New NBTV camera project

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Postby gary » Sat Apr 20, 2013 7:04 pm

Can you post the wave file Troy? I can soon tell you what is going wrong.

EDIT: it may be something as simple as an inverted signal - did you try the invert function on TBP?
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Re: congratulations

Postby Dave Moll » Sat Apr 20, 2013 7:49 pm

aussie_bloke wrote:I foolishly connected the main DC power leads the wrong way around and blew up some components in some of the circuits which really upsetted me greatly!!! :cry:

Not that you're likely to make the same mistake again, but would a series diode in the power input connections be a worthwhile investment for future peace of mind?
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Postby aussie_bloke » Sat Apr 20, 2013 10:16 pm

gary wrote:Can you post the wave file Troy? I can soon tell you what is going wrong.

EDIT: it may be something as simple as an inverted signal - did you try the invert function on TBP?


G'day Gary. Just tried the invert function, no change. Here are 3 wav recordings I've made. Should you get a picture out of them, what you'll see is a glass mosaic bowl.
Attachments
1.wav
(3.25 MiB) Downloaded 290 times
2.wav
(2.65 MiB) Downloaded 281 times
3.wav
(2.59 MiB) Downloaded 274 times
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Postby aussie_bloke » Sat Apr 20, 2013 10:31 pm

Here is a couple of telerecording samples I have made off the NBTV camera's monitor using my late 1960s B&W vidicon camera, one is of a NBTV test pattern I quickly drew up and the other is Che Guevara's face from a Seize Power drink can. I also attached a scan of my drawn up test pattern. I notice when shining a 150W lamp towards the subject there seems to be some shading effects above and below so the picture height looks rather short as a result.
Attachments
nbtv.jpg
nbtv.jpg (80.02 KiB) Viewed 5132 times
nbtvpattern.avi
(4.4 MiB) Downloaded 295 times
can.avi
(10.46 MiB) Downloaded 296 times
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files from the camera

Postby holtzman » Sat Apr 20, 2013 11:02 pm

Well, there is a speed problem, in the files at least. It is too slow, hence any program can't sync to it. I am not sure how much the speed is low, just checked it by my ears. Also no defined sync pulses are found. Of course Gary will understand more...
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Postby gary » Sun Apr 21, 2013 12:07 am

aussie_bloke wrote:G'day Gary. Just tried the invert function, no change. Here are 3 wav recordings I've made. Should you get a picture out of them, what you'll see is a glass mosaic bowl.


Hi Troy, well the first thing is the signal is on the right channel not the left as is required (although you can change that in TBP).

However the sync pulse is very erratic in form and is definitely not at 400 Hz.

More tomorrow
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Postby gary » Sun Apr 21, 2013 4:48 pm

Ok Troy, as can be seen by the following attachments we can say this about the recorded audio:

The video is on the wrong channel (right) it should be on the left.

The video is inverted.

There is little or no sign of any sync whatsoever.

The speed of the disk is not constant and varies between 435 and 415 RPM (approx).

When corrected (except speed) you get a picture that could be that of the mosaic ball (see attached).
Attachments
3.jpg
Notice video is on right channel
3.jpg (62.17 KiB) Viewed 5103 times
no sync.jpg
Notice one the signal is inverted there is no sign of sync pulses.
no sync.jpg (47.85 KiB) Viewed 5103 times
3xx.avi
Notice that once the channels are swapped and the signal is inverted that a picture of sorts is obtained. Not that the rolling of the picture is due to disk speed variation.
(48 KiB) Downloaded 287 times
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Postby aussie_bloke » Mon Apr 22, 2013 10:28 am

gary wrote:Ok Troy, as can be seen by the following attachments we can say this about the recorded audio:

The video is on the wrong channel (right) it should be on the left.

The video is inverted.

There is little or no sign of any sync whatsoever.

The speed of the disk is not constant and varies between 435 and 415 RPM (approx).

When corrected (except speed) you get a picture that could be that of the mosaic ball (see attached).


Hi Gary. Thanks for the details on what's going on with my camera. I admit when testing the camera I wasn't 100% certain whether everything was working properly or not and wasn't sure of whether I was adjusting everything properly, it seemed to look okay and seemed to look synchronized and the encoder output I looked at the scope and going by 400Hz is 2.5ms I adjusted the encoder circuit till I got a 2.5ms pulse. I have to say I'm still a learner, I know up to a point but don't know everything lol.

Also I mentioned in my previous post I stupidly and unwittingly put the main DC power leads in reverse polarity and blew up some components. I have since replaced a blown electro cap on the sync mixer board, all regulators on the boards and the chips on the main sync board. Just wondering if I could of blown up any other components like transistors, could it be possible I've blown up the crystal???

Now that I know I'm getting around 400-450RPM mark at the speed I was running it at, I will adjust it up to near double speed and see how it works out.
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Postby gary » Mon Apr 22, 2013 10:49 am

Hi Troy - we are ALL learners in this hobby, believe me. You have done very well indeed.

Yes it looks as though your sync mixer circuit isn't working at all.

I would suggest that, to test your speed control circuit, that you arrange your monitor-side circuitry to be able to take input from another device like your PC or CD player - that way you will know for sure you are on the money. When working correctly you should have 750 RPM with little or no variation at all.

Yes, once a cap blows it can create a whopping great pulse that can take any component out, let alone the physical damage it can do.

However your crystal oscillator appears to be working fine otherwise you wouldn't have that nice pulse you have.

BTW is the pulse you show on your cro a pulse from your encoder or your crystal oscillator?. Do you measure the 2.5ms between pulse edges (either leading - leading or trailing trailing).

In any case that part could be working perfectly and the rest of the speed control (PLL) may not be.

If you fix up the swapped channel and inverted signal (both settable in TBP if you can't be bothered doing it physically) and then tweak up your speed to 750 you should get a picture in TBP even if you don't have sync - as long as you use TBP V2 (alpha) and turn sync processing OFF in the settings.
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Postby Steve Anderson » Mon Apr 22, 2013 12:41 pm

Scopes are not only useful, but almost essential when doing any electronics work. But, and it's a big but, caution and skepticism needs to be applied when trying to take measurements with any degree of accuracy.

A brand new scope (of the analogue variety) will have an accuracy of around ±3%. If it hasn't been re-calibrated in some years this could easily become ±10%.

So what appears to be 400Hz could be anything between 360-440Hz.

The same applies to the vertical channel(s).

If it's one of the more expensive models with cursors use those as (in the time domain) they should be derived from a crystal. Set to 2.0ms on the 200us/div range should be exactly 10 divisions.

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Postby aussie_bloke » Tue Apr 23, 2013 11:56 am

Thanks for the tips Gary. I have just checked the sync pulse output of the 400Hz clock circuit, all good in that department as I'm getting a pulse width of 2.5ms (see scope pic below). Also checked the waveforms in other areas of the circuits, but haven't got time to post them right now.

I have just discovered a problem with the 22k trimpot that connects to the 555 timer from +12V, when I turn it with the screwdriver I notice that it is glowing when I hit a certain point in the turning (see attached photo below), I am guessing there's some arcing going on inside. I guess I'll have to replace that trimpot. Question though, what does that trimpot adjust, does it adjust the voltage going to the 555 timer or the current?

Anyways more to post later today/night.
Attachments
400hzclock.jpg
400hzclock.jpg (54.52 KiB) Viewed 5049 times
potarc.jpg
potarc.jpg (70.23 KiB) Viewed 5049 times
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Postby gary » Tue Apr 23, 2013 12:43 pm

aussie_bloke wrote:Thanks for the tips Gary. I have just checked the sync pulse output of the 400Hz clock circuit, all good in that department as I'm getting a pulse width of 2.5ms (see scope pic below). Also checked the waveforms in other areas of the circuits, but haven't got time to post them right now.

I have just discovered a problem with the 22k trimpot that connects to the 555 timer from +12V, when I turn it with the screwdriver I notice that it is glowing when I hit a certain point in the turning (see attached photo below), I am guessing there's some arcing going on inside. I guess I'll have to replace that trimpot. Question though, what does that trimpot adjust, does it adjust the voltage going to the 555 timer or the current?

Anyways more to post later today/night.


Hi Troy, since you mentioned my name I am not sure if you are referring the question directly to me or just in general but I can't tell you what the 555 does because you haven't, I don't think, posted that circuit or where it is situated in the over all control system. I would assume, looking at what you have posted that it is just a pulse shaper so that the PLL has a nice clean pulse train being sent to it - the trimpot "probably" is varying the mark-space ratio of the pulse train.

That is certainly an interesting phenomenon you have there with the glowing trimpot - it is hard to judge what is causing it without the circuit, but I feel 99.5% confident that IT IS NOT GOOD ;-)

Possibly the reason is that you are moving to a position on the trim pot where the resistance is low enough that the current is high enough to cause the track to incandesce - it is hard to see how this may happen without seeing the circuit - it probably implies a wiring error.

In order to allow members to help you debug your circuitry it would be a good idea to post/repost your circuits (or links to circuits) and your overall system diagram (which is quite good btw) here in one place - it is hard to go back over the old posts and trying to "pick up the thread" - ha ha that's a good play on words ;-) It would be good too if each element in your system diagram referred to a specific circuit diagram or set of circuit diagrams.
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Postby aussie_bloke » Tue Apr 23, 2013 3:17 pm

I was referring the question to everyone but was replying to your previous post at the same time.

Anyways had a look at the circuit, tested the voltage going through the pot and was surprised it was 13.4V and then it turns out I've connected the main DC power to the output of the 7812 12V regulator instead of the input, whoops, so fixed that up and that fixed that problem. But even on 12V the trimpot still glows, so will investigate further.

I will upload the circuits in my next post.
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Postby Steve Anderson » Tue Apr 23, 2013 5:04 pm

gary wrote: - it is hard to judge what is causing it without the circuit, but...In order to allow members to help you debug your circuitry it would be a good idea to post/repost your circuits (or links to circuits)..

Gary, spot on! Many a time someone says I'm using the club motor control circuit (for example)...but which one? I've seen at least a dozen variations on it, some subtle, some not.

Or..."It's the circuit in the handbook, page xy." ...I don't have a copy of the handbook. I quite enjoy being an "electronic detective"...but like the CSI I need the evidence such that I can draw a conclusion/present my case...

Whatever...glowing trimmers...not good!

Steve A.

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Postby Harry Dalek » Tue Apr 23, 2013 9:38 pm

Hi Troy

I have been busy last few days and i can see you have as well on more interesting things than i have .

I have to double check the problems you have had but a quick read i gather its not working

This is a good thing as you learn from your mistakes never from any thing that works off the bat when you work out why you will never do it again .....; )

learning and still am on cameras a lot of help from Gary got me to the point i could sync the video watch on PC very much a Gary harry win ,see every one is helping here and better mega minds than me .

Troy has been using the circuits i have on the flying spot camera I think Gary ...

Troy 400 to 450 is a big swing you need to have this steady as close to 400 hz no drifting ..I am pretty sure the LM311 and 555 timers monostable the voltage was 5 volts .

Use your frequency meter watch the motor speed as you start it up from power up ,its best to have your voltage to the motor low than high ...i think you have to much voltage feeding that Mosfet ...i always found if it will not get to 400 hz just increase voltage to the motors Mosfet a little till the PLL gets it under control...to much voltage and pll is not controlling the motor your pot is in a sort of manual way not what you want.


Check for mistakes in the video sync mixer fault finding should fix that .

Use Garys software i found the scope very helpful viewing the video and sync and adjusting it all .

Edit/adding stuff as i am reading past posts//////

I used Lm317s for the motor control troy not a 7812 so theres one problem

Again i used 5 volts as i recall it doesn't work well increasing the voltage reason i put in Lm317s to adjust every thing on different circuits just found 5 volts on the timing part worked well.

Don't worry about making mistakes every one does not that we want to but happens i still miss my green laser :oops:
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