[Newbie] : I randomly bought these IC's. Can I do some projects as a complete beginner?

Thread Starter

babaliaris

Joined Nov 19, 2019
44
To tell you the truth I don't even remember digital circuits theory, how a half adder works, how flip flops work, counters, shifters, etc. I used to knew all of these stuff + VHDL but I forgot everything! It's time to start reading again, I have all the books.

But besides that, can I do some cool projects starting with these IC's? I also just started with analog circuits, so in 2 or 3 days I will have a breadboard and a mix of components with different values (resistors, capacitors, diodes, LEDs, transistors, jumper cables).

Can I make Christmas LEDs with these :p


InkedIMG_20191120_022814_LI.jpg
 

panic mode

Joined Oct 10, 2011
1,815
.. or only with with NOR gates.
requirements for that using only one kind of gate is simple:
1. need more than one input per gate (so inverters are not as versatile)
2. gate also must have a built in inverter

gates that meet the criteria are NAND and NOR
 

panic mode

Joined Oct 10, 2011
1,815
you can use those to make astable multivibrator (clock generator) and either shift register or counter and decoder. beware that those are different families (LS and HC) to watch for mixing them. and HC are CMOS so watch for ESD...
 

panic mode

Joined Oct 10, 2011
1,815
to create 4-channel chasing circuit you can use:
1x 7400 as oscillator (with complementary outputs... this is bit0)
1x 7400 as T-flipflop (counter used as freq. divider... this is bit1)
1x 7400 as decoder (gives 1-of-4 output based on previous two bits)
 
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ci139

Joined Jul 11, 2016
1,170
first thing to test is if they appear to be operational (all gates)

for that

• if a PULL-UP or a PULL-DOWN MOS-Fet is faulty(shorted) -- then, when you Open the not faulty Mosfet it'll short your supply =
(-1-) /!\ use Fuse or current limitter /!\ (current should usually be limitted to equal below 50 or 60 mA )
(-2-) multiple check your polarity = that Vcc or Vdd is greater than Vee or Vss
. . . . . & that The Vcc/Vdd goes to iC-s [+] Supply INP & Vee/Vss to [–] INP - - - it may sound stupid but the things "fry" fast under wrong polarity

about a 1 way to setup a test : YouTube
 

Thread Starter

babaliaris

Joined Nov 19, 2019
44
Well, first of all, I need to re-read the theory so I'll be able to know what I'm doing. :p

From what I remember, first we would design the logic using some function values or something, then we would reduce the complexity of the function using a method that looked like division and after that step we where actually able to draw a design plan which shows how to connect all the cables and the IC together to achieve what you want.

Ahh, step two is named Karnaugh maps. Well, I need to revise all of these. But from what I remember from logic design 2, the fun part begins when you combine shifters, counters, and custom logical circuits.
 

dl324

Joined Mar 30, 2015
9,956
I forgot everything!
Did you remember that 74HC are static sensitive and need to be handled accordingly? Also pay attention to input and output voltage swing when trying to interface different logic families. 74LS outputs are only guaranteed to be 2.7V for a HIGH. 74HC inputs require at least 3.15V for a HIGH.
 

Analog Ground

Joined Apr 24, 2019
305
.. or only with with NOR gates.
requirements for that using only one kind of gate is simple:
1. need more than one input per gate (so inverters are not as versatile)
2. gate also must have a built in inverter

gates that meet the criteria are NAND and NOR
What about exclusive-nor (XNOR)? Meets 1) and 2) but is it "logically complete"?
 

Analog Ground

Joined Apr 24, 2019
305
Give it a try and see for yourself. Try to do an AND or OR with XOR or XNOR. If you figure out how to do it without cheating (open drain outputs), you'll be famous.
I presented XNOR as counter to the quoted post and formed it as a question to stimulate thought. Apparently it only produced a challenge and belittlement. XNOR is not logically complete and I will remain not famous.
 

ci139

Joined Jul 11, 2016
1,170
Can I make Christmas LEDs with these
yes , you can
________________________

one thing - that looks like a disease in digital world - is using digital gates for oscillators ...

Why not-s ::

  • digital discrete logic gates are designed for discriminated-quantized signal levels
  • digital discrete logic gates use/dissipate most energy at the HL LH transitions
    in other worlds when their state has not settled to a quantized level
  • digital discrete logic gates use usually little power - but they have a high power output potential (for the quantized levels to be firm)
    /// basically there are few oscillator designs that do somewhat "fit in" to ↑such↑ characteristics . . . but there is CMOS 555 and an "endless" variety of other commercial and custom timers that suit the task better = not exhaustively draining your battery just because you wanted a CLK signal . . .
________________________

another issue is you got fixed supply 74LSxx TTL-Schottky circuits with voltage levels not compliant with the wide supply range 74HCxx CMOS Gates

there are options if you want to make a mixed design :

  1. use logic level converters /// either on-chip or custom ← makes the design layout fuzzy as there will be a converter at each change in between the TTL and CMOS
  2. use resistive level shifters /// slows down the performance -- coz CMOS may lack power to fast drive the "fast" resistive level shifter + introduces the issue as with logic gate oscillators -- that the voltage levels degrade from "discrete"
_________________________

SUM :: the digital iC-s are quite cheap - so make the circuits consisting of the one family only . . . using dedicated timer chips or circuits
 

MrChips

Joined Oct 2, 2009
20,161
Read the spec sheets of 74HCxx family and 74LSxx family and compare.
In particular, make a note of range of supply voltage and guaranteed input and output voltages.

Don't mix the two families.
 

SamR

Joined Mar 19, 2019
1,787
Try and get your hands on a couple of the old classics, TTL Cookbook and CMOS Cookbook. You might even find their PDFs online.
 

ci139

Joined Jul 11, 2016
1,170
...the fun part begins when you combine shifters, counters...
when you have shift reg.-s and counters lying around and decent "pin board space" avail then you may hit a random peculiar function
otherwise
you define what you want to achieve ...

... and whatever you want to achieve is likely best done without too many digital chips -- that is because :

  1. Logic gates are not good LED drivers -- except such as 74HC14 or 74LVC07 / sn74ls07 , etc.
  2. OpAmps and comparators allow greater flexibility × robustness = lesser parts
  3. . . . there simply won't be too many pure logical functions required -- that , unless you go to digital synthesis -- but then it's better to use MCU-s
  4. ? hwo's gonna build/test/debug a large prototype prj.

... and seek a time/$/component_count optimum
 

SamR

Joined Mar 19, 2019
1,787
Yes well, some people actually like messing around with antiques such as vacuum tubes and TTL logic chips.
 
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