Author Options:

Creating a minimal LED clock with Arduino for those with poor eyesight? Answered

I've always had poor vision and cannot see any clocks at night without glasses or contact lenses.  Analog clocks are of no use.  7-segment clocks would have to be so big and bright, that they'd keep everyone up at night.  Clocks that make noise would create similar problems.

I have an idea for a clock that has four, rather dim LEDs flashing the time constantly.  I need a LED for each place value: 10hr, 1hr, 10min, and a 1min LED, in different colors as necessary.  I could also settle with a 5hr, 1hr, and 5min LED setup.  As the clock runs, each place value would be blinked, pause a few seconds, and repeat the process.  That way, just a quick count would let me know how much sleep time I have left.

Since I'm new to Arduino, it's beyond me for now.  I'm looking for pointers as I haven't found any clock projects with such a simple display.

Has anyone seen any code snippets that could help me out?
What would be a good timer (GPS, WWVB, RTC, etc.)?
Where would be a good place to start?

I'm not looking for a finished product, obviously.  I want to write the code myself.  But I also would like some good building blocks to begin with to help me learn the process.

Any help would be appreciated!


You seem to have the basics figured -- arduino can handle the calculations, I would recommend an rtc chip - cheapest accurate time solution.

One thing I would recommend is avoiding blinking -- I find blinking lights extremely annoying, and if you're worried about keeping people up, that would be the worst.  An led artificial analog with different colours for the hands and leds to indicate 12 3 6 and 9 should be easy to extrapolate the time even if totally blurry.

good resources:
arduino playground
arduino forum (all basically on the same website)

Perhaps flashing the time on a single large (6 inch tall) 7-segment display one digit at a time....having them fade in and out would be less obtrusive as well.

Thanks for the quick reply. I appreciate the links and am going to be doing research. I also appreciate the alternative ideas. I think, however, that even if I constructed one of those sparkfun 24" 7-segment displays, I'd still have a hard time making it out from across the room at night. I think my eyes are -9.00 diopters, meaning I could see a raindrop on the end of my nose in great detail, but not much more beyond. I was thinking of using dim LEDs, giving the effect more of the indicator LEDs on a router or similar device. I already have a few of those in the room and haven't been bothered by them.

Another solution is someone posted on hackaday a clock that was different colours to represent the different hours. The hours were roughly related to the sun's movement -- from deep blue through bright yellow, baby blue morning and magenta red sunset. With a little getting used to it could be pretty accurate...so long as you're not also colourblind.

You know, that gives me another idea, not from the clock itself, but from the hackaday review of it:

I could use resistor color codes, do away with the flashing, and just have four, RGB LEDs (or three RGBs and one double-ended LED for the hours' tens place).

I also saw that someone made a single-LED clock using a PIC controller that flashed the hours and minutes...but that would be too annoying.

It was in a mashup a few months ago -- I think the title was 'hard to read clocks"

Make a binary clock : It takes a bit of thinking about, but you can have the LEDs arranged as two rows, one with 4 leds for hours, one with 5 for minutes.

Go with the RTC idea, or use mains frequency, picked off your power supply transformer's LOW voltage side - mains frequency is VERY accurate over long periods of time - its designed to be.


Thanks for the input. I think I'll see what I can learn about the RTC module. GPS and WWVB receivers are way too expensive for a project such as this, and add way more complexity than I need. If I were to use mains, I'd have to find a 9V AC transformer and rectify it. Might prove expensive as well (and big). I think I have an 120V-18V AC transformer around I might be able to use. The binary idea might be even better than my original one, in that I could space the LEDs several inches apart. I'll see what I can find out. Thanks again!

Having seen your idea for the clock, I might have a go myself- I have the same problem at night !

Power supply wise, you might well find a wall-wart that gives AC not DC, and then rectify it in your clock. A simple 5V regulator will do the rest. You don't need an RTC, just a good track on the mains clock ticking away at 50/60Hz - you COULD put a hardware divide x 3600 stage on it, and get one minute ticks, or a div 60/50 followed by another div 60.....or you can do it in software on an arduino.....