Shopping List: Experiments 16 Through 24
150 Chapter 4
Here’s your chip list:- 555 Timer. STMicroelectronics SA555N, Fairchild NE555D, RadioShack
TLC555, or similar. Do not get the “CMOS” version of this chip, or any fancy
versions such as those of high precision. Buy the cheapest you can find.
Quantity: 10. The chip in Figure 4-2 is a 555 timer. - Logic chips types 74HC00, 74HC02, 74HC04, 74HC08, 74HC32, and 74HC86.
Actual part numbers could be M74HC00B1, M74HC02B1, M74HC04B1, and
so on, by STMicroelectronics, or SN74HC00N, SN74HC02N, SN74HC04N,
and so on, by Texas Instruments. Any other manufacturers are acceptable. - Remember, each part number should have “HC” in the middle of it, and
you want the DIP or PDIP package, not surface-mount. Quantity of each:
At least 4. - 4026 Decade Counter (a chip that counts in tens). Texas Instruments CD-
4026BE or similar. Quantity: 4 (you’ll need 3, but because this is a CMOS
chip sensitive to static electricity, you should have at least one in reserve).
Any chip with “4026” in its part number should be OK. - 74LS92 counter chip, 74LS06 open-collector inverter chip, and 74LS27
triple-input NOR chip. Quantity: 2 of each. Note the “LS” in these part
numbers! There will be one experiment in which I want you to use the LS
generation instead of the HC generation.
IC sockets
I suggest that you avoid soldering chips directly onto perforated board. If
you damage them, they’re difficult to remove. Buy some DIP sockets, solder
the sockets onto the board, and then plug the chips into the sockets. You
can use the cheapest sockets you can find (you don’t need gold-plated con-
tacts for our purposes). You will need 8-pin, 14-pin, and 16-pin DIP sockets,
such as parts 276-1995, 276-1999, and 276-1998 from RadioShack. See Fig-
ure 4-5. Quantity of each: 5 minimum.
Low-power LEDs
The logic chips that you’ll be using are not designed to deliver significant
power. You’ll need to add transistors to amplify their output if you want to
drive bright LEDs or relays. Because adding transistors is a hassle, I suggest
an alternative: Special low-power LEDs that will draw as little as 1mA, such
as the Everlight model T-100 Low Current Red, part number HLMPK150.
Figure 4-6 shows a size comparison with a regular 5mm LED. Quantity: 10
(at a minimum).
LED numeric displays
In at least one of our projects, you’ll want to illuminate some seven-segment
LED numerals. You’ll need either three individual numerals, or one package
containing three numerals, such as the Kingbright High Efficiency Red Dif-
fused, part number BC56-11EWA, which will be specifically referred to in
schematics in this book. If you buy a different seven-segment display, it must
be an LED with a “common cathode.” (Don’t buy liquid-crystal LCD numer-
als; they require different electronics to drive them.) If you have a choice of
power consumption, buy whichever product consumes the least current.
See Figure 4-7.
Figure 4-5. When you’re soldering a circuit
onto perforated board, sockets eliminate
the risk of overheating integrated circuit
chips and reduce the risk of zapping them
with static electricity, and enable easy
replacement.
Figure 4-6. An HC series logic chip is rated
to deliver only 4mA at each pin. This is
inadequate to drive a typical 5 mm LED
(right), which is rated for 20mA forward
current. Miniature, low-current LEDs (left)
will use as little as 1mA in series with a
suitable resistor, and are ideal for test cir-
cuits in which you want to see the output
with a minimum of hassle.
Figure 4-7. Seven-segment displays are the
simplest way to show a numeric output
and can be driven directly by some CMOS
chips. For finished projects, they are
typically mounted behind transparent red
acrylic plastic panels.