## Working of the 555 Circuit, in Astable Mode, to Control 3*3*3 LED Cube (Part 2)

by realfinetime  |  in LED Cube at  00:56

We found the circuit to design a pattern in a 3*3*3 LED cube using 555 timer in previous part. In this part, we will see the working of circuit.

Working of Circuit

555 is used to generate rectangular pulses of different frequencies. Frequency of the generated pulses can be varied by changing the values of  R1 and R2.
Frequency of the rectangular pulses generated depends on the values of R1, R2 and C1.

Frequency, F = 1 / ( ln( 2 ) . C1 . ( R1+2R2 ) )

Ton   =  ln( 2 ) . C1 . ( R1 + R2 )

Toff   =  ln( 2 ) . C1 . R2

R1 and R2 - Resistance in Ohms
F - Frequency in Hertz
Ton - Time for which output will be HIGH ( LED will be ON )
Toff - Time for which output will be LOW ( LED will be OFF )

R1 = R2 = 1 Mega Ohm = 1 * 106  Ohm
ln ( 2 ) = 0.693

Substituting these values in the equations, we get
F = 1.457 Hz, Ton = 0.45738 S, Toff =  0.22869 S

neg1, neg3, neg5, neg7 and neg9 terminals of 3*3*3 LED cube are shorted and is connected to the output pin of 555. Similarly, neg2, neg4, ne6 and neg8 terminals are shorted and is connected to the output pin of 7404 (pin 2).

When the output pin of 555 is HIGH, output pin of 7404 will be LOW. LEDs connected to the output pin of 555 will turn on and LEDs connected to the output pin of 7404 will turn off. When the output pin of 555 is LOW, output pin of 7404 will be HIGH. LEDs connected to the output pin of 555 will turn off and LEDs connected to the output pin of 7404 will turn on.

By varying the value of R1 and R2, we can adjust the speed of blinking. Current limiter resistances of 1KOhm should be connected to the anode terminals of LED cube.

Video demonstration of a simple pattern designed in a 3*3*3 LED cube using 555 timer is given in next part.