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Integrated Circuits are usually called
ICs or chips.
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Chip
holders (DIL sockets) |
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| ICs
(chips) are easily damaged by heat when soldering
and their short pins cannot be protected with a
heat sink. Instead we use a chip holder, strictly
called a DIL socket (DIL = Dual In-Line), which
can be safely soldered onto the circuit board. The
chip is pushed into the holder when all soldering
is complete.
Chip holders are only needed
when soldering so they are not used on
breadboards. |
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Removing
a chip from its holder
If you need to remove
a chip it can be gently pressed out of the holder
with a small flat-blade screwdriver. Carefully lever
up each end by inserting the screwdriver blade
between the chip and its holder and gently twisting
the screwdriver. Take care to start lifting at both
ends before you attempt to remove the chip,
otherwise you will bend and possibly break the pins.
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Static
precautions |
Many
ICs are static sensitive and can be damaged when
you touch them because your body may have become
charged with static electricity, from your clothes
for example. Static sensitive ICs will be supplied
in antistatic packaging with a warning label and
they should be left in this packaging until you
are ready to use them.
It is usually adequate to earth
your hands by touching a metal water pipe or
window frame before handling the IC but for the
more sensitive (and expensive!) ICs special
equipment is available, including earthed wrist
straps and earthed work surfaces. You can make an
earthed work surface with a sheet of aluminum
kitchen foil and using a crocodile clip to connect
the foil to a metal water pipe or window frame
with a 10kΩ resistor in series. |
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The
555 and 556 Timers |
| The
8-pin 555 timer chip is used in many projects, a
popular version is the NE555. Most circuits will
just specify '555 timer IC' and the NE555 is
suitable for these. The 555 output (pin 3) can
sink and source up to 200mA. This is more than
most chips and it is sufficient to supply LEDs,
relay coils and low current lamps. To switch
larger currents you can
connect a transistor.
The 556 is a dual version of the
555 housed in a 14-pin package. The two timers (A
and B) share the same power supply pins.
Low power versions of the 555
are made, such as the ICM7555, but these should
only be used when specified (to increase battery
life) because their maximum output current of
about 20mA (with 9V supply) is too low for many
standard 555 circuits. The ICM7555 has the same
pin arrangement as a standard 555. |
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| A PIC is a Programmable
Integrated Circuit micro controller, a
'computer-on-a-chip'. They have a processor and memory
to run a program responding to inputs and controlling
outputs, so they can easily achieve complex functions
which would require several conventional ICs.
Programming a PIC micro controller may
seem daunting to a beginner but there are a number of
systems designed to make this easy. The PIC system is an
excellent example because it uses a standard computer to
program (and re-program) the PICs no specialist
equipment is required other than a low-cost download
lead. Programs can be written in a simple version of
BASIC or using a flowchart. The PIC programming software
and extensive documentation is available to download
free of charge, making the system ideal for education
and users at home. For further information
If you think PICs are not for you
because you have never written a computer program,
please look at the PIC system! It is very easy to get
started using a few simple BASIC commands and there are
a number of projects available as kits which are ideal
for beginners. |
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