Are you still using 7400-Series Logic, if so, where?

RE: Are you still using 7400-Series Logic, if so, where?

shabaz — Mon, 14 Dec 2020 03:49:13 GMT

Here an electronics chain called Maplin was selling 74-series TTL right until 2018, when it closed for good! I guess people were still buying them, perhaps to repair old equipment. I think this is the oldest test instrument I own, it uses about fifteen 7400 logic chips:

[View:/resized-image/__size/804x535/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-52b5002c-a393-4f72-9eae-9705d1427982/7343.contentimage_5F00_193296.jpg:804:535]

It is a counter/timer. I don't use it often (but sometimes handy). I occasionally just use it as a large stopwatch : )

It was in bad shape when I got it (used) a couple of years ago from ebay, lots was oxidised or covered with stains, and the sockets were corroded too.

I took it to pieces to clean it all, and replaced the BNC connectors and some of the buttons, and the large power supply electrolytic, and the display filter which was scratched up.

The main fault (apart from cooked input resistors and some traces) was just bad contact with clogged-up switches (I sprayed isopropanol and then air into them all) and poor contact with one main IC (see photo below, it is the white chip at top-right in the photo, and also visible in the photo above) that was socketed (the rest of the ICs did not have sockets). I removed the socket and permanently soldered the IC, and now it works fine.

The weird round IC in the centre of the photo is a Plessey divider chip.

[View:/resized-image/__size/791x526/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-52b5002c-a393-4f72-9eae-9705d1427982/1462.contentimage_5F00_193297.jpg:791:526]

RE: Are you still using 7400-Series Logic, if so, where?

michaelkellett — Sat, 12 Dec 2020 13:31:28 GMT

The high spot of my 74xxx design works was about 1987 when I designed this beastie.

Subsequent designs used FPGAs or micro-controllers.

I was lucky enough to find one on Ebay recently, not quite working but easily fixed.

It's based on a Motorola 6809 8 bit micro with memory shared two ways between the video system and

the digital arbitrary and test pattern wave form generator.

It could generate digital trios which were modulated at different frequencies to stimulate filters in remote

booster amplifiers so that the gain of the nth booster down the line could be checked.

I did the digital and analogue hardware design and the code in 6809 assembler.

I think it was one of the last board sets we did with tape (before CAD)

These things are never a one person effort and needless to say I didn't do this on my own.

I can't remember all the good people who worked on the project with me but I'll mention the following:

Alan Bodiam - who did the mechanical design

Peter Churchill - who was in charge of the machine shop which made all the metal bits

Peter French and Tim Summers who worked in the lab with me (I think they were both involved on this one)

Bob Odell - production manager

Alan Babs - who inspected every one we made (100s)

[View:/resized-image/__size/620x415/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-52b5002c-a393-4f72-9eae-9705d1427982/0285.contentimage_5F00_193291.jpg:620:415]

[View:/resized-image/__size/620x415/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-52b5002c-a393-4f72-9eae-9705d1427982/7142.contentimage_5F00_193292.jpg:620:415]

Analogue and PSU, CRT on left and just visible at bottom right huge high Q filter inductor in metal pot.

[View:/resized-image/__size/620x415/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-52b5002c-a393-4f72-9eae-9705d1427982/5008.contentimage_5F00_193293.jpg:620:415]

Processor and video

[View:/resized-image/__size/620x415/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-52b5002c-a393-4f72-9eae-9705d1427982/2845.contentimage_5F00_193294.jpg:620:415]

Pattern generator

[View:/resized-image/__size/620x415/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-52b5002c-a393-4f72-9eae-9705d1427982/6622.contentimage_5F00_193295.jpg:620:415]

Camera having trouble with scan speed of CRT !

You could get all this into a decent micro-controller and and a (smallish) FPGA now, not sure if [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-52b5002c-a393-4f72-9eae-9705d1427982/7167.contentimage_5F00_1.png:16:16] or [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-52b5002c-a393-4f72-9eae-9705d1427982/4578.contentimage_5F00_4027.png:16:16]

RE: Are you still using 7400-Series Logic, if so, where?

phoenixcomm — Sat, 12 Dec 2020 02:30:01 GMT

[mention:57a79c8ceae84c06b59d42e67a0ded50:e9ed411860ed4f2ba0265705b8793d05] James, interesting question. 74 /LS/SHCT are workaholics with the HCT has more range for VCC,[View:/resized-image/__size/620x412/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-52b5002c-a393-4f72-9eae-9705d1427982/2055.contentimage_5F00_193290.jpg:620:412]

How many? My Blue bin 4x10 is chock full of parts + more in tubes! its not going away soon.

~~Cris

RE: Are you still using 7400-Series Logic, if so, where?

ralphjy — Thu, 10 Dec 2020 16:52:41 GMT

I just used a couple of 4000 series logic chips in the Pong game that I rebuilt. And I have an assortment of 74 and 74LS (even some 54 mil grade parts) from the late 70s and early 80s when I did a lot of prototyping. I even have early 555s from 1972. And I have a bunch of early op-amps (709, 741, 747) from the 70s. A lot of them in ceramic packages and hand marked because we used to hand screen them for better than spec performance.

The most interesting thing I found that I had forgotten that I had is a National Semi MM5738 8-digit algebraic 5 function calculator chip. Might be a fun retro build for later.

RE: Are you still using 7400-Series Logic, if so, where?

koudelad — Thu, 10 Dec 2020 10:36:58 GMT

I have never used nor seen these logic chips in anything I disassembled that was designed in last 10 years or more. I personally used micro-controllers, but as other say, high speed designs need CPLD or an FPGA.

One great alternative is a PSoC or other MCUs with some kind of configurable logic cells.

RE: Are you still using 7400-Series Logic, if so, where?

ajcc — Thu, 10 Dec 2020 07:40:59 GMT

Yes, for 8-bit microcontrollers the 74HC595 parallel output shift-register is a cheap way to get more outputs, along with the 74HC165 parallel input shift-register for extra inputs. I also like the 74HC4050 hex buffer to get 5V logic inputs for 3V3 µCs.

For modern microcontrollers the 74LVC series have many 3.3V or 5.5V input tolerant ICs that operate down to 1.65V, such as the 74LVC245 octal transceiver. This series also include single logic-gate chips such as the 74LVC1G08 AND-gate which can get you out of a pickle in a mixed voltage system.

As for what I keep in stock is just whatever I have left over from older orders, along with the 74-series and 4000-series logic ICs in DIP that I've been buying whenever someone has been clearing out their old stuff.

[View:/resized-image/__size/620x827/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-52b5002c-a393-4f72-9eae-9705d1427982/5047.contentimage_5F00_193287.jpg:620:827]

RE: Are you still using 7400-Series Logic, if so, where?

ntewinkel — Thu, 10 Dec 2020 07:01:46 GMT

ps, for those interested in playing with logic... https://simulator.io/ is a pretty handy simulator.

But if I recall correctly, not all 7400-series chips are logic - I remember some counters and shifters too.

Oh that reminds me - I used shift registers for my version of an OpenSprinkler.org sprinkler board! And I think OpenSprinkler does too for their own boards.

74HC959 - also still recommended for expanding IO on boards like Arduino. See Oomlout tutorial too: products:ardx:circ-05[.:oomlout:.]

Kinda like the 555 chips - too handy to not use once in a while.

Best,

-Nico

RE: Are you still using 7400-Series Logic, if so, where?

navadeepganeshu — Thu, 10 Dec 2020 05:48:09 GMT

Yes, I do!

I have tens of 74xx ICs kept pricked to a thermocol slab and occasionally use them to cross-check few designs or simply to play around. I think because they are of low cost, easy to understand and use, it's still used in educational institutions and probably they have the majority of worlds 74xx stocks.

RE: Are you still using 7400-Series Logic, if so, where?

jw0752 — Thu, 10 Dec 2020 05:30:29 GMT

Since I do a lot of salvage of older boards I have quite a few 74 series logic chips. I checked my inventory and I have about 50 different bins with a mixture of series in some of the bins. I will keep the 74xx, 74HCxx, 74LSxx, etc chips together in one bin and then go looking for the series I want for a specific project. I use them occasionally in builds and even more occasionally in repairs as they really are quite hardy. Once in a while I come across a number that I didn't have before and I get excited like I did as a kid when I would find a penny that fit in an open hole in the penny collect folder.

RE: Are you still using 7400-Series Logic, if so, where?

dougw — Thu, 10 Dec 2020 03:54:34 GMT

I still have some 7400 parts but I have more 4000 (CMOS) series parts. I only use them when I am breadboarding since they are DIPs (almost all my newer stuff is SMT). I actually use PCBs for prototypes, so it is a bit rare for me to build circuits on a breadboard.

RE: Are you still using 7400-Series Logic, if so, where?

zst123 — Thu, 10 Dec 2020 00:52:49 GMT

According to my lecturers, the 74-series is useful for small glue logic. But for large glue logic, a CPLD is much cheaper, and easy to modify design anytime even after building the circuit PCB.

Recently in school (diploma level) it appears the curriculum is shifting to add some basic CPLD knowledge. I learnt the 74-series but also learnt some simulation by creating schematics in Intel Quartus software.

RE: Are you still using 7400-Series Logic, if so, where?

ntewinkel — Wed, 09 Dec 2020 22:29:11 GMT

Hi James,

Good question, makes me wonder too if better (cheaper, easier, newer, readily-available) solutions are available for them in general.

I have a bunch on hand still.

I remembered using them in one of my university courses so when I got back into electronics I started playing with them again - at that point mostly just learning projects playing with logic.

Recently I tried building a brake/signal light circuit with them, but I'm still having trouble with startup timing causing strange startup states. So I'll likely switch to using an ATTiny eventually.

Best,

-Nico

RE: Are you still using 7400-Series Logic, if so, where?

neilk — Wed, 09 Dec 2020 22:02:09 GMT

I still have a few 7400 series ICs in my inventory. I last used one back in about 1990.

Neil

RE: Are you still using 7400-Series Logic, if so, where?

genebren — Wed, 09 Dec 2020 21:58:49 GMT

I started out in electronics when 74 series logic chips where all the rage. I used to build a lot of prototypes, in basic gates/counters, all in wirewrap and then converted to PCBs.

Now, I have a single 74 series part in my active inventory, 74HC4066D, a quad, SPST, analog switch. A few years ago, I was contracted to design some modules for rack-mount synthesizers. Analog switching is a big part of this work, so I had quite a few different devices that I could use depending on the type of circuit, e.i. audio on control. The 74HC4006D was my go to part for routing/switching control voltages in some of these designs.

RE: Are you still using 7400-Series Logic, if so, where?

michaelkellett — Wed, 09 Dec 2020 21:18:46 GMT

I use the occasional modern 74 series type chip for glue logic, usually single gate things, occasionally multi channel level shifters.

I've done some new designs in the last few years which use shift registers or 4016 type parts (whch I'll count as 74 series for the purpose of this discussion [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-52b5002c-a393-4f72-9eae-9705d1427982/contentimage_5F00_1.png:16:16])

As soon as you need more than a few 74 series type parts you're better off with an FPGA, there are 48 pin parts starting at £2 or £3 even in 10s - and

of course they are much more capable .

My last big 7400 type design was done in about 1985 !