A cleverly designed flashing circuit

My throat has been sore for several days, and no medicine has helped. I finally found a reason for myself to take a vacation and decided to sleep well all day. I took some medicine and slept until 12 noon. I got up, ate something, and slept until half past five in the afternoon. I got up in the afternoon and felt much better. It seems that for me, sleep is the best medicine. No matter how big or small the illness is, as long as I sleep for a day, I can be cured. After dinner at 7 o'clock, I started to feel sleepy, and there was nothing good to watch on TV, so I was ready to go back to sleep. When a person lies down, his mind can't be idle. Keep thinking about various problems. Oh, I'm so busy that I can't take any time off... It suddenly occurred to me that I should design a flashing rear light for my bicycle, so that it would be safer on the road at night. I have seen some similar products before, but the price is on the high side and the battery life is not long. If a flash circuit can be added to an ordinary car rear reflector, the cost should be very low. I didn't want to sleep immediately, so I found a wrench and removed the reflector from the rear of the car. Use a knife to open the outer casing (it's very laborious). When you see it, it's empty inside. It's very good and can hold a circuit board. Looking at the back, there is a small groove that can hold the battery and a small switch. All that's left is the circuit. I want to make it consume less power than the products on the market. The method of reducing power consumption is to reduce the power consumption of the circuit itself on the one hand, and to reduce the power consumption of the light-emitting device on the other hand. Reducing power consumption will inevitably reduce the brightness. In order not to affect the lighting effect, the luminescent tube should be allowed to glow instantly. In this way, although it is very bright momentarily, the average power consumption is still very low. There are many circuits with low duty cycle, but their power consumption is still relatively large, and there is no one that I am very satisfied with. I thought of using a 430 microcontroller to do it. The power consumption is really low. It is a waste of time to kill a chicken with a knife. The cost is too high and it is meaningless. Using CMOS discrete devices to build a circuit has low cost and low power consumption. However, the circuit is relatively complex and large in size, so I am worried that it will not fit in it (actually I am lazy and I am too lazy to solder too many parts). Suddenly it occurred to me that I could use a charge pump. Let the capacitor charge most of the time, then let the capacitor switch to the river LED connection and discharge it momentarily. I found information on the 7660 and found that the oscillation frequency can be reduced to 1Hz through an external capacitor, which is good. Although the duty cycle in the working state is 1:1, once the capacitor is discharged, the light will naturally go out. In this way, the car lights will flash for an instant every second, which is very eye-catching and saves power. The circuit is very simple, excluding the light-emitting tube, there are only 3 components! The circuit is shown in Figure 1. An external 104 capacitor (C2) is connected to pin 7 of 7660, which can reduce the oscillation frequency to about 1Hz. The internal principle of 7660 is shown in Figure 2. In fact, CLK controls 4 switches. When CLK is 1, C1 is connected to the power supply in parallel for charging (Figure 3A). The LED is also connected in parallel to the power supply, but since the two LEDs are connected in series, the conduction voltage is 2X1.7=3.4V, which is not possible at this time. It will light up; when CLK is 0, C1 is connected in series with the power supply. Since there is already a voltage of 3V at both ends of C1, after being connected in series with the power supply, it becomes 6V and is added to both ends of the LED (Figure 3B). LED glows. The light of the LED will quickly consume the charge of C1, and the LED light will turn off. The final effect is that the LED flashes every 1 second. Here, the internal resistance of the analog switch inside the 7660 serves as the current-limiting resistor for all charge and discharge circuits, including LED lights. No additional current-limiting resistor is needed. The function of C3 is to prevent the internal resistance of the power supply from limiting the LED current after the internal resistance of the battery increases. Because the circuit is simple, no PCB is used. The components are glued inside the car light and directly welded on the component legs. It was installed in two hours. The test results are very good. The power consumption is less than 1mA, and even if the battery power is insufficient and the internal resistance increases, as long as the capacitor termination charging voltage remains unchanged, the brightness will basically remain unchanged. That is, the flash brightness has basically nothing to do with the internal resistance of the battery, which improves the battery life. Haha, I got some inspiration from my sleep today, so my sleep was not in vain. Let’s keep trying another day and keep sleeping!