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Electronics

Timer IC 555 NE555P NE555 DIP-8

AED 5.25

1

Description

The 555 timer is a versatile integrated circuit that can be used as a timer, oscillator, flip-flop, and amplifier. It was first introduced in 1972 and is still widely used today due to its low cost and ease of use.

Package Includes:

  • 1 x 555 Timer IC DIP

Features:

  • Low power consumption
  • Easy to use
  • Wide range of operating voltage
  • Multiple configurations possible
  • Wide range of operating temperature
  • Widely available

Description:

The 555 timer is an integrated circuit that has been widely used for a variety of applications, including timers, oscillators, flip-flops, and amplifiers. It was first introduced in 1972 and is still widely used today due to its low cost and ease of use. The 555 timer is available in an 8-pin dual in-line package (DIP) and is powered by a supply voltage ranging from 4.5 to 15 VDC. The supply current required by the 555 timer ranges from 5 mA to 200 mA, while the output current is limited to 200 mA. The operating temperature range for the 555 timers is -55°C to +125°C.

Principle of Work:

The 555 timer has three operating modes: Monostable, Astable, and Bistable. The mode of operation depends on the connections made to the control pins of the 555 timers.

In Monostable mode, the 555 timer acts as a one-shot timer. When a trigger signal is applied to the trigger pin, the output goes high and remains high for a period determined by the RC network connected to the timer. After the specified time has elapsed, the output returns to its low state.

In Astable mode, the 555 timer generates a continuous series of pulses. The frequency and duty cycle of the pulses are determined by the RC network connected to the timer. This mode is useful for generating square waves for applications like flasher circuits and oscillators.

In Bistable mode, the 555 timer acts as a flip-flop. It can be set to either a high or low state and will remain in that state until a trigger signal is applied to the trigger pin, causing the output to change state.

The 555 timer operates by charging and discharging an external capacitor through a resistor. The voltage across the capacitor is compared to a reference voltage, and when the voltage reaches a certain threshold, the output of the 555 timer changes state. By controlling the values of the resistor and capacitor, the timing of the output can be adjusted

Pinout of the IC:

  • Ground (GND): Connects the 555 timers to a ground reference.
  • Trigger (TRIG): Input pin that, when brought low, triggers the one-shot operation in Monostable mode or changes the state of the output in Bistable mode.
  • Output (OUT): Output pin that provides the timing signal.
  • Reset (RESET): Input pin that, when brought low, resets the 555 timers to its low state.
  • Control Voltage (CV): Input pin that can be used to adjust the reference voltage used by the comparator.
  • Threshold (THR): Input pin that is compared to the voltage on the capacitor. When the voltage on the capacitor reaches a certain level, the output changes state.
  • Discharge (DIS): Output pin that is used to discharge the capacitor in Astable mode or to reset the timer in Monostable mode.
  • Vcc (Vcc): Supply voltage input that provides power to the 555 timers.

Applications: 

  • Timers: The 555 timer can be used to generate timed delays in Monostable mode.
  • Oscillators: In Astable mode, the 555 timers can be used to generate square waves for oscillator applications.
  • Flip-flops: The 555 timer can be used as a flip-flop in Bistable mode.
  • Tone generators: The 555 timer can be used to generate audio tones for use in alarms and other similar applications.
  • Voltage regulators: The 555 timer can be used to regulate the output voltage of a power supply.
  • Pulse-width modulation (PWM) circuits: The 555 timer can be used to generate PWM signals for controlling the speed of motors and the brightness of LEDs.
  • Light flashers: The 555 timer can be used to generate flashing light patterns for applications such as automotive turn signals and Christmas lights.
  • Power supply sequencers: The 555 timer can be used to sequence the activation of multiple power supplies.

Circuit:

 

The LED flasher circuit flashes an LED on and off repeatedly, with the rate of flashing determined by resistors R1 and R2 and capacitor C1.

Square waves are the output of the 555 timers. Three important time measurements for a square wave are:

  • Total time of the square wave (the time it is on and off or high and low)
  • Length of time it is high (Thigh)
  • Length of time it is low (Tlow)

The total time of a square wave is equal to the sum of Tlow and Thigh, and the proportion of time the wave is high is called the duty cycle. For example, if the total time of a square wave is 1 second and it's high for 0.2s, its duty cycle is 20%.

The duty cycle is crucial for the LED flasher circuit, as it determines the length of time the LED stays on compared to the time it is off. For example, if the duty cycle is set to 20%, the LED will flash on for 20% of the cycle and off for 80% of the cycle. The larger the values of resistors and the capacitor, the longer the cycle will be. If values are too small, the LED will appear to be constantly on, and if values are too large, the LED will not flash at all.

The formulas to calculate T, Thigh, and Tlow are:

  • T= 0.7 * (R1 + 2R2) * C1
  • Thigh= 0.7 * (R1 + R2) * C1
  • Tlow= 0.7 * R2 * C1

For the LED flasher circuit, a duty cycle of 50% is ideal, with the LED being on for the same amount of time as it is off. With R1= 1KΩ, R2=10KΩ, and C1= 10µF, the calculated values for T, Thigh, and Tlow are:

  • T= 0.147s
  • Thigh= 0.077s
  • Tlow= 0.07s

With these values, the LED will flash in a visible manner, allowing the human eye to detect the flashing.

 

Library:

No library is needed.

Code:  

No Code Needed.

Technical Details:

  • Supply voltage: 4.5 to 15V
  • Supply current: typically around 10 mA
  • Output current: up to 200 mA
  • Trigger voltage: typically 1/3 of the supply voltage
  • Threshold voltage: typically 2/3 of the supply voltage
  • Reset voltage: below 1/3 of the supply voltage
  • Output voltage: can be used to drive low power devices
  • Temperature range: -55°C to +125°C
  • Package types: DIP

Resources:

Comparisons:

The 555 timer IC and microcontroller units (MCUs) are both used for creating timers, but there are some key differences between the two options:

555 Timer IC:

  • Simplicity: The 555 timer IC is a simple and low-cost solution for creating timers. It requires minimal external components and is easy to use for basic timer applications.
  • Limited Functionality: The 555 timer IC is limited in terms of its capabilities and versatility. It only provides basic timing functions, such as astable (oscillator) or monostable (one-shot) modes.
  • Fixed Timing: The timing parameters of the 555 timers are determined by external components such as resistors and capacitors, and are not adjustable once set.

MCU:

  • Flexibility: MCUs offer a high level of flexibility and versatility compared to the 555 timer IC. They can be programmed to perform a wide range of tasks, including timers and other functions.
  • Complexity: MCUs are more complex and require more technical knowledge to use than the 555 timer IC. They require programming and often more external components, such as memory and input/output devices.
  • Adjustable Timing: MCUs can be programmed to adjust timing parameters, making them more suitable for applications that require dynamic timing.