IS Icstation DIY NE555 Red LED Flash Light SMD Soldering Practice Kit

This is a simple sequential lamp kit based on the NE555 and CD4017 chip designed for soldering skill training. It includes basic electronics components such as SMD resistor, ICs, potentiometer, capacitor, LED diode and with a clearly marked PCB board for ease of assembly. When finished, the assembly will turn into sequential LED flashing lamps ideal for the electronic beginner or school basic electronics experiment project. Working Principle: At startup, the power supply charges capacitor C1 thru series resistors R2, R3, R4, the NE555 Timer pin 2 is in low level status and pin 3 is in high level status. When the C1 voltage is equal to 2/3 of the power supply voltage, the NE555 pin 3 will switch to low level status, and the NE555 pin 7 internal discharge circuit will connect to ground. Capacitor C1 then discharges through the R4, R3 resistors and NE555 pin 7 until the C1 voltage drops to less than 1/3 of the power supply voltage. Then the NE555 pin 7 will disconnect from ground, pin 3 will return to high level status, and the C1 will be charged again to 2/3 of the power supply voltage. This process repeats. The charging time is 0.695(R2+R3+R4)C1 and the discharging time is 0.695(R4+R3)C1. Changing the value of potentiometer the R4 controls the output frequency. The NE555 signal at pin 3 is output to the CD4017 Decade Counter pin 14 clock input, and there are LEDs connected to the CD4017 10 outputs. When the CD4017 outputs each go to a high level, the LEDs D1-D10 will light up in sequence to form the water lamp effect.