Old Soviet and pre-revolutionary coins in the market are quite expensive. You can find them, including in abandoned old villages and towns. However, the search for such small objects, in most cases already sprinkled with earth, without a special tool, would, of course, be extremely difficult. Therefore, modern treasure hunters use special detectors for this purpose.
There are many types of such devices in the modern market. And the simplest one is Butterfly. A metal detector (a photo of it is presented on the page) of such a design is relatively inexpensive and at the same time quite convenient to use. Therefore, he earned consumer reviews just excellent.
Design features
This tool got its name for the presence of two coils resembling butterfly wings and located in the same plane . Such a metal detector works on the principle of disrupting the synchronization of frequency generators. Elements of its design are:
Chips on operational amplifiers. Two of them receive coil signals. The third amplifier calculates the difference.
Speaker It is on it that the signal difference is displayed.
The capacitor is variable. This element is designed to prevent distortion of the capacitance during adjustment.
Dielectric box for the circuit. It can be made of different materials.
Base for coils and rods. Its length can be 30-45 cm.
A rod made of dielectric material.
PEL wire 0.3-0.35 mm.
Batteries
Two-core cable.
As you can see, the design of this metal detector is really simple. Including therefore he earned good reviews from consumers.
If desired, today you can buy a metal detector "Butterfly" and with one coil. Such models work, of course, somewhat worse than usual. However, some coin seekers still consider them quite promising.
Operating principle
The distance between the coils of the Butterfly tool is approximately 10 mm. As soon as any metal object, including underground, falls into the range of one of them, the synchronization process of the generators ends. As a result, an audio signal enters the earphones of the coin finder.
Metal detector "Butterfly": reviews
Of course, the Butterfly tools are inferior to most of the more complex and expensive models in terms of ease of use. However, using this metal detector you can find objects in the ground quite effectively. For example, the “Butterfly” “sees” a five-penny coin from the times of the USSR at a distance of about 15 cm, the covers from cans - 30 cm, hatches - 60 cm. Consumers have a good opinion about this device, including because it can work under the water.
The advantages of this metal detector are also attributed to long-term operation. One battery charge "Butterfly" is usually enough for as much as 20-30 hours. According to most searchers, working with this device is also convenient because it does not weigh too much - only about 500 g.
Thus, there are many advantages of this device. However, he also has some disadvantages. For example, many coin seekers note the fact that ears of the coil of the Butterfly device often break. In addition, such devices sometimes fray the cores in the cable. In some cases, the standard coils themselves may fail on these metal detectors.
Another indirect drawback of this device, according to many consumers, is that in the event of a breakdown, it can be difficult to find a master to repair it. For people who have no experience with radio electronics, this often becomes a problem. However, the device of this device is actually simple. And even with a minimum of radio engineering skills, repairing a home foreman with such a metal detector will not be particularly difficult. Moreover, all kinds of parts for it are not too expensive and you can usually find them on sale without difficulty. They are sold both in specialized and just in construction stores.
Metal detector device and circuit
So, reviews about these devices are good, including because of their simple design. What device does the Butterfly metal detector have? Let's deal with this in more detail.
In order for the tool to work effectively, the diameter of its coils should be at least 21 cm. The turns of wire on them should be 30. The tap usually comes from the 10th. A rod is fixed on the base of the device. The sensitivity adjustment system is also fixed here. Inside the bar along with the headphone outputs, a cable is stretched. The power source for metal detectors of this type is sometimes even a simple battery from a mobile phone (in makeshift models).
The cable inside the rod in such metal detectors is pulled along with the headphone jack. This item is designed to turn on / off the device. Reviews about devices of this design exist, therefore, not bad because they start working immediately after the connector is inserted into the headphones.
Above is a simple metal detector circuit "Butterfly" on two transistors. As you can see, it does not differ in particular complexity. In any case, the circuit of this device is not critical with respect to the rating of the parts, the number of turns and power.
For what else earned good reviews the device
Finding coins with this device is actually not too difficult. Consumers also have a good opinion on Butterfly devices because they can automatically tune to any soil. Also, the coin finder can determine the type of metal underground by the sound of the signal. In addition, due to the simplicity of the design of this device, it can be easily improved if desired. For this, of course, he also earned excellent customer reviews.
In some cases, home craftsmen do not even purchase parts for the Butterfly metal detector, but simply take them from old equipment. For example, for the coils of this device, a cable from the deviating system and the demagnetization loop of the TV are suitable. The only thing in such devices are usually used headphones with high resistance. Unfortunately, finding them is rather difficult. Ordinary audio headphones from old equipment cannot be used with this device. The sound on them in the search process simply will not be heard.
The main disadvantage of the device
Thus, according to many consumers, there are practically no disadvantages of the inexpensive Butterfly metal detector. This is especially true for operational efficiency and ease of use. This device finds coins at the same depth as most of the fairly expensive, including imported, models.
However, in terms of ease of use, this device has one rather serious drawback. During operation of the Butterfly metal detector, inconvenience often arises in fine tuning the operating frequency of the generator. Finding the right rod position by a fraction of a millimeter in the steppe or forest is, of course, quite difficult.
Manufacturing nuances
Making a Butterfly metal detector with your own hands, as already mentioned, is quite simple. The circuit of this device is not particularly complex. The only thing when assembling it is to make sure that its left and right parts are the same. The device board is placed in a plastic box. Glue it to the coil frame. The second board is usually supplemented by an amplifier with pads for three batteries and a headphone jack. Petals are cut out of a tin can.
In the presence of an amplifier, the Butterfly metal detector can also be used with conventional 30-60 Ohm headphones. This, among other things, provides an economical mode of operation of the device.
The advantages of this device, many consumers include the fact that, as already mentioned, it can be easily improved. In addition to the headphones, if desired, it will be easy to make the Butterfly metal detector with your own hands and more convenient with respect to fine-tuning the frequency. To do this, on the board to which the petals are soldered, you should place a variable resistor with a resistance of 100 ... 150 Ohms. Next, this board, like the first, is placed in a box, and then the last is attached on a bar near the handle.
How to make a Butterfly do-it-yourself metal detector: detailed instructions
Actually this device is assembled as follows:
a rod is made, for example, from a 26 mm plastic pipe.
a wheel from a bicycle is attached to one of its ends;
a base is made of plywood, polycarbonate, etc.
the assembled circuit with the coils is attached to the base;
also on the basis of fixed rod and node sensitivity adjustment;
a wire is drawn inside the bar;
the battery from the mobile phone sticks to the base;
power wires of generators and a charging connector are soldered to its contacts;
the coil and circuit are covered with furniture varnish, and then with silicone;
a tuning unit is glued next to the coil;
the armrest is made from a water pipe.
To adjust the metal detector during operation, a plastic nut and a screw with a piece of aluminum are used. The threads of this assembly are lubricated with grease.
Instead of a conclusion
So, judging by the reviews, the Butterfly metal detector can be considered a device in operation quite convenient. Finding coins with it, both small and large, as well as any other metal objects in the earth, is easy. Of course, this cheap device has its drawbacks. Some seekers even call it a "toy" for beginners. However, if desired, this device can always be slightly improved and made more convenient and efficient in operation.