Advice & Ideas needed...

Working on a project - a custom wall clock with perler bead NES sprites in the place of the numbers. The figures are mounted to a wood board with cutouts underneath, and during each hour an LED will turn on and light up the NES figure for that hour, and an audio file will play some sound effects/theme music from that particular NES game.

Time, Budget, Experience

  • Time is not a factor
  • $50 - $100 if possible. I already have a bunch of components (resistors, caps, LEDs, wire, etc.) laying around. I don't have any chips or an arduino.
  • I'm an engineer, just not electrical. Mech Eng + lots of math. I did take a couple EE classes in college but that was...a couple...years ago. I'm comfortable with circuits, wiring breadboards, sizing capacitors and resistors, etc. I've built several computers (thanks, Newegg). I'm pretty certian that once pointed in the right direction and with a little advice I can figure it out and build the circuits. My problem is knowing where to start.

Controlling the LED's

My main issue is trying to figure out the best way to sync LED's to a clock. For example, if Mario is at the 3 o'clock spot, then at 3pm the light behind Mario will turn on and stay lit for one hour. Then at 4pm the light behind Mario will turn off and the light behind another figure at the 4 o'clock position (Link) will turn on. The lights will cycle through 12 figures, then restart.

From what I've been researching the last couple weeks, there are lots of options:

  • 555 timer (don't thing this will work with time periods required)
  • 555 timer with decade counter
  • 555 timer, decade counter + 32.768 Hz crystal (can I run a clock off this too?)
  • cascading decade counters with 555 timer
  • arduino board and write code for program
  • raspberrypi (probably overkill)
  • others?

Playing Audio

I want to play a short clip of the theme music for each game at the top of each hour. For example, at 4pm when Link lights up, the overworld theme from Legend of Zelda will play for a minute, then stop.

This is where I'm least familiar with my options. I've looked at stuff like:

  • WTV020SD with arduino
  • taking apart an old mp3 player and setting in to play in a loop
  • various audio chips and boards

Battery life will likely be a problem with the mp3 player route. If I go the arduino route I could probably program the LED's and get an mp3/audio board and control that too, right?


  1. Need to sync 12 LED's to a clock/timer so one LED will stay lit for 1 hour and then turn off for the next 11 hours while the next LED lights up. Repeat.
  2. Need to play an audio file once at the beginning of each hour.

I've looked through the googles, here, sparkfun, buildcircuit, instructables, mdfly, and several other sites. Haven't seen anything that addresses this, or if I did I didn't recognize it. My apologies if this is covered somewhere else already.


I found this:

Sequential circuit with more than 10 LEDs

which talks about using 2 x 4017's to get a bunch of LED's going, and also SIPO shift registers. Seems like it would work, but again, the length of time required makes me think the 555 timer won't work. Am I right on that? Still leaves the issue of controlling the audio...

  • \$\begingroup\$ This should be possible with Arduino (can do all three of the things you want), I'm not sure what the budget reqs will be though.There are plenty of clock projects for Arduino that use a RTC to control LED clock with alarm. Should be able to take that and modify it so at top of the hour it turns off previous hours LED, turns on current hour LED, and plays sound byte. \$\endgroup\$
    – I. Wolfe
    May 13, 2015 at 19:45
  • \$\begingroup\$ Does the clock still have mechanical hands, or just the lights? And are there any pictures of the finished project? \$\endgroup\$
    – Klaws
    Oct 24, 2018 at 12:10

2 Answers 2


An Arduino or other microcontroller with enough gpio will work for the lights. Add the mp3 module and a real time clock ic and you can do everything you want fairly simple.

  • \$\begingroup\$ So if I get a microcontroller (arduino or similar) and mp3 module, I won't need to mess with 555 timers, shift registers, or anything else? \$\endgroup\$
    – meggatron
    May 13, 2015 at 20:18
  • \$\begingroup\$ @meggatron - You'll also want a RTC added to your stack. If I remember correctly, the Arduino has a timer but it's pretty terrible and you'll want a separate one. \$\endgroup\$
    – I. Wolfe
    May 13, 2015 at 23:24
  • \$\begingroup\$ I do not know much about Arduino, but Atmel AVR used there has an excellent timer. \$\endgroup\$
    – ilkhd
    May 14, 2015 at 5:20

You're a mechanical engineer? Do it mechanically.

From your description I assume this is an analog clock. So get access to the shaft that turns the hour hand and use it to control a 12-pole rotary switch. Each pole of the switch will span 30 degrees. Take a piece of copper-clad PC board material and draw a ring in the middle and then another ring concentric with it a little farther out. Drill a hole for the clock shaft through the center and divide up the outer ring into 12 equal pieces. You don't need to etch it: for something this simple a Dremel or other rotary tool will do fine.

You will have a center circle that carries power and coaxial with that, the 12 conductive poles. The clock shaft goes through the center of this backplate. Attach a copper wiper to the shaft so as it turns, it connects the center circle to each of the pole pieces in turn.

OK so far?

Provide power to the center ring and now you have a switched power signal at each pole that switches in sync with the hour hand of the clock. You can figure out the rest :-)

Now, you could do all this with non-contact sensors, etc. But this is likely simpler and will work well enough.

  • \$\begingroup\$ I like the idea. Easier for me to visualize. What I would be concerned about is using the shaft that turns the clock hands. The hands themselves are pretty delicate and so are the gears/shaft. I'd be worried about the added torque required to extend the shaft and rotate it. I'll have to think about it some more. \$\endgroup\$
    – meggatron
    May 13, 2015 at 20:39

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