Sometimes, order doesn't matter. Sometimes you need the players to put a coin in each of six places, and all of the coins are identical. And sometimes it does matter. Sometimes you need the player to put four statues in a particular order. And you can do that with reed switches. Why use reed switches instead of RFID? You don't have to program anything. Sometimes, if you put multiple RFID readers too close together, they interfere with one another. Reed switches can be placed much closer together. Magnets are smaller than RFID cards so you can use much smaller items to trigger them. And of course, reed switches are much cheaper.
So how do you do it? How do you make order matter?
Think planets. Imagine that model of the solar system you were shown as a child. The one with concentric circles. Now imagine that the magnets that you're going to use are planets. Just like real planets, each one needs to be in it's own orbit. All you need to do is orient all your objects in the same way, and then place the sun of your little solar system in the center of each object. Then you choose where your planets are going to be, and that is where you place your magnets. Sound confusing? It really isn't.
Here's your solar system. I'm going to use x's to represent each planet, each magnet. I'm currently making an RFID puzzle for next christmas. You're going to need to put three nutcrackers on the mantle in the correct order. One will be red, one will be blue, one will be yellow. They're going to stand on blocks of wood (that I happened to have in my scrap wood pile that are 4.5 inches square. I only have 3 statues, so I'm going to have 3 orbits. The space between each orbit is going to be .5 inches. Like this.
So now I'm going to choose three places for my planets to be. I'll use x's to show where they are going.
Now, I transfer this drawing to each of my three blocks of wood, the plinths for my nutcrackers. I tend to leave out the circles and just draw the lines because that's easier.
Drill holes where your x's are and insert a magnet. This is now the bottom of your nutcracker, or statue, or whatever you want to attach to the piece of wood. Or you can just paint, etch, burn or otherwise transfer symbols on to the blocks. Whatever works for your theme. You'll want to cover the bottom with something so your holes don't show. We used self adhesive felt at one point, but have found that adhesive vinyl works better.
You'll need some way to make sure that the blocks of wood with their statues or whatever on them are precisely positioned. I tend to do this by making a frame for them out of quarter round, but simply drawing an outline around them that the player can see will work too.
Once you've got your magnets in place, you can line them up in the frame and use them to position the reed switches correctly beneath. It's a really good idea to use a quick rig with a multimeter or wire in an LED so you can test the alignment and make sure everything is in the right place to be triggered. Then hot glue them in place and wire them the same way as the diagram showed in our previous post. As long as each magnet has its own orbit, (and ideally, is on its own axis) the blocks will have to be in the correct position and orientation in order to trigger.