Timer IC and Multivibrators

Analog Circuits: Timer IC and Multivibrators

Contents

Describe the internal diagram of 555 Timer IC 1

Recall the applications of 555 Timer IC 3

Describe the Pin diagram of Monostable Multivibrator using 555 Timer IC 3

Calculate the Pulse Width in Monostable Multivibrator 5

Describe the Pin Diagram of Astable Multivibrator using 555 Timer IC 6

Generate Square Wave using Astable Multivibrator 8

Calculate the Time period and Duty Cycle of Generated Square Wave 9

Generate Triangular Wave using Astable Multivibrator 10

Describe the internal diagram of 555 Timer IC

The 555 Timer IC is a widely used integrated circuit that is commonly used in timing, oscillator, and flip-flop applications. The internal diagram of the 555 Timer IC is shown below:

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The 555 Timer IC contains three 5kΩ resistors (RA, RB, and RC), two comparators (COMP1 and COMP2), a flip-flop (FF), a discharge transistor (DIS), and an output stage.

The three 5kΩ resistors are used to set the voltage levels at the inputs of the comparators. The comparator inputs are labeled as TRIG (trigger) and THR (threshold). When the voltage at the TRIG input falls below two-thirds of the voltage at the THR input, the output of COMP1 goes high and triggers the flip-flop.

The flip-flop output is connected to the output stage, which can be configured in a variety of ways depending on the application. The output stage can be used as a buffer or as a switching output, and can drive loads up to 200mA.

The discharge transistor is used to discharge the capacitor connected to the DIS (discharge) pin, which is typically used to control the timing of the 555 Timer IC. The CONTROL pin can be used to modify the operation of the internal comparators and flip-flop.

The RESET pin is used to reset the internal flip-flop and return the output stage to its default state. The GND pin is connected to ground, and the Vcc pin is connected to a positive voltage source.

Overall, the 555 Timer IC is a versatile and widely used integrated circuit that offers a wide range of timing and control capabilities.

Recall the applications of 555 Timer IC

The 555 timer IC is a versatile integrated circuit that has a wide range of applications in electronics. Some of the common applications of the 555 timer IC are:

  1. Astable Multivibrator: The 555 timer IC can be used as an astable multivibrator to generate a continuous stream of pulses. This is useful in applications such as oscillator circuits, timing circuits, and LED blinkers.
  2. Monostable Multivibrator: The 555 timer IC can also be used as a monostable multivibrator to generate a single pulse of a specific duration. This is useful in applications such as timers, pulse width modulation circuits, and pulse position modulation circuits.
  3. Voltage Controlled Oscillator (VCO): The 555 timer IC can be used as a voltage-controlled oscillator to generate a variable-frequency output signal that is controlled by an external voltage.
  4. PWM Generator: The 555 timer IC can be used as a pulse-width modulation (PWM) generator to control the speed of motors, dim the brightness of LEDs, and regulate the power output of power supplies.
  5. Tone Generator: The 555 timer IC can be used as a tone generator to produce different types of audio signals such as square waves, sawtooth waves, and triangular waves.
  6. Delay Circuits: The 555 timer IC can be used to generate delays in circuits such as relay timers, digital clocks, and time delay switches.
  7. Flip-Flop Circuits: The 555 timer IC can be used to implement flip-flop circuits, which are widely used in digital electronics.

Overall, the 555 timer IC is a versatile component that is widely used in electronic circuits due to its simplicity, low cost, and ease of use.

Describe the Pin diagram of Monostable Multivibrator using 555 Timer IC

A Monostable Multivibrator using a 555 Timer IC is a circuit that generates a single output pulse of a specified duration when triggered. The Pin diagram of a Monostable Multivibrator using 555 Timer IC is shown below:

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The Monostable Multivibrator circuit using a 555 Timer IC has the following pins:

  1. GND: This is the ground pin of the 555 Timer IC.
  2. Trigger (Trig): This is the input pin used to trigger the Monostable Multivibrator. When this pin is brought to a voltage level lower than 1/3 of the supply voltage, the output of the 555 Timer IC goes high.
  3. Output: This is the output pin of the Monostable Multivibrator. When triggered, it goes high for a duration determined by the external RC timing components.
  4. Reset: This is the input pin used to reset the Monostable Multivibrator. When this pin is brought to a voltage level lower than 0.7 volts, the output goes low and the timer is reset.
  5. Control: This pin is used to control the operation of the internal comparators and flip-flops.
  6. Threshold: This is the input pin used to set the voltage level at which the output of the 555 Timer IC goes high. This voltage level is set using an external voltage divider circuit.
  7. Discharge: This is the output pin used to discharge the external capacitor that determines the pulse duration.

Overall, the Monostable Multivibrator using a 555 Timer IC is a simple and commonly used circuit that generates a single output pulse of a specified duration when triggered, and its pin diagram helps understand its working and operation.

Calculate the Pulse Width in Monostable Multivibrator

The pulse width of a Monostable Multivibrator is determined by the values of an external resistor (R) and capacitor (C) connected to the 555 Timer IC. The pulse width can be calculated using the formula:

Pulse Width (t) = 1.1 x R x C

where t is the pulse width in seconds, R is the resistance in ohms, and C is the capacitance in farads.

For example, let’s say we have a Monostable Multivibrator with an external resistor of 10k ohms and a capacitor of 10 microfarads. Using the above formula, we can calculate the pulse width as:

t = 1.1 x 10k ohms x 10 microfarads

t = 110 microseconds

Therefore, the pulse width of the Monostable Multivibrator in this example is 110 microseconds.

Describe the Pin Diagram of Astable Multivibrator using 555 Timer IC

An Astable Multivibrator using a 555 Timer IC is a circuit that generates a continuous stream of square wave pulses with a frequency determined by the values of an external resistor and capacitor. The Pin diagram of an Astable Multivibrator using 555 Timer IC is shown below:

The Astable Multivibrator circuit using a 555 Timer IC has the following pins:

  1. GND: This is the ground pin of the 555 Timer IC.
  2. Trigger (Trig): This is the input pin used to trigger the Astable Multivibrator. When this pin is brought to a voltage level lower than 1/3 of the supply voltage, the output of the 555 Timer IC goes high.
  3. Output: This is the output pin of the Astable Multivibrator. It generates a continuous stream of square wave pulses with a frequency determined by the external RC timing components.
  4. Reset: This is the input pin used to reset the Astable Multivibrator. When this pin is brought to a voltage level lower than 0.7 volts, the output goes low and the timer is reset.
  5. Control: This pin is used to control the operation of the internal comparators and flip-flops.
  6. Threshold: This is the input pin used to set the voltage level at which the output of the 555 Timer IC goes high. This voltage level is set using an external voltage divider circuit.
  7. Discharge: This is the output pin used to discharge the external capacitor that determines the frequency of the square wave pulses.

Overall, the Astable Multivibrator using a 555 Timer IC is a simple and commonly used circuit that generates a continuous stream of square wave pulses with a frequency determined by the external RC timing components, and its pin diagram helps understand its working and operation.

Generate Square Wave using Astable Multivibrator

To generate a square wave using an Astable Multivibrator, we need to connect an external resistor and capacitor to the 555 Timer IC as shown in the circuit diagram below:

In this circuit, the external resistor R1 and capacitor C1 are connected to the Trigger and Threshold pins of the 555 Timer IC. The resistors R1 and R2 and the capacitor C2 are connected to the Control pin of the IC. The Output pin of the 555 Timer IC is connected to the load or any other circuitry.

When power is applied to the circuit, the capacitor C1 starts charging through resistor R1 and discharging through resistor R2. The charging and discharging of the capacitor cause the output of the 555 Timer IC to switch back and forth between high and low states, generating a square wave.

The frequency of the square wave can be calculated using the following formula:

f = 1.44 / ((R1 + 2*R2) * C1)

where f is the frequency of the square wave in Hz, R1 and R2 are the values of the resistors in ohms, and C1 is the value of the capacitor in farads.

By varying the values of the resistors and capacitor, we can adjust the frequency and duty cycle of the square wave generated by the Astable Multivibrator.

Calculate the Time period and Duty Cycle of Generated Square Wave

To calculate the time period and duty cycle of the square wave generated by the astable multivibrator using a 555 Timer IC, we need to use the following formulas:

Time period (T) = 0.693 * (R1 + 2R2) * C1

Duty cycle (D) = (R1 + R2) / (R1 + 2R2) * 100%
where R1 and R2 are the resistances in ohms, and C1 is the capacitance in farads.
Let’s take an example where R1 = 10 kΩ, R2 = 20 kΩ, and C1 = 1 nF.
Using the above formulas, we can calculate the time period and duty cycle as follows:

T = 0.693 * (R1 + 2R2) * C1

= 0.693 * (10kΩ + 220kΩ) * 1 nF

= 46.38 ns

D = (R1 + R2) / (R1 + 2R2) * 100%

= (10kΩ + 20kΩ) / (10kΩ + 220kΩ) * 100%
= 33.33%
Therefore, the generated square wave has a time period of 46.38 nanoseconds and a duty cycle of 33.33%.

Generate Triangular Wave using Astable Multivibrator

To generate a triangular wave using an astable multivibrator with a 555 Timer IC, we can connect a capacitor in series with the output pin (pin 3) of the IC and then feed the output to an RC integrator circuit. The RC integrator circuit will integrate the square wave signal to produce a triangular wave.

Here’s a step-by-step guide on how to generate a triangular wave using an astable multivibrator with a 555 Timer IC:

  1. Connect pins 2 and 6 of the IC to the positive supply voltage (Vcc) through a resistor (R1) and a capacitor (C1), respectively. These components determine the frequency of the output square wave.
  2. Connect pin 1 of the IC to ground.
  3. Connect a resistor (R2) between pins 7 and 6 of the IC. This resistor sets the charging current for the timing capacitor.
  4. Connect a timing capacitor (C2) between pins 6 and 2 of the IC. This capacitor determines the timing of the output waveform.
  5. Connect a diode (D1) between pins 6 and 7 of the IC, with the anode connected to pin 6 and the cathode connected to pin 7. This diode ensures that the timing capacitor discharges quickly when the output goes low.
  6. Connect a resistor (R3) in series with the output pin (pin 3) of the IC.
  7. Connect a capacitor (C3) in parallel with resistor R3 to form an RC integrator circuit.
  8. Connect the output of the RC integrator circuit to a buffer amplifier or an amplifier with high input impedance to prevent loading of the output signal.

When power is applied to the circuit, the astable multivibrator generates a square wave output at pin 3 of the IC. This square wave is then integrated by the RC integrator circuit to produce a triangular wave.
The frequency of the triangular wave is determined by the values of R1, R2, C1, and C2. The amplitude of the triangular wave is determined by the values of R3 and C3.

Note that the shape of the triangular wave may not be perfectly linear due to the non-ideal characteristics of the components and the amplifiers used in the circuit.