Product selling point1: Easy to assemble2: The appearance is small and exquisite3: Wide range of applications, game entertainment, security inspection, search for metal products on the body, etc.4: High sensitivity5: Parts with acrylic shell and without shell are optionalKit parameters:Supply voltage: 3-5VDC, the kit is powered by a 3V 2302 battery; (no battery)Uses: game entertainment, security inspection, search for metal products on the body, including mobile phones, controlled knives, etc.describe:Q1, L1, L2, C2, C3, R1, W form a high-frequency oscillation circuit. Adjusting the potentiometer W can change the gain of the oscillation stage, so that the oscillator is in a critical oscillation state, that is, the oscillator has just been started. Q2 and Q3 form a detection circuit,When the circuit oscillates normally, when the oscillating voltage AC voltage is higher than 0.6V, Q2 is turned on in the negative half cycle, which short-circuits C4 and causes Q3 to turn off; when the detection coil L1 is close to a metal object, the metal conductor will generate eddy current, and the oscillation circuit will The energy loss in the medium increases, the positive feedback weakens, and the oscillation of the oscillator in the critical state weakens, and even cannot maintain the oscillation, so Q2 is turned off, R2 charges C4, and Q3 is turned on, causing the buzzer to sound. According to the presence or absence of sound, it can be judged whether there is a metal object under the detection coil.According to this principle, the circuit can be effectively converted into a proximity switch for elevator floor control. (Optical switches are not suitable for many occasions, because the light-emitting device and the light-receiving device will be blocked by the influence of environmental dust.)Application example 1 of the principle of this metal detector: If you want to detect whether there is a car passing by on a certain road, because the car chassis is more than 0.5 meters away from the road, the cement will be buried at a depth of 5-10CM, so it is buried on the ground. A coil with a diameter of 1 meter can detect whether there is a car on it stably, accurately and reliably, and has great practical value in highway traffic statistics and parking restricted area statistics.Application example 2 of this metal detector principle: Every floor of the elevator controller needs a sensor to detect if the elevator has reached the stop position. With mechanical limit switches, there are factors of longevity and reliability; with optocouplers, long-term dust deposition failures; therefore, the only way to install a metal detector is to determine whether the circuit is open or not based on the presence or absence of metal closure. This will have high practical value in many devices and machines.DIY Parts (Board + Equipment) Shipping List:PCB board*13V Buzzer*1100UF25V electrolytic capacitor*1104 Ceramic capacitor*2222 polyester capacitor*2220K resistor 0.25W*12.2K resistor 0.25W*1100 ohm blue and white potentiometer*19018 triode*19015 Transistor*19012 Transistor*12D07 Toggle switch*12032 battery pole piece*1Debug method:The L1 and L2 of this machine use copper conductors on the printed circuit board to form inductances. You don't need to make your own inductor. It's simple and has a high success rate! The circuit has just used more than ten components, as long as the installation is correct, it can generally work normally. After installation, connect the power supply, the potentiometer should not make a sound (if it is not close to the metal), use the circuit board antenna to approach the metal, and it should make a sound at this time. Turn the potentiometer counterclockwise and try again until desired.common problem:The long beep after power up is because the front oscillator stage is not vibrating. It may be that the components such as resistors and triodes are dislocated, or the circuit board coil has an inter-turn short circuit or open circuit. Double check with a magnifying glass. Also, the gain of Q2 is too low to turn off Q3, president.Effect: This simple detector can easily, stably and reliably monitor and measure metal coins, steel plates, iron plates, aluminum plates, computer CDs, etc. that are about 2.5CM away from the coil plane (circuit board).The package includes:1*Metal detector with Acrylic Sheet/without Acrylic Sheet, optional

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