Keywords: testizer circuit diagram
This has an acoustic electrical appliance is a small instrument for testing 220V AC. Traditional testifiers have 氖 bubbles and resistors, using 氖泡 光 的 发 可 可 检测 检测 和 火 检测 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. 火. The glow of 氖 bubbles is very weak, and it is difficult to see if 氖 氖 泡 发 光 光 光 光 光 电 电 电 电 电 电 电 电... 电..... 电. 电....... 火 火 火 火 火 火 火 火 火 火 火 火 火 火 火First, the components used for the preparation of components are shown in Table 2. Table 2
Serial number
Component specification
R1
2.7MΩ, 1 / 8W carbon film resistor
C1
1000PF porcelain media capacitor
VT1, VT2
9014 and other NPN type three-pole
HA
Buzzer
3V battery holder
30mm × 20mm circuit board
Single wire with insulation skin 5-10cm
The buzzer used here is a small speaker for an intermediary integrated circuit. It is small, easy to use. Attention must be paid to the polarity of the buzzer leads and cannot be received. Its positive electrode and negative electrode are connected to the negative electrode of the power supply. There are many kinds of buzzers, and there are several buzzers, such as 3V, 6V, 9V, etc. It is a small continuous sound buzzer here, and its operating voltage is 3V, and the operating current is about 20 mA. There is also a buzzer's voice, and the sound is so good, but the price is more expensive. Second, the production and commissioning of the circuit first performs the inspection of the components, and the positive and negative electrode of the buzzer will be accepted according to the figure, and the buzzer should sound normally. There are many types of triodes, and there are different, and the above figure shows the most common triode symbols and the physical map of the plastic pipe used in the circuit. The various pins of the triode will be identified before installation. When the pin is facing itself, the pin is sequentially emitted (E), the base (B) and the collector (C) from left to right. The lead wires of the components used should be tinned before mounting welding. If the lead of the component has been oxidized, it is necessary to use a knife to scrape the wires of the components, and then tinned treatment, so that the lead can ensure the reliability of welding quality. For beginners, we must develop good habits and carefully prepare before installing welding. After the preparation is completed, the control electrical material map, the circuit board mounting map element map is shown below, and the resistor, capacitor, triode, and buzzer are subjected to the circuit board and welded. Peeling the two ends of an insulating leather wire each strip 5mm, and one end is soldered in the input of the sound test (i.e., the upper end of the resistor). Finally, the lead wire of the battery holder is welded to the circuit board, pay attention to the positive and negative electrode of the lead in the battery holder must be correct. At the time of the inspection, the long line with the insulating skin touched the fire line in the AC power outlet (to be absolutely paying attention to safety, and the line and zero lines can be separated from the line and zero lines in advance) hand touch the positive or negative electrode of the battery, the buzzer should Echo. Because the testizer is tested for 220V AC power, you must pay very attention to safety. The figure is a circuit board diagram of a small 43mm × 10 mm, for reference. This makes this circuit very small. The circuit board is used is two button batteries, and the location has been reserved, but the homemade battery holder is required, pay attention to the housing of the button battery is the positive electrode of the battery. Third, the principle of circuit work See the figure above, the resistor R in the circuit is a limited flow protection resistor to avoid harm of testers. Since the resistance of this resistor is very too, the base current of the triode VT1 is small, and a triode cannot drive the buzzer, so two three poles are used. Thus, when the left end of the resistor contacts 220V AC power, the AC signal is injected into the triode base by the resistor, and is returned to the earth. The two triodes were magnified to the signal, driving the buzzer. The capacitor C1 is set to eliminate various interference. When the buzzer does not work, the circuit does not consume electric. The resistance of the 2.7MΩ resistor in the electrostatic cannot be too small, otherwise it is not safe. Although there is an emotional appliance, it can also use this circuit to do other purposes. The figure is a dynamic circuit diagram of a touch doorbell, and the left side of the figure is a pair of touchders. Use the human own resistance to trigger the circuit. Think about what other wonderful use this circuit?
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