Key Stage 3-4
555 ic
Using a (555 IC) as a Monostable / Astable Circuit
Live Wire / PCB Wizard - (555 IC) Circuit
555 IC
RA Moffatt
555 ic
555 IC
(555 IC) Circuit
555 IC
WALT
We
Are
Learning
To
This is because ..
Electronics
Understand the concept of a 555IC,
Integrated Circuit.
Use Live Wire / Crocodile Technology
software to construct the electronic
circuit diagram.
We can learn how to use digital
electronic circuits which provides
opportunities for a range of systems
that control timing, flashing effects, etc.
for different applications in project work.
Remember to:
• refer to the Potential Divider principle
• Black Box 555IC
Using the 555 IC Integrated Circuit as a
Monostable Timer:
You will have an opportunity to:-
Design/Model an electronic circuit (Monostable Timer)
using the 555 (IC) Integrated Circuit using Live Wire /
Crocodile Clips / Technology;
Listen to the AVI files (38) and (44) and explain how
each of these circuits work?
Manufacture & Test the PCB printed circuit board.
Circuit (38) will keep the Light ‘off’ for a set-time;
Circuit (42) will keep the light ‘on’ for a set-time.
Using the 555 IC Integrated Circuit in
Astable mode:
You will have an opportunity to:Design/Model an electronic (Astable) circuit (44)
using the 555 (IC) Integrated Circuit using Live Wire /
Crocodile Clips / Technology;
Model and test this circuit using a breadboard;
Manufacture & Test the PCB printed circuit board.
Circuit (44) will switch the Light / LED ‘on’ and ‘off’
intermittently.
555 Pin Connections
0 Volts
1
8
+ve (4.5 – 16V)
Supply Voltage
Trigger
2
7
Discharge
Output
3
6
Threshold
Reset
4
5
Control Voltage
555 IC Circuit Monostable ‘Off for a Time’
8
4
7
3
6
2
1
5
Circuit (38) 112 Working Circuits
Using a 555 IC as a Monostable:
555 timer is configured as a Monostable circuit.
This means when the IC is triggered, the output (pin 3) will go high
(9V) for a pre-determined time i.e. the LED is unlit. Output pin 3 will
then return low, (0V), and remain in this condition until re-triggered.
How circuit is triggered:
Consider PTM switch is open, the voltage at bottom of R2 is 9V
(connection also to pin 2).
When PTM switch is closed the voltage on pin 2 will drop to 0V, and if
immediately released the voltage will again jump to 9V i.e. a negative
pulse has been produced. This negative pulse applied to pin 2,
triggers the IC, and the output (pin 3) goes high for a period that can
be set by theVR1, C1 combination
555 IC Circuit Monostable ‘Off for a Time’
8
4
7
3
6
2
1
5
Circuit (38) 112 Working Circuits
Calculating the Time Delay:
For the 555 timer IC the delay time is given by the
equation –
t = 1.1 x C x R
R = 470 k Ohms
= 470 000 Ohms
t = 1.1 x 470 000 x 0.0001
t = 51.7 seconds
C = 100 micro Farads
= 0.0001 Farads
555 IC Circuit Monostable ‘Off for a Time’
Applications: Egg Timer / Chess Timer Press-ups Timer etc.
555 IC Circuit Monostable Touch-Timer ‘On for a Time’
8
4
7
3
6
2
1
5
Touch Contacts
Circuit (42) 112 Working Circuits
555 IC Circuit Monostable Touch-Timer ‘On for a Time’
8
4
7
3
6
2
1
5
Touch Contacts
Circuit (42) 112 Working Circuits
555 IC Circuit Monostable Touch-Timer ‘On for a Time’
Circuit (42) 112 Working Circuits
555 IC Circuit: Astable
Circuit (44) 112 Working Circuits
555 IC Circuit: Astable
Circuit (44) 112 Working Circuits
555 IC Circuit: Astable
http://www.williamson-labs.com/480_555.htm
Frequency of the Astable Timer:
The frequency of the 555 timer IC can be calculated as
shown:
f = 1.44
R1
R1K
(R1 + 2 R2)C1
R2
68K Ohm
f = 1.44
f = 1000 + 2 x 68000) x 0.00001
C1
f = 1.44
1.37
f = 1.05 hz approximately one flash per second.
10 uF
555 IC Circuit: Astable
Circuit (44) 112 Working Circuits
555 IC Circuit: Astable
Components:
• 555 IC
• 270 ohm resistor
from +9v to the
collector of the NPN
transistor.
• Two 1K resistors
• One NPN transistor
(try any alternative).
• One 100K preset
resistor.
• One 47uf capacitor
• Black and red wire.
• One LED
555 IC Circuit: Monostable – Game/s Timer
NPN
Transistor
NPN Transistor turns-off when the voltage at the base is greater than 0.6 Volts
555 IC Circuit: Monostable – Game/s Timer
NPN Transistor turns-on when the voltage at the base is less than 0.6 Volts
555 IC Circuit: Monostable – Astable (Display Stand)
Monostable
Astable
SW 1 pressed motor ‘on’ for a time ‘off’ then ‘on’ ‘off’ etc.
555 IC Circuit: Monostable – Astable (Display Stands)
Suggested GCSE Projects / Theme (Display Stands – Shop Windows)
Using Electronic / Mechanical Systems
555 IC Circuit: Motor Speed Control Mark_Space
Circuit (87) 112 Working Circuits
555 IC Circuit: Motor Speed Control Mark_Space
555 IC
555 Timer
Projects
Suggested Key Stage 3 Project:
Aroma Fan
Ideas for the box top
Butterfly / Ladybird
Motor ‘on’ for a set time, fan blows air through scented petals into the room
Typical Project applications for a 555 IC: Monostable:
Astable:
Aroma Fan
Shaky Hand Game
Bicycle Hazard Lights
Bicycle Indicators
Egg Timer, Telephone Timer, Game / Chess Timer etc.
Burglar Alarm
Electronic Dice
Sensitive Touch Switch
A Child’s mini electric organ
Simple Siren
Bleeper circuit
Random Number Generator etc, etc..
Monostable Circuit
•
•
•
•
NOR gate Monostable
2
5
3
6
1b
Switch is pressed, potential at pin 2 is 5V (logic 1).
Assuming that pin 3 (output of IC 1b) is at 0V.
Output (pin 1) will switch from logic 1 to logic 0.
Voltage change is transmitted instantly by the capacitor, making
pins 5 & 6 change to logic 0, causing the output pin 4 to change
state from logic 0 to logic 1 and the LED to switch on.
Monostable Circuit
NOR Gate
Monostable Circuit
NOR Gate
Dark Detector:
It will sound an alarm if it gets
too dark. For example, this
circuit could be used to notify
when a lamp (or bulb) burns
out. The detector used is a
regular cadmium-sulphide
Light Dependent Resistor or
LDR, for short, to sense the
absence of light and to
operate a small speaker. The
LDR enables the alarm when
light falls below a certain level
http://www.uoguelph.ca/~antoon/gadgets/555/555.html
Tilt Switch:
Actually really a alarm circuit, it
shows how to use a 555 timer and
a small glass-encapsulated
mercury switch to indicate 'tilt'.
The switch is mounted in its normal
'open' position, which allows the
timer output to stay low, as
established by C1 on start-up.
When S1 is disturbed, causing its
contacts to be bridged by the
mercury blob, the 555 latch is set
to a high output level where it will
stay even if the switch is returned
to its starting position. The high
output can be used to enable an
alarm of the visual or the audible
type. Switch S2 will silent the alarm
and reset the latch. C1 is a ceramic
0.1uF (=100 nano-Farad) capacitor
Metronome:
A Metronome is a device
used in the music
industry. It indicates the
rhythm by a 'toc-toc'
sound which speed can
be adjusted with the 250K
potentiometer. Very handy
if you learning to play
music and need to keep
the correct rhythm up
Ten-Minute Timer:
Can be used as a time-out
warning for Ham Radio.
The Federal
Communications
Commission (FCC)
requires the ham radio
operator to identify his
station by giving his callsign at least every 10
minutes. This can be a
problem, especially during
lengthy conversations
when it is difficult to keep
track of time. The 555 is
used as a one-shot so that
a visual warning indicator
becomes active after 10minutes. To begin the
cycle, the reset switch is
pressed which causes the
'Green' led to light up.
After 10 minutes, set by
the 500K potentiometer
R1, the 'Red' led will light
to warn the operator that
he must identify
A view inside the 555 IC / Black Box
Useful Electronic Web-Sites:
http://www.interq.or.jp/japan/se-inoue/e_menu.htm
http://users.pandora.be/educypedia/electronics/circuitsbysubject.htm
http://www.uoguelph.ca/~antoon/gadgets/555/555.html
http://home.maine.rr.com/randylinscott/learn.htm
http://skyscraper.fortunecity.com/plug/587/index.html
http://ourworld.compuserve.com/homepages/Bill_Bowden/homepage.htm
http://555-timer.clarkson-uk.com/projects/
http://en.wikipedia.org/wiki/555_timer_IC
Acknowledgement:
Thanks to Maurice Lynch (WELB) for use of his excellent and invaluable
112, Circuits resource in this presentation.
Raymond Moffatt.