LED Flashing Circuit using IC

LED FLASHING CIRCUIT USING IC

AIM:

Design and setup a LED flashing circuit using 555 timer.

MATERIALS AND TOOLS REQUIRED:

Solder, flux, knife/blade, soldering iron, desoldering pump and nose pliers.

THEORY:

An astable multi-vibrator, often called a free-running multi vibrator, is a rectangular-wave generating cir­cuit. Unlike the mono stable multi vibrator, this circuit does not require any external trigger to change the state of the output, hence the name free-running. An astable multi vibrator can be produced by adding resistors and a capacitor to the basic timer IC, as illustrated in figure. The timing during which the output is either high or low is determined by the externally connected two resistors and a capacitor. Pin 1 is grounded; pins 4 and 8 are shorted and then tied to supply +Vcc, output (V_OUT is taken form pin 3; pin 2 and 6 are shorted and the connected to ground through capacitor C, pin 7 is connected to supply + V_CC through a resistor R_A; and between pin 6 and 7 a resistor R_B is connected. At pin 5 either a bypass capacitor  is connected or modulation input is applied.

Circuit Diagram:

PROCEDURE

1. The circuit is wired as in the circuit diagram
2. Connect the supply voltage.
3. The LED flashes.
4. Verify the time period.

RESULT: