When did you make it?

I did the prototype in July 2018 on a hand wired LED matrix. I'll send you a schematic in PM. Probably won't be up-to-date because I made some changes along the way and never updated the schematic.

 

PM sent. The circuit for horizontal and vertical scrolling is the same. The program handles scrolling direction which is specified on the command line.

I'm planning to make some of these as gifts and I'll use 5 or 6 digits. I also have other features planned that can be customized by recipients.

 

...I dont have your 74LS74...
If you have any Positive Edge Triggered 74LS series flipflop IC's in your list, try one of those instead of the 74LS74. Should work!

-Hello again. I just looked through all the IC's list and these are all the FF (Flip-Flop) I have:

CDB472E Romania 1990 IPRS Baneasa equivalent to SN7472 Single AND Gated JK Master/Slave FF Flip-Flop with Preset and Clear
CDB476E Romania 1977 IPRS Baneasa equivalent to SN7476A Dual J-K FF Flip-Flop Asynchronous with Preset and Clear
74HCT73 High Speed CMOS Logic Dual Negative-Edge-Triggered J-K FF flip-flops with Reset 2 Gates (found as '74HC73' or 7473)
CD4013 x2 dual D FF flip-flop
CD4027 x6 Dual J-K FF Flip Flop

And by the look of it, I only have a "Negative-Edge-Triggered J-K FF" and not a Positive one.
I am thinking on buying a couple of Positive Edge Triggered J-K FF Flip-Flop
- Who do you recommend? Who is the Best?
Or, what did you used so far and from your experience is good enough or super good to use?
Thank you !
-----------
Heh, nevermind - I buy already this 74LS76

 

I buy already this 74LS76

Unless you're really enthralled with TTL, I'd switch to CMOS. For low speed circuits, CD4xxx offers a wide supply range and lower cost. If you want speed, you can go with 74HC which will give speeds similar to 74xx and 74LSxx. If you want to mix CMOS and TTL, you can use 74HCT. TTL compatibility makes 74HCT have a narrower supply range than 74HC.

From Philips Semiconductor:

74HCT has TTL compatible inputs with fanouts of 1/2 of LS TTL (for standard outputs).

 

I believe I made a mistake.
I believe I also bought a Negative Edge Triggered IC. Aaaaah. And now I see it.
SN74LS76AN

When they say 'LS76A I believe they refer to this sector SN74LS76AN from the name. Correct? Im so screwed.
1- I am totally screwed now that I have Negative Edge Triggered IC instead of Positive as I originally wanted?
2- How can I slow down the original FF CD4027, not to switch this fast, to make it compatible for the diodes circuit?
Thank you.

 

Unless you're really enthralled with TTL, I'd switch to CMOS.

Im not 'enthralled ' with anything. Im simply looking for the cheapest of them all ! Its my #1 priority when I am searching to buy a component (or 10pcs). Im not biased towards anything really. I have no preference since I dont know them that well and good like you do. Im also not that good or advanced as you are into choosing and diferentiate between the technologies used. For me is fine since I am learning them. Is very good that you are telling me all of this, (actually repeating) my friend @dl324. I will try to keep in mind but sincerely when I am after the cheapest, I forget everything else; haha, you know how it is. Thank you for the correction, very cool table comparison. What is the usual name for CMOS that you are recommending? It is the 4000 series that I can see it mentioned in the table? or... something else?

 

What is the usual name for CMOS that you are recommending? It is the 4000 series that I can see it mentioned in the table?

I prefer CD4xxx and CD45xx because they have a wide operating voltage (3-15V). The main drawback, aside from static sensitivity, is their slow speed when compared to TTL.

Note that HE4xxx have different characteristics than CD4xxx.

TTL prices are 4 or more times the equivalent functionality in CMOS. HC/HCT prices may be better than TTL, but the operating voltage for HC is 2-6V and HCT is 4.5-5.5V.

TTL did some screwy things. Like the clock inversion you observed and different pinouts. I got bit once in the 70's. Designed a circuit for a 74LS part and tried substituting a 74L part (but it had a different pinout).

 

TTL did some screwy things. Like the clock inversion you observed and different pinouts.

So I am I am totally screwed now that I have Negative Edge Triggered FF instead of Positive as I originally wanted.
Right? Holly sing. So I have to buy another round but with correct designation this time, right? To be EXACT Positive Edge Triggered FF and no monkey bizniz. Aaaah, my pocket. What a disaster !

 

Aaaand I decided. I buy a couple of 74LS74 as well. I know for sure they are Positive Edge Triggered FF.
A bit costly to my pocket, but hey... if it will get the job done, is worth it.
This way I will have all the FF flavors in the world.

 

So I am I am totally screwed now that I have Negative Edge Triggered FF instead of Positive as I originally wanted.

The solution might be as simple as inverting the clock signal. It depends on the timing requirements.

 

The solution might be as simple as inverting the clock signal

How? (using a Not gate maybe?)

 

How? (using a Not gate maybe?)

That's the most obvious way. If the clock was coming from a flip flop with both polarity outputs, you could use the inverted output.

 

That's the most obvious way. If the clock was coming from a flip flop with both polarity outputs, you could use the inverted output.

Thank you !
Also...
I just remade that circuit just now and still not switching. Here is how I have it right now:
For the 7476 I dont have the original chip. I only --discovered-- that I have a single (1one) CDB476E which is an equivalent. Im not completly sure if the pins are maintained the same. It better be. The D9 LED is ON all the time and not switching when I press the button on CKA of the 7493. Ive also inserted a NOT gate here: but still no effect. It might be switching still too fast ?!
How can --I-- make it work? Thats the question.

 

I believe I made a mistake.
I believe I also bought a Negative Edge Triggered IC. Aaaaah. And now I see it.
SN74LS76AN
View attachment 277982View attachment 277983
When they say 'LS76A I believe they refer to this sector SN74LS76AN from the name. Correct? Im so screwed.
1- I am totally screwed now that I have Negative Edge Triggered IC instead of Positive as I originally wanted?
2- How can I slow down the original FF CD4027, not to switch this fast, to make it compatible for the diodes circuit?
Thank you.

No, you'll be fine with the 74LS76A, it'll just flip a few 10's of nsecs later, on the falling edge of the reset pulse instead of the earlier rising one!
You could try the CD74HCT73 as well.
If you still have the NOT gate in the cct, move the 10K resistor so that it is connected to the INPUT of the gate, NOT its output, so that it pulls the diodes up to +5V.

 

If you still have the NOT gate in the cct, move the 10K resistor so that it is connected to the INPUT of the gate, NOT its output, so that it pulls the diodes up to +5V.

You mean like this:

I did it and still the LED is always on indifferent of my button press. (the led remained there from the last cct)
The 10k is directly on all those 3 diodes links now. But no difference.

 

You mean like this:
View attachment 278024
I did it and still the LED is always on indifferent of my button press. (the led remained there from the last cct)
The 10k is directly on all those 3 diodes links now. But no difference.

Try the 74HCT73 instead, there may be something strange about the one you're using. Use a 74LS14 NOT gate for inverter if you have one.

Edit: I've just noticed that you have the Reset and Clear pins tied Low: They must be tied High to work!

 

Edit: I've just noticed that you have the Reset and Clear pins tied Low: They must be tied High to work!

Yes that was it !!! Thank you very much. Now is working.
BUT
it is randomly working. When I press the button
sometimes the led gets ON - sometimes stays OFF, and not switching as it should. And viceversa
sometimes the led gets OFF - sometimes says ON, and not switching as it should.
The circuit is not counting to 7 yet, but it is flipping the LED on and OFF.
This tells me it is still some very fast switching. Im very happy I can see that led switching now. It is a good sign, even if is not perfectly doing what it should.
I also eliminated the NOT gate and still works exactly the same as with the NOT connected. Like someone here said, it is engaging on the negative clock edge or the positive clock edge, with the NOT or not NOT. Haha.

Try the 74HCT73 instead, there may be something strange about the one you're using.

Im using this CDB476E which is an equivalent to SN7476. Indeed the romanian 7476 that im using right now is an equivalent to the original american 7476. Thats the difference. I bet it is a quality difference as well. I am expecting actually, the original (american) 74LS76's. But they will arrive in 1-2months from now. Which is still a Negative edge trigger; and I also ordered a couple of your 74LS74 that you first recommended which are the Positive edge trigger.

 

Yes that was it !!! Thank you very much. Now is working.
BUT
it is randomly working. When I press the button
sometimes the led gets ON - sometimes stays OFF, and not switching as it should. And viceversa
sometimes the led gets OFF - sometimes says ON, and not switching as it should.
This tells me it is still some delay in play, not quite there yet but is there like more than 50%.
This is my interpretation: it is not fitting perfectly on the clock signal. Is a bit offset. How do I repair that now?
Im very happy we make it work !!! (you did it 100%) Thank you for that.
I also eliminated the NOT gate and still works exactly the same as with the NOT connected. Like someone here said, it is engaging on the negative clock edge or the positive clock edge, with the NOT or not NOT. Haha.


Im using this CDB476E which is an equivalent to SN7476. Indeed the romanian 7476 that im using right now is an equivalent to the original american 7476. Thats the difference. I bet it is a quality difference as well. I am expecting actually, the original (american) 74LS76's. But they will arrive in 1-2months from now. Which is still a Negative edge trigger; and I also ordered a couple of your 74LS74 that you first recommended which are the Positive edge trigger.

You are using your de-bounced switch circuit, yes? Try reducing the 10K pullup resistor to 2K2, or even 1K. This gives a much higher reset pulse, which will help with any randomness in the triggering of the flipflop as well! And do try the 74HCT73.

 

You are using your de-bounced switch circuit, yes?

Yes, I always use it. I have the experience and I learned my lesson. For a clean impulse it is ideal. I love it and I am using it.

And do try the 74HCT73.

I just tried the 74HCT73. I noticed it is Not having a S (Set) pin. Only the R (Reset) that I put to +5V.
The behavior of the 7473 is --the same-- as with the 7476 !
It appeared 'random' in the beginning, but now I am counting and it appears it is counting to 2 and reset back. But sometimes is counting to 1, but more than often to 2. It is kind of random.
This is the updated circuit I used for both 7476 and 7473. (excepting the S pin that 7473 is not having)

Try reducing the 10K pullup resistor to 2K2, or even 1K.

I will do it now.

 

You are using your de-bounced switch circuit, yes? Try reducing the 10K pullup resistor to 2K2, or even 1K. This gives a much higher reset pulse, which will help with any randomness in the triggering of the flipflop as well! And do try the 74HCT73.

Ok... I try it. I changed R4 from 10k to 1k resistor. It does indeed stabilizing the circuit ! I press that clock button like 50 times to catch a count to 1 as it was so obvious before. But it is always counting to 2 every time. Yah, it's an improvement !
But it is counting only to 2 !
I have access to the good camera right now so here are some hirez shots:
this is the equivalent for the 7476 if you were curious: (made in Romania!) hahaha
(enlarge image and zoom in)

and this is the current breadboard cct:
The top IC is the 7473 FF. The 3rd IC on the bottom is the Not gate that is not connected. It remained there in case we need its ass.
You can see the 1k as well. The angle of the shot is a bit too vertical with some pins on the top so you must count the pins to figure out the placement.
Or...see the other shot from aside.

You can always tell me to make you a specific angle shot, and I will do it.