Build an electronic polyhedral die

Dice are fun. Polyhedral dice used in D & D are even more fun, particularly in big handfuls of different sizes. But a handful isn't always practical.

Ever since I saw the dragon bone electronic die wand advertised in the back pages of Dragon magazine when I was a kid, I wanted an electronic device to act as a substitute for all my dice.

This device won't substitute for the tactile feel of rolling a handful of funny dice, but its great for traveling games and is a fun project as an introduction to soldering and micro controllers. Having one of these proclaims to all your geek friends that you are another kind of geek entirely.

If you like this, please vote for it in the laser challenge. The box is pretty enough, but if I had a laser cutter I would make my own in the shape of a 12 sided die, cutting the sides out of acrylic with a precision that I could never achieve on my own.

Please see the notes in step 15 for more of my thoughts on what I would do with a laser cutter if I were to win the contest.

Step 1 What you need

You will need the following tools:

• Soldering iron.
• Dremel and/or other tools to cut and shape the enclosure if needed.
• Diagonal cutters.
• Hot glue gun (optional).
• Vice or Helping Hands to hold the board while soldering (optional, but highly recommended).
• Multimeter for testing.
• USBTinyISP or other AVR programmer to program the firmware. See step 10 for other options.

Electronics (Prices in US $ from mouser.com)

1-	AtTiny2313 microcontroller	-- $1.85
1-	20 pin dip socket	-- $0.17 (optional, for AtTiny 2313)
1-	tilt switch	-- $1.51
1-	Pushbutton switch	-- $0.91 (Use any momentary pushbutton you like).
1-	20 mm battery holder	-- $0.91 (for cr2032 battery)
2-	33 ohm resistor	-- 2 X $0.10 = $0.20
1	cr2032 20 mm 3 V coin cell battery	-- $0.45 (these are ridiculously expensive in stores)
1-	2 X 3 break off pin header	-- $0.10 (For ISP)
1-	eDice printed circuit board	-- ~1.6 square inches = $?? (Depends on how you get it printed)
1-	Common cathode 2 digit 7 segment displays (red)	-- $1.57 (Also comes in Yellow, Green and Blue)

Total = $7.22 + board cost and optional enclosure.

Other Materials:

• Solder.
• Wire (for connecting button and battery)
• Glue (I prefer hot) to attach device in optional enclosure.
• Small bit of heat shrink tubing.
• The optional box or other object you are mounting the die in.

Comments

[theodopolis13]

i have always wanted to make something like this, unfortunately most rpg groups won't let you use electronic die, since there is no way to prove that it's not rigged.

[mkanoap]

I suppose you could show them the code (assuming a sufficiently geeky group) and load it onto the chip right in front of them, but I can think of ways to game that too.

You could also point out that without careful and numerous trials, you can't know that a physical die is true either. You are just trusting your fellow players not to be using loaded dice.

It doesn't really matter, this device is a novelty item and really only good for places where it would be inconvenient to throw real dice. Like on a bus ride or something. I don't really imagine I would use it in place of real dice most of the time.

[bbeal]

Which, if any, of the files in eDie-1.2.zip meets seed studio's gerber requirements? Sorry if this is an ignorant question. I have never done this before and it looks so interesting I am will to break out of my comfort zone.

[mkanoap]

None of them do directly. Unfortunately seeed wants the board to have the order number printed right on them, so you have to order the boards, open the board file in eagle cad to edit the silkscreen with the order number they give you, and then generate the gerber files from that.

http://www.instructables.com/id/Professional-PCBs-almost-cheaper-than-making-them- describes pretty well the process of getting eagle CAD to spit out gerber files.

Gerber files are zip files with images that describe each of the layers that go on the board. In the case of this board, at least 8 (top and bottom each of copper, soldermask and silkscreen plus a file to show where the holes are and another to describe the drill sizes). Each manufacturer may want each of these individual files named and/or formatted differently.

In the case of batchPCB and dorkbotpdx, they each provided a file that tells eagle exactly how to generate gerbers the way they want. In the case of seeedstudio, they didn't but they they wanted a "readme" file in the zip that just described what each layer was named, so I re-used the batchPCB job and then created that readme.

I just got back the ones I ordered from dorkbotpdx and they are very pretty. I have not tested them yet but I'll be happy to upload the gerber file I used once I have in the next week or so. The seeed studio ones are still on a boat somewhere.

Some time soon I hope to launch a kickstarter campaign to raise seed money to make kits of this project, but I don't envision these kits being available until 2012.

[kevinvos]

lol aren't that magic the gathering dices outside that box? :P

[mkanoap]

I don't think so, I don't even remember ever using dice in MTG back when I played it a decade ago. But I gather some people use 20 sided dice to keep track of life totals and I'm not up on current trends/rules. We used to use colored stones.

On the other hand, I can't rule it out. The dice in the picture are just a random assortment from a much bigger collection I have and I don't know the origin of all of them. So some of them may have come from an MTG set of some kind.

Are there special dice for MTG?

[Pie Ninja]

Wizards make dice especially for MTG, D20s with a symbol (usually the icon from a set) instead of the 20. Standard playing starts you on 20 hit points, which makes a D20 a good option for someone wanting a small life counter.

[teufelaffe]

They also have the numbers arranged differently. On a standard d20, opposite faces of the die add up to 21. So, the 1 is on the direct opposite face from the 20, the19 is directly opposite the 2, etc. On the MTG "Spindown" dice, the numbers are arranged sequentially, the 2 is next to the 1, the 3 is next to the 2, the 4 is next to the 3, etc. This is to make it easier to find the next number on the die.

[mkanoap]

Awesome. I think I'll have to see if I can score some.

[mkanoap]

Thanks! In that case, that D20 is definately not a dedicated MTG Die.

[mhunter6]

@ mkanoap - My husband and I have some of the special dice - there are special ones for the Fire and Lightening special prebuilt all foil deck that was released last year I think?

http://www.wizards.com/magic/magazine/article.aspx?x=mtg/daily/arcana/576

also there are six sided die included in the planechase box sets - you might find that interesting...

http://www.wizards.com/magic/tcg/productarticle.aspx?x=mtg/tcg/planechase/productinfo

As a side note as Pie Ninja said, using the 20 sided die is good for life counting - that's how my husband taught me to play - the problem is that we usually have to break out multiple d10 die because one of my decks is a white (almost) all angel deck, with 4 copies of Life Link included - thus the 20 sided die is usually not as useful as the multiple d10s.

>> also, I didn't mean for this post to come out looking like an advertisement for Wizards - I just thought since you said you weren't sure about special die you might be interested lol :) Thanks for sharing this electronic die!

[mkanoap]

Thanks for the info! I googled "magic the gathering dice" and was overwhelmed with auctions for cards and gave up so your links are welcome. I figured people were using D20s for life counters much like how D10s are used in the munchkin games to track level. Which inspired my game counter box (http://www.instructables.com/id/Build-an-electronic-score-keeperstorage-box/). Come to think of it, you could use my game counter for keep track of MTG life as well, since it counts down as well as up. Maybe I'll add a mode to mark a player as losing when they hit zero.

I've always been partial to a big pile of flattened glass beads (usually red) as life counters. That way you get this really visceral understanding of how close to death you are as the pile gets smaller.

[mikeasaurus]

Great writeup, I have a friend who would love this!