Make a very simple test for me

_q12x_ · May 15, 2022

Im asking this question to everyone but in particular to my friend here mister @marconi .
I am a professional artist but I am not an electronist like you guys here. That doesnt mean I dont know anything. I know something but I can't raise to some of your standards and knowledge. I'm happy (sometimes fun) to learn something new here and there.
- Recently, it was suggested to me to buy a frequency counter, because I got into some crystal oscillators I have in my stock and they have no markings anymore and the reason is a bit too long story. I already buy a cheap one from ebay, exactly this yellow version (not the red one)

[ElectriciansForums.net] Make a very simple test for me

but it is on the road. I have about 2-3 months (usually) to wait, until it arrives.
I also have a dinky DSO138 osciloscope that is trembling of Parkinson all the time. So you can imagine, I can't put my 100% trust in it all the time.

So, my first circuit for testing a crystal oscillator I find is this:
"Oscillator Circuit of The First Quartz Wrist Watch"

I had high hopes for this circuit. I used 10k for both Rc(c=collector) and 1k for both Re(e=emitor). And I used BC548 for both Tr.I used a known value of a Quartz of 20MHz. And I used 2V (VB=Voltage Battery). But the oscilloscope just showed me some very weird and random readings that I can not even put head to tail. I build this circuit on my breadboard, and that may had influence the results.

---So this circuit didn't work for me---. But I bet my as it must be a good one and I blame my DSO138 for being crappy.
And also not having (yet) a frequency counter.
- In short, this is more a curiosity for me. I hope it is for you as well.
- My request for you is to help me with the following:
- Because you are a better electronist, you must have better tools than I have. So, using your normal oscilloscope and your normal frequency counter, (I say normal, comparative to my ebay measuring tools), please make this very quick and simple circuit and measure it for me. And confirm to me with some images or a short video, that everything is working as I imagine and hope. It must be. The idea is to measure 20MHz on the "out" pin in respect to the ground (if you used the same values as I used). That's it. Also, feel free to change the resistors or the transistors. It must be GPT (general purpose transistors), but the resistors I used I just guessed their values. I didnt had the values from the page with the circuit. So I had to invent something. And those values are my best guess.
Thank you and hope to hear good news from you.

brianmoooore · May 21, 2022

Nice to see proper resistor symbols have fund their way into this thread!

_q12x_ · May 21, 2022

brianmoooore said:
Nice to see proper resistor symbols have fund their way into this thread!

brianmoooore · May 21, 2022

Nothing American about it. Was the UK symbol as well, until a meaningless rectangular box was foisted upon us by some committee or other.

_q12x_ · May 21, 2022

Russians, man, russians ! Haha

pc1966 · May 22, 2022

brianmoooore said:
a meaningless rectangular box was foisted upon us by some committee or other.

It was to make it easier for pen plotters in the early days of CAD drawings I believe. Now it is slightly irrelevant.

marconi · May 22, 2022

_q12x_ said:
+7V(Max) Vcc to pin4 and gnd to pin 11.
I don't know anything, I just look up in the datasheet.
(Sometimes) my biggest mistake is to presume, and I still have to learn to not doing it that often myself.
View attachment 97761

You are right and I am right! I was talking about the 14 pin dual in line pin layout which is the type I use and have sent you.

_q12x_ · May 22, 2022

Good morning signori @marconi
- I was looking only on the pdf that you post it, later I realized that you may have different package than in the datasheet and you are mentioning them. But I didnt had the chance to add more comments because the timeout for comments on this website will cut your ideas off. Its a good idea to let comments on, not everyone is english speaker and everyone makes mistakes that can be repaired, if is given the chance, im speaking to this website managers/designers.
- It appears all my initiative with reading a 20MHz Before the IC's arrival fail. Because, it appears, the discrete components circuit has some limitations from its RC in there, and the 555 is not up to that fv, and I need a much higher fv than 20 anyway, at least 100MHz to have a normal range of testing these osc's. What matters is that we tried, we moved fast enough and we got results. In part2, we will use your IC's. Im curious if they will raise the the task, until the actual fv counter arrives. Another against time run. I am particularly against making anything against time and in rush !! I like it slow and precise. But this is a strange coincidence how everything falls this way. And the time is not that fast anyway, so about 1 week for an experiment is plenty for me anyway.

marconi · May 22, 2022

Im curious if they will raise the the task, until the actual fv counter arrives. ???

marconi · May 22, 2022

q12x : Since you mentioned the problems caused by resistance and capacitance in integrated circuits operating at high frequencies or switching speeds I thought you might enjoy reading this article:

In processors and graphics cards, what limits your clock speed? - https://techunwrapped.com/in-processors-and-graphics-cards-what-limits-your-clock-speed/

Another limit is temperature rise of the ic. Because many yet small capacitors are being charged and discharged very frequently/at a high rate - Giga Hertz in some devices - there is a significant heating effect caused by the many but small currents moving the electrons in and out of the capacitors. You know that when a current flows through resistance there is heating which causes ics like processors to warm up. So they are fitted with heat sinks and fan blows across them otherwise they would overheat and burn out. Thus, keeping the ventilation holes of your computer unobstructed is a good idea. (In the computers I worked on in the 80s with many microprocessors the air was cooled first by passing over fins cooled by chilled water at 5C.)

pc1966 · May 22, 2022

_q12x_ said:
I could make it myself but I have to make a couple of them, to really bring down the fv to my devices level that I have here. And I probably will, because it will most probably be too much for you. Will it?

I tried a quick SPICE simulation and (a) it did not work properly (toggled only first time) and (b) even then you are looking at switching times of around 10us, placing the max speed at below 50kHz even if it had worked as hoped!

marconi · May 22, 2022

Here is a 74HCT73 dual jk flip flop in cascaded toggle mode with first ff being clocked at 20MHz and scope showing 2Q output of second ff. thus divide by 4 to five 5MHz

I do not have any HCT93s to hand.

_q12x_ · May 22, 2022

marconi said:
Im curious if they will raise the the task, until the actual fv counter arrives. ???

Im curious if they will raise to the task, until the actual fv counter arrives. See? Small shht like this I am not allow to repair in my previous postings because this website is made against user !

marconi said:
q12x : Since you mentioned the problems caused by resistance and capacitance in integrated circuits operating at high frequencies or switching speeds I thought you might enjoy reading this article: In processors and graphics cards, what limits your clock speed? - https://techunwrapped.com/in-processors-and-graphics-cards-what-limits-your-clock-speed/

And I did enjoy it. I do like MCU's, and I only worked with PIC's so far, and very limited range and very few applications I used them. I didn't go nuts with them as I wished when I discovered them in my youth. But they remain a fascinating literature for me. So the RC problem in CPU's, conform to your article, is due to the micro-wiring length and thickness, remaining constant over time while the transistors got smaller. If I understood it correctly. Very interesting. Yes. Actually mister @pc1966 spotted that RC problem in the last FF (flipflop) circuit and I concluded on his finding.

marconi said:
Another limit is temperature rise of the ic. Because many yet small capacitors are being charged and discharged very frequently/at a high rate - Giga Hertz in some devices - there is a significant heating effect caused by the many but small currents moving the electrons in and out of the capacitors. You know that when a current flows through resistance there is heating which causes ics like processors to warm up. So they are fitted with heat sinks and fan blows across them otherwise they would overheat and burn out. Thus, keeping the ventilation holes of your computer unobstructed is a good idea. (In the computers I worked on in the 80s with many microprocessors the air was cooled first by passing over fins cooled by chilled water at 5C.)

I admit, I didnt got this interested like you did about the internals of a CPU. Very nice explanation ! I like it. As a fact, everyone got amused when coming into my room and seeing my desktop PC case with one side open all the time and an external black fan blowing into it (actually towards my 2HDD), and they asked me "is it broken?" and I respond, "no, it is properly cooled". I got into this arrangement from my very first computers and it stay with me until today. I also highly recommend it. The downside it is getting dusty, quite quickly, so 1/year I do a total cleanup, I take out the processor, re-paste it, clean everything from dust, especially its heat sink radiator, that usually develops a fur on it, like a little rat.

By the way, signiori @marconi you worked in computers in the 80's you said, what did you do? Also tell me your expertise, what you did and know the best, what you master, and what you really enjoy. I realized I know nothing about you and now is a good time to ask. The same question to mister @pc1966 as well. Im equally interested.

pc1966 said:
I tried a quick SPICE simulation and (a) it did not work properly (toggled only first time) and (b) even then you are looking at switching times of around 10us, placing the max speed at below 50kHz even if it had worked as hoped!

Thank you for trying that. I am not that good in LT Spice. I have it on my pc but i cant say im good in it. Only to a point and that is a very low point.

marconi said:
Here is a 74HCT73 dual jk flip flop in cascaded toggle mode with first ff being clocked at 20MHz and scope showing 2Q output of second ff. thus divide by 4 to five 5MHz I do not have any HCT93s to hand.

Ahaa, an experiment, very interesting result !
See if you can obtain my results: 1/10, then 1/100, then 1/1000 divisions. As a challenge of course. Also I highly recommend to use the 555 circuit that I used. Extremely helpful but to a limit as we all know it now.

pc1966 · May 22, 2022

_q12x_ said:
Thank you for trying that. I am not that good in LT Spice. I have it on my pc but i cant say im good in it. Only to a point and that is a very low point.

Simulations are useful but ultimately not always understood by those doing them. Generally speaking:

If a simulation tells you it won't work, almost certainly it won't work!
If a simulation tells you it will work, it might - you will need to try it to be sure.

Of course as you get to fancier tools, especially those that will extract PCB layout in to electrical parameters to replace the "wires" in the model, you get closer to reality, but often if is not practical to model everything that way.

More subtly you can get situations where you have two (or more) aspects to the circuit with very different time-constants, for example an RF transistor that can (and will) operate in the GHz region so needs pico-second time-steps to model the changing voltages & currents, and a bias control system that has millisecond time constants, so you need to run the simulation for billions of time-steps to complete it, leading to massive CPU effort and/or the simulator failing to converge normally.

Mathematicians have a term for this problem and lots of fun looking at ways of dealing with it:

Stiff equation - Wikipedia

en.wikipedia.org

And that is even before we get in to non-modelled aspects of the devices!

So a simulation is really about avoiding the alpha breadboard stage to see if it will do anything useful, thus you get to the beta stage quicker and cheaper, and then you can build your PCB or other more realistic prototype to confirm (or otherwise) that you are on the right track for success.

marconi · May 24, 2022

q12x Attached are two short clips. The first shows a divide by 10 counter with a 20 MHz input and 2 MHz output using a 74LS93 like the ones I have sent you. The second clip is this same divide by 10 counter now with its input at 5MHz taken from the output of the divide by 4 counter I made earlier using a 74LS73 - total division by 40 thus 20MHz down to 500kHz. You will be able to do the same soon. Using the 7493 you can divide by any whole number between 2 and 16. Adding 7493s so one provides the output for the next enables further division to be done as I have shown you. Hence my suggestion you build an electronic clock using a crystal as its timing source.

_q12x_ · May 24, 2022

marconi said:
q12x Attached are two short clips. The first shows a divide by 10 counter with a 20 MHz input and 2 MHz output using a 74LS93 .. The second clip ..total division by 40 thus 20MHz down to 500kHz...

to @marconi : very cool ! I like it. And thank you. But you are still limited by the maximum IC fv. Higher than its maximum and you are in the same situation as I am. Btw, what is he maximum fv it can see this 74LS93 ? Actually I will check it as well.

CP0 meaning Clock (at) Pin 0 and is an inverted CP0 with the bar on top. I wonder why 2 Clocks? Maybe because it has 2 sections? and CP1 is half speed? Hmm, very strange. So our CP0 is up to 32MHz. But if I feed him a 42Mhz crystal is dead in the bushes like my 555. But is good for all the crystals under its max value which is still good enough for me. I mentioned already, having a level of 100MHz is good because I can test all my osc's, especially those over 32MHz. But maybe 'my majority' is under 32 so everything will be good? I will see the 'majority' until after I build and test everything. What a strange project. I really didnt want to spent even 2h on it, and it turn out to spent 2 months, haha. Strange, right?