We have a great Dutch Holiday tradition called sinterklaas (5th of december, this is what the US Santa is based on). For the older "non-believers" we make surprises. The purpose is to buy a small present but make a really cool "surprise" around it. Here my arduino based Split-flap game I made as surprise.

I made this for my 15-year old niece that was asking for very expensive presents only, so I thought I would make her a bit more price conscious :-)

The wooden box and all the components for the Split-flap display were made on my CNC machine. I used 2mm thick plastic to mill out the 36 cards in the display. The wheels holding the cards and the pulleys for the cardwheel and stepper motor were milled from left over thick plastic blocks. I milled a 10 teeth pulley (XL037) for the stepper motor and a 40 teeth pulley for the cardwheel, giving me a ration of 4:1 and with my 1.8 degree per step motor, this gives me plenty of accuracy to make sure I display the right cards. I did build into my arduino code I can easily change the offset for each card to fine calibrate. I had to do this, as not all my cards where equal in size.

The arduino (uno) used to run this all was tested to its limit 15 I/O ports :-)
- 5 pins for the score LEDs
- 4 pins for the stepper motor control, via ULN2003a
- 1 PWM pin for Servo to lock or unlock the side door
- 1 PWM pin for piezo speaker so we can make some sounds
- 1 pin for micro switch to align start of cards
- 2 pins for the lower and higher button

Here a video of the game in action:

if you happen to be Dutch (or at least understand that language), you can also watch the Dutch version of the video :-)

UPDATE:Wow, thank you all for the very nice comments! Clearly I am not the only one enjoying the sound and sight of the split-flap display :-) So I thought I would share you a video I made a few weeks back on my initial testing of the display. At some point I want to create 100 units, so I can have a wall in my living room of 25 characters by 4 lines to display "stuff" :-)

<p>Hi, nice thing...</p><p>How do you calibrate the starting position of the stepper motor? Is there some sort of feedback loop from the split flap display back to the arduino?</p>
<p>yes, check out the 40 toot pulley and card holder file. The is a &quot;big bump&quot; in the pulley that passes a micro switch every rotation. I use this for calibration.</p>
<p>This is awesome! Such a creative and fun gift. Can you explain more how the micro switch works to align the cards? Does this help to calibrate the start point for the stepper motor?</p><p>Thanks!</p>
Hey this is great! Brilliant idea. Can I ask how you attached the cards to the card-wheel?
The cards have on each side a bit sticking out, see the &quot;card 8cmx5cm.dxf&quot; file. These bits go into the wholes in the wheel.
the coolest thing on instructables.... by far.
Oh wow this is amazing! Congratulations on the second prize!!!!
Thanks :-) My first win.. up to the next project :-)
Gefeliciteerd met je prijs!!!!
Dank je wel :-)
Dude, epic stuff! Do you use an Arduino Uno?
Yes, normal Arduino Uno :-) It just managed with all the I/O ports, so did not have to use Mega :-)
You sir, are an awesome uncle.
Thanks :-) I do my best
Not only a great idea but a great video, too. I enjoyed it.
I have a challenge for you : you put five more LED and a lever, and when you are in the &quot;easy&quot; game you have to find 5 good answer, and when you are in the &quot;expert&quot; game (the other position of the lever) you have to find 10 good answer ! And more if you feel crazy ! Challenge accepted ?
mooi gedaan man!
so very cool
Sweet! But &quot;Santa&quot; is going to be b'slapped to 'East Gbyp ' after the solution!! But, that's what Uncles are for ! Keep it up.
I had much fun watching your video! I guess your niece got frustrated. Maybe she was clever enough to cheat your box to get to her present .... haha! great!
It is brilliant! It is a really nice hope it will help your 15 years old niece :)! It is always better to diy a gift rather than buy it! <br> <br>Thanks for sharing :)
Prachtig en inspirerend!
Very original idea. Nice to see fresh ideas hit the scene. Nice instructable.
Great idea and very well done! (I also enjoyed your second video... fotokamera!)
Great!! i really like it. Good job
I looked at the picture and was like, &quot;That's cute I guess..&quot; <br> <br>Then... I watched the video... and now I'm like... <br> <br>THAT IS AWESOME!!!!!
This is such a cool thing. Thanks for putting up directions!
This is such a cool project. As everyone is saying, I would LOVE some more detailed instructions. Specifically, I would love to see how your split flap display is put together.
Absolutely great!! But hard to duplicate based on your instructions. Would like to modify as a learning tool for my class room. Are there schematics and more diagrams available? I don't have CNC machine. <br>
Cool! Ik bedoel fris :-)
PS - I voted! <br> <br>To everyone reading - this is an entry in the Holiday Gift Contest, so make sure you vote if you like it as much as I do!
Wow! That's GREAT! This has sparked so many ideas that my brain is actually making the same sound as the flipping cards as it's analyzing each idea...
Man, you are amazing! I love the flip-flap display you've built and the entire idea of this surprise present! Thank you so much for sharing!
Really fantastic work! I also love the sound and visual of the flapping cards! It's not often enough that we see electronic projects with mechanical displays. I love this!
Absolutely fantastic! Using high tech materials to make a seemingly low-tech game- I love it. <br>But what's in the wrapped present?
Koninklijke surprise! Wat een oom!
This is really cool!
This is great! I love it!
leuk hoor!
Gave surprise. (wel met gedicht toch zeker? :P )
This is brilliant!
leuk ontwerp en heel grappig. <br>doe zo voort!!
This would be an awesome thing to make for kids cause they love buttons. Like it showed a picture and showed a word and the kid had to determine if the word matched the object or something like that. Good for learning :)
it would be easy to use it for that purpose as well, especially small kids learning their first words. The split-flap has 36 cards in it, so that is quite a few words to start off with :-) I used stickers I printed my self on the plastic cards, so you can easily replace them.
Oooh, using stickers was a great idea :)
Echt heel gaaf! <br>Had ik maar zo surprise gemaakt. ;D <br>Ga zo door!
impressive! I like the sound of the flipping cards!
Nice job

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Bio: Hi, I am Richard, Father of 1 son + 2 step sons, so we have a house full of Lego. I have had lego for decades ... More »
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