Logic Outputs Problem in 7493 IC

_q12x_ · Jan 3, 2023

Hello from Romania.
I have all the counting ccts, for every number. This is counting to 16 and its the last one this 7493 can count.
I encounter a new and very weird problem. All the [Q] (QA,QB,QC,QD) outputs of the 7493 are not so good at outputting. At least to my components I tested so far.

[ElectriciansForums.net] Logic Outputs Problem in 7493 IC

I simulated more possibilities and all failed. I thought maybe the simulator is not that good. But when I tried the BJT in reality, it still didnt work. I really want to believe it will work with opamps in reality, but if it will not work, it means the simulator is right.
I didnt try with mosfets in the simulator yet, they were just prepared there. I didnt test them in cct.
THe problem is the (-) that 'comes out' after these buffering devices. When they are on (-) on their output.

I actually solved the problem using a tri-state buffer. They are the only component that are solving this issue.
Ive also get 10 pcs from aliespress. I start to value them now, when I actually need them. But they will arrive after 2 or so months from now.
- I want to find a solution (IF POSSIBLE) without them, or at least until they arrive.

This cct I already make and it is working fine (in the simulator) is to output a decimal number for all the 16 binary counts.
Pretty much when is 0100 it will lit the 4th LED. When is 1000 the 8th LED and so on, from 1 to 16 (including 0).
You can see in the screenshot already.
I work on this cct and numerous problems for .... about 10 or more days. Very hard to do it alone !!! But I did it. so far.

I even have an easier output method than this very complicated cct I already built.
- Simply to display in binary. Like these 4 LogicProbe from Proteus simulator that I am always take for granted.
So we can do these first !

To make a simple binary counter [LED display], I will still need some sort of buffer, like the ones I specified already.
I wait for your response. This is a very complicated cct and a big problem for me.
Thank you and hope I will get some interesting answers! (mister @marconi , my Logical friend?haha)
And also Happy New Year 2023 to everyone that are reading my posts !

_q12x_ · Jan 12, 2023

An Update on the Progress:

Slowly but surely...
You can see the board # number - fix in the middle of it.
I plan to make a mini-BUS wiring for these 4 ... probably... and actually put them to work in the cct on the breadboard...
We'll see. Im so bored of them... already, at the 4th one....

marconi · Jan 13, 2023

_q12x_ said:
I dont understand what you mean by that... You mean that I figured out how to connect these 4inputs to get my 16 modes ?
I actually searched and didnt find a BCD for 4 bits(binary) to output 16 modes (decimal). I didnt searched well enough I guess, because here you are with it. Very good that you show it to me !
Are they even bigger that this? with 32 outputs maybe? or 64? That will be cool to see ! Haha.

One can use two 4 bit to 16 line decoders to make a 5 bit to 32 line decoder by using the enable (EN) logic inputs on the decoders to select which decoder outputs to use depending on the state of the 5th bit. I cannot find an image for 5 bit to 32 line but the idea is expressed well enough by this attached image which shows the use of two 3 bit to 8 line decoders making a 4 bit to 16 line decoder. You can see how the 4th bit is connected a NOT gate and then one decoder connected to its output and the other decoder connected to its input - thus only one decoder is enabled at any time depending on the logic state of the 5th most significant bit. When the 5th bit is zero the decoded output is one of 0 to 7 and when the 5th bit is one the decoded output is one of 8 to 15. I leave to you to draw out how to use two 4 to 16 decoders to produce 32 outputs, and then how to use four 4 to 16 decoders to produce 64 outputs.

_q12x_ · Jan 13, 2023

marconi · Jan 14, 2023

One-hot - Wikipedia - https://en.wikipedia.org/wiki/One-hot

As you are experimenting with n bit patterns/sequences I thought you would like to learn the names of those for binary, unary and one-hot. See the table top right of the wiki link above which illustrates them. Your project is a 16 bit one-hot generator.

_q12x_ · Jan 14, 2023

I have to receive this chip but later in the mail.
to arrive: 4028 CD4028BM x10 BCD-to-decimal Decoder
[Can you check for me, if it is possible to cascade multiple of them? Thanks.]
I re-checked and I have NO BCD in all my arsenal of chips. These are the first ones for me.
Also Im looking to your 4514 4- to 16-Line Decoder/Demultiplexer.. maybe is good to get some as well.
I call them BCD but maybe they work the same as Demultiplexers? Im not sure here. It sounds it might be.
If its the same thing, then I have already
74138-74LS138 x10 1-OF-8 DECODER/DEMULTIPLEXER (10pcs)
And thanks for looking into my video !

marconi · Jan 14, 2023

I will be back in touch but not today because I am cooking and have my in-laws this evening.

marconi · Jan 15, 2023

The 4028 can be cascaded. See Figures 13 and 15 in this link:

https://www.ti.com/lit/ds/symlink/cd4028b.pdf?ts=1673700179941&ref_url=https%3A%2F%2Fwww.ti.com%2Fproduct%2FCD4028B

The 4028 is a 3 bit binary to 8 line one-hot or 4 bit binary coded decimal ( 0 to 9 in 4 bit binary ie 0000 to 1001) to 10 line one-hot device.

The 4514 can also be cascaded. The nice thing is that this one is a 4 bit binary (ie 0000 to 1111) to 16 line one-hot device. It can do bcd to 10 line one-hot.

See: https://www.ti.com/lit/ds/symlink/cd54hc4514.pdf?ts=1673772594066&ref_url=https%3A%2F%2Fwww.google.com%2F

The 74LS138 is a 3 bit binary to 8 line one-hot device. Since there are only 3 input bits (0 to 7) it can only select one of 8 output lines and thus does not do conversion of binary coded decimal (BCD) into 10 line one-hot. You need a 4 bit binary coded decimal word to do 0 to 9. The 138 can be cascaded.

See: https://www.ti.com/lit/ds/symlink/sn74ls138.pdf

_q12x_ · Jan 15, 2023

marconi said:
Since there are only 3 input bits (0 to 7) it can only select one of 8 output lines and thus does not do conversion of binary coded decimal (BCD) into 10 line one-hot. You need a 4 bit binary coded decimal word to do 0 to 9.

Yes, so my real question with 74138 was if (any) DECODER/DEMULTIPLEXER IC can be used as BCD. And viceversa, any BCD as a DECODER/DEMULTIPLEXER. For you these things are trivial but they are very new to me. I really dont see the similarities/diferences between these 2 types. Very interesting.... thanks. I will have to pay more attention to my 74138 and see what you've seen/explained.
Also thanks for checking the cascade IC's for me.
I am currently hitting some very hard wall of errors with my boards I make. 1-from the scrappy components, 2-from very intricate connections, even if they are 4 to make, but when 1 goes to 3, in words sounds ok and easy, but there with those tiny wires, aaah, is hard. 3-not very, but too small spaces between the rails and the leg of the diode must hit 'in the zone' and not too much left or right. Get me? So there are even much more details like these, I will not enumerate all, but they are making this entire component extremly hard to make. I had to unsolder over 10 times the same board(s) and search and repair what was buggy and still I didnt figure it out. I did figure out 1 board, 1 diode that is functioning ok alone when measured but not in the cct, very strange. After I replace it, all got to normal working. But until I discovered the -------, took me 1 day. And the fun part, now when I put the second board on the rail, everything goes to hell again...aaaaah. I was VERY lucky with the 1234 module. No errors whatsoever. This one Im working right now is 5678. Im thinking to change tactics and make everything even bigger, to be able to repair and test and check and solder in the same time. Like I did on the breadboard. Well see. Very challenging. But I will make it work, one way or another. I dont like it BIG, but if this is what it wants to be...

marconi · Jan 16, 2023

A coder/decoder or multiplexer/demultiplexer can do BCD to 10 lines one hot or vice versa provided that 4 bits are used for the binary input/output. Three bit words only covers the numbers 0 to 7 and therefore cannot cover the decimal numbering system which uses 0 to 9.

I am glad you are having fun! The effort required makes the success more satisfying (perhaps).

marconi · Jan 16, 2023

Stripboard - Wikipedia - https://en.wikipedia.org/wiki/Stripboard

what about using stripboard/veroboard or making up your own version of it?

Moley · Jan 16, 2023

Sorry to jump in. This thread has been bringing back lots of memories of messing around with logic chips over 40 years ago. I've forgotten most of it now but it was fun at the time. My first design was a keypad operated car imobiliser for my Astra GTE.
Did you know there are companies in China such as JLCPCB that will produce PCBs for next to nothing if you can supply a Gerber design file. That would make your life so much easier. For example, 20off 100 x 50mm single sided boards are £9.52 plus delivery. Uk delivery is from £5.60. I know it takes away the fun(!) but it would make your life a lot easier.

pc1966 · Jan 16, 2023

Unrelated directly to this thread but maybe of some interest is this transistor data book from 1964, more fo the hundreds of pages of information on how they work and circuit ideas:

https://worldradiohistory.com/BOOKSHELF-ARH/GE-Books/GE-Transistor-Manual-1964.pdf

I guess most of the devices are long-obsolete, but I do see the 1N4148 diode listed at one point which is still around, and I have used a 2N709 transistor many decades ago...

marconi · Jan 16, 2023

pc1966 - the sort of reading material I was weaned on. I have to say, that like many engineers, I was glad when 'electronic functionality' did not have to be designed and built from scratch each time, and instead one could take ics with reliable and repeatable functionality and combine them together to do things.

I love following q12 as he works through his projects, confronts problems head on, analyses them to come up with a fix and then as every good engineer should be able to do actually makes a design himself and tests it to confirm it does indeed work.

_q12x_ · Jan 16, 2023

Oh, WOW, VISITORS ! Haha. Im glad to see you guys here.
I read everything you write. I was 100% preocupied with the very problematic construction I am into now, if you remember I complained it didnt work for some very elusive reason and indeed it was VERY strange ! The mistery come only from diodes. I guess, they are special ones... the hell... but I figure it out.
I made a movie about the entire thing, I am also showing the 'stage' when it was giving the error and what kind of error it was, and then in the end of the movie, the working version that is now final. WOW, what a day, I literally worked all day long on it, with almost no breaks. Usually I work with breaks. But amazingly, I didnt get so many and mostly work-work-work. And Im very glad I did. Now I got the working thing. Please watch the video (after I will upload it) and tell me your thoughts what possibly can be the reason for failure. Also I have the first module 1234, that is also having these diodes in that special place- I mention in the video where it is and showing everything clearly what is what there. But that was the thing that puzzled me enormously, why it worked fine with 1234 and here on 5678 didnt. Although I only used them in 56. The 78 were with more (possibly) modern diodes than those sphere ones. Very weird stuff. I like it ! Haha. I am specially pleased that I could used these scrapped components and re-purpose them into something new and practical. Hopefully it will be practical, we'll see. Haha.
Thanks everyone for the kind words and comments. Always a pleasure.
I will post the video soon enough.
PS. Also I bet that @marconi will like very much how I solved the problem ! I like it too, although is not easy, but it is WAY more clear and visible to work with this new board setup/configuration.

_q12x_ · Jan 16, 2023

marconi said:
Stripboard - Wikipedia - https://en.wikipedia.org/wiki/Stripboard
what about using stripboard/veroboard or making up your own version of it?

I have both versions. Also from you that you send me, I still have it, un-violated, virgin and shiny. And also I have custom copper board that I made LOOOOOOOooooong time ago. Still have them, also never used them. My idea 100% on them. Only a small one that I used it to death. But after that, I never touch it.
I know exactly what you say... but what Im doing here is partly prototyping(my own customized way of boards), partly finish product(as small as I can possibly make it), partly experimenting(because weird scrapped components). I have to choose what is ---convenient--- to me. Not everything that flies is also good (is a saying in my place).
But I like your way of thinking, you start to get more closer on my direction of thinking and doing things.
A deserved 10+ from me for your direction of thinking. Haha.

_q12x_ · Jan 16, 2023

-Voila, enjoy:

Moley · Jan 16, 2023

I've just watched the video and there's one thing I can't work out - you are either a genius or totally insane

_q12x_ · Jan 16, 2023

Moley said:
I've just watched the video and there's one thing I can't work out - you are either a genius or totally insane

Both ! An insane genius - Muahahaha. But thanks ! I'll take the compliment. And thanks for watching my video.
What did YOU like from it? mister @Moley

Moley · Jan 16, 2023

I like the passion that you seem to put in to this project of yours. It also brings back memories of 4xxx series chips that I used to play around with. I wish I had kept some of my old projects but that was in the early '80s. If I had kept everything I had worked on over the years my house would be full.

_q12x_ · Jan 17, 2023

I just buy 10pcs of your suggested CD4514 (4 to 16 Line Decoder/Demultiplexer)
And I give it a quick simulation and is doing the thing alright.
A bit expensive for my very poor pocket ... but is good to have interesting chips around.

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