CN110542770A

CN110542770A - non-contact test pencil

Info

Publication number: CN110542770A
Application number: CN201910840335.7A
Authority: CN
Inventors: 黄勇
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-09-06
Filing date: 2019-09-06
Publication date: 2019-12-06

Abstract

The invention discloses a non-contact test pencil, which is characterized by comprising: the device comprises a 4.5V direct-current power supply, a key switch AN, a micro-voltage detection and homopolar Darlington circuit and AN acousto-optic drive circuit. The test probe of the traditional test pencil must directly contact the charged metal body, so that the test pencil can normally work only when forming a complete loop. The non-contact test pencil can normally work without directly contacting with a charged object, and the charged object can be metal or an object with static electricity or a non-metal object. The non-contact test pencil is suitable for detecting low voltage below 100V and 220V AC with high voltage, and can replace traditional test pencil for electrician.

Description

Non-contact test pencil

Technical Field

the invention belongs to the technical field of electrician and electronics, and relates to a non-contact test pencil.

background

The test pencil is composed of test probe, current-limiting resistor, neon tube, metal spring and hand-touch electrode which are connected in series. When the probe is contacted with the charged metal body to be tested, the finger must be contacted with hand to touch the electrode to form a loop, when the metal body to be tested has relatively high voltage, the neon tube is lighted, and it shows that the metal body to be tested is charged. However, in actual work, many electrical appliances have certain voltage on metal shells or metal components, and the electrical appliances do not pose electric shock risks to human bodies. The general test pencil cannot identify the induced electromotive force lower than 100V by the lower voltage generated by the induction of the metal shell of the electrical appliance, so that the limitation on judging whether the electrical appliance metal shell leaks electricity is greatly realized.

the non-contact test pencil of the invention is suitable for detecting low voltage below 100V and 220V alternating current with higher voltage, and the function and function of the non-contact test pencil can replace the traditional test pencil for electricians.

the following describes the related technical matters related to the implementation of the non-contact test pencil of the present invention in detail.

Disclosure of Invention

the invention has the following advantages: the test probe of the traditional test pencil must directly contact the charged metal body, so that the test pencil can normally work only when forming a complete loop. The non-contact test pencil can normally work without directly contacting with a charged object, and the charged object can be metal or an object with static electricity or a non-metal object. The non-contact test pencil of the invention is suitable for detecting low voltage below 100V and 220V alternating current with higher voltage, and the function and function of the non-contact test pencil can replace the traditional test pencil for electricians.

The working principle of the circuit is as follows: when the circuit of the non-contact test pencil is connected with a 4.5V direct-current power supply, and a weak voltage signal of a detected object is induced by the inductance detection head L1, the weak voltage signal is transmitted to the base electrode of the NPN transistor VT1 through the coupling capacitor C1, and the coupling capacitor C1 is used for conducting alternating current, blocking direct current, conducting high frequency and blocking low frequency. The capacitor can filter out most of interference signals, otherwise, the sensitivity is too high, and the response can be made even close to the zero line. The weak voltage signal is amplified through the NPN type transistors VT 1-VT 3 in a compounding mode, a circuit of the circuit is completed through a distributed capacitor, after 3 NPN type transistors VT 1-VT 3 are rapidly conducted in sequence, a light emitting diode LED connected in a collector circuit of the NPN type transistor VT3 is lightened, and meanwhile, a buzzer HA is also electrified to emit buzzing sound. The electrolytic capacitor C2 is connected to relieve the dynamic power supply load of a 4.5V direct current power supply (battery pack).

The technical characteristics are as follows: the non-contact test pencil comprises a 4.5V direct-current power supply, a key switch AN, a micro-voltage detection and homopolar Darlington circuit and AN acousto-optic drive circuit, and is characterized in that:

little voltage detection and homopolar Darlington circuit: the device comprises an inductance detection head L1, a coupling capacitor C1 and 3 NPN transistors VT 1-VT 3, wherein one end of the inductance detection head L1 is connected with the base electrode of the NPN transistor VT1, the other end of the inductance detection head L1 is vacant, the emitter electrode of the NPN transistor VT1 is connected with the base electrode of the NPN transistor VT2, the emitter electrode of the NPN transistor VT2 is connected with the base electrode of the NPN transistor VT3, the collector electrode of the NPN transistor VT1 and the collector electrode of the NPN transistor VT2 are connected with a circuit anode VCC, the emitter electrode of the NPN transistor VT3 is connected with a ground GND, and the collector electrode of the NPN transistor VT3 is connected with an acousto-optic drive circuit;

The acousto-optic drive circuit: the LED driving circuit comprises a Light Emitting Diode (LED), a resistor R1 and a buzzer HA, wherein a collector of an NPN transistor VT3 is connected with a cathode of the LED and a cathode of the buzzer HA, an anode of the LED is connected with a circuit anode VCC through a resistor R1, and an anode of the buzzer HA is connected with the circuit anode VCC;

The anode of the 4.5V direct current power supply is connected with the anode VCC of the circuit through a key switch AN, the cathode of the 4.5V direct current power supply is connected with the circuit ground GND, the anode of the electrolytic capacitor C2 is connected with the anode VCC of the circuit, and the cathode of the electrolytic capacitor C2 is connected with the circuit ground GND.

drawings

Fig. 1 is a circuit schematic diagram of an embodiment of a non-contact test pencil according to the present invention.

Detailed Description

The present invention can be implemented according to the working schematic diagram and the illustration of the drawings of the non-contact test pencil circuit shown in fig. 1, the connection relationship between the components in each part of the circuit according to the invention, the technical parameter requirements of the components and the circuit manufacturing points in the implementation manner, and the related technology of the present invention will be further described with reference to the following embodiments.

Technical parameters of components and selection requirements thereof

VT1, VT2 and VT3 are NPN transistors, the model is 2SC9014 or 2SC945, the withstand voltage is required to be more than or equal to 60V, and the beta value is more than or equal to 160 when the withstand voltage is higher;

The LED is a light emitting diode, and a phi 5 ultrahigh bright red light emitting diode is selected;

HA is a buzzer, a micro buzzer of a 2Hz audio oscillation circuit is arranged in the HA, and the working voltage is 5V;

L1 is an inductance detector, and a finished I-shaped inductance coil with the inductance of 15 muH is selected;

r1 is a resistor with the resistance value of 220 omega;

C1 is a coupling capacitor, a common ceramic chip capacitor is selected, and the capacity of the common ceramic chip capacitor is 47-68 PF;

c2 is electrolytic capacitor with CD11-16V type capacity of 220-330 μ F;

AN is a key switch, and a normally open microswitch is selected;

The 4.5V direct current power supply can be obtained by connecting 3 7# batteries in series.

Circuit manufacturing key points and circuit debugging

Because the circuit structure of the non-contact test pencil is simpler and easier to manufacture, generally, only selected electronic components have good performance and are welded according to the connection relation of the components in the attached figure 1 of the specification, after physical connecting lines and welding quality are carefully checked to be correct, the circuit of the invention basically does not need to be debugged, and the circuit can normally work after being connected with a 4.5V direct-current power supply.

Inductance detection head L1: or an enameled wire with the diameter phi 1 and the length of about 18cm is wound on a metal rod with the diameter phi 5 for 8-10 circles, then the blank is removed to form a spiral shape, and any end is subjected to paint removal and then welded to the base electrode of the NPN transistor VT 1;

because the non-contact test pencil has few circuit elements, all the elements can be correctly welded according to the attached drawing without using a circuit board, and then are arranged in the plastic tube and fixed;

The capacitance value and the inductance value of the inductance detection head L1 depend on the actual test effect, and the capacity of the common capacitor C1 is dozens of PF; the circuit wiring also has certain influence, and the interference is smaller as the distances among the inductance detection head L1, the coupling capacitor C1 and the NPN transistor VT1 are closer;

The test pencil is tested: the test pencil can emit sound and light when the distance between the inductance detection head L1 and the conductor with the insulating layer is about 1.0cm away from 220V alternating current.

the circuit structure design, the component layout, the structural characteristics, the appearance shape, the size and the like of the circuit are not the key technology of the invention and are not the key technical content required to be protected, and the specific implementation process and the realization of the invention aim are not influenced, so the circuit structure design, the component layout, the structural characteristics, the appearance shape, the size and the like are not described in the specification one by one.

Claims

1. The utility model provides a non-contact test pencil, it includes 4.5V DC power supply and key switch AN, little voltage detection and homopolar Darlington circuit, reputation drive circuit, its characterized in that:

the micro-voltage detection and homopolar Darlington circuit consists of an inductance detection head L1, a coupling capacitor C1 and 3 NPN transistors VT 1-VT 3, wherein one end of the inductance detection head L1 is connected with the base electrode of the NPN transistor VT1, the other end of the inductance detection head L1 is vacant, the emitter electrode of the NPN transistor VT1 is connected with the base electrode of the NPN transistor VT2, the emitter electrode of the NPN transistor VT2 is connected with the base electrode of the NPN transistor VT3, the collector electrode of the NPN transistor VT1 and the collector electrode of the NPN transistor VT2 are connected with a positive electrode VCC NPN, the emitter electrode of the NPN transistor VT3 is connected with a circuit ground GND, and the collector electrode of the NPN transistor VT3 is connected with an acousto-;

the acousto-optic drive circuit consists of a Light Emitting Diode (LED), a resistor R1 and a buzzer HA, wherein a collector of an NPN transistor VT3 is connected with a cathode of the LED and a cathode of the buzzer HA, an anode of the LED is connected with a circuit anode VCC through a resistor R1, and an anode of the buzzer HA is connected with the circuit anode VCC;

the anode of the 4.5V direct current power supply is connected with the anode VCC of the circuit through a key switch AN, the cathode of the 4.5V direct current power supply is connected with the circuit ground GND, the anode of AN electrolytic capacitor C2 is connected with the anode VCC of the circuit, and the cathode of AN electrolytic capacitor C2 is connected with the circuit ground GND.