Author Topic: what can eight 8 input NANDs do that an octal latch can't?  (Read 2656 times)

kvb

what can eight 8 input NANDs do that an octal latch can't?
« on: July 31, 2007, 05:31:35 PM »


bigger pic in the gallery http://aronnelson.com/gallery/kvb

right board is a LM317, 9v, 5v, power supply
--------------------------

OK, first of all the circuit in the pic works.  It's a one of 8 switcher

Thanks to Soul Sonic for the 4 way switcher drawing - this is the 8 way NAND craziness.

Maybe I should just get an octal latch as per R.G.'s solution. I went with the NANDs because they are not too hard to figure out.
I do not understand how the octal latch works - plus, it's $7

The only problem with all of these NANDs is all of the connections and wires.
When I build this, I'll be using wire, but I'll probably change the layout to having the NANDs side by side instead of end to end.

This circuit uses cd4050 non-inverting ( "is" gates? ) for debouncing.  This came from RG's drawing

cd4068 8 input NANDs

at the top are the cd4044 S/R latches - these will control cd4066 switches

I'm serious about the question - I know it's  up to me to figure it out, but does this set-up have any advantages over the octal latch?
« Last Edit: July 31, 2007, 05:48:56 PM by kvb »

~arph

Re: what can eight 8 input NANDs do that an octal latch can't?
« Reply #1 on: August 13, 2007, 10:08:02 AM »
Yeah I think this one mixes better with the carpet  ;D

..sorry

CGDARK

Re: what can eight 8 input NANDs do that an octal latch can't?
« Reply #2 on: August 13, 2007, 10:35:55 AM »
Maybe I should just get an octal latch as per R.G.'s solution. I went with the NANDs because they are not too hard to figure out.
I do not understand how the octal latch works - plus, it's $7

I don't know where you buy, but the 74c373 octal latch don't cost $7.00.

Check this:
http://www.mouser.com/search/refine.aspx?Ntt=74c373

http://www.jameco.com/webapp/wcs/stores/servlet/KeywordSearchResultView?langId=-1&storeId=10001&catalogId=10001&searchType=k&searchValue=74c373&categoryId=104235&rscount=2

BTW, you can replace it with a cheaper one like the 74hc373 and 74hct373.

Check this:
http://www.mouser.com/search/refine.aspx?Ntt=74hc373

http://www.jameco.com/webapp/wcs/stores/servlet/KeywordSearchResultView?langId=-1&storeId=10001&catalogId=10001&searchType=k&searchValue=74hc373&categoryId=104245&rscount=2

CG

R.G.

Re: what can eight 8 input NANDs do that an octal latch can't?
« Reply #3 on: August 13, 2007, 11:11:37 AM »
Quote
I'm serious about the question - I know it's  up to me to figure it out, but does this set-up have any advantages over the octal latch?
Uses up all that excess board space?
Keeps you occupied longer building it?
Helps you maintain your debugging skills?

The short answer is "no". They do the same thing in this application.

Notice that a midrange PIC costs about $2.50 in ones, less than that in quantity. If you're looking at $7 a chip for any low speed logic, it's cheaper with a PIC. A PIC would do this job in a bang-up way.

However, both Mouser and Digikey list the 74C373 for $3.89, in stock in both places.
R.G.

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