to assemble. Therefore, using his example, you can disassemble the assembly process of a home-made device.

If you still can't make a metal detector at home, then you can go to the store and buy a branded device or order a homemade product from the masters who assemble at home. You can find craftsmen through friends or the Internet.

Attention! Newbies who first took up the assembly of a metal detector with their own hands are often confused about electronics. As a result, they give up this activity, because they are afraid of formulas, diagrams and technical terminology. To build a homemade device, it is enough to delve into the essence of the system, plunging into school physics lessons.

Printed circuit board

One of the most important parts of the device is the board. In the future, all detector assemblies will be attached to it. The most optimal method for creating a board is LUT (laser-ironing technology). Manufacturing involves adherence to all stages, the implementation of which must take place in a strict order.

A detailed description of assembling a circuit on a homemade metal detector or how to make a board from scratch:

1. To make a board, you should use a laser printer, which prints a specific layout made using the Sprint-Layout program. Use lightweight photo paper for printing.
2. The textolite blank is brought to the proper state: it is sanded and cleaned with a special solution. Its parameters are 85 * 32.
3. The printed circuit is laid with the front part on the workpiece. A regular A4 album sheet is applied on top. An iron is taken and lightly rubbed over the paper. Ironing continues until the image of the circuit is printed on the textolite.
4. When the toner image is transferred, everything should be placed in a container with water and the paper removed.
5. Some lines of the diagram may be smeared on the PCB. They are corrected with an ordinary needle.
6. You need to stir ferric chloride or copper sulfate in the container, then place the board there for a couple of hours.
7. Toner is removed with acetone. Any other solvent can be used.
8. Holes are made in certain areas of the board, which serve for the further placement of structural elements. The holes are made with the smallest drill.

The luds of the board tracks are the last step. The entire surface is treated with LTI-120 solution.

Soldering elements

The manufactured board must be inspected. You need to make sure that all the path lines are clearly visible, and the holes are in place. After that, all the necessary elements are soldered to the made metal detector board:

1. It is advisable to use a domestic-made microcircuit KR1006VI1, if it is difficult to find, then a foreign analogue of NE555 will do. Before installation, a jumper is soldered under the microcircuit.
2. An amplifier for 2 channels K157UD2 is mounted. You can find it in tape recorders made in the USSR or simply purchase it via the Internet.
3. Attached resistor MLT S2-23 and capacitors 2 SMD.
4. 2 transistors are soldered. The first one has a PNP structure and the second one is NPN. It is preferable to use BC547 and BC557. If these are difficult to find, then any analogs will do.
5. A field-effect transistor IRF-740 or another version with identical characteristics is attached.
6. Capacitors are mounted last. To enhance the thermal stability of the product, they should be selected with low TKE values.

The most difficult thing is to find the K157UD2 amplifier. Because it has not been produced for a long time. Therefore, it is preferable to look for modern analogues that fit the characteristics of the Soviet version.

Coil creation

To make a coil, you need a frame with a section of 20 cm. On average, 25 turns are wound on it, but the total number can be changed up or down. Craftsmen advise to adjust the amount of wire wrapping by checking the device on the coin. It can turn out to be 23 or 26 wikis. This is the only way to determine the farthest detection distance of a small object. It is advisable to apply PEV wire half a centimeter thick.

After the master has determined the amount of wire, it should be wound onto the frame with a tight pressure. Insulated tape is applied to all homemade reels. It is not necessary to make a thick protective coating, one layer is enough so that the turns are not visible. Work with a homemade coil can be considered complete.

Additional equipment

In addition to the board and the coil, you will have to supplement the metal detector with other necessary accessories that will significantly improve its performance. Experienced experts recommend equipping the device with the following devices:

1. Signal speaker. It can be removed from an ordinary radio. An important condition: it must have a resistance of 8 ohms. In order to save money, it is better to purchase a portable version of the Chinese production.
2. 2 potentiometers, their power must be different. One model is 10k ohms and the other is 100k ohms. It is almost impossible to eliminate interference, so you will have to minimize them as much as possible. For these purposes, a shielded wire connecting the coil and the circuit will serve. The metal detector must be powered by 12 V at least.
3. The L7812 voltage regulator enhances the stability of the electrical microcircuit. It is mounted at the entrance.
4. Frame for the detector. It is assembled from any materials at hand. However, for convenience, it is better to use a 5 m long PVC pipe. They are often used for laying pipelines. You will also need to buy a few jumpers. A semicircular hand rest is installed on the upper part. Then you need to find a sealed plastic box that will fit the board. After that, it is mounted above the middle of the boom.
5. A screwdriver battery is suitable for powering the system. The plus is that the battery is lightweight and long-lasting.

Important! The entire skeleton and other parts of the metal detector must not be metal. Their presence can distort the electromagnetic field. Better to give preference to plastic.

Setting up and checking

The first step on the detector is the potentiometers sensitivity is adjustable. It is necessary to achieve a uniform crackle. It is desirable to set up on a small object. A DIY metal detector made at home should detect it at a distance of 30 cm. He will show the Soviet ruble at a depth of 45 cm. Larger objects are captured from a distance of 100 cm.

At a very great depth, the device will not be able to find coins and similar small pieces of iron. Experienced treasure hunters, of course, are capable of to roughly understand the parameters of the detected object by sound, but the type is unrealistic. In this case, a beginner will very often stumble upon nails and other unnecessary pieces of iron.

Making a metal detector with your own hands is not too difficult. Homemade models are great for training beginner treasure hunters. You can get a lot of experience and even an important find on them. In addition, you do not have to spend money on the purchase of a device. And after honing your skills, you can buy a professional detector with a monitor that will even look for coins at great depths.