Fiche composant 1 : le NE555 et le NE556 partie 1

Introduction

This tutorial will guide you through the essential components and functioning of the NE555 and NE556 integrated circuits. These components are widely used in electronics for timing, pulse generation, and oscillator applications. Understanding their pin configurations and operational principles will help you implement them effectively in your projects.

Step 1: Overview of the NE555

• The NE555 is a versatile timer IC used for various timing applications.
• It can operate in different modes: astable, monostable, and bistable.
• Key applications include pulse width modulation, timers, and oscillators.

Step 2: Pin Configuration of the NE555

• The NE555 has 8 pins, each serving a different function:
  1. Ground (Pin 1): Connects to the negative supply voltage.
  2. Trigger (Pin 2): Initiates timing when a negative pulse is applied.
  3. Output (Pin 3): Provides the output signal.
  4. Reset (Pin 4): Resets the timing operation when activated.
  5. Control Voltage (Pin 5): Allows external voltage control for timing adjustments.
  6. Threshold (Pin 6): Resets the flip-flop when a voltage exceeds 2/3 Vcc.
  7. Discharge (Pin 7): Discharges the timing capacitor.
  8. Vcc (Pin 8): Connects to the positive supply voltage.

Step 3: Overview of the NE556

• The NE556 is a dual version of the NE555, allowing for two independent timing circuits in one package.
• It shares similar functionality and pinouts with the NE555.

Step 4: Pin Configuration of the NE556

• The NE556 also has 8 pins with similar functions:
  • Pins 1-4 function as two NE555 timers.
  • Pin 1: Ground
  • Pin 2: Trigger for Timer 1
  • Pin 3: Output for Timer 1
  • Pin 4: Reset for Timer 1
  • Pin 5: Control Voltage for Timer 1
  • Pin 6: Threshold for Timer 1
  • Pin 7: Discharge for Timer 1
  • Pin 8: Vcc (positive supply voltage)
• Pins 1-4 can be mirrored for Timer 2.

Step 5: Working Principle of the NE555

• The NE555 operates by charging and discharging a capacitor through resistors.
• In astable mode, it continuously switches between high and low states, generating a square wave output.
• In monostable mode, it produces a single pulse in response to a trigger.

Step 6: Using the NE555 in Astable Mode

• To configure the NE555 in astable mode:
  1. Connect resistors (R1, R2) and a capacitor (C) to the appropriate pins.
  2. Use the formula for frequency:
     Frequency (f) = 1.44 / ((R1 + 2*R2) * C)
  3. Adjust R1, R2, and C to set the desired frequency and duty cycle.

Step 7: Practical Implementation of Astable Mode

• Build a simple circuit on a breadboard:
  • Connect the components as per the pin configuration.
  • Ensure the power supply is correct.
• Test the circuit with an oscilloscope to observe the output waveform.

Step 8: Measuring with an Oscilloscope

• Use an oscilloscope to visualize the output from the NE555:
  • Connect the probe to the output pin.
  • Adjust the time base to capture the waveform clearly.
  • Measure frequency, duty cycle, and voltage levels.

Conclusion

In this tutorial, you learned about the NE555 and NE556 ICs, their pin configurations, and how to operate the NE555 in astable mode. This foundational knowledge is crucial for various electronics projects involving timing and signal generation. For further exploration, consider building more complex circuits or experimenting with different resistor and capacitor values to see their impact on frequency and duty cycle.