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Topic: IC Logic Gates  (Read 436 times) previous topic - next topic

CrossRoads

I think the switch can be imagined to be whatever, as long as it opens & closes.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

MarkT

So when the switches are "on" you have logic-low and when the switches are off you have "logic high".

With 74 series chips an open is high.   But it's still standard-practice to use pull-up resistors.
No, 74LS series require 10k pullups on any high input, and inputs should not be wired to
5V directly.  Low inputs can be strapped to 0V.

But first why 74LS family?  They are decades old and obsolete in modern design.  The 74HC series
is the go-to general purpose logic family these days, and are CMOS, not TTL.  74HC inputs can be directly
connected to the 5V rail.  Still will need pullups or pulldowns for switch inputs, but the resistor value is not
very critical.

74HC series are more flexible, can be powered from 2 to 6V.  74LS must have a 5.0V supply.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

sterretje

OP might have gotten them cheap. And for building experience with logic gates, there is not much wrong with the LS family.
If you understand an example, use it.
If you don't understand an example, don't use it.

Electronics engineer by trade, software engineer by profession. Trying to get back into electronics after 15 years absence.

Paul__B

That is certainly true!

"Building experience" it is.  Building something useful - no!  :smiley-cool:

ReverseEMF

So how it is wired?


FYI 2: The LED in the first example is backwards.
"It's a big galaxy, Mr. Scott"

Please DON'T Private Message to me, what should be part of the Public Conversation -- especially if it's to correct a mistake, or contradict a statement!  Let it ALL hang out!!

raschemmel

Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

Paul_KD7HB

Logic is logic.
The USNAVY Is still using four file cabinets full of vacuum tubes that comprise 2 FLIP FLOPS in the Bremerton Naval Shipyard in Washington. I saw them with my own eyes.

"If it ain't broke, don't fix it."

They also lost the Missouri!

Paul

raschemmel

#22
Aug 16, 2019, 10:55 pm Last Edit: Aug 17, 2019, 01:02 am by raschemmel
Quote
They also lost the Missouri! 
When ?
I saw the IOWA class battleship Missouri there in Bremerton Washington back in '83 or 84 .
They sent her back in '92
Missouris returns to Bremerton for deactivation

and then sent her to Pearl Harbor

Quote
I]In January 1998, the Navy reopened the U.S.S Missouri for the public's last opportunity to visit the famous ship before she left for Hawaii. Open for only three weekends, the "Mighty Mo" received 24,000 visitors. The Missouri departed Bremerton forever on May 26, 1998, and was towed to her new home on Ford Island near the USS Arizona Memorial in Pearl Harbor.
Quote
Logic is logic.
The USNAVY Is still using four file cabinets full of vacuum tubes that comprise 2 FLIP FLOPS in the Bremerton Naval Shipyard in Washington. I saw them with my own eyes.
I think the Arizona is the only IOWA Class battleship thy lost

On second thought, I think it was 2 file cabinets of vacuum tubes that comprise 4 flip-flops.
(not that it matters...)
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

herbschwarz

In case anyone is interested, the flip-flop was invented by William Eccles and F. W. Jordan who applied for a patent in June 1918! It used two triode vacuum tubes, six resistors, two relays, two light bulbs, two push buttons and four power supplies: 6V, 9V, 63V and 99V.

raschemmel

#24
Aug 17, 2019, 03:49 am Last Edit: Aug 17, 2019, 03:49 am by raschemmel
You know what they say ,
"You can never have too many flip-flops..."
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

dougp

I think the Arizona is the only IOWA Class battleship thy lost
Arizona is a Pennsylvania class battleship.
Everything we call real is made of things that cannot be regarded as real.  If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet. - Niels Bohr

No private consultations undertaken!

raschemmel

Quote
Arizona is a Pennsylvania class battleship.[/quote

See, that's what happens when an Air Force person tries to talk about the Navy...
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

dougp

See, that's what happens when an Air Force person tries to talk about the Navy...
:D
Everything we call real is made of things that cannot be regarded as real.  If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet. - Niels Bohr

No private consultations undertaken!

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