# Puzzle piece circuit board

#### Robino90

Joined May 8, 2020
4
Hi!

Please speak to me like I'm an idiot, because I don't know much about circuits, or even how to make this box idea. ^_^

My goal is to host a treasure hunt for friends and family. I thought it would be cool to have the final box with the prizes inside, have to be opened by assembling a row of puzzle pieces that are made from a circuit board (or some other idea you may have) . Once all pieces are in place it completes a connection that retracts some small pistons that allow the box to be opened. The puzzle pieces will be the reward for completing riddles and such throughout the day.

I have the wood working skills to be able to make a nice looking treasure chest type box for this. But I wanted to see if anyone could help me out with my electrical theory for this chest.

- is it even possible?
- what parts would I need to order?
- any better ideas you may have?

Thanks!

#### jpanhalt

Joined Jan 18, 2008
11,088
First you need a circuit that does something. A electric lock, flashing LED, clock ticktock, etc. Then I would divide it into sections and connect each section with the same physically sized connector. Something like this:

That is, male and female connectors. Then get "polarizing pins" which you can stick in the female socket to block any male connector with a pin in that position. Lets say you block 2 holes. There are lots of possibilities. Now on the male side, remove the corresponding pins so everything only goes together one way.

Make the circuit such that each piece has just 2 connectors (that is not a requirement but will make it easier). They can be both female, both male, or one of each. Doesn't matter. The important thing is it can only go together one way,

You don't actually need to buy the polarizing pins. You could take one of the pins you remove from the male header cut it short and put it in the female side. One might want to insert it far enough so it can't be seen, but I wouldn't. It is pattern recognition, so I would leave the polarizing pin visible. The purchased pins are plastic and usually white or black.

Finally, I show only single row connectors. They are available with multiple rows. Two and three row connectors would make the puzzle more challenging.

As for the shapes of each component, You cold make them any shape. I would lean toward simple geometric shapes that when assembled would be a cube or other geometric shape. Maybe something like a Soma cube:

#### Robino90

Joined May 8, 2020
4
Both helpful and I'm learning a lot! But, I think I failed in my description. I was picturing.

Solionid lock (Google the proper part in my head lol) one wire going to the power source(battery pack?).

Then the other end of the battery pack and the remaining wire would meet up, one wire on each end of a (guessing on sizes but) 1" by 10" by (however thick a jigsaw puzzle piece is) deep. Then when all puzzle pieces are fitted in, the connection would complete and open the lock.

#### MrChips

Joined Oct 2, 2009
23,268
Have any number of wheels in any pattern, straight line, circle, square, etc.
On the wheels you can have numbers, letters, pictures, whatever you choose.
The wheels must be all turned to a certain position before the solenoid can be activated.
For example, letters may spell out a word, a number could be the correct answer to a multiple choice question, a picture could be to match a certain animal, or the photo of a famous person's face, a building, monument or work of art.

#### jpanhalt

Joined Jan 18, 2008
11,088
Then the other end of the battery pack and the remaining wire would meet up, one wire on each end of a (guessing on sizes but) 1" by 10" by (however thick a jigsaw puzzle piece is) deep. Then when all puzzle pieces are fitted in, the connection would complete and open the lock.
In my description, the part of the circuit that would be missing could be a single wire, e.g., a wire necessary to make a connection to the battery. In other words, view each pair of connectors as a short. When all the shorts are properly mated and not before, power is restored.

There are connectors that are not plug and socket and are reliable. Think of "pogo pins" (that's what they are called), which are spring-loaded contacts. My concern was that without some sort of spring loading, of which a plug and socket is just one type, your electrical contact may not be reliable. That is, you would have the risk of someone getting the puzzle put together properly and still not working.

There are also magnetically activated switches. Thus, it wouldn't be plug and socket, but magnet and switch. A magnet and piece of steel would also work, but I think you need to incorporate a good electrical connection in the presence of relatively poor physical alignment. I would call that "springiness."

#### BobTPH

Joined Jun 5, 2013
3,129
If the puzzle only makes contact between two points to open the box, one could cheat by using a piece of wire. Is the box to be monitored to prevent that? Is not, there are many ways to overcome this with a more complicated circuit.

Bob

#### jpanhalt

Joined Jan 18, 2008
11,088
I assume the rewards in the game don't justify cheating.

#### Tonyr1084

Joined Sep 24, 2015
5,868
I have some magnets that are for holding a cabinet door closed. You could use something like that to connect pieces together. Have your competitors construct the key that unlocks the final box. But the puzzle pieces you describe (if I get you correctly) aren't going to make good contact. The only other solution I could think of is to have a puzzle board where you put the pieces in their correct location to complete a circuit. The connectors would have to be all the same on all the pieces but only certain pins in the correct orientation would actually complete the key. Assemble it wrong and the treasure will not open.

I was thinking of pieces with letters that spell out a word. Two rows of three letter words for a total of six key pieces. I - N - O - U - W - Y Arrange them to spell out two words that form a simple sentence. I won't give you the answer, but it's pretty easy to see. If someone else wants to unscramble them - fine. But when each word is spelled out correctly they complete a circuit.

Each piece could be a resistor of some value. When assembled properly they create a specific resistance that activates the unlocking mechanism. Something like two comparators where the first determines a minimum value and the other determines a max value. If the resistance assembled is too low then the lock doesn't open. If it's too high again, it doesn't open. But if just right, the lock is activated and the box opens.

Not the easiest approach, will require some help designing the comparator circuit but it can be done. Or you could use an Arduino or some other micro-controller to determine the proper value. There's lots of options. The trick is finding the solution that fits your vision.

#### MrChips

Joined Oct 2, 2009
23,268
You can DIY your own puzzle using Lego blocks.

Here is how I would do it for your puzzle.

Use square blocks. Fold brass shims over the edge of each of the four sides. Solder a short piece of wire between two shims only. (Solder the wire before gluing the shims (electrical contacts) in place otherwise you will melt the plastic.)

On the top face of the block, paste a picture of your puzzle. The correctly placed blocks must form a continuous electrical path from the first block to the last.

#### SamR

Joined Mar 19, 2019
3,256
Or a 2 step game process. Find all the pieces and find the map (Ckt. Diagr.) to put all the pieces together to make the circuit work. Or visa versa.

#### Robino90

Joined May 8, 2020
4
Hey, some really good ideas! The Legos would be small enough to hide too! May have to go that route.

But, the jigsaw puzzle route, I had an idea to make it more consistent. What if where the puzzle pieces go, (for the example, each puzzle piece is 1") the bottom of the puzzle pieces is a wire, and on the box the pieces go, there are little quarter inch bridges between each piece, so even if the prices don't perfectly touch, it should at least touch that bridge and go to the next piece?

Would this possibly work? If so, what materials could I use to transfer the electricity? What materials would be best to make the puzzle pieces out of? What power source should I buy? Thanks!

#### Toughtool

Joined Aug 11, 2008
63
There are also magnetically activated switches. Thus, it wouldn't be plug and socket, but magnet and switch.
I am thinking about magnetic reed switches mounted to a prototype board, like these:
https://www.ebay.com/i/143190431123...MIgZbf5tqn6QIVyp6zCh2hHQs_EAQYASABEgL5dfD_BwE

and magnets like these:

Then create a series circuit of magnetic reed switches, covered with a piece if opaque plastic to (hide) the circuit. Create a wooden jigsaw puzzle using a jigsaw. Counter bore a hole using a Forstner bit and glue the small magnets to the underside of all pieces. Assemble the puzzle and glue an image or messages on the top side. Sounds like a fun project.

Prototype board (7X11.8 inches):
https://www.amazon.com/BLS-180MMX30...ywords=large+perfboard&qid=1589060304&sr=8-10

#### MrChips

Joined Oct 2, 2009
23,268
Electrical contacts on the bottom of each puzzle piece making contact with similar contacts on the top of the box would work.
The problem you can anticipate is making reliable contact with all puzzle pieces. All it takes is one bad contact and the box will not open.

#### SamR

Joined Mar 19, 2019
3,256
Which is sorta why I mentioned "Snap Circuits". The snapping action between the pieces is pretty reliable. They come highly recommended by my grandkids. I'm not recommending buying them but take a look at how they are constructed. They can sometimes be found at yard sales or thrift shops if you want to see them hands-on.

#### Tonyr1084

Joined Sep 24, 2015
5,868
I am thinking about magnetic reed switches mounted to a prototype board, like these:
https://www.ebay.com/i/143190431123...MIgZbf5tqn6QIVyp6zCh2hHQs_EAQYASABEgL5dfD_BwE

and magnets like these:

Then create a series circuit of magnetic reed switches, covered with a piece if opaque plastic to (hide) the circuit. Create a wooden jigsaw puzzle using a jigsaw. Counter bore a hole using a Forstner bit and glue the small magnets to the underside of all pieces. Assemble the puzzle and glue an image or messages on the top side. Sounds like a fun project.

Prototype board (7X11.8 inches):
https://www.amazon.com/BLS-180MMX30...ywords=large+perfboard&qid=1589060304&sr=8-10
Suggest you delete everything in the link from the question mark on. It's there for tracking only. You still go to the same site. Here's your links after being cleaned up:
https://www.ebay.com/i/143190431123
https://www.wish.com/product/5c74aec7bbc78109654c3e77

https://www.amazon.com/BLS-180MMX300MM-Prototype-Solderable-Universal/dp/B073VK972W/ref=sr_1_10
They should still work.

#### Toughtool

Joined Aug 11, 2008
63
Suggest you delete everything in the link from the question mark on.
OK! I like that, thanks very much.

#### Robino90

Joined May 8, 2020
4
Thanks everyone! First trial I'm going to try making puzzle prices out of wood or plastic, with a strip of copper on the bottom, and make the copper bridges.

Battery pack and maybe 2 solinoids for the lock. I suppose I need sodder at some point. Adventure!

Magnet idea seems like a solid backup if this isn't reliable, along with the Legos.