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simple logic circuit Answered

uuhhh..I'm not really sure about this..
i'm an electronics engineering student
and my instructor in Logic Circuit and Switching Theory
requires us to make a project which will include logic gates.

now i searched in the net for some ideas
i found two..but i know i shouldn't copy their projects..
can anyone help me?


thanks guys!


we have to use those logic gates. our instructor in Logic circuit and switching theory told us to use ICs but when we asked for an advice from another instructor he told us that we should make our own logic gate since it's impractical to use ICs if (for example) we only need to use one inverter gate, if we would buy one Hex inverter IC then its like buying 6 logic gates!

Your second instructor is whacked. The hex inverter has 6 gates, but it will typically cost less than the parts to "build" a single inverter from scratch.

Your instructor may have meant that if you build something that only takes a single inverter, you're not going to get full credit unless you make it worth his while. Kinda like how a circuit consisting of a single diode could be OK for an electronics class, but only if you were to build the diode yourself! :-)

I agree and the CMOS # 4000 - Dual 3-Input NOR Gate and Inverter or the # 4002 - Dual 4-Input NOR Gate OR Gate are Duals.


10 years ago

Sooo many choices. Let's approach it from another direction - do you have any hobbies that you'd like to add a little automation to?


10 years ago

More suggestions:
  • a clock. Not so original, but try one of the "interesting" display formats that have been done or mentioned on Instructables.
  • dice. Ditto on not original, but how about dice with more than 6 "sides" (gamer dice!) For extra credit, have the max count be an input via switches of some kind.
  • TV display. While a full "TV typewriter" is probably too complex, you might be able to do something that blinks a computer monitor through its several possible colors (full screen of color each time.)


10 years ago

So do you have to build something out of your "basic" logic gates (and, or, not), or do you get to use the more complicated chips that are available in "logic" families like flip-flops, shift registers, counters, and so on?

yeah yea..i mean we have to build something (a circuit) example: 1. intruder alarm/alert 2. phone in use indicator 3. countdown timer but they have been made before! we need a UNIQUE one.. :(

Ask if anyone's made a traffic light set with pedestrian crossing, the timimg etc is so simple and you only need one input and three outputs...

i think somebody made a traffic light already..
but no pedestrian crossing.. waw!
you're a genius.. :)
thanks more suggestions please.. :)

The program's dead easy, for a simple crossing it's just. - output 1 on (the green light output) - input 1 on? - Output 2 on (amber) - wait 30 (count is in tenths of seconds) - outputs 1, 2 off output 3 on - wait 150 (fifteen seconds is just random, however long it should be) - output 2 on - wait 30 - output 2 off, output 1 on That may be wrong but that's the general gist of it to add crossing lights you need two more outputs, there aren't too many commands either, we used a random program so language may change...

Oh there are lots of things that could be conceived: anything that requires a choice: coin sorting, fish tank temp regulator, monitor brightness adjustment (depending on the ambient light in the room), etc.

one good thing to build out of logic gates is ... bigger logic gates. Adders, flip-flops, assorted encoders or decoders from basic gates. Shift registers or counters (led sequencers) from flip flops. Digital clocks from counters. (oops; that's almost an application.) Other ideas: "game show" circuit, digital lock...

yes! of course a circuit using encoders, decoders, half adders, full adders

Or: it's possible to build any other logic gate out of only NAND or NOR gates. Actually doing so might be interesting and educational... (for instance, an inverter is a nand with its input connected together, and an "AND" is a NAND followed by an inverter, etc...)