Práctica 9: Circuito integrado 555

Summary

In this tutorial, we build two different circuits using the 555 timer IC. The first circuit demonstrates monostable mode, where a triggered LED stays on for a set time, determined by the resistor and capacitor values. The second circuit operates in astable mode, creating an oscillator that makes the LED blink on and off at a frequency controlled by resistors and capacitance. The video explains how adjusting these components affects the timing and frequency of each circuit, providing a practical introduction to 555 timer applications in electronics.

Takeaways

• 😀 The circuit uses the 555 IC, along with resistors and capacitors, to regulate the timer.
• 😀 Pin G of the 555 IC is crucial for the proper functioning of the circuit.
• 😀 In the first setup, the 555 IC operates in monostable mode, where a button press turns on a LED for a specific time.
• 😀 The LED's duration depends on the resistance and capacitance values in the circuit.
• 😀 The timer duration in seconds can be calculated by multiplying the resistance value by the capacitor's value in farads and then multiplying by 11.
• 😀 The 555 IC is connected to the breadboard, with the positive and negative pins clearly marked (pin 1 to negative, pin 8 to positive).
• 😀 The circuit also includes a 220-ohm resistor in series with the LED, which is connected to the negative terminal.
• 😀 A push button is connected between the negative terminal and pin 2 (trigger) of the 555 IC.
• 😀 The second setup configures the 555 IC in astable mode, where the LED blinks on and off at a regular frequency.
• 😀 The charging and discharging of the capacitor through resistors R1 and R2 set the timing for the LED's on/off cycles.
• 😀 The circuit frequency can be adjusted by changing the resistance values or the capacitor's capacitance.
• 😀 In the final step, another LED is added to the output, alternating states with the first LED to create a blinking effect.

Q & A

What is the main purpose of the 555 timer in this circuit?

The 555 timer is used to create time delays in the circuit, either in monostable mode (one-time pulse) or astable mode (continuous oscillations).

What is the function of the resistor and capacitor in the monostable 555 timer configuration?

In the monostable configuration, the resistor and capacitor determine the time duration the LED stays on. The time delay is calculated by multiplying the resistor value (in ohms) by the capacitor value (in farads) and then multiplying by 1.1 to obtain the time in seconds.

What happens when you press the trigger (discharge pin) in the monostable circuit?

Pressing the trigger pin (pin 2) causes the 555 timer to generate a pulse that turns the LED on, and the LED stays on for a period determined by the resistor and capacitor values.

How is the frequency of the circuit determined in the astable configuration?

In the astable configuration, the frequency of the oscillation is determined by the resistors (R1, R2) and the capacitor (C), which control the charge and discharge times of the capacitor, creating high and low states in a repeating cycle.

What is the role of the capacitor in the astable configuration?

The capacitor in the astable configuration charges through resistors R1 and R2, and discharges only through R2. This charging and discharging process creates the alternating high and low voltage states necessary for oscillation.

What change is made to the circuit when switching from a monostable to an astable configuration?

In the astable configuration, the 555 timer is connected to continuously charge and discharge the capacitor, which causes the LED to toggle between on and off states continuously, unlike the monostable mode where the LED stays on for a fixed period.

How do the resistance values affect the frequency in the astable circuit?

Increasing the resistance values (R1 and R2) or decreasing the capacitance of the capacitor reduces the frequency, while decreasing the resistance or increasing the capacitance increases the frequency.

What happens if you replace the 15kΩ resistors with two 10kΩ resistors?

Replacing the 15kΩ resistors with two 10kΩ resistors increases the frequency of the circuit, causing the LED to blink more rapidly.

What is the significance of the 220Ω resistor in the monostable configuration?

The 220Ω resistor is used in series with the LED to limit the current flowing through it, preventing damage to the LED and ensuring proper functionality.

How does adding a second LED to the astable circuit affect the output?

Adding a second LED causes the two LEDs to alternate states. When one LED is on, the other is off, and vice versa, creating a visual alternating pattern.