Make a very simple test for me

[_q12x_]

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)

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.

 

[_q12x_]

yes, I definetly like your circuit more now, because is way more simple than mine.
Very good !
I managed to solder every component now on that board. But I have to add copper wire links between the pads and it is done. Today I will finish it. Oh boy, you have no idea how intense and hard is to do it like I do. But I get results so, I say is worth the effort.

 

[marconi]

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)
View attachment 97596
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...
View attachment 97599
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.

So that I can sleep tonight without the worry - please tell me this 50Hz signal is from the secondary side of a low voltage eg less than 25V double insulated safety transformer.

 

[marconi]

So that I can sleep tonight without the worry - please tell me this 50Hz signal is from the secondary side of a low voltage eg less than 25V double insulated safety transformer.

q12x : It is not wise and I have always assumed you are wise - to be directly (galvanically) connected to the mains or other unsafe to touch voltages. You know from what you have taught yourself that it is easy to construct a perfectly safe circuit which provides a low level 50Hz signal derived from the oscillations of the mains which is galvanically isolated from the mains. In my workshop, because I work alone for long periods, I only do projects operating at up to 20V dc. There is enough amusement for me in doing these low voltage safe projects which do not risk my life and making my wife a widow. I strongly recommend this same approach to you.

 

[_q12x_]

Dont worry man, its fine.

 

[_q12x_]

Huuuuiuuuuiuiui it was hard and intense.
But I finish it. Its a PWM using a 555 (SOT23) driving a mosfet (A09T) that can drive a small DC motor like a computer fan at 12V. Already test it and is working like a dream.
So now I have something to oscillate for further testings.

This circuit is from internet but the blue inscriptions are mine. Also the blue circuit I design it. Is not much but is doing what I want. (Is looking so much simpler in the circuit schematic, right?)

Next, is to research and find a way to make a D Flip-flop from discrete components.
This is contra-time until mister @marconi IC's package arrives in a week he said... but not the european postage is the problem, but my romanian postage is slowing EVERYTHING down, because they have the power and they know it. We'll see. It would be nice to have it in 7days.
So I must hurry more now, haha.
Im so tired but very happy this circuit now is alive. I worked all day at it. Probably 9h straight.
I will update here what D Flip-flop from discrete components I will find. And tomorrow I MUST build the first one ! That's the plan.

 

[Lucien Nunes]

Dont worry man, its fine.

I think this means you are using a voltage divider that is not isolated from the mains. Please don't. In real industry it would get you fired because it's an unnecessary risk. The key point is 'unnecessary.'

I am following with interest and I admire your determination to build logic blocks from discrete components. It is, in theory, a good way to understand what goes on inside and I would think it good exercise to build a few gates using different technologies. But to build a reliable multi-stage frequency divider is truly hard work. It was done in the past, yes, but in the days when only a large multinational corporation could afford to own a computer, and they had to hire a full-time technician to keep it functioning.

I have electronic organs from the 1960s that use discrete-transistor frequency dividers. Each stage of division uses about 15 components and needs to be set up for a particular frequency range, like the blocking monostable idea with the 555. |The best of those organs cost as much as a good car, and you got a total of 72 divider stages. At the time it was 'hi-tech' but immediately became obsolete when ICs were designed to do the same job.

So experiment if you wish, but do not beat yourself up if your discrete multistage divider takes too much time or misbehaves at higher frequencies. It was always like that.

 

[_q12x_]

Interesting... but I still have to see a circuit with discrete components. That's what I'm after.
See if you can help me with one (or more if possible).

 

[Lucien Nunes]

OK, no schematics but here you go, this is the sort of thing you want to build. I had forgotten about this organ, it was a very good model from 1967 that cost as much as a house. It uses about 300 transistors in total. Each divider stage has two transistors for the multivibrator and one as an output buffer. Each divider board has 7 stages plus an oscillator. It is only designed for frequencies up to about 12kHz and would not operate at 20MHz.

 

[_q12x_]

So with a 555 then.........

 

[Lucien Nunes]

If a man was holding a gun to your head saying: "Make a prescaler NOW! Divide by 8192. NOW!" and you had only 555s, then, maybe. But later you would be saying "OK sir, here it is, I think it's dividing by, let's see, 13 x 7 x 9 x 10 which is 8190, that's very close, or it might be 11 x 12 x 6 x 9 which is 7920, that's not as close but is it OK sir? Please will you let me go now sir?

Only it will be you holding the gun to your own head.

 

[marconi]

So with a 555 then.........

If I remember well, you used a 555 in your wings project, without a capacitor as a two state/bistable and thus as a flip flop to control a relay. You may be able therefore to adapt that circuit and have a number cascaded together ie the output of one feeding the input of the next and thereby form a divide by 2expN circuit where N is the number of 555s. I do not have time now to research or think further on using 555s as FFs but you are good at doing these and negotiating the 'Innovation Funnel' to success -

 

[marconi]

View attachment 97610

I will have a go at constructing this circuit tomorrow.

q12x: I have just spent an hour trying this circuit out but without success. Re values of 2.2kR and 10kR and Rc values of 47KR and 10kR. Tr1 and Tr2 BC549s. VB between 1.5 and 15V. I have given up with it.

 

[pc1966]

q12x: I have just spent an hour trying this circuit out but without success. Re values of 2.2kR and 10kR and Rc values of 47KR and 10kR. Tr1 and Tr2 BC549s. VB between 1.5 and 15V. I have given up with it.

You need Rc to be significantly less than Re for it to have any chance of working.

For 20MHz crystal try Rc = 1k and Re = 4.7k from 5V and see if you get anywhere.

 

[_q12x_]

An important update.
I didn't check this before, because I was thinking on a bigger picture, but... today for 2h or so, I was desperately trying to find a way of measuring the frequency.
I have 2 instruments here:
Number 1, the famous golden boy toy
DSO 138 Oscilloscope

that is showing the waveform alright but it doesnt put the numbers !
Or at least I don't think I know very well how to get them from only its waveform.
And number 2:
GM328A Transistor Tester

And I completely forget I have a fv counter build in, until I checked its menu today. And I checked its manual as well and it doesnt say anything useful for my problem with fv counter. I had to literally guess every port it has, and multiple times, switching polarities, and all that shi...fun. But looking now more carefully on its naked picture posted here, I noticed it has a BACK port as well.... I have a cardboard cover on him, I made it myself and I didnt see the back port. Oh my god. Haha. And indeed that was the Input port for the frequncy counter. Ohoha. What a ride. Im happy to report I have a way of measuring the fv now. But this is also limited 1Hz-2MHz. But it is good I discovered this somewhat hidden functionality. I had a very vague idea I have something related to frequency counting but I was not very sure what I had. It appears I read its menu some years ago and something remained like a shadow memory about it. Im so Lucky I even remember it. Those who have this functionality ready build into your osciloscope, kiss all his 4 rubber feet !
The fv counter that is coming should be much better than this one I have, 1Hz-50MHz.... Hmmm now that I can see and compare the 2, its not that bigger difference. I should have something to Giga or TeraHz, to really see a difference. Eh well.
What a experience.
So, I measured my newly PWM with the 555, @5V, and I got 953Hz(max) to 850Hz(min). So 100Hz range. It was not the reading I was expecting. But I had planB, with a astable flipflop, also @5V and that give me straight 9Hz not variable. So I tested 2 diferent pulsating and oscilating devices that I know for sure their value and that they work. I wished I had a more larger fv range with my 555 PWM.
Im thinking to make another board that is a pure frequency variable generator with greater range than 100Hz and not a PWM. I also think what I have already is good enough as well. So this new board remains in plan.
I am thinking out loud here a bit... thinking a little bit more on my options, I also have a fv generator in my small GM328A. But the problem is that I also have to measure with it as well, so I should have 2 of these GM328A, one for fv gen and one for fv counter.... hmmm. But the other fv counter is arriving so in theory, this GM328A can be the fv gen and that will be the fv counter. So 2 devices after all. I didn't stop to analyze these problems until now.
In conclusion, Im good. Haha.

 

[marconi]

You need Rc to be significantly less than Re for it to have any chance of working.

For 20MHz crystal try Rc = 1k and Re = 4.7k from 5V and see if you get anywhere.

PC1966: I had another try with Rc = 1kR and Re = 4.7kR, 10kR and 22kR over a range of voltages from 3-15V. Not a twitter at 20MHz. I also tried two other crystals.

Next I will try keeping Re at 4.7kR and reducing Rc but at the moment it is too hot in my shed to do so.