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The 555 Timer

The 555 Timer. What is a 555 timer?. The 555 timer is one of the most remarkable integrated circuits ever developed. It comes in a single or dual package and even low power CMOS versions exist

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The 555 Timer

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  1. The 555 Timer

  2. What is a 555 timer? • The 555 timer is one of the most remarkable integrated circuits ever developed. It comes in a single or dual package and even low power CMOS versions exist • The 555 timer consists of two voltage comparators, a bi-stable flip flop, a discharge transistor, and a resistor divider network.

  3. Applications for 555 timer • The 555 timer can be used in many ways and is very versatile. • Common uses are for precision timing, pulse generation, sequential timing, time delay generation and pulse width modulation (PWM). –(ie.motor speed control)

  4. Pin Configuration Pin1: ground Pin2: trigger input to lower comparator Pin3: output high ( 200mA max) Pin4: reset latch to low state

  5. Pin Configuration Pin5:gives access to voltage divider Pin6: input to upper comparator Pin7: an open collector to discharge Pin8: power source

  6. Astable Acts as a timer Pulses at precise intervals. Most popular Monostable(one-shot) Outputs only a single pulse Two operations

  7. 555 timer Wiring 1st step is to connect pins 2 and 6 together.Then give power to pins 4,and 8 and ground pin 1.

  8. 2nd part • 3 components are needed to make 555 timer work. • 2 resistors(R1,R2), and a capacitor(C1). These components determine how fast the timer will work in hertz. The equation to figure out what hertz they will run at is: 1.44 / ((R1 + (2 * R2) * C)

  9. Resistors • R1 goes between pins 8 and 7, so we'll put a 1,000 ohm resistor there. R2 goes between pins 7 and 6, so we'll put a 5,000 ohm resistor there.

  10. Capacitor • Now it's time to add the capacitor. It goes between pins 6(threshold) and pin 1 (ground). Now this circuit is ready to be used!

  11. Output to LED • The output of the timer is pin3 so now its time to connect an LED with a wire, then connect a resistor from the negative end of the LED to ground for protection.

  12. What is my frequency?? • If I used a 1,000ohm resistor for R1, and a 5,000 ohm resistor for R2, and a 130 microfarad capacitor(0.00013 F), at what hertz is my LED going to be flashing? 1.44 / ((1000 + 2 * 5000) * 0.00013)= 1.44 / ((1000 + 10,000) * 0.00013)= 1.44 / (11,000 * 0.00013)= 1.44 / 1.43= 1 (Approximately)

  13. Overview • 555 timer is very versatile. • Consists of two voltage comparators, a bi-stable flip flop, a discharge transistor, and a resistor divider network. • Can be wired as Astable or monostable multivibrators. • Astable most popular (timing)

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