Blinking LED with NE555 on 5V

Here is a walkthrough of a simple introductory project, a blinking LED using a solderless breadboard and NE555 IC. Total component cost is about US$10.

I’ve provided links to sources for the components — but all of these can be found from many different vendors. Bangood does have good prices for the breadboard and wiring kit.

Materials needed:
(1) solderless breadboard (almost any type will do for this circuit)
(1) breadboard wiring kit
(1) LED (any color)
(1) 555 timer IC
(1) resistor kit, containing:
(1) 470-ohm resistor
(1) 1k resistor
(1) 6.8k resistor
(1) 100uF capactor
(1) 0.1uF capacitor

The circuit we will be building is an “astable oscillator,” using the venerable (read, “so cheap, ubiquitous, easy-to-use, and reliable that it’s still very popular despite its age”) 555 timer IC. The IC allows C1 (100uF in this example) to charge from +5V via both resistors until it reaches 2/3 of Vcc, then discharges it through R2 (6.8k) until it reaches 1/3 of Vcc. This action provides a regular timing function, which is converted into a TTL rectangular-wave output by the 555. A 470-ohm resistor is used to limit current to an LED, which blinks at about 1Hz (that is, about once per second.) Changing the values of the resistors and/or C1 would change the blinking frequency. For instance, if a 50uF capacitor were used instead of a 100uF one, the LED would blink twice as quickly.



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