Ultra-low power consumption LCD liquid crystal display circuit module design - dimming circuit diagram

　　LCD display module: LCD liquid crystal display is an extremely low-power display device. It has small operating current, light weight, low power consumption, long life, and clear and beautiful writing. It is widely used in portable instruments and higher-end instruments for low-power applications. is widely used in. Pin 1: VSS is the ground power supply; Pin 2: VDD is connected to the 5V positive power supply; Pin 3: VL is the contrast adjustment terminal of the LCD. When connected to the positive power supply, the contrast is the weakest, and when connected to the ground, the contrast is the highest. When the contrast is too high, it will "Ghosting", you can adjust the contrast through a 10K potentiometer when using it; Pin 4: RS is register selection, when it is high, it selects the data register, when it is low, it selects the instruction register; Pin 5: R/W is for reading and writing Signal line, read operation is performed when the level is high, and write operation is performed when the level is low. When RS and R/W are low level at the same time, instructions or display addresses can be written. When RS is low level, R/W is high level, Read busy signal, when RS is high level and R/W is low level, data can be written; Pin 6: E terminal is the enable terminal, when the E terminal jumps from high level to low level, the liquid crystal module executes Command; Pins 7-14: D0-D7 are 8-bit bidirectional data lines; Pin 15: Positive pole of backlight source; Pin 16: Negative pole of backlight source.

　　Display circuit principle analysis: The circuit design is shown in the figure. In the figure, DB0~DB7 of LCD1602 are connected to the P00~P07 ports of the microcontroller AT89C52, which are used to display the user's power consumption information; P25, P26, and P27 respectively control the register selection input terminal RS and the read-write control input terminal R/W of the LCD1602. , enable signal input terminal E; control the contrast of the liquid crystal display by adjusting the resistance value of R58.

　　IC card interface: The circuit uses Atmel's storage IC card AT24C01, which is used to store passwords, card numbers, electricity degrees, etc. written by the electricity sales management system. It is a bridge connecting the power management department and users. In order to improve the reliability of IC card operation, there must be auxiliary circuits such as card upper and lower electronic control circuits, card insertion detection circuits, and card short-circuit detection circuits. Combined with software, the accuracy and reliability of reading and writing can be greatly improved. The IC card interface circuit design is shown in the figure:

　　In the figure, R12, D5, and Q6 form the card power-on and power-off circuit. When P16 of AT89C52=0, Q6 is turned on, and the VCC of the IC card holder is powered; when P16 of AT89C52=1, Q6 is turned off, and the VCC of the IC card holder is powered off. The VCC of the IC card is also sent to P15 of the CPU via D6 to detect whether there is a short circuit in the card power supply to prevent artificial damage. K1 and K2 are a pair of normally closed contacts of the IC card holder. When a card is inserted, K1 and K2 open circuit and Q2 conducts, sending a low level to the P12 port of AT89C52. This signal is used to detect whether a card is inserted. .