LED display control circuit diagram in the counter

As shown in the figure, the decimal seven-segment storage-decoding-drive unit 74143 is used in figure a. This unit has constant current output for all segments. When the voltage is 5V, the current of each segment is about 15~22mA. The BCD data of the seven-segment decoder can be taken out from pins 17 to 20. Pin 22 is used for carry, that is, when the count value reaches 9, it is low level, and the rest is high level. This signal can be used to control the previous counter .

Figure b is used to control a 1-digit or 1 and 1/2-digit seven-segment LED display circuit. SAB3211 is used for 4-bit binary counting. A binary counter (FZJ151) or a decimal counter (FZJ141) can be connected as needed . The power supply voltage is 9~16V.