Micro Word Clock

A word clock – a clock that tells time with words, not dials or numbers – is one of those builds that’s on every Arduino neophyte’s ‘To Build’ list. It’s a bit more complex than blinking a LED, but an easily attainable goal that’s really only listening to a real time clock and turning a few LEDs on and off in the right pattern.

One of the biggest hurdles facing anyone building a word clock is the construction of the LED matrix; each LED or word needs to be in its own light-proof box. There is another option, and it’s something we’ve never seen before: you can just buy 8×8 LED matrices, so why not make a word clock out of that? That’s what [Daniel] did, and the finished project is just crying out to be made into a word watch.

[Daniel]’s word clock only uses eight discrete components: an ATMega328p, a DS1307 real time clock, some passives, and an 8×8 LED matrix. A transparency sheet with printed letters fits over the LED matrix forming the words, and the entire device isn’t much thicker than the LED matrix itself.

All the files to replicate this build can be found on [Daniel]’s webpage, with links to the Arduino code, the EAGLE board files, and link to buy the board on OSH Park.

45 thoughts on “Micro Word Clock

    1. Hi! The current prototype does not have a battery yet. Try fitting a coin cell holder on 20x20mm! I have thought of using a stack of PCBs, one for the ICs and LED, the other for the backup battery (sandwiched) and maybe a USB port on the back for plugging it in. I hope to build a better version soon. A 30x30mm LED matrix might be a bit more readable, too (e.g. as a desktop clock). I did this one mostly for the challenge of making everything fit behind the LED matrix.

      1. You can certainly fit smaller Lithium coin cells inside 20mm with battery holders made out of PCB. CR16xx or CR12xx (16mm and 12mm diameter). See here for sizes:
        http://en.wikipedia.org/wiki/List_of_battery_sizes#Button_cells_-_coin.2C_watch

        You can still use the on-chip RTC with battery backup (using a pair of diode). Detect the absence supply voltage, shut off LED, sleep/wake up on interrupt when you are on battery. It just need a bit of imagination.

  1. Wow! Never thought my project would be featured on Hackaday, much less in its own article :) Thanks! Feel free to ask questions or give feedback here. I haven’t made a write-up for the project yet but I’ll be glad to help out!

      1. Yes, I simply designed it in Inkscape using the LED matrix’ datasheet, printed it on a OHP transparency and glued it in place! Since my toner did not completely block the light, I used two copies on top of each other.
        Using regular paper with a dark enough toner/ink also works, this is how I developed the first prototype.

        I am thinking of doing a mini-crowdfunding to see how many people want assembled or DIY kits, still have to think about it.

        Yes, a 30x30mm matrix would be best for a desktop clock.

        1. Hi formatc1702
          Can you share the inkscape design file?
          That would be very helpfull for me.

          btw. i am in the progress to make a dutch version.
          Problably not with the fancy pcb, like the auther use, but a breadboard version of a atmega328

  2. Hey Daniel. Your werb site works again. But in the process your email broke.
    In case you wonder why you get no emails recently. ;)

    Final-Recipient: rfc822; mail@danielrojas.net
    Original-Recipient: rfc822;mail@danielrojas.net
    Action: failed
    Status: 5.7.1
    Remote-MTA: dns; mail.danielrojas.net
    Diagnostic-Code: smtp; 554 5.7.1 : Relay access denied

    1. The original idea was to simply push the programming header onto the pads or onto some solder blobs on each. That didn’t work out so well and I ended up having to solder a 6 pin header onto the pads and desolder it after. Through-hole soldering does not work because the opposing layer is cramped. I have looked into alternative, smaller ISP headers but haven’t tried them out. Suggestions are welcome!

  3. The original idea was to simply push the programming header onto the pads or onto some solder blobs on each. That didn’t work out so well and I ended up having to solder a 6 pin header onto the pads and desolder it after. Through-hole soldering does not work because the opposing layer is cramped. I have looked into alternative, smaller ISP headers but haven’t tried them out. Suggestions are welcome!

  4. Genius design!!!
    Not built yet, but here is another Dutch lay-out:

    K W A R T I E N
    V I J F V O O R
    O V E R H A L F
    T W A A L F * D
    I W * C V I E R
    E Z E S H Y L I
    N E G E N T F E
    Z E V E N U U R

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