Here is a simple project that can be mounted easily by beginners. It is an electro-mechanical game to see who has the quickest reactions. It is fitting quite interesting to be used in science fairs and even in the early stages of the mechatronics courses and practical work gathering work with electricity and mechanics at the same time.

   This game has a roulette wheel to be rotated quickly. This roulette is made with a ferrous metal (which may be attracted to magnets) and around there are 4 small electromagnets that should be triggered when the "judge" scream "now!" or when a lamp is lit for the competitors.

   Roulette will be attracted by the electromagnets but depending on their position in working to stop pointing one of them only.

   An interesting factor to note is that roulette can stop such a way to indicate the winner just the player who is in the opposite position to that tightened first. This unpredictability allows join the rapid reaction a random factor to the outcome of the game.

   The circuit is powered by common batteries that have good durability because of the fact that players must not keep tight buttons for more than a few seconds each time.

   Assembly requires more skill than mechanical electronics.

   In Figure 1 the diagram of the apparatus.




   In figure 2 we have the appearance of the tray when the assembly is made.




The wheel is made with a common metal pieces which can be folded and the point of engagement should be made with a nail, so that encaixer nail or pin serving for support. This roulette must be well balanced to be able to turn quickly with a push given by the operator's fingers.

   Each of the small electromagnets is made by coiling 100-300 enameled wire turns very thin (32 to 36) in a common nail.

   To connect the enameled wire in cells (support) and pressure switches (S1 to S4), and need to shave the tips because without that the solder does not "catch".

   The connecting wires to the switches should be extended to facilitate management by the players.

   To play proceed as follows:

   Turn with your fingers quickly the arrow or roulette. Each competitor from 1 to 4 must wield your switch without pressing and pay attention to the judge. When the judge says "now!" all should seek tighten the fastest buttons as they can. The wheel must stop abruptly getting pointed in the corresponding electromagnet to the winner.

   Before you try playing the unit checking that all electromagnets can draw the arrow to its position when the corresponding button is pressed.


   B1 - 4 small or medium-sized batteries

   S1 to S4 – Push Buttons NO

   L1 to L4 - electromagnets - see text


   Tray, tin arrow, battery holder, wires, welding, etc.