Intelligent control neon circuit

The neon lamp is a low-pressure, cold-cathode glow discharge type lamp. Its working voltage is usually 12~15kV, and the 450V transformer is used to boost the voltage. In order to enhance the display effect, large neon signs usually use special dimming control circuits. Realize the dynamic display of the pattern. The smart neon controller diagram shown in the figure. It is controlled by single-chip microcomputer and is controlled by thyristor. It is suitable for all kinds of neon signs in large, medium and small. It can also modify the software to control any pattern with varying degrees of complexity according to user requirements. It is a better performance neon control circuit.
Circuit principle: The control circuit expands the input/output (I/0) port through the serial communication mode 0 of the 8031 ​​MCU, and the number of I/O is not limited. The first power driver board is formed by using three 4094 shift registers in series to obtain 24 I/O ports. If the number of I/O ports is insufficient, the second block, the third block, and the like can be constructed and connected in series.
The Rxd, Txd, and P1.7 of the 8031 ​​MCU realize level conversion through the 74LS06 open-collector OC gate and are connected to subsequent CMOS devices. The zero-crossing trigger signals a, b, and c generated by the zero-crossing signal generating circuits of the three-phase alternating current of A, B, and C are connected to the STR pins of three pieces of 4094 on each power driving board (a1, b1, c1) ), so that the load is triggered at the zero crossing of the AC voltage of each phase. The power drive unit circuit uses optical isolation to eliminate external interference and improve system reliability. The optocoupler output first drives the thyristor SCR1, and then the SCR1 drives the SCR2. The illuminating LED in the circuit is used for analog display during programming and debugging; the RC snubber circuit composed of the resistor-capacitor is used to absorb the neon light when the transformer is an inductive load. A large reverse surge current is generated to ensure smooth power drive.
The controller circuit is easy to expand, does not change the hardware circuit, and only needs to modify the data table arranged in the program memory and sent to the peripheral port 4094 for the user's request, and is generally easy to implement.