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gary wrote:Hi Harry, it varies between 384 Hz and 436 Hz.
harry dalek wrote:My scope frequency meter must be way off i am just seeing 396 397 steady on the adjustments tonight .
But i can see the changes in hight in lines which is due to the frequency changes in the lines on play back i suppose .
I am taking the readings from after the lm311 would the monostable wouldn't change it ?
What i don't under stand is the clock is 400hz shows 400hz on the meter...i might test it via the pc and my multi meters ...
I might record my crystal clock as well.
I was thinking i had this problem beat looks like its going to be a bit more work..darn!
BTW i recorded them in mono 16k for some only seems to play on garys Alpha big screen and rolling a bit in Doms software
Well it is probably just showing an average - the variation is too fast to display in any meaningful sense of a frequency meter - it would be nice if it gave the variation though.
Well the clock is probably spot on, but I think your disk maybe "hunting" in a manner similar to Albert's nipper.
Not a bad idea.
Well to be honest it did seem to come together just a little too easily, my experience with speed control is it takes a lot of "tweaking" to get it spot on.
Harry, by far the best way to test it would be to modulate a led or leds with NBTV and view it through your disk - that will tell you immediately if you have correct speed.
EDIT: OTOH when viewing your output through TBP, WITHOUT sync processing selected, you will get a steady picture with a flat sync bar when you have 400 Hz.
Sorry, Harry, I don't quite understand that comment, what has recording mono 16k (too low BTW as you will be chopping of the top 2k or so of bandwidth) got to do with playing the file? If you could elaborate on that I might be able to recommend a better sample rate.
gary wrote:Harry, further to measuring your disk speed. When viewing on TBP with sync processing turned OFF - the "sans TBC" video is what you will see with your current setting, and the "TBC" video is what you will see when speed is correct.
gary wrote:Well that's certainly more consistent Harry.
Max freq = 424.8 Hz @ 0.7 seconds
Min freq = 372 Hz @ 4.481 seconds
Average freq = 400 Hz
Still a bit of a swing...i had 3 gos at it and 3rd was the best ...the strobe disk doesn't move but must be a slight vibration happening ..and on the vibration side or wobble do you think a slight disk wobble on the mechanical side cause the above effect to ....the mechanical side must cause more trouble than the electronics .
But i will adjust it bit more .Yes the wavy sync bar could be hunting as in Albert's case, or aperture position inaccuracy.
Again it so reminds me of vibration on a drum monitor ...i noticed because i cut my encoder slots out theres a slight difference in pulse widths perhaps this is a problem ...may be i should of tried the pot on the photo transistor for the encoder least i would of known this is not a cause .
I will do some reading and thinking about this tonight .BTW I suppose that your clock pulse train doesn't include a missing pulse? If not, then for testing purposes, it may be worth adding in the missing pulse from the disk to see if it locks better.
do you think a slight disk wobble on the mechanical side cause the above effect to
....the mechanical side must cause more trouble than the electronics .
...may be i should of tried the pot on the photo transistor for the encoder least i would of known this is not a cause .
No gary i have not even thought of that i am thinking its not in the sync for a monitor should work in reverse for a camera but ...are you saying feeding back the encoder pulses to sync the crystal clock ....if so thats an interesting idea ...
Possibly, but I would think it would have to be a huge wobble to produce that much of a wave. Don't forget it is only the encoder/sensor that is involved and the little distance change due to wobble would not make that much difference I wouldn't have thought.
Come to think of it, I mentioned earlier it could be due to a variation in aperture position but that can't be as it is having an effect on the sync which, of course, doesn't travel through the apertures.
OTOH, if the encoder itself wasn't running concentrically with the sensor then the wedge shape of the segment may possibly cause this effect - again it would need to be quite out of concentricity.
Well yes when you were asking about adding a missing pulse to the crystal clocks i was wondering if you were meaning that .
my mistake
But then back to what I was saying if your clock has 32 pulses and your encoder has 31 I would expect that to have some effect as in fact you are then comparing apples with oranges, or at least Granny Smiths with Delicious' Ideally with this kind of an arrangement, which I support as a good way of doing things - but have never implemented myself, you would have 32 segments on your encoder and a separate sensor and encoder to detect frame, you would then electronically remove the "missing pulse" based on that information*. I shouldn't think that would be too difficult, but not having gone down that track (well done Harry!) perhaps some other reader who has done something similar would care to comment?
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