Piezoelectric ceramic, light emitting diode test pen, LED Probe
Keywords: piezoelectric ceramic, light emitting diode test pen
Passive piezoelectric ceramic, light emitting diode test pen
This article introduces a novel low-voltage electrical pen, which is identical to the traditional neon-tube-based electric pencil. It does not require a power supply when the test is required, and only the weak test current can flash the light-emitting diode, piezoelectric The ceramic sheet sounds, and the test point is displayed in the form of sound and light double indication, which makes it more eye-catching, but also overcomes the disadvantage of the vented air leakage failure, and realizes the solidification of passive test displacement devices.
It is well known that the test current allows the test current is generally a micro-level. Such a small current is not possible to directly push the luminous tube luminescence and piezoelectric ceramic sound, but from the perspective of energy, the lifting voltage of the neon tube is around 100V, and the glow current is 1μA, and its minimum light emission power is 0.1mw. The light-emitting diode is 1.6V to 2V, and the minimum light emitting current can be as low as 0.1 mA, and the minimum light emission power is about 0.16mW, the minimum light emitting power of the neon tube is the same order. If the polymer circuit is added to increase the pulse power, it is fully capable of pushing the light-emitting diode to emit light. In addition, the current of the piezoelectric ceramic sheet is in operation, and the test electricity of the tube is weak, and there is no problem.
According to the above analysis, the author designed the electric pen principle circuit shown in the drawings. The voltage limit resistor R, the test end CS, the touch end CM, etc. are similar to those of the conventional type electric press. Diodes VD1 to VD4 constitute a rectifying bridge, and piezoelectric ceramic sheet YD is used only to act both as a sounding element, and a charging polymer and pulse discharge effect using itself. The thyristor VS is constituting the electronic switch to the trigger VS1 to VS4, and the charging time is controlled by the YD capacitor, and the trigger voltage can be adjusted by changing the number of trigger tubes, thus adjusting the "lifting" voltage of the measurement pen. At the time of the test, the rectifier bridge-weak AC test current into direct current, charges the capacitance of the YD itself to aggregate energy. When the voltage rises to the trigger voltage of VS1 ~ VS4, Vs is triggered, and the Vs is triggered and quickly turned on. YD is discharged from the LED to the LED through VS, and the LED has a pulse current that is high than its minimum illuminating current at a very short period of time, with a higher brightness flash, and YD also issues a sound sufficient to hear. As the YD capacitance continues to charge, discharge, the LED is constantly flashing, YD is constantly intermittent, so that the power has a function of sound and light double indication. Of course, you can use YD, and use a capacitor generation, at which time the test is only the light indication function, but the brightness will increase; or the luminescent tube can be removed, and the sound test pen of a single function can be removed.
The brightness of the neon tube measurement is very large, and the flash brightness and sound size of the test electric pen are only determined by the circuit, which is not related to the use environment, which is basically constant. It is just that it flicks and the speed of vocality changes with the size of the test current, the test current is large, the speed of flashing and vocal is fast, and vice versa. This makes the mesh flashlight, and the speed of vocality can generally reflect the operator's high-level resistance size or high test voltage, because these two factors determine the size of the test current.
When the meter is working, the circuit is in a micro-current state, so it has a long service life. After more than a year, the penalties have proved that the electrical parameters of the electric pen are fully compliant with the requirements of electrical safety technical procedures, and the working performance is stable and reliable. As for the design and production of its outer casing, it can be flexible to meet the technical specifications.
This circuit is tested by 1kV megaphuri table, equivalent resistance 3 ~ 4mΩ; after adding 120V DC voltage test after 20MΩ resistor, its sound and light flashing frequency is 3 ~ 5Hz; the test is compared with the neon tube-tube-sensitive pen, under the same voltage, When the tube is very weak, the test electric pen is still 3 Hz
Frequency sound light double blinks. Test conclusions, the comprehensive performance of this measurement is better than the neon tube measurement.
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