Simple IC 555 PWM Generator Circuit

Think of a tiny translator for your electronics!

This IC 555 PWM circuit is like that translator, but for messages and electricity.

It uses a special chip IC 555 to take a message and turn it into a special pulsing signal.

This pulsing signal can be used to control things like brightness of lights or speed of motors.

The circuit changes the length of these pulses called duty cycle to send the message.

So, even though you might not see the message itself this circuit can use pulses to control all sorts of cool electronic effects.

Circuit Working:

Parts List:

This circuit is a pulse generator utilizing the 555 IC featuring an adjustable PWM cycle.

It functions as an astable multivibrator, typically producing a 50% PWM cycle.

The key variation from the standard 555 IC design is the inclusion of a custom resistance network between pins 6 and 7 consisting of P1, P2, R2, D1 and D2.

D1 and D2 serve to establish a specific charging time for capacitor C1, resulting in the desired 50% PWM under normal conditions.

The PWM (n) is determined by the settings of P1 and P2 as given by the formula below.

In cases where P2 is set to 0 (n = 100%), the frequency can be approximately calculated using the formula below.

Formula:

Understanding the PWM (n) Formula for a 555 PWM Generator.

555 Timer Utilized as a PWM Generator:

One flexible integrated circuit that may be set up to produce PWM signals is the 555 IC.

It generates a continuous square wave output in astable mode.

We may regulate the outputs duty cycle by carefully choosing each component value.

What Part P1 and P2 Play:

Resistors P1 and P2 are critical in setting the PWM duty cycle (n) in your particular circuit.

The IC 555 pin 5, which represents the control voltage, is linked to these resistors.

P1: This resistor affects how long the timing capacitor takes to charge.
P2: The timing capacitors discharge time is influenced by this resistor.

The PWM duty cycle (n) and the values of resistors P1 and P2 are related by the formula below.

n = 1 + P2 / P1

here,

• n: shows the duty cycle as a percentage, For instance, n = 2 would indicate a 50% duty cycle.
• P1: the resistor P1s value.
• P2: the resistor P2s value.

The Formulas Functions:

The formula shows that the ratio of P2 to P1 directly affects the duty cycle.

• When P2 is significantly less than P1, the duty cycle approaches 1 (or 100%).
• This implies that there will usually always be a high output.
• A low duty cycle will come from the duty cycle being substantially bigger than 1 (i.e., P2 is much larger than P1).
• The most of the time, the production will be low.
• P2 and P1 equaling each other will result in a duty cycle of 2, or equal on and off periods, or 50% of the total duty cycle.

Important Points

The formula offers a basic method for figuring out the PWM duty cycle using resistor values.

You can accurately regulate the circuits average output voltage by altering P1 and P2.

Due to its adaptability, the 555 IC is a widely used option for PWM generation in a variety of applications.

With the 555 IC, you may efficiently build and execute PWM circuits by knowing this formula and the functions of P1 and P2.

Knowing the 555 IC PWM Generators Frequency Formula with P2 = 0

f = 0.69/((2P1 + P2 + 4.7kΩ)C1)

When P2 is set to 0, the formula simplifies to:

f = 0.69/((2*P1 + 4.7kΩ)C1)

where,

• f: is the output square wave’s frequency expressed in hertz Hz.
• P1: ohms Ω of resistance of resistor P1.
• P2: resistor P2s resistance, which is 0Ω in this instance.
• 4.7kΩ: is the 555 IC internal resistance.
• C1: The timing capacitors capacitance expressed in farads F.

Important Points:

The calculation is only for the situation where P2 equals 0, which leads to a duty cycle of 100%.

The frequency and the product of (2*P1 + 4.7kΩ) and C1 are inversely related.

The frequency will go down when P1 or C1 is increased, and the frequency will go up when they are decreased.

Realistic Aspects to Take into Account:

The internal resistance of 4.7k is an estimate that may change significantly between various 555 ICs.

You should think about utilizing a simulation tool or measuring the frequency experimentally for more accurate frequency calculations or modifications.

Ideal component values are the foundation of the formula.

Tolerances in real world components might alter the actual frequency.

Understanding this method and the variables that affect it will let you calculate and modify a IC 555 based PWM generators frequency with 100% duty cycle.

How to Build:

To build a Simple IC 555 PWM Generator Circuit you need to follow the below mentioned connections steps:

• Connect pin 1 ground and pin 8 VCC of the 555 timer IC to the ground and the positive terminal of the power supply respectively.
• Connect pin 4 to VCC to disable the reset functionality.
• Connect pins 2 and 6 together.
• Connect pins 6 and 7 with a series connection of R2 4.7k and D1 1N4148 in parallel with D2 1N4148.
• Connect C2 10µF capacitor to positive power supply.
• Connect pin 5 through C3 capacitor 0.1µF
• Connect pin 3 OUT to PWM output
• Connect pin 6 to pin 2 through a series combination of P1 and P2.
• Adjust P2 to vary the PWM of the output waveform.

Note:

• This circuit provides an approximate 50% PWM.
• Adjusting P2 allows you to vary the PWM as per your requirement.

Conclusion:

To conclude, the 555 PWM generator circuit is a versatile and widely used circuit that utilizes the 555 timer IC to produce PWM signals.

Its ability to adjust the PWM makes it suitable for a variety of applications, including motor speed control, LED dimming and audio tone generation.

References:

DESIGN OF PULSE WIDTH MODULATOR USING NE-555

555 PWM circuit set frequency shifting after 2 months