Description
Working principle
From the schematic diagram, it shows the 18 LEDs are divided into 3 groups. Whenever the power is turned on, the 3 transistors will be turned on first, but due to the differences in the components, only one transistor will be turned on first. It is assumed when Q1 is turned on first, the group of LED1 lights up. Since Q1 is turned on, the collector voltage drops and the left end of capacitor C2 drops, which is close to 0V. Since the voltage across the capacitor cannot change suddenly, the base of Q2 is also pulled to approximately at 0V, Q2 is off, so the LED2 group connected to its collector goes out. At this time, the high voltage of Q2 increases the collector voltage of Q3 through capacitor C3, Q3 will also be turned on quickly, and the group of LED3 will light up. Therefore, during this period of time, the collectors of Q1 and Q3 are both low, the two groups of LED1 and LED3 are lit, and the group of LED2 is turned off. However, as the power supply charges C2 through the resistor R2, the base of Q2 is The electrode voltage gradually increases. When it exceeds 0.7V, Q2 changes from the off state to the on state, the collector voltage drops, and the LED2 group lights up. At the same time, the voltage dropped by the collector of Q2 reduces the base voltage of Q3 through the capacitor C3. Q3 changes from on to off. The collector voltage rises and the LED3 group goes out. Next, the circuit circulates according to the process described above, and 18 LEDs in 3 groups will be lighted in turn. At the same time, 12 LEDs in 2 groups will be lighted. These LEDs are arranged crosswise to form a heart-shaped pattern, which flashes and glows in a continuous cycle to achieve the effect of dynamic display.
