CD 4001 is a quad, 2 input NOR gate IC made by Fairchild Semiconductors. It is a monolithic CMOS transistor based IC having efficient source and sink capabilities. Circuits that use this IC can be easily operated using battery as CD4001 is a low power consumption IC. A 14 pin DIP package, this IC can work at temperatures upto 1250. The circuit in this project is built around a commonly used CD4001 IC and few more discrete components.
This lighting system circuit described can be used to decorate your Christmas tree with colorful lights. The blinking of LED’s will create a festive appearance which will enhance the Christmas mood.This lighting system can also work as night light or can work as an accessory for internal decoration purposes. Here, you can use different colors of LEDs to make it more colorful or, if you want to increase the number of LED, you can do it by replacing the transistor with some more powerful transistor.
This circuit doesn't draw much of power and can be powered using a battery or an AC source with an adapter.
In this decoratin light circuit, pin 3 always oscillates back and forth from high to low. During one cycle, capacitor charges in one direction, giving output and again charge in opposite direction to remain off. Consider the case when you switch ON the circuit for first time: voltage at pin 3 is zero and voltage at pin 1 and 2 is high or one may be low. This voltage is fed to pin 4 which gets high and pin 5 ,6 (initially connected to pin 3 through capacitor and resistor) get low. After some time capacitor connected between pin 3 and 5 starts charging. With the help of C1 and R1 voltage at pin 3 also start building which is internally connected to pin 12 and 13. As a result, output pin 11 becomes high and this is supplied to pin 8 and 9. Pin 10 becomes low and we will get output. Transistor connected to pin 11 will start working and transistor connected to pin 10 will not work hence at this time LED10-LED18 will glow and rest will remain switched OFF.
After preset interval of time, the polarity of the charge across C1 & R1 gets reversed. Pin 4 is low and pin 3 is high. C1 again starts to charge once more. But this time, in the opposite direction. Since pin 3 is now high and pin 4 is low, the junction of C1 & R1 would represent the negative side of the capacitor. As the capacitor charges, the voltage on this junction will fall. This means that the voltage on pins 5 and 6 will also fall. When it falls to just below half the supply voltage, the inputs change from high to low and the output of gate 2 will go low. Pin 4 will take pins 1 & 2 low. So pin 3 will go high. Hence, output pin11 gets low and is supplied to pin 8 and 9, As a result, output connected to pin 10 (LED1-LED9) will now glow. In other words the first cycle is complete.
If you want to increase the time period just change the value of R1 and C1 and see the difference.
Filed Under: Circuit Design