Making a Shift Register

Hi -

I am trying to make a shift register using NOR Gates. I have been given multiple HD74LS02P Quad 2-Input Positive NOR Gates, LED lights, resistors, a breadboard and an Arduino UNO.

I have been trying to do this for a long time now, but I don't think I really understand how it works (the flip flop, shift register), and I'm kind of lost as to what to do to start.

Thanks,
Bob Duko

So....essentially, you're asking us to give you a course in digital logic? Did, whomever tossed these components at you, also include a book?

START BY MAKING A FLIP FLOP. Sounds like a lab assignment to me. When I first studied electronics we had to make all our own digital circuits out of discrete components. Try making the flip flop out of transistors. Not old enough to have made them out of vacuum tubes.

There was a Nuts and Volts article, in the July 2009 issue, about a digital clock made exclusively from transistors (194 of them to be exact). Talk about discrete dedication!

It's now a kit: http://store.nutsvolts.com/product.php?productid=16865&cat=407&page=1

So, Bob, be grateful they didn't hand you Transistors

Good suggestion.

Would doing it in software on the Arduino board be considered cheating? :o)

Absolutely!

You learn more doing it the hard way - you retain the knowledge. Unlike software, you tend to forget how you did it unless you heavily document your program. Besides breadboards make it much easier - unlike the days when you use to have to actually do wiring and soldering to make a prototype. Now it is just plug in and use jumper wires.

Here's a Digital Circuits tutorial that looks pretty good;

http://www.asic-world.com/digital/tutorial.html

And this one, at least, shows how to use NOR gates to make a flip flop:

http://www.allaboutcircuits.com/vol_4/index.html

And if you get to that stage, I've yet to find anything that beats BatchPCB.com for one-off (or just small quantity) prototypes (for the hobbyist, because there is no guarantee of quick turn-around -- though, the service is so popular the turn around is currently excellent).

And DipTrace (diptrace.com) is _very_ "easy" PCB designing software (I mean, as easy as it gets, 'cuz designing a PCB is always going to be fairly complex). And there is a FREE full-featured (300 pin limit) version of DipTrace!

Eagle trace is also free, but it uses the old CAD/CAM paradigm, and unless you're used to that, there are at least two learning curves, the interface, and the technique.

Actually there's even a free 500 pin non-profit license if you register on DipTrace's website.