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CRT project ideas

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BobW

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I picked up a surplus 5 inch CRT many years ago (electrostatic deflection, with long persistence phosphor). At the time, I had the idea of building a vector graphics display. I may still do that, but lately I've been trying to think of other unique ideas. So, I thought I'd just throw this out here to see what you folks might come up with.

BTW, don't even think of mentioning a scope clock.
 
I have built a vector monitor from scratch with a tv crt.
Unfotunately I cannot mention any more as it is actually a device you said not to mention.
 
I saw one guy make a video display using a scope, not sure how he did it, XY mode I think?
 
Linear ramp x and y deflection,and amplitude modulation of the z input, all timing controlled by the video sync signals. Other than electric deflection as opposed to magnetic, a TV is a TV.

Another oldie you can recreate is a flying spot scanner, the original way of converting a photograph into some form of electric signal representation.

ak
 
Linear ramp x and y deflection,and amplitude modulation of the z input, all timing controlled by the video sync signals.

So how do you connect the Video Sync signals? Is that the linear ramp you speak of? I better google how video works, been a long time :confused:
 
electrostatic deflection
We should find data on the monitors!
If they are really electrostatic deflection then there is no sync signals.
What are the inputs on the monitors? X,Y,Z or Video + sync?
long persistence phospho
I want to get a sonic distance measuring thing. It sends out a pulse and records the bounce back like radar or sonar.
The idea is to mount the head to a servo motor so it scans left to right. It might take some time to scan from side to side.
With long persistence phosphor you can set a "sonar picture" of the front yard.
 
I think the easiest way would be to create the ramps with a DAC on the output of of a counter with a maximum count value of the numbet of pixels per line for the horizontal axis and a counter with the maximum count equal to the number of lines. The overflow of the horizontal counter would clock the vertical counter. I think the long persistance of the tube would make it unsuitable for a flying spot scanner. I used a long persistance CRT in the early 1970s to display pictures from weather satellites aon about 137 MHZ. The picture took about 2 minutes to scan so you had to be in a dark room and you could just about see the picture at the end of the scan. I even remember the tube was a 5FP7 (Magnetic deflection.) Prior to that I had built a very basic oscilloscope while I was still at school. That used an electrostatic deflection tube. (VCR97) All of the elctronics was valves.

Les.
 
Analogue spectrum analyser? / some other kind of anyalyser?
I was going to say get yourself a vidicon and build a tv camera, but the long persistence phosphor might not work too well for that!
I was always fascinated by the way Tektronix 'scopes put writing on the screen - perhaps you could make something that writes?
Ooooh ooooh! Just spotted my typo - an "any-alayser"! There you go :)
One of the early video games had vector graphics - perhaps you could make one like that?
 
Thanks for the ideas.
- I had been contemplating some sort of spectrum analyzer. Still undecided. I see that some people have built them using a digital TV dongle in SDR mode. Can't find the link at the moment.
- The flying spot scanner would have to be a crawling spot scanner, due to the long persistence phosphor.
- The sonar idea is interesting. The polar vector display could be handled with a microcontroller and sine/cosine lookup tables. I'd thought about this several years ago, but at that time, sonar CRT deflection was typically done with a sine/cosine pot that rotated with the ultrasonic transducer. Not an easy part to find.
- I'm also thinking of a curve tracer. In fact, I have most of the electronics already put together. It connects to my regular scope at the moment.

Still thinking about it. Keep the ideas coming.

BTW, The reason why I vetoed the scope clock idea, is that I'd like to have a bit more active display than a clock. Actually clock projects of any kind have never really turned my crank. (I've got a lifetime supply of Nixie tubes, and no desire to build a Nixie clock.)

Also, I may not have been clear, this CRT is just the barebones tube, no electronics. I'll have to build the HV supply and all of the deflection circuitry.
 
I picked up a surplus 5 inch CRT many years ago (electrostatic deflection, with long persistence phosphor). At the time, I had the idea of building a vector graphics display. I may still do that, but lately I've been trying to think of other unique ideas. So, I thought I'd just throw this out here to see what you folks might come up with.

BTW, don't even think of mentioning a scope clock.

Hy Bob,

Your first task is to build a chassis to mount the tube. You may get away without a mu metal screen, but not normally for that type of CRT.
You then need to generate the tube DC supplies. Typically a tube that size would need a 15KV EHT. You also need to generate and around - 2KV. You then put a 100V or so Zener diode in series with the -2KV supply and connect the tube cathode to -2KV +100V. You them connect a 10 M Ohm resistor across the Zener and that is your brightness control when the grid is connected to the wiper. You then string a potential divider across the -2KV to derive the voltages for the focus plates, accelerator plates etc. If you connect the X & Y plates to OV, you will then be able to get a spot on the tube face by adjusting the brightness control.

Typically you would have a mains derived 12V DC supply as the main supply rail and from this you would typically have a Royer inverter with multiple turns producing all the various voltages that you will need, including the EHT (voltage multiplier) and -2KV.

Then you get to the long tailed pair high voltage, high speed X & Y plate amps... I don't like to be a kill joy, but I just thought you need to know that you are contemplating one hell of a development program. How do I know? I spent about 15 years designing, developing, and building scopes. I never finished any- but did learn a lot along the way- and ended up buying a scope. :rolleyes:

spec
 
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The EHT voltage will depend on the CRT If it is a VCR97 or similar it will only need about 2.5 KV. If it is a tube with PDA (Post deflection acceleration.) such as the 5CP1 then it will need the higher voltage. PDA tubes have a the EHT connector on the side of the tube. (Like on a TV tube.) VCR97 type tubes have no side connector.

Les.
 
The video was my first ever. Sorry for the quality.

Basically simple proper programming. Not precisely this but it could spark ideas :
 
So how do you connect the Video Sync signals? Is that the linear ramp you speak of?

For composit video you have to strip off the sync train, separate it into vertical drive and horizontal drive signals and use those to time the operation of the two ramp generators, whatever their technology is. Separate H and V sync signals as in VGA eliminate the first two steps.

Raster scan image display (television) is based on the electron beam being moved all over the screen in combination of two carefully controlled zigzag patterns. A ramping voltage on the horizontal plates moves the beam side to side, and a ramp on the vertical plates moves it up and down. At any moment in time the two ramp voltages put the beam (and spot) at a known location. The voltage at the z input sets the intensity at that moment. Synchronize everything and you have video.

ak
 
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I don't like to be a kill joy, but I just thought you need to know that you are contemplating one hell of a development program. How do I know? I spent about 15 years designing, developing, and building scopes. I never finished any- but did learn a lot along the way- and ended up buying a scope. :rolleyes:
No problem. I'm aware of what has to be done to get it fired up. I did have it operating on my bench a few years ago. Fortunately, this one doesn't require any negative HV supply. Cathode and grids operate at or close to ground. Focus is 0 to +300V, and anode is +9kV. However, I'll operate the anode at a much lower voltage, because I don't plan to have any high deflection rates, and that will allow me to use lower control voltages on the deflection plates.

Atferrari, Nice work. A text display terminal is an interesting idea too.
 
No problem. I'm aware of what has to be done to get it fired up. I did have it operating on my bench a few years ago. Fortunately, this one doesn't require any negative HV supply. Cathode and grids operate at or close to ground. Focus is 0 to +300V, and anode is +9kV. However, I'll operate the anode at a much lower voltage, because I don't plan to have any high deflection rates, and that will allow me to use lower control voltages on the deflection plates.

Oh, sorry I was lecturing to the wise.

At about four-years-old I first saw a scope in the workshop of one of my Dad's friends, before I ever saw a TV. Since then I have always been fascinated by scopes and displays in general and, once I got to know a bit about electronics, spent literately years building scopes and modifying TVs to be data monitors. At one time I had around ten TVs in the garage for parts cannibalization, along with nude CRTs of various types. My first scope used the cheapest CRT you could get at the time, a government surplus VCR138 which had a 3.5 round goldfish bowel face. What a pig that CRT was to drive: it needed hundreds of volts to move the spot across the tube face.

Good luck with your project- be great to know how it progresses.

spec

(one thing that is very impressive in science fiction movies is lissajous figures)
 
QUOTE atferrari: The video was my first ever. Sorry for the quality.

Basically simple proper programming. Not precisely this but it could spark ideas :


Very neat atferrari.

(don't keep minimizing your achievements- see underlined and bold in quote above)

spec
 
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