The PMT in control of the Devil

Moderators: Dave Moll, Andrew Davie, Steve Anderson

Re: The PMT in control of the Devil

Postby Steve Anderson » Tue Jul 25, 2017 3:58 pm

I've corrected the schematic posted above after noticing another error.

The two channels are identical, just the input frequencies are different.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5361
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: The PMT in control of the Devil

Postby ppppenguin » Tue Jul 25, 2017 6:02 pm

Steve Anderson wrote:Harry, here's the second part of the timebase circuits.......


I don't know if this is significant for the intended application but there will be glitches in the analogue outputs. Those HC devices are ripple counters so higher order outputs will transition later than lower ones. The difference is only nanoseconds but it's definitely there. Looking at the HC404 data sheet it will be typically 80 nanoseconds between the LSB and MSB feeding the DAC.The problem will be worst at the MSB transition (from 127 to 128 in an 8 bit system) where all the bits changes at the same time.

The problem is avoided by using synchronous counters or by interposing a register (HC374 or similar) between a ripple counter and the DAC. As I said before, a 100ns or so glitch may be unimportant for the application but it's best to be aware of it.
Jeffrey Borinsky www.borinsky.co.uk
User avatar
ppppenguin
Research Scientist
 
Posts: 44
Joined: Fri Nov 04, 2016 5:30 am

Re: The PMT in control of the Devil

Postby Steve Anderson » Tue Jul 25, 2017 6:28 pm

Quite correct, there will be glitches but there are ways around them in this application. The simplest answer is to place a small cap on the current output of the D-A and/or restrict the bandwidth of the downstream circuits. The bandwidth requirements are quite modest. Should these artifacts be visible some corrective action is called for, but for the moment I doubt it'll cause any major strife.

Synchronous counters are of course the answer but they generally are only available in 4-bit versions, so more packages. Unless you can create your own with programmable logic - I can't. One of the reasons I'm tending to a micro-based version where the ports are 'broadside'. Though I would probably go the PWM route. Undecided.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5361
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: The PMT in control of the Devil

Postby Harry Dalek » Tue Jul 25, 2017 6:49 pm

Steve Anderson wrote:I forgot to mention, if you need a negative-going ramp, swap pins 2 & 4 on the DAC-08, though this could also be done in the deflection amps. Also an arrangement for swapping line/frame between vertical/horizontal. More later...though it is quite simple.


OK i have time now to look at the circuit Yep i will make it so i can swap pins 2 and 4 if needed ,i know you mentioned the 4040 pin 11 to ground this is a temporary...is there another ic going to be added just asking work out PCB spacing noticed the wire coming out of pin 10 of the 4040

I am going to fit it in the PMT case the power supply is via the bench knowing the wiring has to be short on the frequency switch i will see what i can do with board placement i want it under the PMT but i might be able to put it just under the case lid.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: The PMT in control of the Devil

Postby Steve Anderson » Tue Jul 25, 2017 7:06 pm

Yep the two 4040s generating the ramps (IC201/203) will be reset using external sync detection circuitry via the MR input, pin 11. Pin 10 is the clock input from the precious circuit via the two switches. That won't change.

Now, I'm aware of the NBTVA standard sync arrangement, but all the other modes I have no idea about beyond the line and frame rates. How do you propose doing line and frame sync apart from the NBTVA standard 32-line, 12.5Hz system? As far as I know there are no standards for these other formats.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5361
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: The PMT in control of the Devil

Postby Harry Dalek » Tue Jul 25, 2017 8:08 pm

Steve Anderson wrote:Yep the two 4040s generating the ramps (IC201/203) will be reset using external sync detection circuitry via the MR input, pin 11. Pin 10 is the clock input from the precious circuit via the two switches. That won't change.


Will that be needed Steve ? as that would be good for a monitor but as a camera or scanner (depending on the experiments) its the master and the monitor is the slave to this as far as syncing.

Now, I'm aware of the NBTVA standard sync arrangement


Yes to be wise since i have the 32 line monitor all the first tests will be done here .

I was thinking of using the same Klass circuit i used on the PMT Nipkow camera add the sync to the video ..no missing sync here but it seemed to work there so should work with less head scratching with no mechanical things to go wrong apart from trimmers switches. Framing if i have it right is already correct via the 4046
So i pretty much want it to output the video signal to the Devil for 32 line .


,
but all the other modes I have no idea about beyond the line and frame rates.


May be some of the lower rates should be viewable on the devil with some tweaking to the line and frame rates but i have in mind the next monitor for the higher rates (The Thylacine :wink:) I need some thing that can display fine line or fine raster dot ,I have the problem here if i am correct a electostatic tube would have to be over 5 inches or more ? i am thinking to go with a magnetically deflected small 625 line tube if it can do that it should be able to do 100 200 lines ...it could be very similar my Deep image SSTV on the defection circuit side speeding it up

[code]
How do you propose doing line and frame sync apart from the NBTVA standard 32-line, 12.5Hz system? As far as I know there are no standards for these other formats.

Steve A.
[/quote]

There were be soon you have invented them ! i was thinking it would be nice over 100 lines to add the vertical sync to the video signal as well may be a first Steve for rates under 405 line or did RCA 120-line 24fps system do it first ?
As far as displaying.....a monitor will have to be made and playing around with garys 120 line sync free video i managed to display it on the devil so with a synced video it can only be easier .
I want it to happen but this will take a some work a bit of time ......but see how the best case works for 32 line then move onto the higher rates .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: The PMT in control of the Devil

Postby Steve Anderson » Wed Jul 26, 2017 1:45 pm

Yes, both pin 10 & 11 will be required in both a camera and a monitor. The arrangement on pin 10 will be the same for both, though you could delete the switching if you want a single-standard arrangement.

Pin 11, the MR, will be needed in a monitor to synchronise the timebases to the incoming video - as usual. In a camera they need to be reset at switch-on and when you change standards to make sure that a vertical sync doesn't happen part way through a line. If this were a single-standard camera you would arrange the logic to ensure this could never happen.

If there is/are standards 'out there' for the other non-NBTVA rates, I'm unaware of them, more correctly those for 64/128/256 lines. 120/240 come from pre WWII times and used some rather odd sync arrangements.

I suggest for 64 and above lines adding a 'proper' vertical sync, not using the missing pulse system. You lose one line, but you don't really notice it. Plus adding front and back porches (blanking) to the signal to eliminate sync-width modulation by the video. The more resolution you have the more you notice it.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5361
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: The PMT in control of the Devil

Postby Harry Dalek » Wed Jul 26, 2017 7:45 pm

Steve i finished the first half of your circuit ,so far i could just find a 57pf cap for the 4046 oscillator , i used that for testing and the ics i had handy ,i will have to wait till the HC versions turn up .
Top frequcey out of the 4046 64khz but could be a harmonic i am looking at have to recheck
The frequencies i got out of the 4040 is out of interest below ...
checking next to your readings i know they are off but only took one reading of each quick so odd reading needs rechecking still i can't do any thing right till i have the HC ic's
Pin 1 263 hz
2 16.8 khz
3 33.6 khz
4 8.4 khz
5 67.2 khz
6 115.5 khz
7 19 khz
9 37.5 khz
12 2.1khz
13 4.2 khz
14 1 khz
15 525 hz

Steve Anderson wrote:Yes, both pin 10 & 11 will be required in both a camera and a monitor. The arrangement on pin 10 will be the same for both, though you could delete the switching if you want a single-standard arrangement.


Oh ok ,i will keep the switching idea otherwise i will have to open unscrew the case every time for that adjustment ,i have a few panel multi postion switched i could use for this when i get around to using one .

Pin 11, the MR, will be needed in a monitor to synchronise the timebases to the incoming video - as usual. In a camera they need to be reset at switch-on and when you change standards to make sure that a vertical sync doesn't happen part way through a line. If this were a single-standard camera you would arrange the logic to ensure this could never happen.


Yes i am forgetting what is happening here i get ya :wink:

If there is/are standards 'out there' for the other non-NBTVA rates, I'm unaware of them, more correctly those for 64/128/256 lines. 120/240 come from pre WWII times and used some rather odd sync arrangements.


Doms software NBSC that does 64 line says its NBTVA standard i am not sure if 60 line or 64 line is and who says what is standard ,Standards are there to copy i suppose and have to start one to make one So your systems here are not wrong just new .
Yes the prewar systems were odd mostly just for one upmanship .

I suggest for 64 and above lines adding a 'proper' vertical sync, not using the missing pulse system. You lose one line, but you don't really notice it. Plus adding front and back porches (blanking) to the signal to eliminate sync-width modulation by the video. The more resolution you have the more you notice it.

Steve A.

I agree on the adding the vertical pulse thats fine with me ...the back porch i am not sure how to add this blanking to the video signal ,i would have to ask your advice here ... :roll:

BTW thinking on the frequency switching i know i am going to regret this but could you have 2 4066 ics and a 4017 and a momentary switch to switch the frequencies via the 4066 ic's controlled from the 4017 and a switch just to pulse it ..the 4066 might have a frequency limit .. a multi position switch is fine it was just on my mind thinking about it
Attachments
IMG_3394.JPG
IMG_3394.JPG (325.21 KiB) Viewed 10526 times
IMG_3395.JPG
IMG_3395.JPG (319.17 KiB) Viewed 10526 times
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: The PMT in control of the Devil

Postby Steve Anderson » Wed Jul 26, 2017 8:27 pm

Quite frankly you're just wasting your time if they're not HC, don't bother. you'll get a whole load of nonsensical outputs. Which it appears you have.

When all of the HC parts arrive you have a fighting chance. Quite simply CD/HEF cannot run at the frequencies required. End of subject. A Ford Focus can't do 200kph, same deal. CD/HEF is like a bus.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5361
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: The PMT in control of the Devil

Postby Harry Dalek » Wed Jul 26, 2017 8:33 pm

Steve Anderson wrote:Quite frankly you're just wasting your time if they're not HC, don't bother. you'll get a whole load of nonsensical outputs. Which it appears you have.

When all of the HC parts arrive you have a fighting chance. Quite simply MC/HEF cannot run at the frequencies required. End of subject.

Steve A.


It was mainly just used to check the wiring ,i expected these results would be way off but i was also curious ..any case just have to plug in the HC's when they turn up .
I will work on part 2 of your schematic and again i will have to wait .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: The PMT in control of the Devil

Postby Harry Dalek » Thu Jul 27, 2017 8:15 pm

Just working out the line and frame multi position switches today and how to mount the board on the lid above the PMT ,best i can get with my case space ,
Work on the other part of the circuit tomorrow .
Attachments
IMG_3397.JPG
IMG_3397.JPG (243.67 KiB) Viewed 10518 times
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: The PMT in control of the Devil

Postby Harry Dalek » Fri Jul 28, 2017 6:59 pm

More wiring today part 2 of the circuit ,whats left so far is the multi position switch wiring and the output transistors .
getting there . :!:
Attachments
IMG_3402.JPG
IMG_3402.JPG (256.32 KiB) Viewed 10511 times
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: The PMT in control of the Devil

Postby ppppenguin » Sat Jul 29, 2017 3:48 am

They may be hidden but I can't see any decouplers on that board. Old, slow 4000 series CMOS will work more or less whatever you do but HC/HCT must have decent decoupling. I automatically fit a 100n ceramic cap right by each device. This is probably overkill but it give peace of mind. Plus an electrolyic or 2 on the board as a whole.

A little story. Over 30 years ago I designed a high resolution graphics framestore board. A monstrous thing with 128 of the then current 64kilobit DRAM chips. 100n across each chip as a matter of routine. I think I put 10uF at the end of each row and thank goodness I left space for a big capacitor on the board too. The way the design worked all those chips did their refresh cycle at the same time causing the supply to dip by too much. I think I needed a 4700uF decoupler to keep that within sensible limits. That was an extreme case but it shows what inadequate decoupling can do.
Jeffrey Borinsky www.borinsky.co.uk
User avatar
ppppenguin
Research Scientist
 
Posts: 44
Joined: Fri Nov 04, 2016 5:30 am

Re: The PMT in control of the Devil

Postby Harry Dalek » Sat Jul 29, 2017 8:57 am

ppppenguin wrote:They may be hidden but I can't see any decouplers on that board. Old, slow 4000 series CMOS will work more or less whatever you do but HC/HCT must have decent decoupling. I automatically fit a 100n ceramic cap right by each device. This is probably overkill but it give peace of mind. Plus an electrolyic or 2 on the board as a whole.

A little story. Over 30 years ago I designed a high resolution graphics framestore board. A monstrous thing with 128 of the then current 64kilobit DRAM chips. 100n across each chip as a matter of routine. I think I put 10uF at the end of each row and thank goodness I left space for a big capacitor on the board too. The way the design worked all those chips did their refresh cycle at the same time causing the supply to dip by too much. I think I needed a 4700uF decoupler to keep that within sensible limits. That was an extreme case but it shows what inadequate decoupling can do.


HI Jeff i have 2 10nf under the board on the first 2 ics have not got around to the others yet i did under as i think Steve mentioned once to keep cap decoupling wiring short ...i will do the other 4 ics but never tried any thing over 10nf here .
The 2 ics plugged in are cmos i think just there to test the circuit wiring via the multi position switches to to pin 10 of where the hc 4040's will be leas i will know it should work up to there when those ics turn up .
But yes i have kept decoupling capacitors on mind just finishing off the wiring and i will fit the others .
So size wise 10 to 10uf is a range would the 4700 uf be like a little battery enough to keep the voltage stable ,i might put something like that in for the 5 volt supply Thanks Jeff advice is well worth it !
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: The PMT in control of the Devil

Postby Steve Anderson » Sat Jul 29, 2017 1:43 pm

Good to see someone else also has a fetish for bypassing/decoupling. I generally put the decoupling caps on the underside of the board, right on the supply/ground pins on every chip, and I mean every. Again it may seem overkill but if you have problems you can rule out supply problems and glitches. Except in extreme cases as above. If buying 10n/100n disc-ceramic caps, buy them by the hundred or a multiple thereof. In quantity they're dirt cheap. View it as an investment/insurance.

Crappy power supplies and decoupling probably make up 70% of all non-performing circuits. Some use spare USB battery chargers, these are usually a simple (read CHEAP) design which is fine for charging a battery but with bags of noise on the output it is almost guaranteed to upset logic and inject noise into analogue circuits.

Another 'gotcha' is long thin meandering ground/earth lines, keep 'em short, direct and fat.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5361
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

PreviousNext

Return to The Tasmanian Devil VCR139....A for Andrew

Who is online

Users browsing this forum: No registered users and 1 guest

cron