ang13t / 555-led-chaser

LED Chaser circuit based on the NE555 and the CD4017 sponsored by Hack Club 🚀

555 LED Chaser

LED Chaser circuit based on the NE555 and the CD4017 created for a San Diego workshop sponsored by Hack Club!

Circuit Explanation

This circuit creates a sequential flashing animation of 10 LEDs which is operated by the CD1017 and 555 integrated circuits. It requires a VCC and GND from a 9V battery and allows you to monitor the clock output with an auxiliary pin header. The clock speed of the 555 can be altered using the trim potentiometer.

Schematic

PCB

Components

• 555 Timer IC
• CD4017 IC
• 10x LED Lights
• Resistors: 470ohm and 1K ohm
• 1uF Capacitor
• 9V Battery
• 50Kohm Trim Potentiometer

EasyEDA Symbols

Name	Component Name	Footprint Name
555 Timer IC	NE555P	DIP-8_L9.8-W6.6-P2.54-LS7.6-BL
CD4017 IC	CD4017KIT	DIL16-KIT
LED	LED_5MM	LED-TH_BD5.0-P2.54-FD_C9900023552
1uF Capacitor	CD4017KIT	DIL16-KIT
470ohm Resistor	470Ω	RES-TH_BD3.3-L9.0-P13.00-D0.6
1K ohm Resistor	1k	AXIAL-0.3
Trim Potentiometer	50k	RES-ADJ_3296X
VCC and GND Pins	Header	HEADER-FEMALE-2.54_1X2
CLK Pin	C81276	HDR-TH_1P-P2.54-V-M

555 IC Overview

The 555 IC is configured to be in astable mode. This causes the IC to behave like an oscillator switching its output between HIGH and LOW states to generate a square wave signal which can be fed into the CD4017 IC.

The pinout characteristics of the 555 is as follows:

Pin Number	Name	Function
1	GND	Ground
2	TRIG	Trigger Input: Used to trigger the timer
3	OUT	Output: Provides the timer's output signal
4	RESET	Reset: Resets the timer's internal flip-flop
5	CTRL	Control Voltage: Used to control the threshold
6	THRES	Threshold Input: Sets the threshold for timing
7	DISCH	Discharge Output: Used to discharge timing capacitor
8	VCC	Supply Voltage: Typically +5V

The internal mechanism of the 555 consists of two comparators

CD4017 Overview

Belonging to the CMOS 4000 series of logic chips, the CD4017 is a decade counter with 10 decoded outputs (labeled Q0 through Q9) used to light up our 10 LEDs! It sequentially counts from 0 to 9 on its outputs for each clock pulse applied to its clock input (CLK) and then resets back to 0.

The pinout characteristics of the CD4017 is as follows:

Pin Number	Name	Function
1	CLK	Clock Input: Accepts clock pulses to count
2	Q0	Output 0: Output for count state 0
3	Q1	Output 1: Output for count state 1
4	Q2	Output 2: Output for count state 2
5	Q3	Output 3: Output for count state 3
6	Q4	Output 4: Output for count state 4
7	Q5	Output 5: Output for count state 5
8	GND	Ground (0V): Reference voltage
9	Q6	Output 6: Output for count state 6
10	Q7	Output 7: Output for count state 7
11	Q8	Output 8: Output for count state 8
12	Q9	Output 9: Output for count state 9
13	RESET	Reset Input: Resets the counter to state 0
14	VDD	Supply Voltage: Typically connected to +5V or +9V
15	ENABLE	Enable Input: Enables counting operation
16	CLOCK INHIBIT	Clock Inhibit: Disables clock pulse input

Support

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To check out my other works, visit my GitHub profile.