Self-defense Anti-theft Bag: Traditional Chinese Circuit Design Guide

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Self-defense anti-theft bagHow can we prevent the bag (or box) containing valuables from being stolen, or prevent the valuables in the bag from being opened and stolen by thieves? Now it has become a problem that people are very concerned about when they go out.In order to meet the requirements for people to carry handbags with them to prevent theft when they go out, handbags with anti-theft alarm functions have emerged. However, anti-theft bags with complete functions are expensive and complex in structure, making them difficult to be accepted by people; while anti-theft bags with simple functions are cheap but poor in practicality. As a result, bags with anti-theft alarm functions cannot be popularized.To this end, we designed and tested the "Self-defense Anti-theft Bag". Its characteristics are: when someone else moves the bag to make room for it or mistakenly takes it and puts it down, the bag does not alarm and does not generate high-voltage electricity; if the bag is carried away by a thief, as long as it goes out a certain distance (that is, more than a certain time), the bag immediately alarms and generates high pressure on the handle, forcing the thief to drop the bag; in addition, , when someone attempts to open the zipper or lock of the bag without moving the bag, and steal the valuables in the bag while the owner is not paying attention or is asleep, as long as the thief's hand touches the lock on the metal zipper or nylon zipper or the lock on the bag, the anti-theft bag will immediately alarm and generate high voltage in the relevant parts, making it impossible for the thief to start. With the above features, the possibility of the bag being stolen or the items inside the bag being stolen will be reduced to a minimum.1. Circuit working principleThe circuit diagram of the self-defense anti-theft bag is shown in Figure 7-1. It is composed of a touch switch circuit, an audio sound circuit, a delay switch circuit and a high-voltage generating circuit. Among them, the audio sound circuit and the high-voltage generating circuit are common circuits of the anti-theft device.Figure 7-1The touch switch circuit is composed of a sensor M that accepts the voltage induced by the human body and combined switch tubes BG1 and BG2. BG3 and BG4 form a complementary audio circuit, which can emit an alarm sound similar to that of a steamboat.The delay switch circuit is composed of resistor R4, capacitor C5 and single-junction transistor BG5. In fact, it is a delay relaxation oscillator.The high-voltage generating circuit is composed of three parts: oscillation, amplification and power amplifier. BG6 and BG7 form a free multivibrator, which generates an oscillation frequency of about 24kHz. It enters the base of BG8 through C8 and R12 for amplification. After amplification, it is coupled to BG9 by transformer B1 for power amplification. The base of the power amplifier tube BG9 is not biased by DC, so the signals amplified by BG9 are pulse AC signals. The load of the power amplifier is the step-up transformer B2, and the boosted voltage is about 5000V.When no one touches sensor M, there is no signal voltage at the base of composite tube BG1, and BG1 and BG2 are in a cut-off state; when a human hand touches M (that is, touches a metal zipper or lock), the induced voltage of the human body is added to the base of BG1 through R1, causing BG1 and BG2 to The resulting composite switch tube is saturated and conductive. The potential of the emitter of BG2 is close to the voltage of the power supply, causing a voltage drop on the resistor R1. The isolation diode D1 conducts forward and sends the signal voltage to the base of BG3, causing the complementary audio oscillator to work and the speaker to sound an alarm. When the human hand leaves the sensor, the base of the BG1 tube loses the human body induced voltage, and the alarm is cut off and inactive.In normal times (that is, in the alarm waiting state), the power switch K1 of the touch switch circuit and the complementary audio sound circuit is placed in the on position.In order to synchronize the high voltage with the alarm after K2 is turned on, the electric relay J and the one-way thyristor SCR form a high-voltage power switching circuit.When the power switch K2 is turned on, the alarm cannot immediately alarm or generate high voltage. Only when the charging voltage on C5 reaches the trigger voltage of the single-junction transistor emitter, the emitter E and the first base B1 are turned on, causing a voltage drop on the resistor R7. This signal voltage is sent to the base of BG3 and the control electrode of SCR respectively, so that the alarm can sound and the J action can generate high voltage.In this way, no matter whether the thief attempts to open the bag or take away the bag, the anti-theft alarm device installed in the bag will work reliably according to people's needs.2. Component selection and productionBG1~BG3, BG6~BG8 are 3DG6 or 9013, 9014, with a β value greater than 100; BG4 is 3AX31 or 9015, with a β value greater than 60; BG9 is a high-power transistor, and 3DD12 or 3DD15 can be used, with a β value greater than 25.BG5 is a single-junction transistor, and BT33 or BT32 can be selected. …

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