Make a very simple test for me

[_q12x_]

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_]

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.

 

[_q12x_]

Do you see that under 1mm distance between pin 7 and pin 8?
Made on cardboard and handmade cut and bent all the solder tabs !!!
Cool, yes?

 

[marconi]

I will have a go at constructing this circuit tomorrow.

 

[marconi]

The circuit for the 20MHz oscillator. It is similar in design to a Colpitts Oscillator circuit. See:

https://www.electronics-tutorials.ws/oscillator/crystal.html

Colpitts was an American engineer:

Edwin H. Colpitts - Wikipedia - https://en.wikipedia.org/wiki/Edwin_H._Colpitts

 

[_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.

 

[pc1966]

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.

OK, I will see if I have the parts to try it as well.

At one point we had loads of stuff for this sort of experiment but sadly it was thrown out when my last work ended. We saved some stuff "just in case" but space did not permit all of the items I wish we had kept.

 

[pc1966]

@marconi Was the DC bias condition much as expected? I guess around (Vcc - 0.7) / (Rc + Re) per transistor current, at 5V supply around 3.5V over emitter resistors?

 

[marconi]

@marconi Was the DC bias condition much as expected? I guess around (Vcc - 0.7) / (Rc + Re) per transistor current, at 5V supply around 3.5V over emitter resistors?

I will check tomorrow morning. We are heading for thunder and lightning this evening and it feels very muggy right now.

 

[pc1966]

This is a handy web site for current activity:

Lightning & Thunderstorms - United Kingdom, England, Scotland, Wales, Ireland

Blitzortung.org provides lightning and thunderstorm information in real-time on maps for USA, United Kingdom, Australia, new Zealand, Europa, Africa, Asia and other Countries.

www.blitzortung.org

However we have seen the odd flash here that did not register on their detectors.

 

[_q12x_]

Im loughing how everyone is preoccupied: me with the fv reading, marconi with lightning and pc1966 with stuff that doesnt find or have anymore. Hahaha.

 

[marconi]

Regarding the circuit Symmetrischer Oszillator I have included below again. I don't think this is the working circuit - it is an outline schematic of a circuit missing some key detail. I reckon the circuit idea is a classical astable transistor circuit - see second circuit - which has resistance and capacitance to make it oscillate at a frequency close to that of the quartz crystal as in the second image. The purpose of the crystal connected between emitters is to 'force' operation at its frequency. This is what I am going to pursue.

 

[Lucien Nunes]

I was just going to say, it looks like a circuit from a patent which shows enough to define the principle that is claimed, but not enough to construct a replica directly. I too would be inclined to provide AC feedback and bias in the usual way, and probably make the emitter coupling somewhat tunable.

It seems a very long time ago that I had the opportunity to make with circuits that might not function, to see whether something can be done some particular way. In my work I am so often against time pressure that the solution has to be guaranteed to work first time even it is technically ridiculous or extravagant. I have used a 14-bit 40-pin PIC running at 20MHz as a monostable to generate a 10 second pulse, because it was already built and reprogramming took 2 minutes vs. 5 minutes to make something specific.

If you asked me to test the frequency of a vanilla-flavour crystal now I would reach for the PIC prototyping board again and have an answer in 20 seconds.

 

[_q12x_]

We know that is a symbol of a BJT NPN but try with 2 N-ch Mosfets.
Also... Im thinking to use different types of npn's. 1 BC548 and another BD139. To induce a instability in the circuit...
Just putting some ideas on the table.

 

[pc1966]

A crude simulation attempt, did not work at 20MHz with 2N2222 but OK with BC548, also used low-Q crystal model so faster to build up (along with 1mV kick at t=0)

Time-domain for test point in Tr1 collector:

 

[Lucien Nunes]

I gave myself 5 minutes to do this, just to prove we can all build a discrete transistor crystal oscillator that doesn't work...
First transistors I came to - ZTX753s - should have enough zing to work. The circuit has a name but I can't remember it, a common-base stage driving an emitter follower. I made the values up as I went along, they won't be far out but it still doesn't work. I've no interest in simulating it or debugging it, time's up!

 

[Lucien Nunes]

So then I decided to give myself another 5 minutes to build a crystal oscillator the way I would have done if somebody had said: "Build a simple crystal oscillator." I.e. with an 'HC00. Of course this one works just fine. I didn't bother tuning it, I used the first capacitors that I picked up from the drawer, which turned out to be 22pF. Build time was just under 3 minutes including stripping some wire to make links.

 

[Lucien Nunes]

And this is how it looks with a 4MHz xtal.

*BONUS POINTS for anyone who noticed I had the scope's 20MHz bandwidth limiting switched on. The actual output waveform is very ringy because I did a lousy job of decoupling the power supply (stood a ceramic 0.1 across the IC without chopping its leads down). You can change the W/F just by bending this component about. It could be fixed but... time's up!

E2A, I semi-fixed it (relocated the bypass cap and poked the probe direct into the breadboard)

 

[_q12x_]

very interesting update.
I managed to split 1/10 of my test PWM original fv. From its 850Hz down to 85Hz
Now Im playing with some capacitors values to bring it down to 1/100.
My target end result will be 1/1000.
And, I did managed to --average-- the 1/100 values. I say average because the fv counter is jumping a couple of Hz up and down. It should be 8.5Hz but is heavily fluctuating with diverse values between 10Hz and 6Hz. So I am theoretically at 8 but because is jumping all around these values, it was hard in the beginning to understand where I stand. But staying and watching these values for a while, a couple of minutes, I concluded it is jumping around these margins. That might be from the High resolution of the splitting, all the circuit(s) combined might present some tolerances, especially the capacitors and resistors and why not the chip(s).
At 1/10, it does not jump at all, it stays put at that fv. So.... I think im good at this point.
I might have to make a second circuit that will split another 1/10 from this one that is 1/100 and in the final output will get 1/1000. And I expect it will be extremely jumpy at that Very High resolution. If it is a way of "average" all these jumping, especially at 1/100 stage I am right now. That will give a good clear chance for the 1/1000 stage. Hmmm. But it is in plan. For now, I have to reach that 1/1000 target and Im GOOD, literally. Haha.

 

[marconi]

A crude simulation attempt, did not work at 20MHz with 2N2222 but OK with BC548, also used low-Q crystal model so faster to build up (along with 1mV kick at t=0)
View attachment 97652

Time-domain for test point in Tr1 collector:
View attachment 97653

I had another go this morning after thinking about the small signal model of this circuit and why the ratio of Rc to Re matters so much- see first attachment. I tried Rc = 1kR and Re = 4.7kR and even exchanged the BC549s for two new but in my construction it did not oscillate. Not enough feedback methinks so I swapped Rc for 100R and the symmetrischer oszillator found its 20MHz voice. We did it Sir and self starting to boot!

 

[pc1966]

Not enough feedback methinks so I swapped Rc for 100R and the symmetrischer oszillator found its 20MHz voice. We did it Sir and self starting to boot!

Excellent!

While the E-E impedance should be roughly -2*Rc quite possibly the higher Rc values along with stray capacitance might cause too much phase shift. I seem to recall that 10-20MHz crystals are below 100R series resistance so indeed 100R values for Rc would be adequate, as you have so well demonstrated!

 

[marconi]

q12x. : My next step is to take the small amplitude 20MHz sine wave and turn it into 20MHz pulse stream of TTL logic 0 and 1s to feed into the divider circuit.

 

[_q12x_]

Congratulation mister @marconi I am really happy you made it !
But I am not sure I understand completely your values.
So I grabbed all the information you provided so far:

Rc for 100R and the symmetrischer oszillator found its 20MHz voice.

did not work at 20MHz with 2N2222 but OK with BC548

I tried Rc = 1kR and Re = 4.7kR

and I redraw the circuit with the new values:
- Are these the values you used?

 

[marconi]

Congratulation mister @marconi I am really happy you made it !
But I am not sure I understand completely your values.
So I grabbed all the information you provided so far:



and I redraw the circuit with the new values:
- Are these the values you used?
View attachment 97682

Yes. VB is 5 Volts not 1.35V. The npn transistors are BC548B types. the letter A, B or C after BC548 indicates the so-called direct current gain of the transistor - the hFE - and relates the emitter-collector current flow to the base-emitter current flow eg: Ice/Ibe. Which BC548s do you have? Cs have higher gain than Bs than As so I used the mid-range gain type.

See top of page 2 of:

BC548B datasheet - https://datasheetspdf.com/pdf-file/1292183/Kingtronics/BC548B/1

 

[marconi]

Which operational amplifiers do you have please and I will use the same ones to amplify the small amplitude 20MHz sine wave.

 

[_q12x_]

Mine are BC548 B - coincidence! like yours.
I have uA741(not that used anymore) and LM358(most used)
Updated circuit after your last specifications:
Ive added + and 5V and gnd symbol. Also B after tr name.