The 555 timer IC is a popular integrated circuit that can be used for various applications including timing, oscillator, and flip-flop circuits. In this article, we will discuss 555 wiring diagram and its applications in detail.
Overview of 555 Timer IC
The 555 timer IC is a versatile chip which is widely used in electronic circuits. It was first introduced by Signetics Corporation in the year 1971. The IC consists of 23 transistors, 2 diodes, and 16 resistors on a single silicon chip. The chip is available in 8-pin DIP (Dual In-line Package) and SOIC (Small Outline Integrated Circuit) packages.
The 555 timer IC can work as an oscillator, timer, flip-flop, and many other applications. The IC has three modes of operation: Monostable, Astable, and Bistable modes. Let’s discuss these three modes of operation in detail:
Monostable Mode
In Monostable mode, the 555 timer IC operates as a one-shot pulse generator. When a trigger pulse is applied to the trigger pin (pin 2), the output pin (pin 3) of the IC goes high for a fixed time duration determined by the value of the external components connected to the IC. The time duration of the pulse generated can be calculated using the formula:
Time Duration = 1.1 x R x C, where R is the resistance and C is the capacitance
Table 1 shows the 555 wiring diagram for the Monostable mode.
| Pin No. | Pin Name | Description |
|---|---|---|
| 1 | Ground (GND) | Ground Reference Voltage |
| 2 | Trigger (TR) | Input that initiates timing cycle (Active LOW) |
| 3 | Output (OUT) | Output Voltage |
| 4 | Reset (RESET) | Input that resets the IC (Active LOW) |
| 5 | Control Voltage (CV) | Analog Input for adjusting the output frequency |
| 6 | Threshold (TH) | Input that terminates timing cycle (Active HIGH) |
| 7 | Discharge (DIS) | Output that discharges timing capacitor |
| 8 | Vcc | Positive Supply Voltage |
Astable Mode
In Astable mode, the 555 timer IC operates as a free-running oscillator. The output pin (pin 3) of the IC alternates between high and low states continuously at a frequency determined by the external components connected to the IC. The frequency of oscillation can be calculated using the formula:
Frequency = 1.44 / ( ( R1 + 2 x R2 ) x C ), where R1 and R2 are resistances and C is capacitance
Table 2 shows the 555 wiring diagram for the Astable mode.
| Pin No. | Pin Name | Description |
|---|---|---|
| 1 | Ground (GND) | Ground Reference Voltage |
| 2 | Trigger (TR) | Input that initiates timing cycle (Active LOW) |
| 3 | Output (OUT) | Output Voltage |
| 4 | Reset (RESET) | Input that resets the IC (Active LOW) |
| 5 | Control Voltage (CV) | Analog Input for adjusting the output frequency |
| 6 | Threshold (TH) | Input that terminates timing cycle (Active HIGH) |
| 7 | Discharge (DIS) | Output that discharges timing capacitor |
| 8 | Vcc | Positive Supply Voltage |
Bistable Mode
In Bistable mode, the 555 timer IC operates as a flip-flop. The output pin (pin 3) of the IC remains in the state in which it was last set until the next trigger pulse is applied to the trigger pin (pin 2). The IC toggles between two stable states. Table 3 shows the 555 wiring diagram for the Bistable mode.
| Pin No. | Pin Name | Description |
|---|---|---|
| 1 | Ground (GND) | Ground Reference Voltage |
| 2 | Trigger (TR) | Input that initiates timing cycle (Active LOW) |
| 3 | Output (OUT) | Output Voltage |
| 4 | Reset (RESET) | Input that resets the IC (Active LOW) |
| 5 | Control Voltage (CV) | Analog Input for adjusting the output frequency |
| 6 | Threshold (TH) | Input that terminates timing cycle (Active HIGH) |
| 7 | Discharge (DIS) | Output that discharges timing capacitor |
| 8 | Vcc | Positive Supply Voltage |
Applications of 555 Timer IC
The 555 timer IC can be used in various electronic circuits. Some of the applications of the IC are listed below:
Pulse Width Modulation (PWM)
The 555 timer IC can be used to generate PWM signals with varying duty cycle. The PWM signal can be used to control the speed of DC motors, dim the LED lights, and many other applications. Figure 1 shows the 555 wiring diagram for PWM circuit.
Variable Frequency Oscillator
The 555 timer IC can be used as a variable frequency oscillator by varying the control voltage (CV) pin. The frequency of oscillation can be changed by varying the voltage applied to the CV pin using a potentiometer. Figure 2 shows the 555 wiring diagram for Variable Frequency Oscillator.
Sequential Timer
The 555 timer IC can be used as a sequential timer by connecting multiple 555 ICs in a chain. Each IC can be configured in Monostable mode, and the output of one IC can be used as a trigger for the next IC. Figure 3 shows the 555 wiring diagram for Sequential Timer.
FAQ
What is a 555 timer IC?
The 555 timer IC is a popular integrated circuit that can be used for various applications including timing, oscillator, and flip-flop circuits.
What are the modes of operation of 555 timer IC?
The 555 timer IC has three modes of operation: Monostable, Astable, and Bistable modes.
How can I calculate the time duration in Monostable mode?
The time duration of the pulse generated can be calculated using the formula: Time Duration = 1.1 x R x C, where R is the resistance and C is the capacitance.
How can I calculate the frequency of oscillation in Astable mode?
The frequency of oscillation can be calculated using the formula: Frequency = 1.44 / ( ( R1 + 2 x R2 ) x C ), where R1 and R2 are resistances and C is capacitance.
What are the applications of 555 timer IC?
The 555 timer IC can be used in various electronic circuits, including Pulse Width Modulation (PWM), Variable Frequency Oscillator, Sequential Timer, and many other applications.
References:
[1] Horowitz, P., & Hill, W. (1989). The art of electronics. Cambridge university press. [2] Sedra, A. S., & Smith, K. C. (2004). Microelectronic circuits. Oxford university press.