Solar Flash Light

Solar Flash Light

This is a 1ED flashlight (see attached picture). It does not flash during the day, but uses solar cells to charge the battery. At night, the battery is powered to emit flashes. It is suitable for use as a warning light at temporary construction sites and other places. Flash circuit: The RC oscillator is composed of the NAND gate of IC1.

If R2 and D2 are not included, the duty cycle of this oscillator is 50%, and more power will be consumed when the 1ED flashes. After adding R2 and D2, the duty cycle can be adjusted by changing the resistance value of R2. When R2 is 68kΩ, the duty cycle is about 5%, and when R2 is 33kΩ, the duty cycle is about 2.5%.

1ED driving circuit: The oscillation signal is output from the ⑧ pin of IC1 to the (12) pin, and the signal of the over-discharge detection circuit is output from the ① pin of IC3 to the (13) pin of 1C1: When the battery is not in the over-discharge state, the (13) pin of IC1 is high level, and the ③ pin of IC2 will output the same oscillation signal as the ⑧ pin of IC1. During the high level period of the signal, drive T1 to conduct and make 1ED light up. If the battery is in the over-discharge state, the (13) pin of IC1 is low level, then the (11) pin is high level, and the ③ pin of IC2 will be low level, so that T1 is cut off and 1ED does not light up.

Over-discharge prevention circuit: The over-discharge detection uses the reset dedicated integrated circuit S-80819. When the voltage between its pin ② (input terminal) and the ground is lower than 1.9V, its output terminal ① is low level. That is, the (13) pin of IC1 is low level. 1ED cannot light up. When the voltage between pins ② and ③ of IC3 exceeds 2.0V (there is a 0.1V hysteresis inside 1C3). The over-discharge state is released, and its output terminal ① is in an open circuit state. It is high level due to the existence of the pull-up resistor R4.

Day and night discrimination circuit: Use the output voltage of the solar cell to judge. During the day, the voltage of the solar cell is higher than the threshold of IC1, IC1 pin ③ is low, the oscillator stops, 1ED does not flash, and R5 connected in parallel with the solar cell is used to adjust the sensitivity of day and night discrimination and prevent abnormal oscillation.

The solar cell is made of polycrystalline silicon material, with a maximum output voltage of 4.7V and a maximum output current of 95mA; the battery is 4W2.5Ah; DI is a charging anti-backflow diode; 1ED is eight high-brightness light-emitting diodes in parallel; IC1 and IC2 use 2-input four-NAND Schmitt trigger 74HC132, and the unused NAND gate should have its two input terminals short-circuited and connected to the power supply "+" terminal.