Disco lights Circuit have been quite famous among the lighting circuits made using LED’s. 555 timers are widely employed in lighting circuits like this to spice up the lighting effect produced by the circuit. Here we are about to see a similar lighting circuit using a timer IC 555 and a decade counter CD 4017. The IC CD4017 was a Johnson counter which gives decoded outputs with inputs of clock signal, clock inhibit, carry out and this it produces counters as output. Here is a similar Disco Lights Circuit which uses the same IC 555 and CD 4017. Lets move into the working explanation of this lighting circuit.
WORKING OF DISCO LIGHTS CIRCUIT:
The Circuit operation starts with the IC 555 which is wired as a Astable Multivibrator to generate clock pulses for the counter IC CD4017. The frequency of the MUltivibrator decideds the speed with which the LED’s switch ON and OFF. The values of the variable resistor RV1, resistor R1 and Capacitor C2 decides the output timing of the Astable multivibrator.
|CD4017 Pin diagram|
Johnson COunter IC2 CD4017 forms the next part of the circuit. This IC takes clock input from the astable multivibrator through the pin 14. There are ten decoded ouput pins in this IC starting from Q0 to Q9. The output of the Johnson Counter increases one by one with each clock input signal and therefore the high signal moves from Q0 to Q9 pins with each pulse. The 13 Clock Enable pin should be given active low to give clock input to the IC. The reset 15th pin was used to reset the counter and when this pin goes high the Q0 output pin will be enabled for the continuation of next cycle.
Connection patterns of the LED’s play a very important role in this circuit , since wrong patterns may produce undesirable results. Two LED’s are connected to each ouput pins of the IC CD4017 and are connected in a manner two have a common cathode and two anodes. With the first clock pulse Q0 goes high while all other decoded outputs are low. This lights up the LED D1 in which the anode is positive with respect to the common cathode point. The high signal from the Q0 was also connected to the anode of the D11 which is also positive with respect to the common cathode. Therefore a high signal in Q0 pin will make the LED D1 and LED D11 glow.
This cycle continues as the high output moves to Q1 for next clock pulse input from the multivibrator. This makes the LED D2 and D12 to glow at the same moment. And the cycle continues with high output proceeds to Q3, Q4, ……..Q9 making the LED’s D3 & D13, D4 & D14, ……..D10 &D20 to glow in pairs. This will produce a great lighting pattern similar to disco lights and remember adding different color LED’s will make this Lighting circuit even cooler.
I have also added the Proteus simulation file along with this article , Download the design file from below link to get a better idea of its working.