If you mean the brightness of an 8-segment LED digital tube with more than two bits, and all the pins of the LED digital tube are controlled by the digital IO port, then you can replace it with a * * * negative digital tube (it is estimated that you are using a * * * positive one now), so that you can improve some brightness without changing the circuit. In addition, check the program to ensure that 1 digital tube can be displayed at any time, especially not to let other ms-level delay programs occupy the display time of each digital tube. Interrupts should be used in the software, and the display should be sent regularly.
In other cases, the circuit needs to be modified. There are four main methods to improve the brightness of LED digital tube, the first two are aimed at dynamic scanning mode, and the last two are static display mode.
1, adopts * * * negative LED digital tube, and the male * * * terminal is directly connected to P0 port. Because the general digital IO port absorbs current when it outputs 0, its capacity can reach about 20mA (P0 port is stronger than other ports 1 times, which can reach more than 30 mA), but when it outputs 1, it can only provide the load with about 4mA of current. The recommended working current of LED is generally around 15mA, and the current determines the brightness of LED. In this way, the maximum input current of LED digital tube in * * * Yang mode is divided into eight LED segments, which are almost few, such as 1, 7, which may be ok, but I'm afraid 8, 9 and 0 are not visible. On the contrary, using cathode digital tube and directly controlling the male terminal with P0 port can increase the total current through LED, thus achieving the purpose of moderately improving brightness. However, the method of controlling digital tube directly with digital IO is mainly used in teaching, and generally has no practical value.
2. Drive the port of LED with triode. This is the most common method in practical application. There is only one purpose, to increase current and brightness. The original control terminal only needs to control the on-off of the triode. It can also be realized by chips such as ULN2003 Darlington array.
3. The static scanning mode is adopted, that is, the IO port is expanded by chips such as 74LS 164, and then the expanded IO port is connected to the eight segments of each digital tube, so that each digital tube can always be on, and the brightness can be greatly improved under the condition that the current is not too large. Only in this way, a digital tube with separated segment signals is needed, and a digital tube with two or more signal lines cannot be used.
4. Use high brightness digital tube. This method also needs to increase the driving circuit, which will be greatly improved in the static scanning display mode; Not necessarily in dynamic mode, and controlling 10 digital tubes at a time may not improve.