Newbie alert - measuring voltage around a NPN transitor

[bitman]

I cant really tell what you are doing with the circuit - a schematic of your pulse generator section would be nice.   If you give us a better idea of what you actually need for a test signal we can suggest better or easier circuits to generate it.

Thanks Ian, you've given me plenty to think about and learn from here.
As to the purpose - learning I'm trying to create - strike that - understand how to create a sync'ed clock signal I can use for some logic circuits I want to use (buffers, registers etc). Thing real fancy and nothing that will make it past the bread-board.  So while I understand the principles of the timer circuit, it seems very very rough, noisy and imprecise to me. It also found that a single clock signal wouldn't cut it, so I finally discovered "dividers" and it looks like it's exactly what I needed to create a few synchronized but slightly offset pulses so I can synchronize data/signal better. In essence I'm trying to build a simple bus - as a project to get some electronic principles under my skin.  In the past I've simply connected in/out pins on a controller to a sensor or motor etc. - I need to make slightly more complex circuits as my next stage, and that means actually understand (prove) how small circuits work. Ie. amplifying signals and using pullup/down at the right places. I've already had to correct a lot of misunderstandings I had about signal processing. My purpose is to know enough to build very small circuits without needing a microcontroller where I'm comfortable.

Yes, it's basic VERY CHEAP NE555P chips I'm using. All they've proven to me so far, that they suck at generating a consistent/stable frequency. Or maybe it's just me that screw it up - it could very well be both   I finally got a 1-2% duty cycle setup working, but still the frequency according to my scope is jumping quite a lot particular in the 100s of KHz. Hence my idea of using simple crystals. It got a handful or so of Quartz Crystal (VAPKER), unfortunately the smallest I can find is 4MHz and well, I think that's too fast based on my reading of the CMOS/74xx datasheets. However, that's what that divider is for - for now, I would just like to see a rather steady frequency that doesn't change with 1000s of Hz every second. I don't really care if it's 4MHz or 2MHz - I just want it steady. Taking all what you wrote, it's clear you understand why it's unstable right now - and it's my hope I get to that moment too. So far I'm reading a lot, watching a ton of youtube like EEVBlog attempting to gain a better understanding. I'm fumbling around slowly - day job only gives me a few hours a day (at best) to study/learn. And there are weeks when I'm on the road with no access to my small collection of components, breadboards etc. so things move slowly here which is OK. I'm in no real hurry.

Thanks again. I'll need to google quite a bit of what you wrote to understand the answer. So I have a lot to work with here.

[Ian.M]

Hmmm.

Probably the easiest option if you want a crystal controlled oscillator, would be to use a 74HC4060.  A CD4060 wouldn't be fast enough for a 4MHz crystal below 10v Vdd.   The 74HC4060 needs a 5V supply (though you can also use it at 3.3V as long as you avoid the 74HCT variant) and consists of an input buffer section that can accept an extewrnal clock or be configured as a RC or crystal oscillator, followed by a chain of 14 flipflops each dividing the input frequency by two.  Assuming a 4MHz crystal, Its highest frequency output is Q3, Fosc/16 or 250KHz  and it also has outputs all the way down to Q13, Fosc/16384, or fractionally over 244Hz, except Q10, Fosc/2048 (1953 Hz) which isn't brought out to a pin.

If you follow that by a 74HC4017 decoded decade counter, you can get up to ten sequential active high pulses on separate pins that you can combine with logic gates to get any possible sequence of overlapping or non-overlapped clocks, that should finally be gated through a D type latch clocked by the opposite clock edge to the 4017 to de-glitch any clock that's derived from more than one consecutive 4017 output.

[bitman]

Hmmm.

Probably the easiest option if you want a crystal controlled oscillator, would be to use a 74HC4060.  A CD4060 wouldn't be fast enough for a 4MHz crystal below 10v Vdd.   The 74HC4060 needs a 5V supply (though you can also use it at 3.3V as long as you avoid the 74HCT variant) and consists of an input buffer section that can accept an extewrnal clock or be configured as a RC or crystal oscillator, followed by a chain of 14 flipflops each dividing the input frequency by two.  Assuming a 4MHz crystal, Its highest frequency output is Q3, Fosc/16 or 250KHz  and it also has outputs all the way down to Q13, Fosc/16384, or fractionally over 244Hz, except Q10, Fosc/2048 (1953 Hz) which isn't brought out to a pin.

So I don't have a 4060 - CMOS or otherwise. But I do have a CD4017 and reading it's data-sheet didn't seem to indicate a max frequency (it was a blank box, not sure what that meant). So I took a chance. Based on a different thread here, I figured out my "crystal problem" - turned out to be a power problem (5v wasn't connected to the chip so no wonder things didn't work!). It measured out at 4GHz straight on my meter - no change what so ever. My scope also showed a steady frequency down to 1KHz ranges (3 decimal points) so that was exactly what I had hopped for. I then connected it to my CD4017 and all 10 input lines all show 400KHz signals minus about 0.001KHz or so, but I get the same on all of them. It also produced duty cycles in the 2-12% range, somehow each line seems slightly different not only sync wise but in duty cycle. That's probably a property I wasn't aware of.  Showing two lines on the scope clearly showed how each line was slightly shifted, so it's just a matter of figuring out what line to pick. It SEEMS to be something I can use. There's still a few aspects of the CD4017 I'm not sure I'm getting but at least it seems to do what I wanted - so I can get rid of the 555

I also had a 8GHz crystal and a 16GHz crystal. The 8GHz works too - but 16GHz was too much for it I guess.

It was strange - as I was searching around looking for CD4017 with an oscillator examples, all but a few hits were about CD4060 (or I guess the 74HC version).  I never figured out what the 3 clock lines were sbout. The PDF I found was a scan I of the real data-sheet and it was so low res that I couldn't read the symbols. I did gather from the many many MANY pages I found that it's a popular chip, so I guess I need to see if I can get my hands on one or two of them.

If you follow that by a 74HC4017 decoded decade counter, you can get up to ten sequential active high pulses on separate pins that you can combine with logic gates to get any possible sequence of overlapping or non-overlapped clocks, that should finally be gated through a D type latch clocked by the opposite clock edge to the 4017 to de-glitch any clock that's derived from more than one consecutive 4017 output.

This is what I love reading posts here. Stuff like using a logic gate to generate lower/different frequency waves would never have occurred to me.  As I wrote above, the 4017 doesn't seem to overlap any of the pulses (except for the carry signal that still puzzles me). Maybe that's connected to the short duty cycle - no clue. Anyway, lots of of stuff to think about in the next couple of weeks while I'm on the road.

[Ian.M]

For a decent CMOS 4060 datasheet, try http://assets.nexperia.com/documents/data-sheet/HEF4060B.pdf and for the 74HC4060 try http://assets.nexperia.com/documents/data-sheet/74HC_HCT4060.pdf

If you want to see what's going on with the outputs of a '4017,  as the ten sequential outputs are virtually identical apart from being time shifted, you cant really distinguish them on a single channel scope.  If that's all you've got, ASK as there are a few tricks that can be used to mix in a marker pulse so you can see the relative timing.

To see them properly, you need to use a scope with at least two channels, DC coupled, and keep channel 1 on the Q0 output, with rising edge triggering on channel 1.   Probe around with channel 2, and you will see the timing relationships between the other signals and Q0 exactly as diagrammed in a '4017 datasheet.

The carry signal is just the input signal divided by 10, with a 50% duty cycle.  Its rising edge to trigger the next counter in the chain occurs fractionally after the tenth input clock pulse rising edge.

Experiment with dividing by numbers other than 10 - e.g. to divide by 7 connect Q7 to MR.