introduction
In electronic technologies, the triode is a measurement scheme using extremely general components, the parameters of the tertiary tube and many electrical parameters, and the measurement results have a very close relationship. Therefore, in electronic design, the tip of the triode, Type judgment and measurement are very important. There are a variety of methods for measuring the triode pin, in which the laboratory is commonly used by the characteristics of the multimeter and the triodes, but due to the voltage between the three pins of the triode, the current relationship is complex, and the triode itself is small, give The measurement brings very inconvenient, and the current market has not yet been discriminated with the triode pin, the type of type. Therefore, it is especially important to design a circuit that automatically discriminates the triode pin.
1 Hardware circuit composition principle
According to the type and pin arrangement of the currently used triode, the automatic discrimination circuit is designed contains four parts of the center control unit, the conversion circuit, detects the amplifying circuit, and the display circuit, as shown in FIG. 1, wherein the AT89C2051 is used as the center control unit.
2 hardware circuit design
Figure 2 shows the score of the triode pin type automatically discriminating the hardware circuit, which mainly includes a single chip AT89C2051, an inverter CD4069, photocoupler 4N25, 74LS06, 74LS07, several resistors, and capacitance and other components.
Figure 2 Discount circuit schematic
First, three binary codes (high and different levels) are sent from the P3.0 to P3.2 port of the single chip, and the 1, 2, 3, respectively, to the triode. For different triodes, when different codes are sent out in a single chip, the current direction on the 1, 2, 3 pins is different, and there are two cases of inflow and flow, and the two photocouplers are reversed in the direction in which direction There is current through, and the three binary code codes becomes six-bit binary code. The detected electrical signal of the photocoupler is enlarged. Since the signal output is not standard at this time, it cannot be directly recognized by the microcontroller, and the phase does not meet the requirements, so the first stage inverter CD4069 is inverse Then, then send the standard six binary code output from the inverter to the P1.0 ~ P1.5 port of the single chip. The single chip microcomputer compares the data pre-written in advance from the P1 port, and outputs the detection result from the P3.3 to P3.7 port when the corresponding condition is satisfied, and finally use the light-emitting diode to display the corresponding triode type.
3 software design
Due to the sequential order of the NPN in the common small and medium-sized power triode, three of the EBC, ECB, BCE (with a few exceptions, negligible), and only EBC of PNP is arranged. Therefore, the software is written in accordance with this law. Overall programming idea is to add different voltages on three pins of the three-pole arrangement of different pins, test their current and convert it into binary code. These binary code is written to the single chip microcomputer, and the external input data is compared to the binary code inside the single chip, if the read data is equal to some data written in advance, the measured triode is the triode corresponding to this data. The tubular and pins are then indicated by the corresponding light-emitting diode point to indicate the tube type and pin.
The software main program flow chart is shown in Figure 3.
Be
The corresponding program is:
ORG 0000H
Ajmp main
ORG 0030H
Main: Mov A, # 00H
EBC: MOV P3, # 0f8h
MOV P3, # 0f9h
ACALL DEL1
MOV P1, # 0ffh
MOV A, P1
CJNE A, # 0e9h, BEC
S1: MOV P3, # 0f4h
AJMP S1
BEC: MOV A, # 00H
MOV P3, # 0f8h
MOV P3, # 0f9h
ACALL DEL1
MOV P1, # 0ffh
MOV A, P1
Cjne a, # 0e1h, ECB
S2: MOV P3, # 0ech
AJMP S2
ECB: MOV A, # 00H
MOV P3, # 0f8h
MOV P3, # 0fdh
ACALL DEL1
MOV P1, # 0ffh
MOV A, P1
CJNE A, # 0D9H, EBC1
S3: MOV P3, # 0ddh
AJMP S3
EBC1: MOV A, # 00H
MOV P3, # 0f8h
Mov p3, # 0feh
ACALL DEL1
MOV P1, # 0ffh
MOV A, P1
CJNE A, # 0D6H, E
S4: MOV P3, # 7bh
AJMP S4
E: MOV P3, # 00H
ACALL DEL1
MOV P3, # 0f8h
ACALL DEL1
AJMP E
DEL1: MOV R5, # 01h
D1: MOV R6, # 0ffh
D2: MOV R7, # 0ffh
D3: DJNZ R7, D3
Djnz R6, D2
Djnz R5, D1
RET
End
Figure 4 shows the PCB board diagram of the production, after the physical production is successful, take a triode, insert the tube foot into the test hole of the product in order 1, 2, and 3 to ensure good contact, then press the power button, the system is automatically After the reset is run, the tube and pin corresponding to the measured triode are indicated by the LED. The order of the LED lamp is corresponding to the pin tube type. If the first LED light on the left is bright, the measured triode is the NPN type, the pin is arranged in BEC; if the left side of the LED light is on the left, the measured triode is PNP. The sequence of the pin is EBC; if the third LED light is on the left, the measured triode is an NPN type, and the pin is arranged in ECB; if the fourth LED light on the left is bright, the measured triode is NPN type, the pin is arranged sequence For EBC; if four LED lights flicker simultaneously, it may be that the triode has been bad or the pin contact is poor, and the program is not written in the single-chip microcomputer.
During the production of the actual product, the corresponding pin and type can be indicated from the left to right side, or different pins and tubes can be displayed in different colors of LED lights.
4 Conclusion
According to the hardware circuit and software design, the circuit welding and debugging is designed. The resulting discriminator can quickly and accurately determine the pin and type of the small power triode, and display the result of the judgment by the corresponding indication circuit, which is more convenient than the multimeter measuring. a lot of.
This design is strongly scalable due to the use of a single chip microcomputer as a central control unit. For example, a circuit that measures the measurement of the triode β value can be increased on the basis of this work, and the β value can be displayed using the digital tube. In addition, this design can now only measure common medium and small three-pole, and if the drive circuit, the current limit circuit, the modification of the partial source can also measure the high power triode.
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