Thursday, July 17, 2014

New kit in store: simple clock with HDSP-2534 display

Update July 31, 2020: See the latest revision here.

The centerpiece of this clock kit is the vintage-style 8-character display HDSP-2534 originally from HP, currently manufactured by Avago. The assembled clock looks like in the photo below. The dock, not included in the kit, is a miniB USB phone charger; it can be easily sourced from ebay, if you don't already have one. (You can even get a fancy one, e.g. custom-made exotic wood, on

The kit includes the following components:

  • PCB;
  • ATmega328P, with bootloader and fuses for 8MHz internal clock, and the sketch preloaded (also downloadable from here);
  • HDSP-2534 display;
  • 595 shift register;
  • DS1307 real time clock;
  • 32kHz crystal
  • CR1220 battery;
  • battery holder;
  • push buttons (x2);
  • capacitor 100nF (x3);
  • 10k resistor (x3);
  • 28-pin socket;
  • 16-pin socket;
  • 8-pin socket;
  • 6-pin machined female header (x4).

   $40, free shipping to North America

Note: The kit is currently out of stock. Please send me an email (my address is in the top right corner of the page) if you want one. I will put together only a small number of kits at this price, since the display itself is sold by digikey for about $40.

Schematic and board layout are shown below. Preliminary Eagle files can be found here.

The kit is super easy to assemble. It is really impossible to misplace components on the board.
Still, here is some advice:
  • pay attention to the orientation of each of the three integrated circuits, when you insert them in their respective sockets;
  • before soldering the battery holder, put some solder on the big center pad;
  • avoid solder bridges between the USB miniB connector's terminals by wetting their pads (on the bottom side) with a flux pen;
  • it is recommended, for aesthetic purpose, not to solder the FTDI connector to the board; if you need to upgrade the existing software (download from here), you can just hold the 6-pin make header tightly in place while uploading the sketch;


  1. I'll send you some money Florin...;-)

  2. Because I don't have enough 'blinky' in my life already....and this fits the bill nicely! ;-) Put me down on the list please!

  3. could you PLEASE opensource the PCB CAD files (for DIY etching)? :)

    (BTW, BIIIG fan you your site: nixies, 7SegLEDs, Clocks, arduino and DIY…im in heaven)

    1. I will, don't worry, as soon as I get the PCB re-worked.
      I could have just shared the project on oshpark, but a couple of traces are missing, so I don't want to waste people's money and energy.
      In the meantime, I added the schematic.
      As I said, as soon as I get the PCBs back and they prove correct, I will publish them.

    2. Angel, the eagle files are now available for download.

  4. wow that was fast. thank you very much.

    i’m trying (i’m very new to arduino in specific and programming in general) to make a alarm/clock very much like the ones you make on your blog.
    one difference though is that i’m trying do do it with a dfc77 receiver. the chip wit integrated antenna is very small and cheap. the dfc receiver tunes into the regional broadcast clock signal so it adjusts the time automatically.

    1. From what I know, DCF77 works only in Europe. Some time ago I tried using the equivalent North-American version (WWVB), with no success, since Toronto (where I reside) is quite far from Colorado (where the transmitter is).
      In any case, this DCF tutorial may help you:

    2. GPS may be a better (accuracy-wise) and easier (using just serial port) solution for synchronizing a clock.

    3. the problem with GPS is that its expensive and bad (if at all) reception indoors.

      no idea what the system in canada is like but thats what i found:

    4. RE: GPS may be better and easier:

      the implementation is realy not that difficult. i managed to make a funtioning clock output through serial port. now i have to figure out how to combine dot matrix/sevseg output with the dcf77 data (dcf77 library are readely available. if you want i can provide you with links)

      accuracy wise i think dcf77 is on par with gps. from wikipedia:

      ...the control unit of DCF77 in Mainflingen is expected to neither gain nor lose a second in approximately 300,000 years.

    5. From what I remember, it takes 1 minute to get the time data, if the reception is good. Compare that with 10 times a second with GPS. That's what I meant by accuracy.

      As far as "how to combine dot matrix/sevseg output with the dcf77 data", I imagine that you only have to set the time values after you receive the time.
      For example, your clock already uses variables hours, minutes, seconds to display the time. Normally, your clock also reads these values from RTC. Once in a while (e.g. every hour or even once a day), you read the data from DCF and set these variables.
      (I assume you are still using an RTC.)

  5. Hi Florin! Put me down on the list as well. Although to make your life a little bit easier, I really don't need the display. I will be using the HDSP-2533, which is the same display, only in Green instead of Red. (red is a little hard on my eyes). Thanks! ~Chuck

  6. Hello, I am a friend living in Taiwan, may I ask if this product package is still sold, if so, can you send to Taiwan, thank you

    1. Simon,
      Yes, still sold, and I can ship to Taiwan.

  7. Hello, I am a friend living in Taiwan, may I ask if this product package is still sold, if so, can you send to Taiwan, thank you

    1. Sorry my friend, I missed your comment. (Better contact m directly at the email address provided in the top right corner of the main page).
      Yes, this kit is still for sale.

  8. Hello
    I have a problem when compiling the program.
    Could you put a hex result file?

    1. Here it is: