WHAT IS IC555
The 555
series is an integrated circuit (IC) or chip used in a variety of timer, pulse generation, and oscillatorapplications. The 555 can be used to provide time delays, as
an oscillator, and as a flip-flop
element. Derivatives
provide up to four timing circuits in one package.
Figure 1. Pins of IC555
The
functions of the pins:
Pin 1 is pin GROUND and pin is connected to ground.
Pin 2 is the TRIGGER, this pins use to start the 555
timer running. the timer starts when voltage on pin 2 drops to below 1/3
voltage. the output on pin 3 goes high, When the 555 is triggered via this pin.
Pin 3 is the OUTPUT pin. The output is either low,
which is very close to 0 V, or high, which is close to the supply voltage
that’s placed on pin 8.
Pin 4 is the RESET pin, this pin can be used to restart the 555’s timing
operation. Like the trigger input, reset is an active low input. Thus, pin 4
must be connected to the supply voltage for the 555 timer to operate.
Pin 5 is the CONTROL pin. In most 555 circuits,
this pin is simply connected to ground, usually through a small 0.01 μF
capacitor to level out any fluctuations in the supply voltage that might affect
the operation of the timer.
Pin 6 is called the THRESHOLD. The purpose of this pin is
to monitor the voltage across the capacitor that's discharged by pin 7. When this
voltage reaches 2/3 of voltage (Vcc), the timing cycle ends, and the output on
pin 3 goes low.
Pin 7 is called the DISCHARGE. This pin is used to
discharge an external capacitor that works in conjunction with a resistor to
control the timing interval.
Pin 8 is connected to VCC the positive voltage. This voltage
must be 4.5 V and max 15 V.
SOURCE http://en.wikipedia.org/wiki/555_timer_IC
Figure 2. real 1C555
DATASHEET
we can donwload and check the specification of this component from
One of schematic diagram listing on datasheet is shown in here.
Figure 3. Schematic diagram of IC555
The
555 has three operating modes:
MONOSTABLE mode:
MONOSTABLE mode:
In MONOSTABLE mode, the 555 functions as a
"one-shot" pulse generator. Applications include timers, missing
pulse detection, bouncefree switches, touch switches, frequency divider,
capacitance measurement, PULSE-WIDTH MODULATION (PWM) and so
on.
Figure 4. IC555 in Monostable Mode
In
ASTABLE mode or 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.
The 555 can be used as a simple ADC, converting an analog value to a pulse
length. E.g. 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 TRIGER: 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.
Figure 5. IC555 in Bistable Mode
This is dummy text. It is not meant to be read. Accordingly, it is difficult to figure out when to end it. But then, this is dummy text. It is not meant to be read. Period.
ConversionConversion EmoticonEmoticon