【Digital Circuit】Network Cable Detector Design

1 Project Introduction
  This is a simple network cable detector based on NE555 and CD4017. It can intuitively and accurately determine whether the crystal plugs at both ends of the network cable are unobstructed and whether the network cable is intact and usable. This circuit is simple, convenient and practical.
2 Overall Scheme
  The overall scheme system block diagram of the simple network cable detector is shown in Figure 2-1. The power supply supplies power to the multivibrator circuit, which in turn drives the LED that displays the network cable detection to achieve the function of detecting the network cable. 
Figure 2-1 System Block Diagram of Simple Network Cable Detector
3 Circuit Principle
  The design of the simple network cable detector is mainly composed of a power input circuit, a multivibrator drive circuit composed of a NE555 timer and a CD4017 count divider, an RJ45 network port and an LED detection display circuit.
3.1 Power Input Circuit
  The power supply part uses a 2Pin direct plug Type C female socket as the power input port, SW1 is a toggle switch, and C1 is a power filter capacitor.
Figure 3-1 Power input circuit
3.2 Multivibrator drive circuit The
       NE555 time base circuit forms a multivibrator circuit. The power supply VCC charges the capacitor C2 through the resistors R1, R2 and the potentiometer RP1. When the capacitor C2 is charged to a certain level, the voltage of the 2nd and 6th pins of the NE555 timer increases. When the voltage of the 2nd and 6th pins increases to 2/3VCC, the output of the 3rd pin is low level, and the 7th pin is in a low impedance state. The capacitor C1 discharges to the ground through the potentiometer RP1 and the resistor R2 to the internal 7th pin of the timer. When the discharge voltage of the 2nd and 6th pins is lower than 1/3VCC, the output of the 3rd pin is high level, and the 7th pin is in a high impedance state. Reciprocating charge and discharge.
  By adjusting the resistance value of the potentiometer RP1, the pulse frequency and duty cycle generated by the NE555 can be changed. The oscillation pulse output from the 3rd pin is used as the clock pulse for the CD4017 counter divider to work. When the CD4017 counter is working, the output terminal outputs high level in sequence, and continuously cycles, thereby changing the LED water flashing rate of the subsequent network cable detection display circuit.
Figure 3-2 NE555+CD4017 multivibrator drive circuit
3.3 Network cable detection display circuit The
  detection display circuit consists of 2 RJ45 network ports and 16 LEDs. The anodes of the 8 LEDs connected to the network port RJ1 are connected to the CD4017 output of the multivibrator drive circuit, and the cathodes of the 8 LEDs connected to the network port RJ2 are connected to the ground. When the two ends of the network cable are inserted into the RJ45 network port, the CD4017 output to ground circuit is turned on, and the LEDs display the running light effect accordingly, thereby achieving the effect of detecting whether the network cable is connected intact.
Figure 3-3 RJ45+LED network cable detection display circuit
4 Schematic design
4.1 Create a new project
  Open Jiali Chuang EDA, create a project and name it [Digital Circuit] Network Cable Detector Design, and name the schematic file: SCH_Network Cable Detector. Draw the circuit schematic according to the following circuit.
Figure 4-1 SCH_Network Cable Detector Design
4.2 Device Selection
  In the component selection of this project, all components can be directly searched in the component library of Jiali Chuang EDA. If you are not familiar with the components, you can also search by copying the product number in the material (each component has a unique product number in Li Chuang Mall). Figure 4-2 Schematic diagram of component
searchFigure
 
4-3 Schematic diagram of searching by product number4.3
Bill of MaterialsSimple


network cable detectorItem Bill of MaterialsNo. NameParameter Device Position


NumberQuantityPackageProduct Number1Resistor 2.2kΩ R1 1 RES - TH_BD2.2-L6.5-P10.50-D0.6 C61295 10kΩ R2 1 RES-TH_BD2.5-L6.5-P10.50-D0.6 C57436 2Potentiometer 200kΩ RP1 1 RES-ADJ-TH_3362P C111655 3Capacitor 1uF C1 , C2 2 CAP - TH_BD4.0 - P1.50 - D0.8 - FD C1222408 4LED D =3mm LED0~LED15 16 LED -TH_BD3.0-P2.54-FD C99761 5 Slide switch SK12D07VG3 SW1 1 SW-TH_SK12D07VG3 C431547 6 Timer NE555 U1 1 DIP-8_L9.8-W6.6-P2.54-LS7.6-BL C398063 7 Counter CD4017 U2 1 DIP-16_L20.2-W6.6-P2.54-LS7.6-BL C34519 8 IC socket 2.54*8 U1 1 DIP-8 C146580 2.54*16 U2 1 DIP-16 C398063 9 Ethernet port RJ45 RJ1、RJ2 2 RJ45-TH_RC0113 C708616 10




















 



 































































































































































 



 

























































USB


TYPE-C


USB1


1


USB-SMD_KH-TYPE-C-2P


C2919656


11


Copper pillars


M3x10+6


H1~H4


4


TH_BD4.7-D3.0


C551322

 

5 PCB design
  After completing the schematic design and checking the circuit and network connection correctly through DRC, click "Design" → "Schematic to PCB" in the top menu bar (the shortcut key is Alt+I), save the PCB file to the same project and name it: PCB_Simple Network Cable Detector.
5.1 Frame design
  Before drawing the PCB, the shape and frame size of the PCB should be determined according to personal wishes and the space occupied by the number of components. If there is no special shell requirement, it is generally designed as a rectangle, circle and square. When designing this project, the principle of appropriate size and beautiful appearance should be adhered to.
  The rectangular frame we placed under the top tool menu bar is 70mm wide, 55mm high, and the fillet radius is 10%. The actual board frame size will be adjusted during layout and wiring. If it is too small, it can be appropriately enlarged. If it is too large, the frame can be reduced accordingly. Try to control it within 10cm*10cm, so that you can go to Jiali Chuang for free proofing~
5.2 PCB layout
  During the layout process, it is necessary to pay attention to the placement of interfaces close to the board edge. The TYPE C interface is placed on the right side of the board, the RJ45 network port is placed on the left side of the board, the toggle switch is placed below the TYPE C, the LED and the RJ45 network port are horizontally centered, and the two groups of LEDs are arranged at equal intervals. The potentiometer is placed on the left side of the TYPE C, and other devices are placed below the PCB. The layout reference is shown in Figure 5-1.
Figure 5-1 PCB layout reference Figure
5.3 PCB routing
      PCB routing, the full name is printed circuit board wiring (PCB LAYOUT). Since the circuit board has two surfaces, the top surface and the bottom surface, the PCB routing can also be divided into the top layer and the bottom layer routing. The top layer routing is the default red line and the bottom layer is the blue line. You can also set other colors according to your personal preferences. The routing is to connect the wires in the circuit board according to the flying line to connect the same network.
  First, select the layer that needs to be routed (switching top/bottom layer shortcut key: T/W), and then click the single-path routing in the top toolbar to connect (the shortcut key is W). Although it seems simple to connect the dots, we need to make adjustments patiently. The placement and layout of components will also affect the difficulty of routing, so we need to further adjust the layout and optimize it during the routing process. The PCB layout introduced above is equivalent to paving the way for routing. Once the layout is good, the routing will be smooth. The following reference suggestions are provided for the routing of this project:
(1) The power line is set to 25mil and the signal line is set to 10mil width
(2) The routing is mainly based on the top layer. If it is not possible, you can switch to the bottom layer for connection
(3) Straight lines are preferred during the routing process. Obtuse angles or arcs are mainly used for turning places
(4) Finally, teardrops are added and silk screen markings are added. The size of the PCB board and the interface function wiring
reference are shown in Figure 5-2. For the initial design, you can refer to the figure below for routing.
Figure 5-2 PCB routing reference Figure
5.4 Copper coating and silk screen
      After the PCB routing is drawn, copper coating is performed, and the GND network can be connected. Silk screen characters follow the principle of from left to right and from top to bottom. Mark the project name and logo.
Figure 5-3 PCB top layer copper coating and silk screen reference
6 Circuit debugging
6.1 Device welding
  First weld the Type-C connector/toggle switch; then weld the resistor/capacitor/LED; then weld the IC socket, never weld the IC directly; finally weld the RJ45 network port and install the M3 copper column.
Figure 6-1 Unsoldered PCB board
  Pay attention to electrical safety during welding. Do not touch the soldering iron tip with your hands to avoid burns. Align the components during welding and check whether the model is correct. During the welding process, pay attention to whether the tin wire is cold soldered or leaked to avoid affecting the circuit performance and causing the circuit to not work properly.
Figure 6-2 PCBA physical picture
Figure 6-3 3D rendering Figure
6.2 Hardware debugging
  After welding is completed, you need to use a multimeter to check whether the power supply and ground are short-circuited, and whether there is a short circuit or open circuit during the welding process. Only after the inspection is correct can the power-on test be carried out. After
      TYPE-C is connected, turn on the toggle switch, the board starts working, and after the crystal heads at both ends of the network cable are connected to the network port, the LED lights up accordingly. Adjusting the resistance value of the potentiometer RP1 can change the LED flashing rate. Then achieve the effect of detecting the on and off of the network cable.
Figure 6-4 Simple network cable detector working diagram