The aim of this presentation is to introduce the audience to the integrated circuit, The 555 timer.
First, a brief introduction and description.
Second, a brief description on how to count the pins of an IC and the functions of The 555 timer pins.
Finally, how to use this IC in Astable mode with two examples, flashing lights and siren.
2. It was invented by Hans Camenzind in “1971”
abdalrazak.zk@gmail.com 2
3. About of “The 555 Timer”
is sold every year
abdalrazak.zk@gmail.com 3
4. It can be used for many functions ,
most commonly for precision timing
ranging from microseconds to hours,
and
Insha’ Allah you will know how to do it.
Now let’s investigate its pins.abdalrazak.zk@gmail.com 4
6. the clocking mark
We start numbering from
the upper left pin
closest to the clocking
mark
abdalrazak.zk@gmail.com 6
The pins on an IC are numbered
counter-clockwise
starting with the upper left pin
closest to the clocking mark
8. You should first look
at the………..
Now, where is the first pin???
abdalrazak.zk@gmail.com 8
9. Now we can talk about The 555 Timer pins
and learn briefly the function of them
abdalrazak.zk@gmail.com 9
I think these pins are obvious
Control Voltage
You can override the internal
trigger circuit
Threshold
When the voltage
reaches a certain level
the timing cycle ends
This is the output
Reset
Applying a low voltage
to this pin will reset the timing
function and the output becomes low
Discharge pin
You connect a
capacitor to pin 7
Triggering pin
If you apply a low
voltage on this pin
you’ll trigger the
internal circuit
11. abdalrazak.zk@gmail.com 11
Generally, if you want to know the function o
an IC, its specification, and how to connect
it correctly you should look at its “Datasheet”
12. abdalrazak.zk@gmail.com 12
In the Astable mode, the 555 timer produces
a continuous stream of rectangular pulses having
a specified frequency.
If you want to have an Astable mode you should
connect “The 555 Timer” as shown in the next figure
17. abdalrazak.zk@gmail.com 17
First you should choose the value of the
capacitor according to the desired frequency
((0.01-0.001 uF for high frequency and
0.1-10 uF for low one))
Then you should choosing the value of R2
according to the desired Tlow by using
the equation number 2.
18. abdalrazak.zk@gmail.com 18
The last step is to determine the value of
R1 from the equation number 1
((The values of C1 and R2 are known, so
the only unknown variable is R1))