Logic Outputs Problem in 7493 IC

[_q12x_]

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.

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 !

 

[marconi]

I will answer soon but not today.

 

[_q12x_]

Hello,
Very interesting observation that you made with the current through the 7493 !!!!
"The Q outputs of the 74LS93 can only source -800 uA (Ioh) whereas they can sink 16mA (Iol) See page six at this link."
I couldnt see it myself, without your help, not in a million years. Yah, very good catch there. Respect for that !
- - -
I've --simulated-- YOUR (private) suggestion with the PNPs. And I made it work !
Of course from the 100th time, but it did.
I had to include those NOT gates to normalize the output from the PNP's. Also I had to tweak some resistors values as well, to make it work at full capacity. 10k on the Base of the tr's was too much and the voltage was too small on those bus wires. I made them 3k and I got 5V per PNP output, on each colector.
Sourcing and sinking the current through the transistors... Very interesting tweak !
Now Im very curious how it will actually work in reality. The simulator is giving (sometimes) false positives. I'll update you soon.
Thanks so far !

f

 

[marconi]

Seems we make a good partnership.

 

[_q12x_]

Seems we make a good partnership.

Yes....heh....dont say 'hop' yet.
---in reality--- it didnt work. I told you, I get false positives from the simulator.
Is a bit of explanation of what I did.
I used c556b for the PNPs. I have them brand new from 2000's. Rarely used, once or twice.
For the NOT gate, I used 74LS04

I got 150mA through the entire cct (read from the PSU) because I used the 100R on the gnd. And I change them to 300R and I get 80mA through the entire cct. Without them in the cct, I get 10mA. The 100R were getting very hot as well, while the 300R not so much.
I marked as -Ds1- and -Ds2- the 2 sets of Diodes I used on my breadboard. I didnt build ALL of this, only parts to see if its working.

What all this means?
Ds1 are set to count to a fixed number. Ok? In this case I set it to count to 8 for testing purposes.
Ds2 are set to --display-- number #1. It's their only job. When counter pass through #1 from its counting program(to 8), this part will display #1 is activated. Very simple.
I hope it is very clear now.
The problems:
- #1 LED is not lighting at all ! It should, as in the simulator.
I probe with osc the base of the tr next to #1 and no visible signal.
I probe the 300R, all of them , and no visible signal.
I probe the base of all 4 PNP tr's , and no visible signal.
I only get a ~3Vish(or so) signal on the NOT output to the base of the first PNP. No signal on the input of the NOT gate.
And the probes of the osciloscope I had to inverse them. I connected the (+) probe to the (+)rail of 5V. And the (-) probe on the output and I could get a reading - only this way !

I got a very-very-VERY low reading, almost imperceptible on the #1 diode in Ds2 group. And only when using the 300R !!! When I used 100R, nothing. Very perplexing ! Also with the osc probes inverted (probing with the (-) on the pins there, to actually see a reading !!! ).

Ive also did an experiment. Initially I put a white LED on #1. And I thought, well, maybe is not sensitive enough (and I was very right) and I change it to a red LED as you can see in the picture. I get crazy sometimes and try everything. You know. And from my MANY permutations I did, I reach this stage when I eliminated some 300R and some diodes in Ds2. The effect was interesting to mention to you. The LED was LIT but like 50% lit. Ok? But it was pulsating. It was getting even more lit, to 75% LIT. Ok? And back to 50 and back to 75 and so on. So it is a signal on the line !!!!! Thats my observation.
The VERY small imperceptible signal confirmed this LED LIT exception experimentation.

Thats it.

 

[marconi]

I will take a closer look over the next few days.

 

[marconi]

Are the LEDs in an array with their cathodes all connected together like this:

Or are the LEDs all separate and you have connected their cathodes together and then to 0V?

 

[marconi]

For circuit around #1 transistor the diode connected to the left of R199 is incorrect. Have you done the same for the transistor circuit below numbered #2?

 

[marconi]

How are the 16 LEDs to be lit? One LED of 16 or n of 16 where n is the count state?

eg for count state n=3 where count starts at state 0 and goes up state 15:

off off off on off off..off

or

on on on on off off off….off

 

[_q12x_]

Here is the full cct. Zoom in it to see the details. Its a big file.

or here where you can really see it in original resolution https://www.deviantart.com/q12a/art/CountingOutputLEDs-v1A-944060484
also you can download the image and inspect it in your favorite image viewer in your windows.
Hmmm.... I am using some custom LEDs in my drawing and you cant see the direction they are pointing. They are towards GND. All of them.

Hold on I actually show their direction ...I guess was not that clear to others...it was very clear to me. You see that green bar next to the led? Like a diode that has a line designating the (-) side. I really thought is intuitive enough. Hmmm. is not looking like a conventional LED, that is very true....