Scope clock with a difference

[morrisodell]

Hi all,

Here is a video of the prototype of my latest clock. It's a GPS locked
scope clock with a PPI radar type display using a CRT with a P7 type
long persistence screen. I haven't finished packaging it up yet and
the display should be a little better once the power transformer
fields are shielded by the steel case. The focus is razor sharp but
the iPhone I used to take the video didn't focus well in the dark.

http://youtu.be/RnsaXkfxygo

Enjoy!

Morris

[jb-electronics]

Looks amazing! Have you designed a single-PCB version yet?

Jens

[J Forbes]

Very interesting!

I did something slightly similar to that with a Tektronix 4010....but
it's a storage tube, so it drew a line every minute, and cleared the
screen every hour. Not nearly as exciting to watch as yours is!

http://www.selectric.org/tek4010/index.html

[threeneurons]

Cool ! Hey, Morris am I seeing it right. Is the image swept in a polar fashion ? Real cool !

http://youtu.be/RnsaXkfxygo

Enjoy!

Morris

[Allen Wisbey]

That is nice! Let us know if you decide to kit them.

73 de W1SBY

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[Lucky]

Very nice Morris well worth the effort you must have put into it.
Dave.

On Tuesday, 6 March 2012 18:22:15 UTC, W1SBY wrote:

That is nice! Let us know if you decide to kit them.

73 de W1SBY

On Mar 6, 2012 3:27 AM, "morrisodell" <vilg...@bigpond.net.au> wrote:

Hi all,

Here is a video of the prototype of my latest clock. It's a GPS locked
scope clock  with a PPI radar type display using a CRT with a P7 type
long persistence screen. I haven't finished packaging it up yet and
the display should be a little better once the power transformer
fields are shielded by the steel case. The focus is razor sharp but
the iPhone I used to take the video didn't focus well in the dark.

http://youtu.be/RnsaXkfxygo

Enjoy!

Morris

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[Tidak Ada]

Splendid idea, however, a bit restless.
A longer persistence and a lower scan time should make it more adapted to a
living room. Anyhow an eye catcher, especially in commercial situations.

eric

[morrisodell]

Hi all,

Here is the radar clock again, pretty well in its final form. The HV
wire to the CRT needs tidying up before it can be make a safe
debut :-)

http://youtu.be/Jjs7AWL8B1k

Morris

[Dan Harboe Burer]

Wow. Impressed I am.
I would love to build a clock like that :o)

Dan

[Tidak Ada]

Intriguing design !
Aren't there also tubes with orange luminance and green phosphorescence or
isn't that the right phosphorescence time ? I should like that colour
combination.
Sorry for my lack in knowledge, but what is the reason the clock isn't
exactly smooth round. Is that a technical difficulty ?

eric

Dan

Hi all,

http://youtu.be/Jjs7AWL8B1k

Morris

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[morrisodell]

That tube uses the standard P7 (or P in the European nomenclature)
phosphor which is a 2 stage system. There's a blue/UV short
persistence layer which excites a greenish long persistence layer.
They are usually mounted with an orange filter to suppress the bright
blue flash which some people find unpleasant. I think there are also
very long persistence orange phosphors which work the same way - I
have a couple of old radar display units with such tubes which I plan
to make into clocks but they both use magnetic deflection so lots of
developmental work to do! One of them has a rotating yoke and the
other a static one.

I'm not 100% sure why the circle is not perfect. I suspect it's
because of nonlinearity or marginal headroom in the deflection
amplifiers. I'm running the CRT at 4 kV which maximizes the required
swing for deflection voltage. I used a different design in this clock
from a previous P1 clock which did display a perfect circle. This one
has a differential cascode topology with a CA3054 chip for the long
tailed pair and a couple of MJE340s for the common base level
shifters. At least there's no thermal drift and excellent common mode
rejection allowing the use of a very simple power supply.

Incidentally I was driven crazy while developing this clock because I
was using an old Solartron scope which had a P7 CRT for a test bed . I
couldn't get the origin of the hands to stop rotating with the scan.
It turned out to be the very poorly designed deflection amplifiers in
the scope that were at fault. It's amazing to compare what Tektronix
was doing at the same time in the 1960s. Such a thing would never have
happened with one of their scopes. Crap British engineering of the
60s wasn't just confined to their cars :-)

I don't have any plans to produce boards or designs for this clock.
It's very complex and uses boards with bits of circuitry from other
clocks I've made. I'm happy to give advice though. I think the design
is half the fun!

Morris

[David Forbes]

On 4/5/12 2:35 AM, morrisodell wrote:
> ... I think there are also
> very long persistence orange phosphors which work the same way...

I have a couple of 3JP12 tubes with long persistence orange phosphor.
That phosphor is VERY delicate, and has a ridiculously short lifetime
when run at a brightness that's visible in a normally-lit room. Thus,
it's no good for scope clocks.

> Incidentally I was driven crazy while developing this clock because I
> was using an old Solartron scope which had a P7 CRT for a test bed . I
> couldn't get the origin of the hands to stop rotating with the scan.
> It turned out to be the very poorly designed deflection amplifiers in
> the scope that were at fault. It's amazing to compare what Tektronix
> was doing at the same time in the 1960s. Such a thing would never have
> happened with one of their scopes. Crap British engineering of the
> 60s wasn't just confined to their cars :-)

Tektronix scopes were head and shoulders above anything else produced at
that time. I have no qualms about copying their circuits, since they are
very good circuits that I wouldn't be able to design myself in several
years.

--
David Forbes, Tucson AZ

[Tidak Ada]

Thanks for your extended reply. Highly interesting ! I didn't know about the
Solartron problems, was even in the mind they where of good quality
(However, never used one).

The fact the circuitry is very complex I already suspected. I put aside a
plan to make a graphics card, end seventies, for that reason, despite it was
a design in a magazine.

Trying to develop a digital clock with analogue scales as read out, I know
what your experience will have been during developing this clock !

[Charles MacDonald]

On 12-04-05 12:35 PM, David Forbes wrote:
> On 4/5/12 2:35 AM, morrisodell wrote:
>> ... I think there are also
>> very long persistence orange phosphors which work the same way...
>
> I have a couple of 3JP12 tubes with long persistence orange phosphor.

If you have access to the TCA data Cache shold by the tube collectors
association, the details of the P7 and P12 Phospour are in JEDEC release
3097 of 1961, with a mention that they in use long before the offical
release.

It looks like the P7 actually has a much longer persistence than the P12.

The P12 is described as being made of Zinc Magnesium Floride : Magnaise

The P7 is described as Zinc Sulphide : Silver and zinc cadmium sulphide
: Copper
--
Charles MacDonald Stittsville Ontario
cm...@zeusprune.ca Just Beyond the Fringe
http://users.trytel.com/~cmacd/tubes.html
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