How 555 timers Work - The Learning Circuit

element14 presents
13 Nov 201907:48

Summary

TLDRIn this episode of 'The Learning Circuit,' Karen explores the 555 timer, a versatile and popular IC in hobby electronics. She delves into the internal workings of the 8-pin chip, detailing its components like comparators, flip-flop, and voltage divider. Karen explains the function of each pin and how they interact to create a timer, oscillator, or flip-flop. The video promises a future episode on practical applications of the 555 timer in various circuit modes.

Takeaways

  • 🌐 The 555 timer is a widely used integrated circuit (IC) in hobby electronics, known for its versatility in various applications.
  • 🔌 It features 8 pins, including ground (pin 1), trigger (pin 2), output (pin 3), reset (pin 4), control voltage (pin 5), threshold (pin 6), discharge (pin 7), and VCC (pin 8).
  • 🏭 Inside the 555 timer, there are two comparators, a flip-flop, an inverter, two transistors, and a voltage divider made up of three 5kΩ resistors, which might be the origin of the '555' name.
  • 🔋 The voltage divider divides the supply voltage (VCC) and feeds the comparators, with typical VCC values ranging from 5 to 15 volts.
  • ⚖️ Comparators compare voltages at their inputs and output a digital signal indicating which input is larger, playing a crucial role in the 555's operation.
  • 🔄 The flip-flop within the 555 timer is of the SR type, with set and reset inputs that control the output state, and only the NOT Q output is utilized.
  • 🔧 The output of the flip-flop determines the state of the 555 timer's output pin, which is inverted before being outputted, creating a toggling effect.
  • 🔩 Pin 5, the control voltage pin, can adjust the voltage at the negative input of comparator one, allowing for some control over the 555's operation.
  • 🔄 Pin 4, when connected to VCC, ensures the 555 timer functions correctly; if grounded, it triggers a reset, causing the output to go low.
  • 🔌 Pin 7, the discharge pin, is used with external capacitors to control the timer's duration, discharging the capacitor when the circuit is reset.

Q & A

  • What is the 555 timer and what is its primary function?

    -The 555 timer is a widely used integrated circuit (IC) that functions as a timer, oscillator, or flip-flop. It is contained in an 8-pin IC and is popular in hobby circuits due to its versatility and ease of use.

  • How many pins does the 555 timer have and what are their typical functions?

    -The 555 timer has 8 pins, which serve various functions: pin 1 is for ground, pin 2 is the trigger, pin 3 is the output, pin 4 is for reset, pin 5 is the control voltage, pin 6 is the threshold, pin 7 is the discharge, and pin 8 connects to VCC.

  • What are the main components inside the 555 timer?

    -Inside the 555 timer, there are two comparators, a flip-flop, an inverter, two transistors, and a voltage divider made up of resistors.

  • How does the voltage divider inside the 555 timer work?

    -The voltage divider is composed of three 56 kilo-ohm resistors and divides the supply voltage, feeding two comparators. It typically divides the VCC voltage so that one comparator receives two-thirds of the supply voltage and the other receives one-third.

  • What is the typical supply voltage range for the 555 timer?

    -The typical supply voltage range for the 555 timer is from 4.5 to 16 volts, but VCC is usually between 5 and 15 volts.

  • How do the comparators in the 555 timer function?

    -The comparators compare the voltages at their inputs and output a digital signal indicating which input is larger. If the positive input is larger, the output is high; if the negative input is larger, the output is low.

  • How does the flip-flop within the 555 timer contribute to its timing function?

    -The flip-flop in the 555 timer has set and reset inputs that control its output. The flip-flop's output is used to control the timing function by setting and resetting based on the comparator outputs.

  • What is the purpose of the discharge pin (pin 7) on the 555 timer?

    -Pin 7, the discharge pin, is used with external capacitors to control the timing duration of the timer. It connects to a transistor whose base is controlled by the flip-flop output, allowing the capacitor to discharge quickly when the circuit is reset.

  • How can the control voltage pin (pin 5) be used to modify the 555 timer's behavior?

    -Pin 5, the control voltage pin, can be used to adjust the voltage at the negative input of comparator one, which typically receives two-thirds of VCC. This pin can be used to modify the timing behavior of the timer in certain applications.

  • What happens when both comparators in the 555 timer output high?

    -When both comparators output high simultaneously, it is considered an invalid state because it causes the flip-flop's outputs to behave unpredictably. This situation should be avoided in proper circuit design.

Outlines

plate

Dieser Bereich ist nur für Premium-Benutzer verfügbar. Bitte führen Sie ein Upgrade durch, um auf diesen Abschnitt zuzugreifen.

Upgrade durchführen

Mindmap

plate

Dieser Bereich ist nur für Premium-Benutzer verfügbar. Bitte führen Sie ein Upgrade durch, um auf diesen Abschnitt zuzugreifen.

Upgrade durchführen

Keywords

plate

Dieser Bereich ist nur für Premium-Benutzer verfügbar. Bitte führen Sie ein Upgrade durch, um auf diesen Abschnitt zuzugreifen.

Upgrade durchführen

Highlights

plate

Dieser Bereich ist nur für Premium-Benutzer verfügbar. Bitte führen Sie ein Upgrade durch, um auf diesen Abschnitt zuzugreifen.

Upgrade durchführen

Transcripts

plate

Dieser Bereich ist nur für Premium-Benutzer verfügbar. Bitte führen Sie ein Upgrade durch, um auf diesen Abschnitt zuzugreifen.

Upgrade durchführen
Rate This

5.0 / 5 (0 votes)

Ähnliche Tags
Electronics555 TimerCircuit DesignHobby CircuitsKarenLearning CircuitOscillatorFlip-FlopElement14Engineering
Benötigen Sie eine Zusammenfassung auf Englisch?