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.

pc1966 · May 16, 2022

marconi said:
q12: Good morning. Thank you for your nice email. Gathering dust in my shed I have some 74LS273 octal D type flip flop ics.

https://www.ti.com/lit/ds/symlink/sn54ls273-sp.pdf?ts=1652639946774&ref_url=https%3A%2F%2Fwww.google.com%2F

Those are usually intended as bus registers and not so easy to turn in to dividers, though they are fast enough. However, you can covert them in to ring counters with the addition of an inverter:

Ring counters (Johnson Ring Counter)

Ring counters and John counters are special type of counters made of shift registers are being explained here in this article.

www.electronicshub.org

Those examples rely on a not-Q output that is inverted, but a 74LS04 or 74LS14 stage would allow the shift-register-feedback loop to be implemented.

marconi said:
I will post you some as a gift. Please private message me your address or somewhere to post them to from where you can collect them.

That is a kind offer of help

marconi said:
Each chip will divide by 2exp8.

https://www.electronics-tutorials.ws/counter/count_1.html

I will include some 74LS14 Schmitt triggered inverters chips so that you can input the 20 MHz sine wave and output from it a square wave to clock the 74LS273.

https://www.ti.com/lit/ds/symlink/sn74ls14.pdf?ts=1599590379543

You could use a circuit like this using two Schmitt triggered inverter gates as your test rig for the crystals which would in turn output square pulse to drive the frequency divider:

https://electronics.stackexchange.c...nverters-in-quartz-crystal-oscillator-circuit

I see that a later circuit uses 74HCU04 inverters. I will see if I have any. I know I have some 74LS04 ones.

https://www.infinite-electronic.kr/datasheet/54-74HCU04D.pdf

http://web.mit.edu/6.111/www/f2017/handouts/labs/74LS04.pdf

The LS versions are OK with high frequency crystals with low impedance but are far harder to make work reliably than the CMOS types. You generally can't use the single-inverter mode for parallel resonance as you need quite a low feedback resistor to pull the LS style of device in to its linear amplification region, so typically they are best used in series resonance using two inverters.

See page 164 of the linked book for circuit 11.3(a) as an example of forcing TTL in to dirty analogue activities.

Generally the LS14 and similar Schmitt triggers don't make good crystal oscillators as they never go "linear" but are great for cleaning up circuit outputs to get good square waves to reliably clock flip-flops.

pc1966 · May 16, 2022

If all you have ar LS14 then using a single transistor (or the original two-transistor example) as oscillator and the inverter for clean-up is worth a go.

pc1966 · May 16, 2022

_q12x_ said:
I believe you are trying to tell me it will not work using discrete D flip-flops or the 555 version of it, because they will not be fast enough for the 20M (or more) speed. If this is the case, please be clear with me now, before I start doing anything ((stupid)ly hard and slow).

Typically the data sheets only show the 555 going up to 100kHz operation. They were typically seen doing audio and below speeds, with newer variants having additional dividers inside to allow very long time constants without crazy sized capacitors.

marconi · May 16, 2022

-q12- Good spot by pc1996. I may have a pile of jk flip flops and 8 bit shift registers instead of 273s but we can make 273s do the division. I have ordered some 20MHz crystals to work in parallel with you.

_q12x_ · May 16, 2022

To mister @marconi
Thank you for your very nice and unexpected gift. I really-really appreciate it and is more than welcomed. I really like that you jumped into my crazy project. Its not an easy project and is very new to me with new challenges. That's why I am PUSHING it before the fv counter arrives. Its more like an experiment or an exercise. Hopefully everything will fit before the fv counter arrives and confirm the findings from this experiment, if successful. We'll see.
I will still PUSH with all I have, until your package arrives, and when is here, I will use your chips to simplify the entire experiment. At least this is the plan.
If your components (the 20Mhz OSX) will come faster than me doing my thing here, please do the entire Splitting circuit. Its a bit of a race with time what Im doing here. No matter from what corner of the world the results will come, the important thing is to get the results. So if you are faster than me in getting this thing working, please do it, because I am equally curious. If you can do it today, do it today, it will be awesome.
Thank you again !

_q12x_ · May 16, 2022

Im looking on the 74HC4060 datasheet right now.
And from the look of it, it appears it has all these D Flip-flops linked , so pretty much for each advancing output pin, Ill get a greater signal splitting (in my case lower and lower frequency). It is very customizable. Is my observation correct? If it is, then this is a very nice chip !

And... I took a good deal of 3.77$ for 10pcs for SN74HC4060N.
Is always better to have more than less.
So mister @marconi if you happen to read this in time, you can option to not send me your D flip-flops chips. But if you do, is as much very welcomed as before.

marconi · May 16, 2022

I do not have any 74HC4060 to send you. I have a selection of other logic ics though which you may find useful. I have kept them all 74 series.

_q12x_ · May 16, 2022

marconi said:
I do not have any 74HC4060 to send you. I have a selection of other logic ics though which you may find useful. I have kept them all 74 series.

No. What I'm saying is that I already bought 10pcs of 74HC4060 because like mister PC1966 said, they run at a bigger frequency and probably are newer IC's.
So if you want, you can or you can not - send me your IC's that are containing D-flip Flop inside them. You have 74LS273 octal D type flip flop. So now you have the option to send or not to send them. I will like them as well, so for me is still a good batch of IC's even if I will get these other ones. Like I said to you in particular, I have a grand list of IC's waiting for a long time. So every chip have its own characteristics that is always good to have a bit from everything. So im not saying no.

_q12x_ · May 16, 2022

marconi said:
Could you give me some idea of what you will constructing next?

Yes, I have a line of engagement
1- In the immediate days, until all these packages arrive, I am very concentrated on how to make a D flip-flop from discrete components. And I would like very much you to help me in this little endeavor.
2- Then, I will try the 555 circuits for splitting the fv. See how those will do. Im planning something very simple to test, a very basic oscillation in a couple of Hz, like 10Hz or something, by rotating a wheel in front of a LDR or something fast to make. Or even another oscilator using the 555 again. I dont know. Then, after reading and being sure the real fv of the test device, I will try to read it through the 555 splitter circuit (splitter is faster to write than D flip-flop).
3-Next, if I get good results, I will try to make a couple of 'splitting' modules. Either from discrete or from 555's. All, hopefully until everything arrives.
4- after the IC's arrive, I will make some splitters with these IC's. I presume I will not be even close with my discrete components way, to finish anything important. But who knows, if I work hard enough.... we'll see.
5- in the very end when the fv counter will finally arrive, is check mate. I can test every OSX, put a label on them and mission accomplished. And the project is done.
Again this is more as an experiment or a test. Nothing really to remain in time. Well, only if I will make a video about it, if I make some important progress with all of this.

marconi · May 17, 2022

Here is my circuit to test the 20MHz crystals I bought. You can see the waveform and its frequency on my scope. I will draw out the single transistor circuit which uses an npn BC549.

The lower trace shows frequency in 25MHz horizontal divisions. You can see there is a second peak of lower amplitude at 40MHz to the right of the main peak which means the circuit is oscillating at two frequencies. The scope shows the waveform of these oscillations when they are added together.

_q12x_ · May 17, 2022

A very small update:
This one is a variable PWM using a 555.
(The 555 Im using is a SOT23 smd fix in the middle, that black square)

But this is a second circuit. A clone if you like.
Because I build another one a couple of weeks ago and install it and run it for a device I make but is on hold at the moment for some other components to arrive for its upgrade.
I hope is clear enough...I tend to give too many details...

This is the exact same circuit that I am making from scratch (again) but the difference is it will be a portable and testing circuit, and not a fixed one as in the example.
I dont really have to make it but it was in plan so I will make it these days. I started it last night and now its pads are finished.

Ive also thought on other 2 sources of test oscilators.
An astable flip flop that I already have in stock for a long time, made from smd components. Very cute and small and I almost completely forget it.
And a voltage divider hooked up to mains for a nice 50Hz input oscillations with 1:100 ratio. Nice eh?
So in total I will have 3 [test] sources of oscilations.
Why? because I mentioned, I will have to test the D Flip-Flops I will make. Thats why. Aaaaah, right?
Stay tuned.

_q12x_ · May 17, 2022

marconi said:
Here is my circuit to test the 20MHz crystals I bought. You can see the waveform and its frequency on my scope. I will draw out the single transistor circuit which uses an npn BC549.

The lower trace shows frequency in 25MHz horizontal divisions. You can see there is a second peak at 40MHz to the right of the main peak which means the circuit is oscillating at the two frequencies of the crystal which explains the distorted sine wave.

Oooh, very nice and I totally can see the 20Mhz in the display counter of the osciloscope.

VERY NICE TOOL you have there. VERY NICE ! Aaah.
Yes, put the circuit here.
I really wish you could test my original quartz circuit in the original post on the top. Just to have peace of mind that circuit is good and running. I really love that circuit, how simple and efficient it looks.
Thank you mister @marconi for making these tests with me ! Really great and is a pleasure to see such fine equipment you have there, oooh.