Perpetual Countdown Clock Project

[DaveC426913]

TL;DR Summary

I want to make a countdown clock that doesn't need maintenance to reset it every year.

I want to (try to) build a "Countdown to Launch Day" clock for my sailing club. Ideally, it should require no maintenance (meaning, once I'm gone, it will keep working). Even as my right brain was thinking how cool it will be, my left brain started counting the ways it would be problematic:

• Launch Day is always the last Friday of April, so not always the same every year (but abides by the 28 year perpetual calendar).
• If it were a web page, it would be trivial, but I want a gadget - that sits on a shelf.
• It would be super cool if it were electro-mechanical in nature (like an electric clock is) - as distinct from electronic, such as an Arduino*.
• With the exception of a backup battery, I don't know how it would survive the occasional unplugging and loss of time sync.
• With the exception of a Wifi connection, I don't know how it could recalibrate itself if/when it does get unplugged.

Casting about for inspiration.

*if it were Arduino-powered - which I suspect might be the only viable option - does that have everything I need? Notably, a small display screen and a web connection so it can keep its clock in sync after power-reset?

 

[Baluncore]

Powered by wall plug, no battery backup.
GPS module, on an Arduino, that controls all display segments.
When power fails it stops, but when GPS returns, it quickly shows the right numbers again.
Display cannot be a mechanical counter.

If the display is mechanical, 7 segment modules with each segment being a cylinder rotated against a stop, to show a black or a white side, by a $2 DC motor, with direction controlled by the Arduino.
If electronic, use jumbo 7 segment LED displays.

 

[DaveC426913]

I'm sensing you may have had similar projects in your past...

 

[Baluncore]

I'm sensing you may have had similar projects in your past...

Not even similar. I relaxed your constraints to what I could do if it needed an entertaining and novel prototype.

Fuel pump displays and airport schedule boards have cyclic character sets, or rings of numbers, that must be reset first, then stepped forwards to the required display.

Some fuel pump displays, with 7 segment numbers, are driven by a ten-digit code wheel, but could be modified for direct segment control.

 

[DaveC426913]

I suspect I would have to go the Arduino route if it's going to be maintenance-free.

A little bit of research reveals that Arduinos are even more useful than I imagined!

A few years ago I had an idea for a water-level meter for our lagoon. (Actually, I became intrigued by the seiche (sloshing) of Lake Ontario):
https://www.physicsforums.com/threads/tidal-effects-on-long-lakes.975092/#post-6210183
and wanted to build a seiche-meter, and was exploring how I might build a water-level sensor:
https://www.physicsforums.com/threads/diy-tide-sensor.993440/

Well, there's an Arduino beginners kit that comes with a water-level sensor! My project is half-done for me!

 

[Baluncore]

The Arduino could get time from the net, or from GPS. GPS does not suffer from access problems like the internet. The choice might depend simply on exposure to the constellations.

If you have daylight saving during summer, you might want it to count straight through to the start time on the specified day, without any one hour quirks.

You appear to be up-to-date on seiche-ometry.

 

[Borek]

Arduino + RTC DS3231.

 

[Rive]

It would be super cool if it were electro-mechanical in nature

Regarding displays: maybe you can look for 'flip display'
There are seven segment and pixel versions too. Also there are several Arduino projects as references
I don't think it would worth to shoot for complete electro-mechanical these times. Especially, since the target date moves.

With the exception of a backup battery, I don't know how it would survive the occasional unplugging and loss of time sync.

Poor man's UPS: run it through an USB power bank. Some (most?) types can handle parallel charge and discharge.

... don't forget to reserve some space in the box for the printed documentation (schematics and source)
With some care it'd work longer than the memory of 'where did I put those papers'
I guess that's the point

 

[DaveC426913]

... don't forget to reserve some space in the box for the printed documentation (schematics and source)
With some care it'd work longer than the memory of 'where did I put those papers'
I guess that's the point

Indeed. This is one of my primary design considerations - no one (but me) will take any responsibility for such a device (in a board / committee environment). So if it stops functioning, it will just get put in a drawer.

I suppose the take away here for me really is make gadgets that other people actually appreciate rather than becoming a responsibility.

 

[anorlunda]

With a bit of effort, you could make it draw energy only when it is picked up, then use a solar panel to power it.

I once owned a pocket calculator like that. When you unfolded the case, it got a shot of PV power from room light and it started itself up. The rectangle on top in the picture was the solar panel.

The secret is that there is no need to draw any power when nobody is using it.

 

[Baluncore]

Someone must have developed a countdown application for a mobile phone by now.

 

[DaveC426913]

Someone must have developed a countdown application for a mobile phone by now.

Without a doubt. I could do that myself (and have).

I don't want an app on a phone. And neither do the stodgy old sailors at the club. I want a device on the wall next to the classic brass thermometer and barometer:

 

[anorlunda]

Stodgy old sailor, hanging on the wall. https://www.craiyon.com/

 

[Baluncore]

Months, weeks, days, hours, minutes, seconds. What units and resolution do you require?
How do you want to display the time, with digits or a dial ?
Please sketch a likeness of the display.

 

[anorlunda]

Please sketch a likeness of the display.

There's only one answer for that group. When the countdown reaches zero, show this.

 

[berkeman]

There's only one answer for that group. When the countdown reaches zero, show this.
View attachment 321628

A cheerleader?

 

[BillTre]

View attachment 321631

A cheerleader?

Go time!

 

[berkeman]

TL;DR Summary: I want to make a countdown clock that doesn't need maintenance to reset it every year.

I want to (try to) build a "Countdown to Launch Day" clock for my sailing club. Ideally, it should require no maintenance (meaning, once I'm gone, it will keep working). Even as my right brain was thinking how cool it will be, my left brain started counting the ways it would be problematic:

• Launch Day is always the last Friday of April, so not always the same every year (but abides by the 28 year perpetual calendar).

So thinking a bit outside the box (pun intended)...

You could make it an exterior display, with a tall vertical mast-like rod (perhaps with a thin sail added for decoration) that supports a long-vertical-travel weight that powers a grandfather clock type mechanism. The weight takes a year-ish to fall the full vertical distance, and there are marks along the mast for the months/weeks/days. The oscillating pendulum for the clock could be down in the club, but the falling mass would be the marker that told folks how long it was until the next race.

The grandfather clock mechanism would not have to be super-accurate, since all you need is for the falling mass to contact the low stop of the mast within a day or two of the race. Nobody will care if it's not accurate to the nanosecond, they will be too excited about the upcoming race near the end of the clock's yearly voyage...

You could add a tradition that the winning crew for the race must hoist the clock weight back up to the top after they win, as part of the awards ceremony. I suppose you could get creative and make the falling mass an anchor or some other such maritime symbol...

 

[anorlunda]

View attachment 321631

A cheerleader?

No, LOL. I guess you're not a boater. A semaphore signaler.

 

[Baluncore]

... but the falling mass would be the marker that told folks how long it was until the next race.

That seems backwards to me.
There was a time when the astronomical observatory of a port, marked time by raising a ball in stages up a mast. The ball was dropped at the instant of either 12 noon, or 1PM, so chronometers on vessels could be checked or set.
https://en.wikipedia.org/wiki/Time_ball

 

[berkeman]

That seems backwards to me.

So apparently you never had a grandfather clock in your house when you were a kid (the weights go down, and need to be "wound" back up periodically to keep the clock running). Chiming every quarter hour. And chiming and dinging off the hour count every hour. Hour after hour, day after day... (No it didn't drive me crazy. Why does everybody think I'm crazy!)

https://www.premierclocks.com/blogs/clock-blog/grandfather-clock-pendulum-and-weights

 

[BillTre]

A Victorian way to impose order on time.

 

[DaveC426913]

Months, weeks, days, hours, minutes, seconds. What units and resolution do you require?

Days till launch:
109

How do you want to display the time, with digits or a dial ?

Interesting thought.
I think the priority is that it is visible from a distance of yards. Like numerals are maybe an inch in size. On a dial, numbers that size would make for a prohibitively large device. However, I am intrigued by the intuitive aspect of a physical counter - maybe you wouldn't need to see the exact numbers unless you got close.

I like that line of thinking.

 

[Baluncore]

So apparently you never had a grandfather clock in your house when you were a kid (the weights go down, and need to be "wound" back up periodically to keep the clock running).

In that, you would be wrong.
I grew up winding our English Oak Longcase clock, originally built circa 1795. It was restored and given to my grandfather as a wedding present in 1908. I have now inherited it.

The term "grandfather clock" comes from a popular song, originally from the 1880s, but revived, about a longcase clock that stopped after 90 years.

 

[berkeman]

I grew up winding our English Oak Longcase clock, originally built circa 1795.

$Sorry \: brother...$

I have now inherited it.

$Sorry^2$

(I was only half joking about the crazy part)

 

[hutchphd]

And we only think you are half-crazy.....

 

[berkeman]

And we only think you are half-crazy.....

Thank you. That's the nicest thing anybody has said to me lately.