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Switches

These are devices which are operated either manually or via remote control and are used to turn electrical circuits on and off. In its simplest form, a switch has a lever which moves a conducting piece of metal into a position where it makes contact with another fixed conductor, thus bridging the two and allowing an electrical current to flow between them. Each of these is called a terminal (or pole) and is connected to the wires within the circuit, thus controlling the current in that circuit, Figure 3.

Manual switches are used in model boats to turn on and off the power from the batteries to the various loads. Usually these switches have an extra terminal, so that the moving contact is touching one or the other of two fixed terminals at any time. This can be used to divert the flow of current from one circuit into another and is called a changeover (or double-throw) switch, Figure 4. A simple switch which only has one set of terminals is called a single-pole switch, while a switch which can operate two independent circuits with just one toggle is called a double-pole switch, Figure 5. You will find switches referred to by their abbreviations SPDT and DPDT, which are respectively Single Pole Double Throw and Double Pole Double Throw. The centre contact of a set of three is always the common contact.

The choice of switch depends upon what you want it to do and also what current it will be conducting as switches are rated for voltage and current. I recommend a 16A toggle switch for motor circuits and either a 2A or 5A toggle switch for lower current circuits, Photo 8. Note that these ratings are for the 'switching' current at a mains voltage, i.e. the current which will flow instantly as soon as the switch is thrown. In practice they are capable of conducting a higher current once they are 'on'. In nearly all cases in a model boat we are dealing with much lower voltages and there will be very little current flowing initially until you actually move a transmitter stick and energise something like a motor. I don’t personally use slide switches, but they are still fitted by radio manufacturers in the wiring harnesses which they supply to connect receivers to battery packs, Photo 9.

Switches being what they are, the toggle or slide needs to be accessible from outside the model. This means either leaving it standing proud but in a less visible place (e.g. inside an open cockpit); hiding it under a removable hatch, or modifying a deck feature so that it moves and operates the switch. For submarines none of these options are practical, so you might want to fit a magnetic switch. This is based on a magnetic reed switch and is mounted on the inside of the model, right up against the outer skin. To operate it, you simply 'wipe' a permanent magnet along the outside of the skin from front to back of the switch area. This energises the thin reed switch, trips a latching relay and makes the circuit. Alexander Engel KG sell two different types; one for models with a BEC (Battery Eliminator Circuit) speed controller and one for those without, each in either 6v or 12v versions They are however, as the Editor says, not exactly cheap, Photo 10.

Remotely-controlled switches do essentially the same job as manual ones, except that instead of moving the slider or toggle of the switch with your finger (or a magnet), you operate a control on the transmitter of your radio which sends a signal to a special sort of switch inside the model to turn on and off the particular load e.g. lights and more about these later.

 
 
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