It’s the 1970’s. The cold war. The U.S. and Russia aim nuclear weapons at each other. How do you prepare for the worst? Why, you build a bunker, of course!
Today, [Ian] has done just that. Not a real nuclear fallout shelter, of course, but a period-themed bar called the Bunker Club. What better way to face disaster, than over drinks with the mates!
Ian decided to pepper his bar with vintage equipment that looked the part. But he wanted to make them truly functional, to entertain his retro-loving customers. So, he commissioned the Bunker Club VectorClock!
Now, regular followers of the blog will easily recognize the base unit here as a Tektronix 520A Vectorscope. So far a total of four of these delightfully-lighted machines have been converted to retro Oscilloclocks – see the Gallery for other examples.
But as always with any model, Ian wanted to make some cool customizations. Let’s look at two of them.
1. External XY Input
First introduced in the Metropolis Clock, this feature allows Ian to input two signals and visualize them in X-Y format on the screen. This is very, very useful for generating custom Lissajous figures externally – using either a cheap signal generator, or even an iPhone!
Cool Lissajous figures – even from a humble iPhone! (note, this picture is of the Metropolis Clock)
The external signals are rendered within a rectangular ‘window’, pre-configured to look nice alongside other standard parts of the Oscilloclock screens. For some screens, the window is drawn large but with a lower intensity, forming a kind of ‘watermark’. This is an awesome effect!
2. Custom Logos
Nearly all Oscilloclocks feature some kind of customized logo. Past examples include the customers’ business’ name, the name of the oscilloscope manufacturer, or even the name of the customer’s favourite film:
In Ian’s case, the obvious candidate was his new bar’s official logo – a very chunky-looking rocket blasting through the atmosphere!
Further enhancements … on the way
It seems Ian enjoyed his first clock so much, that he has commissioned a second, with a completely different physical look. Some further special effects and display animation are planned, to further enhance the nuclear theme and keep his customers happy. Stay tuned!
Like what you see?
Do you own a bar? Well, normally you wouldn’t want a clock in your premises, as it would help customers keep track of their time, which would be bad for business. But Oscilloclocks are so much more than timekeepers! Recent feature additions make them lots of fun to watch and fiddle with. If you have special ideas, let me know!
(Disclaimer: Oscilloclock.com hopes that no-one is offended by the deliberately light-hearted tone of this post, in referring to the decidedly serious topic of nuclear warfare.)
Many folks have asked whether screenburn-in, or phosphor burn, is not a problem. They are concerned by what was a frequent occurrence in the CRT monitors and oscilloscopes of yesteryear: a permanent scar prominently visible on the screen…
Phosphor burn – this old spectrum analyser looks ‘on’ even when it’s off!
To understand why this occurs, first think of an iron burn. If you deliver too much heat for too long into the same spot, your nice new Oscilloclock brand T-shirt will feature a prominent (and permanent) mark as shown below.
Iron burn – this shirt’s fibres have been literally scorched!
(I could push for another analogy, and describe livestock branding – but I think you get the message.)
In a CRT, a beam of fast-moving electrons bombards the phosphor coating on the screen to produce an image. If the beam is too intense, or it is allowed to trace the same route on the screen over a long period of time, the phosphor compound may degrade and lose its luminance. The end result is:
The screen won’t light up well in those spots any longer.
The damaged areas may appear dark even with the power off – a ‘ghost image’.
Interestingly, this damage does not actually shorten the working life of the CRT! (It does not affect the longevity of the heater, or the amount of gas permeating the vacuum.) However, it is certainly not attractive, and is most definitely NOT an effect you wish to observe on your fancy custom-crafted Oscilloclock…
Keeping the ghosts at bay
Happily, screen burn-in is not much a problem with the Oscilloclock. Let’s see why.
1. CRT selection
Some CRT types and brands are more susceptible to screen burn-in than others. There are a number of factors for this, and all of these are considered during CRT selection to minimize the risk of burn-in:
First, there is the phosphor compound used. Some phosphors, just by their chemical makeup, degrade faster than others. More significant, though, is the fact that some phosphors require more energy (electron beam intensity) to produce the same level of visible light output as others.
For example, a long-persistence blue P7 phosphor, such as used in the Model 1-S and the Prototype, is by its nature ‘darker’; it requires a higher beam intensity than the crisp green P1 or P31 phosphors used in many other models. The higher beam does make the P7 more vulnerable to burn-in.
Different phosphors need different intensities to appear ‘bright’ – so some will burn faster
Fortunately, the simple protection mechanisms in place in the Oscilloclock (we’ll get to these later) will avoid burn-in even on sensitive phosphors. The customer need not be concerned about this risk factor, and can select any of the available phosphors.
The second factor is the thickness of the phosphor coating. The thicker the phosphor, the less burn-in for the same beam intensity. Some CRTs are infamous for having ridiculously thin phosphor coatings, making them extremely susceptible to burn-in. Sadly, some CRTs that are most readily available today fall into this category, and their data sheets even specify an incredibly short maximum longevity of 1000 hours. That’s less than 2 months of continuous use!
Beware CRTs with short lifetime ratings – they may have ridiculously thin phosphors!
Most CRT manufacturers did not publish lifetime ratings, nor did they publish specifications of phosphor thickness. In the Oscilloclock lab, I rely mainly on my and others’ experiences with the manufacturer, and pick and choose only the highest-quality CRTs. Expensive – but definitely worth it!
The third factor is the use of any additional technology in the CRT that would allow for reduced beam intensities. The most common example is the aluminized screen, an additional coating on the rear of the phosphor. This coating reflects the light that would normally emanate from the phosphor towards the rear of the CRT, back into the phosphor (and the front of the screen). A much more efficient use of energy!
However, this technology was a later development, so many CRTs with an aluminized screen tend to be rectangular and have an in-built graticule. These may not be as visually pleasing in a standard Oscilloclock as non-aluminized CRTs.
2. Software (Firmware) protection mechanisms
My favourite screensaver – Flying Toasters! (Image used under Fair Use terms)
Remember the phrase “screen saver”? In the pre-LCD monitor days, most computers employed some form of software that would stop the same image being displayed for too long, to avoid screen burn-in.
While there is nothing as fancy as flying toasters, the Oscilloclock has several mechanisms in place.
Hourly XY Bump screen saver This feature simply shifts the image by a small amount in the X and Y directions every hour. The shift pattern repeats every 31 hours (a prime number), to ensure that every hour numeral will be placed in every screen position.
Auto screen switch This feature simply cycles through the screens (clock faces) at regular intervals, configurable from 0 (off) to 90 seconds. This is by far the most commonly enabled feature, as it allows one to enjoy all the Oscilloclock screens without touching the control!
Auto power off Strongly recommended by Oscilloclock labs, this feature simply turns the Oscilloclock off after a period of non-activity (not touching the control), configurable from 0 (off) to 90 minutes.
This may sound counter-intuitive, but in practice, nearly all Oscilloclock owners are comfortable to turn their unit on just when they intend to enjoy it, and allow it to switch itself off. The exceptions are clocks that are permanent fixtures in offices and restaurants, in which case the owners manually turn their clocks on and off together with other appliances in the premises.
These features are of course highlighted in the Operation Guide that accompanies every Oscilloclock.
Summing it up
So there we have it – there’s not so much to be concerned about after all. While CRTs do have a delicate phosphor coating, by selecting a decent CRT in the first place and looking after it in use, the risk of screen burn-in is drastically reduced. In fact, in 7 years of constructing Oscilloclocks, as of today not a single unit has come back for a CRT replacement!
Spring… a beautiful time of year! I particularly enjoy the warm rains, with the soothing effects of raindrops pit-pattering into puddles outside my window.
But no longer do I need to look outside! Inspired by a recent post on Hackaday, a suggestion from [A-Nonamus] in the neonixie-l group, and by Spring itself, I can now enjoy Timedrops on my Oscilloclocks:
See this in HD, and find more exciting videos on my YouTube channel Music credits: Space Bazooka by Kirkoid (c) 2013 Licensed under a Creative Commons Attribution (3.0) license. http://dig.ccmixter.org/files/Kirkoid/43005
Assembly?!
A sprite engine
The current Oscilloclock firmware is written entirely in PIC 18F Assembly. The Timedrops feature leverages a Sprite Engine module, first developed for Halloween Seasonal Treats and later utilized in the Santa’s sleigh feature.
To display Timedrops, the sprite engine is initialized with 10 sprites – 4 digits for hours and minutes, a colon, and 5 ellipses as ‘ripples’. The 5 characters are set at the top of the screen with a randomized negative velocity. When a character reaches the bottom boundary, the sprite engine’s default explode sequence is started, and the associated ripple sprite is made visible and set to expand. When the explosion sequence for a character sprite is complete, the sprite is reset at the top of the screen.
Looking for the source code? Sorry – refactoring is still under way, and the latest revision with the Timedrops feature will be uploaded in the near future.
Here we see the original Oscilloclock Prototypeleaping for joy with the glorious Leap Second! The Hourly XY Bump screen-saver even bumps the screen twice, just for added effect.
Note: Flicker is due to camera effects and is not visible to the human eye.
