Author: Duan Xi Xiang Star
Contact market Electronic Communication Tooling Appliance (commonly known as "electric pen") Everyone has used, its use principle requires the form of the pen must contact the line (ie, the fire line), but in some case it seems unable to force, such as looking up the electric blanket, The trace hidden in the wall is open. Here is an inductive communication testizer, which does not have to contact the fire line directly, it can detect the presence of alternating current, easy to use. Here, the filament of the electric blanket is an example of its production process and use skills.
Circuit work principle
as the picture shows. Composite triodes composed of transistors VT1, VT2, which are directly coupled to a direct coupling pole and randing dog circuit. The base of the base of VT1 M, the load M, VT3 is loaded as a light emitting diode Vd and its current current resistance R.
When the metal check sheet M is adjacent to the heat transfer wire on the side of the electric fire line on the side of the electric fire line due to the disconnection of the electric fire line, the very weak 50 Hz AC signal is sensed. After amplifying VT1 to VT3, the driving light-emitting diode VD is driven. However, when the metal check sheet M is adjacent to the heat wire only on one side of the line, the VT1 to VT3 is closed, and the VD does not illuminate. Thus, according to the brightness of the VD, the overalls of the electric heating wire in the electric blanket can be found.
Selection of components
Transistors VTL ~ Vt3 are selected from 9014 or 3DG8 silicon NPN small power triode, and the current amplification of β>50. VD uses BT-20L ordinary red light emitting diode.
R uses RTX-1/8 W-type carbon film resistors, and its main role is to limit excessive current through the light emitting diode VD. Due to the particularity of the circuit, it can also be saved in practical applications.
The metal check sheet M is a copper sheet or iron sheet of φ15 mm. The power source G is used in series with two button bucklers, and the buckle oxide battery SR44 (φ11.6 mm × 5.4 mm) or Ag13, G13-A, and voltage 3 V are selected. Due to the normal power consumption of the whole machine (measured. 1881.1 μ a), there is no need to set up a power switch.
Skill
As shown in the right, the printed circuit board wiring diagram of the electric blanket breaking detector is shown. The actual size of the printed circuit board is only 55mm × 20mm, which can be made by a blade. The specific method is: First, cut the size of a single-sided copper plate, in addition to the foil line, use a knife to draw the copper foil without the need, peeled off; then, use the electric drill to punch the hole on the circuit board, pay attention A square hole of 12 mm × 12 mm is also available at the position of the battery G to make the battery holder; finally, rub the copper foil surface with the wet cloth to rub the copper foil surface, apply a layer of rosin alcohol solution, dry It can be used.
Be
At the time of welding, the metal check sheet M is directly perpendicular to the circuit board according to the left side of the left, and the two pieces of 7 mm × 7 mm copper skin, bent into the "L" shape, according to the figure 3 The right side is shown on the right. Welding the copper-copper foil of the square hole in the circuit board, i.e., the battery clamp g is fastened, and the electrode sheet is connected to the battery set as a circuit board.
After the circuit welding is good, it is fitted within a plastic empty pharmaceutical cylinder having a size of about φ22 mm × 65 mm. The author uses the "watermelon frost" empty plastic cartridge, which has an outer dimension of φ22 mm × 85mm, and a barrel of the tubular end 20 mm length is just satisfied. The opening of the tip of the VD is exposed at the appropriate position of the cylinder to facilitate observation. When the cartridge is used to remove the circuit board from the cartridge when replacing the battery g.
Instructions
The internal fixed metal check sheet M is close to the electric blanket of the energized electric blanket and moves the electric blanket inside the electric blanket to the moving detector. When the light-emitting diode VD is defined by the bright, it means that the detector just passes through the wire of the electric blanket.
This inductive alternator is convenient than using a normal contact test pen in some cases. The specific method of operation is similar to that of the detection of the electric blanket. Because of its small size, use flexible and convenient, is indeed a very useful tool for electronic enthusiasts.
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