555 Timer primarily based 5-Color LED Flasher Circuit

This 5-color LED flasher circuit might be constructed utilizing the favored 555 timer and 4017 decade counter ICs. It doesn’t require any costly parts like a microcontroller.efy tested

The timer IC is used as an astable multivibrator to generate a clock pulse, which is fed to the clock enter of the 4017. Outputs of the 4017 are related to bases of 5 transistors to drive 20 LEDs of various colours, every with its current-limiting resistor.

The 4017 advances to the subsequent output each time it receives a clock pulse, inflicting the LEDs to activate and off in sequence. The pace of the flashing might be adjusted by altering the values of the resistors and capacitors within the 555 timer circuit. The writer’s prototype is proven in Fig. 1.

The circuit diagram of the 5-color flasher is proven in Fig. 2. The circuit contains a 12V battery (or 12V adaptor), timer IC 555 (IC1), decade counter IC 4017 (IC2), 5 BC548 transistors (T1 by T5), 5 units of 5mm purple, inexperienced, blue, white, and yellow LEDs every, and some different parts.

In case you have constructed 555 timer-related tasks, you’d be aware of the IC. The timer IC’s pin 4 (reset) and pin 8 (Vcc) are related to the voltage provide, which might be wherever between 9V and 12V.

On this circuit, a 10k resistor (R1) is related between Vcc and discharge pin 7 of IC1. A 1k resistor (R2) is related between pin 7 and the junction of pin 2 (set off) and pin 6 (threshold).

A 10µF capacitor is related between pin 6 and the bottom pin of the 555 timer, whose floor pin 1 (GND) is related to the circuit’s floor. A 100nF capacitor is related between pin 5 (CV) of the timer and the bottom. The IC’s out pin 3 is related to clock pin 14 of IC4017 (IC2).

Pin 16 of the last decade counter IC2 is related to the availability. Its pins 8 (VSS), 13 (CKEN), and pin 15 (Reset) are related to the bottom. The opposite pins of IC 4017 are outputs used to drive the LEDs for flashing.


As talked about earlier, the 555 timer IC works in astable multivibrator mode. Primarily based on the above-mentioned parts, the frequency of the output pulse is round 12Hz.

The output of the 555 timer is provided as a clock enter to the 4017 decade counter. This 12Hz frequency might be modified by altering the timing parts R1, R2, and C2. Instead of R2, you should utilize a pot to fluctuate the output frequency.

At any time when there’s a low to excessive transition on the clock sign, that’s, on the rising edge, the output of the counter is incremented by 1. You can not change the flash fee on this venture because the astable multivibrator constructed round IC1 generates a set frequency.

IC2’s 5 outputs Q0, Q2, This autumn, Q6, and Q8 are related to the anodes of respective 1N4148 diodes D1 by D5. The remaining 5 outputs Q1, Q3, Q5, Q7, and Q9 are related to the cathodes of respective 1N4148 diodes.

So, two consecutive outputs drive particular person transistors T1 by T5. The bases of all these 5 transistors are related to the outputs of 4017 to drive numerous colour LEDs.

Right here, we have now used all ten outputs of 4017 to flash the LEDs. Outputs Q0 and Q1 management the purple LEDs, outputs Q2 and Q3 management the inexperienced LEDs, outputs This autumn and Q5 management the blue LEDs, outputs Q6 and Q7 management the white LEDs, and outputs Q8 and Q9 management the yellow LEDs.

The 4 purple LEDs are pushed by transistor T1 when outputs Q0 and Q1 of IC2 go excessive. Likewise, the 4 inexperienced LEDs are pushed by transistor T2 when outputs Q2 and Q3 of IC2 go excessive. This goes on for the blue, white, and yellow LEDs pushed by transistors T3, T4, and T5, respectively.

The working of the circuit is straightforward. As quickly as the ability is switched on, the 5-color flasher begins flashing. Initially the 4 purple LEDs glow, then the 4 inexperienced LED glow, adopted by the 4 blue, white, and yellow LEDs. Thereafter the cycle repeats endlessly.

An actual-size, single-side PCB format for the 5-color flasher is proven in Fig. 3 and its element format is in Fig. 4. After assembling the circuit on PCB, enclose it in an appropriate field. Repair all of the 20 LEDs in a sample of your liking, like a star or a circle.

555 based LED Flasher Circuit PCB
Fig. 3: Precise-size PCB sample

Component layout of the PCB
Fig. 4: Part format of the PCB

CON1 is used to attach the 12V battery to the flasher circuit in an appropriate field. If you’re utilizing a compact 9V battery, it may be accommodated inside the field.

Obtain PCB and Part Format PDFs: click on right here

S.C. Dwivedi is an electronics fanatic and circuit designer at EFY

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