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555 timer
555 timer;
- What is the 555 timer?
- Pin configurations of the 555 timer ;
- 555 timer in astable operation ;
- 555 timer in monostable operation ;
- What are the 555 timer applications?
555 Timer;
The 555 timer is one of the most remarkable
integrated circuits ever developed. It comes in
a single or dual package and even low power
cmos versions exist - ICM7555.
Common part numbers are;
LM555, NE555, LM556, NE556.
Pin configurations
The 555 timer consists of;
two voltage comparators
a bi-stable flip flop
a discharge transistor
and a resistor divider network.
555 timer in astable operation ;
555 timer in monostable operation ;
Applications using 555 timer;
- Random Flashers ;
- A light dimmer ;
- A car tachometer ;
- Traffic Lights ;
- Infra Red (IR) remote control ;
Random' Flasher for 8 LEDs Project'
What is a light dimmer?
A light dimmer is a means of controlling the
"brightness" level of a lamp
For the light dimmer to work the 555 timer
is configured as a "variable cycle", astable
oscillator running some where around 300
Hz.
What is a car tachometer?
A tachometer is simply a means of
counting the engine revolutions of an
automobile engine.
In this suggested idea a NE555 timer is
configured as a monostable or one shot.
The period of the 555 timer for our car
tachometer is determined by the resistor from
the 9V regulated supply to pin 7 (50K) and the
capacitor from pin 6 and ground (0.1 uF). Time
"T" = 1.1 RC or 1.1 X 50,000 X 0.1 X10 6 = 0.0055 or 5.5 mS (milli-seconds).
Extra:
Supply is taken from the 12V automobile
system and for the NE555 timer car
tachometer is reduced to a regulated 9V by the
15 ohm resistor in conjunction with the 9V
zener diode. Note that the 10 uF polarised
capacitor must be placed physically as close
as possible to the supply pin 8. It is depicted in
the schematic diagram in this manner purely
for clarity.
Traffic Light
The time taken for the complete red - red & amber - green – amber
sequence can be varied from about 7s to about 2½minutes
by adjusting the 1M preset.
IR Remote Control
We know that if we want to calculate charging, discharging
time and the frequency, we will use these equs.
http://ourworld.compuserve.com/homepages/Bill_Bowden/555.htm
Questions
If you ask or even try