25-08-2017, 09:32 PM
555 TIMER IC
[attachment=65494]
Abstract
The Apple II microcomputer used a quad timer 558 in monostable (or "one-shot") mode to interface up to four "game paddles" or two joysticks to the host computer. A similar circuit was used in the IBM PC. In the joystick interface circuit of the IBM PC, the capacitor © of the RC network (see Monostable Mode above) was generally a 10 nF capacitor. The resistor ® of the RC network consisted of the potentiometer inside the joystick along with an external resistor of 2.2 kilohms. The joystick potentiometer acted as a variable resistor. By moving the joystick, the resistance of the joystick increased from a small value up to about 100 kilohms. The joystick operated at 5V. Software running in the host computer started the process of determining the joystick position by writing to a special address (ISA bus I/O address 201h). This would result in a trigger signal to the quad timer, which would cause the capacitor © of the RC network to begin charging and cause the quad timer to output a pulse. The width of the pulse was determined by how long it took the C to charge up to 2/3 of 5 V (or about 3.33 V), which was in turn determined by the joystick position. Software running in the host computer measured the pulse width to determine the joystick position. A wide pulse represented the full-right joystick position, for example, while a narrow pulse represented the full-left joystick position. The LM555/NE555/SA555 is a highly stable controller capable of producing accurate timing pulses. With monostable operation, the time delay is controlled by one external resistor and one capacitor. With astable operation, the frequency and duty cycle are accurately controlled with two external resistors and one capacitor. It has High Current Drive Capability (200mA) with Adjustable Duty Cycle with a Temperature Stability of 0.005%/°C. The timing varies from µSec to Hours and turn off time Less Than 2µSec. The applications are Precision Timing, Pulse Generation, Time Delay Generation,Sequential Timing
INTRODUCTION
The 555 timer is an integrated circuit (chip) implementing a variety of timer and multivibrator applications. It was produced by Signetics Corporation in early 1970. The
original name was the SE555/NE555 and was called "The IC Time Machine". The 555 gets its name from the three 5-KΩ resistors used in typical early implementations. It is
widely used because of its ease to use, low price and reliability.It is one of the most popular and versatile integrated circuits which can be used to build lots of different circuits. It includes 23 transistors, 2 diodes and 16 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8) The 555 Timer is a monolithic timing circuit that can produce accurate and highly stable time delays or oscillations. The timer basically operates in one of the two modes—monostable (one-shot) multivibrator or
as an astable (free-running) multivibrator. In themonostable mode, it can produce accurate time delays from microseconds to hours. In the astable mode, it can produce rectangular waves with a variable duty cycle. Frequently,
the 555 is used in astable mode to generate a continuous series of pulses, but you can also use the 555 to make
BRIEF HISTORY
Introduced in 1971 by Signetics, the 555 is still in widespread use, thanks to its ease of use, low price, and good stability. It is now made by many companies in the original bipolar and also in low-power CMOS types. As of 2003, it was estimated that 1 billion units are manufactured every year. The IC was designed in 1971 by Hans R. Camenzind under contract to Signetics, which was later acquired by Philips. Depending on the manufacturer, the standard 555 package includes 25 transistors, 2 diodes and 15 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8). Variants available include the 556 (a 14-pin DIP combining two 555s on one chip), and the two 558 & 559s (both a 16-pin DIP combining four slightly modified 555s with DIS & THR connected internally, and TR is falling edge sensitive instead of level sensitive). There is no 557. The NE555 parts were commercial temperature range, 0 °C to +70 °C, and the SE555 part number designated the military temperature range, −55 °C to +125 °C. These were available in both high-reliability metal can (T package) and inexpensive epoxy plastic (V package) packages. Thus the full part numbers were NE555V, NE555T, SE555V, and SE555T. It has been hypothesized that the 555 got its name from the three 5 kΩ resistors used within, but Hans Camenzind has stated that the number was arbitrary Low-power versions of the 555 are also available, such as the 7555 and CMOS TLC555.[4] The 7555 is designed to cause less supply noise than the classic 555 and the manufacturer claims that it usually does not require a "control" capacitor and in many cases does not require a decoupling capacitor on the power supply. Such a practice should nevertheless be avoided, because noise produced by the timer or variation in power supply voltage might interfere with other parts of a circuit or influence its threshold voltages
PIN CONFIGURATION
The pin connections of the 555 timer are as follows:
Pin 1: Ground: All voltages are measured with respect to this terminal.
Pin 2: Trigger: The external trigger pulse is applied to this pin. The output of the timer is low if the voltage at this pin is greater than 2/3Vcc. If a negative going pulse of amplitude larger than 1/3Vcc is applied to this pin, the output of comparator 2 becomes low, which in turn makes the output of the timer high. The output remains high as long as the trigger terminal remains at low voltage.
Pin 3: Output: There are two ways a load can be connected to the output terminal — either between pin 3 and ground (pin 1) or between pin 3 and the supply voltage +V (pin 8). When the output is low, the load current flows through the load connected between pin 3 and pin 8 into the output terminal and is called the sink current. However, the current through the grounded load is zero. Therefore, the load between pin 3 and + is called “normally on load” and that connected between pin 3 and ground is called “normally off load”. On the other hand, when the output is high, the current through the load connected between pin 3 and +Vcc (“normally on load”) is zero. However, the
output terminal supplies current to the “normally off load”. This current is called the source current. The maximum value of sink or source current is 200 mA.
Pin 4: Reset: The 555 timer can be reset or disabled by applying a negative pulse to this
MODES
The 555 has three operating modes:
1. Monostable mode: in this mode, the 555 functions as a "one-shot" pulse generator. Applications include timers, missing pulse detection, bouncefree switches, touch switches, frequency divider, frequency divider, capacitance measurement, pulse-width modulation (PWM) and so on.
Astable: free running mode: the 555 can operate as an oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation and so on. Selecting a thermistor as timing resistor allows the use of the 555 in a temperature sensor: the period of the output pulse is determined by the temperature. The use of a microprocessor based circuit can then convert the pulse period to temperature, linearize it and even provide calibration means.
Bistable mode or Schmitt trigger: the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bounce-free latched switches
[attachment=65494]
Abstract
The Apple II microcomputer used a quad timer 558 in monostable (or "one-shot") mode to interface up to four "game paddles" or two joysticks to the host computer. A similar circuit was used in the IBM PC. In the joystick interface circuit of the IBM PC, the capacitor © of the RC network (see Monostable Mode above) was generally a 10 nF capacitor. The resistor ® of the RC network consisted of the potentiometer inside the joystick along with an external resistor of 2.2 kilohms. The joystick potentiometer acted as a variable resistor. By moving the joystick, the resistance of the joystick increased from a small value up to about 100 kilohms. The joystick operated at 5V. Software running in the host computer started the process of determining the joystick position by writing to a special address (ISA bus I/O address 201h). This would result in a trigger signal to the quad timer, which would cause the capacitor © of the RC network to begin charging and cause the quad timer to output a pulse. The width of the pulse was determined by how long it took the C to charge up to 2/3 of 5 V (or about 3.33 V), which was in turn determined by the joystick position. Software running in the host computer measured the pulse width to determine the joystick position. A wide pulse represented the full-right joystick position, for example, while a narrow pulse represented the full-left joystick position. The LM555/NE555/SA555 is a highly stable controller capable of producing accurate timing pulses. With monostable operation, the time delay is controlled by one external resistor and one capacitor. With astable operation, the frequency and duty cycle are accurately controlled with two external resistors and one capacitor. It has High Current Drive Capability (200mA) with Adjustable Duty Cycle with a Temperature Stability of 0.005%/°C. The timing varies from µSec to Hours and turn off time Less Than 2µSec. The applications are Precision Timing, Pulse Generation, Time Delay Generation,Sequential Timing
INTRODUCTION
The 555 timer is an integrated circuit (chip) implementing a variety of timer and multivibrator applications. It was produced by Signetics Corporation in early 1970. The
original name was the SE555/NE555 and was called "The IC Time Machine". The 555 gets its name from the three 5-KΩ resistors used in typical early implementations. It is
widely used because of its ease to use, low price and reliability.It is one of the most popular and versatile integrated circuits which can be used to build lots of different circuits. It includes 23 transistors, 2 diodes and 16 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8) The 555 Timer is a monolithic timing circuit that can produce accurate and highly stable time delays or oscillations. The timer basically operates in one of the two modes—monostable (one-shot) multivibrator or
as an astable (free-running) multivibrator. In themonostable mode, it can produce accurate time delays from microseconds to hours. In the astable mode, it can produce rectangular waves with a variable duty cycle. Frequently,
the 555 is used in astable mode to generate a continuous series of pulses, but you can also use the 555 to make
BRIEF HISTORY
Introduced in 1971 by Signetics, the 555 is still in widespread use, thanks to its ease of use, low price, and good stability. It is now made by many companies in the original bipolar and also in low-power CMOS types. As of 2003, it was estimated that 1 billion units are manufactured every year. The IC was designed in 1971 by Hans R. Camenzind under contract to Signetics, which was later acquired by Philips. Depending on the manufacturer, the standard 555 package includes 25 transistors, 2 diodes and 15 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8). Variants available include the 556 (a 14-pin DIP combining two 555s on one chip), and the two 558 & 559s (both a 16-pin DIP combining four slightly modified 555s with DIS & THR connected internally, and TR is falling edge sensitive instead of level sensitive). There is no 557. The NE555 parts were commercial temperature range, 0 °C to +70 °C, and the SE555 part number designated the military temperature range, −55 °C to +125 °C. These were available in both high-reliability metal can (T package) and inexpensive epoxy plastic (V package) packages. Thus the full part numbers were NE555V, NE555T, SE555V, and SE555T. It has been hypothesized that the 555 got its name from the three 5 kΩ resistors used within, but Hans Camenzind has stated that the number was arbitrary Low-power versions of the 555 are also available, such as the 7555 and CMOS TLC555.[4] The 7555 is designed to cause less supply noise than the classic 555 and the manufacturer claims that it usually does not require a "control" capacitor and in many cases does not require a decoupling capacitor on the power supply. Such a practice should nevertheless be avoided, because noise produced by the timer or variation in power supply voltage might interfere with other parts of a circuit or influence its threshold voltages
PIN CONFIGURATION
The pin connections of the 555 timer are as follows:
Pin 1: Ground: All voltages are measured with respect to this terminal.
Pin 2: Trigger: The external trigger pulse is applied to this pin. The output of the timer is low if the voltage at this pin is greater than 2/3Vcc. If a negative going pulse of amplitude larger than 1/3Vcc is applied to this pin, the output of comparator 2 becomes low, which in turn makes the output of the timer high. The output remains high as long as the trigger terminal remains at low voltage.
Pin 3: Output: There are two ways a load can be connected to the output terminal — either between pin 3 and ground (pin 1) or between pin 3 and the supply voltage +V (pin 8). When the output is low, the load current flows through the load connected between pin 3 and pin 8 into the output terminal and is called the sink current. However, the current through the grounded load is zero. Therefore, the load between pin 3 and + is called “normally on load” and that connected between pin 3 and ground is called “normally off load”. On the other hand, when the output is high, the current through the load connected between pin 3 and +Vcc (“normally on load”) is zero. However, the
output terminal supplies current to the “normally off load”. This current is called the source current. The maximum value of sink or source current is 200 mA.
Pin 4: Reset: The 555 timer can be reset or disabled by applying a negative pulse to this
MODES
The 555 has three operating modes:
1. Monostable mode: in this mode, the 555 functions as a "one-shot" pulse generator. Applications include timers, missing pulse detection, bouncefree switches, touch switches, frequency divider, frequency divider, capacitance measurement, pulse-width modulation (PWM) and so on.
Astable: free running mode: the 555 can operate as an oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation and so on. Selecting a thermistor as timing resistor allows the use of the 555 in a temperature sensor: the period of the output pulse is determined by the temperature. The use of a microprocessor based circuit can then convert the pulse period to temperature, linearize it and even provide calibration means.
Bistable mode or Schmitt trigger: the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bounce-free latched switches
![[Image: 555-block-diagram.jpg]](http://electronicsforu.com/wp-contents/uploads/2016/11/555-block-diagram.jpg)
![[Image: pin-configuration-555-timer-8-pin-dip.png]](http://electronicsforu.com/wp-contents/uploads/2016/11/pin-configuration-555-timer-8-pin-dip.png)