Wireless Video Intercom System Wireless Video Intercom System,Wireless Video Intercom,Wireless Video Door Phone,Wireless Door Intercom System Zhuhai Mingke Electronics Technology Co., Ltd , https://www.mingke-tech.com
First, the circuit principle
The schematic diagram of the metal detector is shown in Figure 1. The inductor IC1 and the peripheral inductor and capacitor form a three-point capacitor oscillator. The oscillation frequency is mainly determined by the inductor L and the capacitors C2, C3 and C4. Adjusting the potentiometer RP allows the circuit to be in the state of just starting. The tiny oscillating signal is amplified by an amplifying circuit composed of IC2 and R1. After diode VD rectification, capacitor C5 is filtered, and after Zui, it is amplified and shaped by inverters IC3 and IC4. Two inverted output signals are obtained at the outputs of IC4 and IC5.
When the probe inductance L of the metal detector device is not close to the metal object, the circuit starts normally, and the oscillation signal is amplified and rectified and filtered by the inverter IC2, and a negative voltage is formed at the input end of the inverter IC3 to make the output of the IC3. It is high level, the output of inverter IC4 is low level, the output end of IC5 is high level, and the LED emits light, which is beneficial for the controller to pick up the signal. When a metal object approaches, the Q of the inductor L drops, causing the circuit to stop. Since the input terminal of the inverter IC3 pulled Vcc through resistor R2, the output terminal is low IC3, IC4, IC5 output terminals are two high <br> <br>, component selection
In Figure 1, the inverter IC1 is required to operate in a linear state, so the CD4069 six-inverter integrated circuit is selected. Vcc is connected to the positive power supply, Vss is connected to the negative power supply, and the power supply voltage can be 3V~15V (DC). It can be directly connected with the single-chip microcomputer with +5V power supply.
Level and low level, the LED does not emit light.
Inductor L probe is a very important component, its performance is directly related to the sensor's sensing performance. The following options are available in production:
(1) It is possible to use a winding inductor with a magnetic rod that has been removed from the old radio. It is required to allow the oscillator to start normally, but the sensing distance is relatively close, generally about 2 cm. (2) Select a vertical inductor of about 6.8mH. The resistance value of the inductor is better than 10Ω. The larger the resistance of the inductor, the smaller the detection distance. (3) Self-made high-Q inductive probe can be wound around 300φ on φ10mm magnetic bar with φ0.15mm～φ0.2mm enameled wire, and the detection distance can reach more than 20cm.
Capacitor Zui uses polyester capacitors. This type of needle detector capacitor is relatively stable. The diode can be used with 1N4148, and the potentiometer uses a small trimmer potentiometer.
Third, debugging and installation
Metal detector manufacturer. PCB diagram shown in Figure 2, the board size is 37mm × 29mm (if the chip component design size will be smaller), all components can be soldered on the circuit board, pay attention to leave the edge of the installed inductor, the whole The board is mounted in a box that allows the inductor to probe the metal. If the oscilloscope can detect a square wave at the output, no additional debugging is required. Be careful not to use a metal box to make the installation box, so as not to affect the normal work. I have used this metal sensor for smart car detection of metal blocks and non-contact switches to achieve good results.
When we do some intelligent control design, we need to detect the position of metal objects or detect the presence of metal. These intelligent control devices, such as smart car induction iron, robot probe "lei" and metal proximity switches. Buying a metal sensor in the usual production is expensive and the effect may not be satisfactory.