555 Timer

What are the types of multivibrators?

1. Astable 2. Monostable 3. Bistable

How does an astable multivibrator work?

1. Capacitor C begins to charge up to 2/3 Vcc 2. Pin 6 switches comparator 1 which resets flip-flop 3. High output 4. Pin 7 triggered which causes capacitor to drain to 1/3 Vcc 5. Pin 2 switches comparator II which sets the flip-flop 6. Low output and discharge transistor is turned off 7. Capacitor C again charges

How does a monostable multivibrator work?

1. Pin 2 switches comparator II which resets flip-flop 2. High output 3. Capacitor C begins to charge up to 2/3 Vcc 4. Pin 6 switches comparator 1 which sets flip-flop 5. Low output

What is a multivibrator?

Circuit used to implement two state devices 15 v or 0 v High state or low state 1 or 0

What is the function of pin 5?

Control voltage - for 2/3 Vcc derivation or for resistor to ground, external voltage, capacitor to ground greater than or equal to uF

What is a 555 timer?

Controller than can produce accurate time delays or oscillations

What is the function of pin 7?

Discharge timing capacitor (usually)

What is the function of pin 1?

Ground

What is a monostable multivibrator?

One stable state and one unstable state where output stays in stable until triggered into unstable state The resistors and capacitors determine the time intervals

What is the function of pin 3?

Output which is normally low unless time interval is triggered

What is the function of pin 8?

Power supply voltage

What is the function of pin 4?

Reset, when voltage is less than 0.4 volts, timing cycle is interrupted and returned to non triggered state Timer cannot be triggered unless reset is released Good for a stable power start up

What is an astable multivibrator?

Stays between two states as shown in square waves and is never stable The resistor and capacitors determine the time intervals

What is a duty cycle and what is the equation for the duty cycle for t1 and t1 for a multistable vibrator?

The duty cycle is the ration between the pulse width (t1) to the period (T)

What is the function of pin 6?

Threshold - if the voltage is greater than 2/3 Vcc then flip-flop is reset causing pin 3 to produce a low state

What is the function of pin 2?

Trigger - if the voltage below of 1/3 Vcc flip flop is set causing pin 3 to produce a high state

What is the equation for t1 (charging), t2 (discharging), and T (period) for a multistable vibrator?

f = 1/T