Video-game for NBTV?

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Video-game for NBTV?

Postby DrZarkov » Sun Apr 29, 2007 7:43 am

Thanks to Klaas there is a testcard-generator for NBTV. I wonder if it would be very dificult to create a simple video-game for NBTV-monitors, I thought about "Pong" (for the UK "Ping") or a game like that. The original "Pong" was created in the sixties using tubes, the first commercial Pong from 1972 (the Magnavox Odyssey) used only 36 transistors and no ICs! For 32 lines it should be much simplier und could me more fun than just a normal testcard on the screen.
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Re: Video-game for NBTV?

Postby Roland » Sun Apr 29, 2007 11:34 am

DrZarkov wrote:For 32 lines it should be much simplier und could me more fun than just a normal testcard on the screen.


It sort of had crossed my mind too.

Another application might be an oscilloscope. True the Nipkow disk is not ideal for this (as it doesn't have a beam which is controllable like a CRT) but it must be possible - in much the same way that computer based oscilloscopes don't manipulate the CRT beam - instead the generate a video signal which is displayed like any other picture.

I also wondered if a mirror drum could be used a scan a light beam across a screen. The vertical deflection would be caused by bouncing the light beam off a mirror attached to a loudspeaker fed by an appropriate signal.

I seem to remember in a 1970s issue of Byte magazine a design for a 'Scramble' arcade game using a 2 beam oscilloscope and a 6809? cpu. Maybe a mechanically scanned version of this is possible too?

:-)

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Postby DrZarkov » Sun Apr 29, 2007 3:56 pm

A mechanical oscilloscope would be very difficult to make with Nipkow-discs, in fact it would be a digital oscilloscope with a low definition display, you could better use two string galvanometers to build a mechanical oscilloscope. (But why? CRTs are known since the late 19th cetury, even in the time of Baird they had oscilloscopes with CRTs.)

Microcontrollers are not technic of the thirties, but a "Pong" is possible with tubes, so this would be acceptable. (Even in transistor-technic)
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Re: Video-game for NBTV?

Postby ac7zl » Sun Apr 29, 2007 3:58 pm

This reminds me of an image in an old science book I have. Picture this mechanical "oscilloscope."

Start with a cylindrical enclosure... rigid sides and a rigid top, but a thin, diaphraphm-like bottom. Natural gas is admitted to the interior of this cylinder through a fitting that passes through the wall of the cylinder.

The rigid top of the cylinder is drilled with a tiny hole, through which the gas can escape. When the gas is lit, a thin, pencil-like column of flame rises from the device.

Here's where it gets interesting...sound waves impinging on the diaphragm causes corresponding pressure variations in the gas inside the container. In response the flame "dances," i.e., it bounces up and down.

Now, adjacent to this flame we install a speed-controlled mirror drum that rotates about a vertical axis. In the case of this device, speed control is accomplished with a mechanical governor.

The height of the flame is the "scope's" Y or amplitude axis. The shifting of the flame image in the mirror drum gives you an X or time axis.

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Roland wrote:
DrZarkov wrote:For 32 lines it should be much simplier und could me more fun than just a normal testcard on the screen.


It sort of had crossed my mind too.

Another application might be an oscilloscope. True the Nipkow disk is not ideal for this (as it doesn't have a beam which is controllable like a CRT) but it must be possible - in much the same way that computer based oscilloscopes don't manipulate the CRT beam - instead the generate a video signal which is displayed like any other picture.

I also wondered if a mirror drum could be used a scan a light beam across a screen. The vertical deflection would be caused by bouncing the light beam off a mirror attached to a loudspeaker fed by an appropriate signal.

I seem to remember in a 1970s issue of Byte magazine a design for a 'Scramble' arcade game using a 2 beam oscilloscope and a 6809? cpu. Maybe a mechanically scanned version of this is possible too?

:-)

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Re: Video-game for NBTV?

Postby Stephen » Mon Apr 30, 2007 12:38 am

Roland wrote:[quote=Another application might be an oscilloscope. True the Nipkow disk is not ideal for this (as it doesn't have a beam which is controllable like a CRT) but it must be possible - in much the same way that computer based oscilloscopes don't manipulate the CRT beam - instead the generate a video signal which is displayed like any other picture.

I also wondered if a mirror drum could be used a scan a light beam across a screen. The vertical deflection would be caused by bouncing the light beam off a mirror attached to a loudspeaker fed by an appropriate signal.
This is a very sensible approach for a non-CRT based oscilloscope. Actually, CRTs of the high-vacuum type were expensive, unreliable and short-lived well into the 1930s and therefore were generally eschewed. Furthermore, the high-tension power supplies to drive them were also very costly. Gas-filled CRTs of the cold cathode "Braun" type were better and did not have the high-tension drive requirements of high-vacuum types, but they were incapable of z-axis beam modulation. In fact, Karl Braun demonstrated the first cathode ray oscilloscope with such a tube in 1897.

Now, if you wanted a totally non-electric oscilloscope, like a non-electric television as proposed in another thread on the forum, you could substitute a diaphram coupled to the throat of a horn for the loudspeaker and have a mirror attached to the diaphram, perhaps through a fulchrum much like the sound head of an acoustical gramophone. This would provide vertical displacement of the beam for sound captured by the horn. A mirror drum or lens disc could provide horizontal displacement of the beam.
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Mechanical oscilloscope

Postby Roland » Mon Apr 30, 2007 11:22 am

Glad to hear my ideas for a Mechanical oscilloscope are not completely crazy and I wasn't aware people had actually made such devices in the past. I do concede though that a Nipkow disk version is pretty pointless and now I think about it - actually creating the video signal for it is more difficult that just driving the vertical axis by a loudspeaker.

Anyway - I'll stick it on the list of future projects. I can see that calibrating it might be 'fun' and that vibration is also going to be an issue.

I really should go and buy a CRT oscilloscope - as I'm sure anything I buy will be considerable better than anything I can build ;-)

:-)

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Postby DrZarkov » Wed Jun 06, 2007 4:51 pm

What I thought about, was something like that:
http://www.sparkfun.com/commerce/present.php?p=Tetris, which
is kind of a NBTV Tetris.
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Re: Mechanical oscilloscope

Postby Steve Anderson » Wed Jun 06, 2007 5:20 pm

Roland wrote:I really should go and buy a CRT oscilloscope - as I'm sure anything I buy will be considerable better than anything I can build ;-)

:-)

Roland.


Once you've had access to an oscilloscope, it's almost impossible to do anything in electronics without one! Can you imagine life now without mobile phones or the Internet? It's like that!

I had to send my old Goldstar scope away some years ago for a repair and re-calibration, it was away for three weeks. It was like having my right arm cut off.

Everything I wanted to do I would reach for the probes...but they weren't there! It was so frustrating! Now the Goldstar has been retired and only re-awakened if its replacement is unavailable. (I had to send the new one back under warranty repair one time).

An oscilloscope is the best investment as far as test equipment goes that you can ever make in electronics, perhaps next to a multi-meter. Within the requirements of NBTV there are new models you can buy for just over 100 pounds, they're not super-duper, but they're good enough for NBTV unless you want to get into digital standards convertors and the like.

Put off that new PC, buy a scope! Even a second-hand one, you won't regret it!

However, if you don't mind mucking around with a few hundred volts, building your own is not that hard.

There are also PC based scopes, I have one I sometimes use with the laptop when 'on the road'...

http://www.picotech.com/

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Last edited by Steve Anderson on Wed Jun 06, 2007 5:45 pm, edited 1 time in total.
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Postby AncientBrit » Wed Jun 06, 2007 5:27 pm

Steve,

I found that the biggest problem building your own scope was getting the input attenuator to have a flat response.

TB, and X/Y amps design was not too bad.

BTW the best approach to power supplies is to use a mains transformer for scope heaters, LV supplies and +250v.

The -2kV I derived from a single transistor driven ringing transformer.

Regards


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Postby Steve Anderson » Wed Jun 06, 2007 6:09 pm

AncientBrit wrote:I found that the biggest problem building your own scope was getting the input attenuator to have a flat response.

Graham


Yes, that's a tricky area, but it also depends on what sort of bandwidth you're looking for. For 99% of NBTV applications 20MHz would probably be plenty enough, perhaps even less. On the old scope the 20MHz bandwidth limit switch was in most of the time to reduce pre-amp noise, it was only occasionaly put to the full 100MHz.

I remember an article in 'Wireless World' in 1969 whereby a chap extended(!) the bandwith of an old 5CP1 scope to 5MHz! This was a professional application so he could work on and develop colour TV circuits! If anyone has a copy of that I would love a scan.

I have designed a pre-amp for a scope that does not have an input attenuator, the gain of the deflection chain is varied. That does away with all those resistors and trimmer caps on the input, but it's not 100MHz bandwidth! (Remember those Heathkit scopes in the 60s, I'm sure someone had shares in the switch manufacturer! Mind you, Tektronix weren't that far behind!).

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Postby AncientBrit » Wed Jun 06, 2007 10:23 pm

Steve,

5CP1 ?

I'm old enough to remember VCR97 and VCR517 tubes!!



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Postby Viewmaster » Thu Jun 07, 2007 12:04 am

AncientBrit wrote:Steve,

5CP1 ?

I'm old enough to remember VCR97 and VCR517 tubes!!
Graham


Me too, and further back to PM1HF/LF ! :shock:
Back to the good old daze! :)
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Postby Steve Anderson » Thu Jun 07, 2007 12:42 pm

I have a growing collection of CRTs, it's not vast as I'm pushed for space, one is a VCR138 which I got at an amateur radio swap-meet in the early 80s in Plymouth, Devon.

I did get it going on the bench around that time, so it still should be OK.

But with all due respects gents, I'm sure that it's older than I am!

I'm always amazed when you fire up an old tube, used or otherwise, and it still works. The skill used in maintaining the seals between the glass and the lead-out wires or pins is incredible.

We'll probably look back in fifty years time and think the same of an OC71! (An early Germanium transistor). It's educational to see just how these early devices were made...

http://www.thevalvepage.com/trans/manufac/manufac1.htm

In addition I attach a similar themed pdf about valve/tube manufacturing. Don't pictures of the factory conditions bring back memories? Now where did I park my Ford Anglia?

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Re: Video-game for NBTV?

Postby Andrew Davie » Thu Jun 07, 2007 5:51 pm

DrZarkov wrote:Thanks to Klaas there is a testcard-generator for NBTV. I wonder if it would be very dificult to create a simple video-game for NBTV-monitors, I thought about "Pong" (for the UK "Ping") or a game like that. The original "Pong" was created in the sixties using tubes, the first commercial Pong from 1972 (the Magnavox Odyssey) used only 36 transistors and no ICs! For 32 lines it should be much simplier und could me more fun than just a normal testcard on the screen.


As it happens, a week or two back I converted a video of a game to NBTV format and played on my monitor, just to see what it might look like. SO this isn't quite the real thing, but I was very very surprised to see that a quite complex game (Boulder Dash(R)) looked very clear and would be easy to play on a mechanical tv.

The video in question is footage of a conversion of Boulder Dash(R), one of my all-time-favourite games, running on an Atari 2600. I wrote this conversion a few years ago but didn't come to any arrangement with the copyright holder to release it. So it's never been released.

In any case, the attached file will let you see a real game in action on your monitors. The image is a hurried blurred set of screenshots I took at the time I first tested it.
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Postby DrZarkov » Thu Jun 07, 2007 7:35 pm

Hello Andrew, there are so many Boulder Dash clones arround, I bet none of them has a licence of the original Boulder Dash. Just change the name a little bit, and I'm sure nobody will sue you for a Atari VCS version of it. (BTW.: You don't want to come on 28/29 September to Stuttgart to the "Classic-computing 2007"?). There are enough enthusiasts for that. Of course an NBTV monitor is good enough for games like "Tetris", "Pong" or games like that. I think to create a new logic for that would be easier and cheaper than just use a converter.
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