I've been developing puzzles and artifacts for Escape Room since 2018 and most of the time, I've been using some kind of Arduino as a controller. At this point, I already have a considerable repertoire of solutions. Many of them I created myself, others I adapted from things I found in my searches on Instructables, Github, Hackster.io and many other sites.

There are countless puzzles for Escape Room, but I've grouped many of them into sets that make it a lot easier for me when it comes to developing solutions. For example, there are puzzles that are sequential, that is, the player needs to activate a certain number of sensors in a specific order for the puzzle to unlock. Others, which I usually call closed circuit, are those where the player needs to trigger all sensors to unlock the puzzle. Others are combination games, in which the player needs to place objects in certain positions for the puzzle to unlock the next stage.

In this first post, I want to present some possibilities of the simplest of all devices, which is the closed circuit.

Many Examples of Closed Circuit

This puzzle is so simple and allows for so many variations, that most of the time, we don't need to use any controller. You must have seen that puzzle where you have to put all the pieces of a puzzle, or where people make a human chain between one point and another… I made a really cool version of this puzzle myself, where players need to find the parts of a radio and gradually fix the radio. Currently, this device is in one of the Escape Junior rooms, an Escape room for children that works here in S?o Paulo.

All these variations use the same principle, which is the Closed Loop, which I exemplify in the diagram below.

See, in this circuit, the solenoid will be activated when all switches are activated. This type of switch will make the connection between the center terminal and the left or right terminals.

You can play around a bit and create a little more complexity if you swap the switch actuation positions. Or add more switches to the system.

In the diagram below, the yellow wires have been swapped.

If you want to go a little further, still using only switches, you can add several multi-pole selector switches (Rotary Switches).

In the diagram below I have indicated only the connections between the terminals that result in the solenoid working. But you can solder other wires between the various terminals, just to throw the player off.

In this type of rotary switch, the center pin is connected to any of the others, depending on the rotation of the switch. The example rotary switch have twelve positions!

In all of the previous examples, you may have noticed that I am using a retractable pin solenoid. When the circuit closes, the solenoid is activated and the pin retracts. A few times I have used this type of lock. But it is much more common that we use a Maglock type. In this case, the operation is different. The magnetic lock must be energized to keep the door closed. If we use this same circuit, when the player deactivates any of the keys, the lock will turn off and the door will open.

In that case, we can use a parallel circuit. With as many keys as needed. And the player will need to disable them all for the system to turn off the lock. In the circuit below, the solenoid will be inactive only when there is no magnet in any of the reed switches.

A well-known puzzle in escape rooms is the one in which the player needs to find and assemble all the pieces of a Tangram. This is another example of a closed loop, and if we're going to use a Maglock, we're going to have to be a little more creative. In this kind of puzzles, we usually use a series circuit of reed switches. On the back of the pieces, we glued a neodymium magnet. When the player finds all the pieces and assembles them on the board, the lock is released.

This circuit works completely differently from all the others. In the first examples, the series circuit energized the solenoid when all switches were active. In the parallel circuit example, the circuit de-energized the MagLock lock when all reed switches were inactive. Now we want the circuit to disable the lock when all reed switches are active.

How to solve this?

In the diagram below, I present the solution I usually use, with two additional components: a DC DC module and a Relay module.

I use a 12V supply and decrease the output to 5V, using a DC DC module set to 5V. Next, I feed 5V to the relay module and set up my reed switches circuit by breaking a 5V line that I connect to the Relay module's Signal pin. On the Relay module, I connect 12V to pin C (Common) and then connect my magnetic lock to pin NC (Normally Closed). When the Signal pin on the relay module is de-energized, the NC output of the relay will be connected to the C pin. When the Signal pin receives high level, the relay module activates the NO output and turns off the NC output.

A lot of attention is needed because there are relay modules on the market that are active at a low level. In this case, the circuit is slightly different.

Short Circuits, Connect the Wires

Other variations on these circuits that I exemplified use wire terminals and jumpers that, when connected in the correct position, release the lock. The radio I built for Escape Junior used just a combination of these solutions. The player needs to find a set of valves, a transformer and fit the pieces into the correct locations on the radio board. As it is being assembled, its functionalities increase until the moment it works and transmits a message. Obviously, a system like this implies the use of a controller. But the assembly of the parts in the radio was nothing more than a circuit like these.

In the next tutorials, I'll show you other types of puzzles and some simple solutions to them.

Keep connected!