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3 Aspect Signal with Toggle Switch.

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SW313 Mini Toggle Switch
British System
Controlling these on a Model Rail layout can be done with a Toggle Switch. Rotary
switch, or automatically with magnetic switches. This Project describes how to use
a toggle switch to control the 3 aspect lights on a layout.
The 3 aspect signal is Green, Yellow, & Red. Green at the top means 'All Clear'
Yellow in the middle means 'Warning - next signal could be Red', and the Red
means 'Stop,
Using a toggle switch requires the switch to have three 'ON' position and three
lever positions. This is achieved with or SW313 switch. The terminals on the base
of the switch are numbered 1 to 6. Please follow these numbers on the drawing
carefully as the sequence of wiring is important.
The first thing to do is to ensure the Keyway is to the top of this diagram
Then put a link between terminal 3 and terminal 5 as shown.

Start by connecting the Green LED to terminal 6 on the switch (Long lead on the LED), the Yellow LED to terminal 5, and Red to terminal 1. The short leads from the LED’s are joined together and then connected to a 1K resistor before connecting to the negative supply.
Now connect 12v DC supply to terminal 2. Your switch is now ready.
(Note: If you are using filament bulbs such as Wheat Germ or LES or MES bulbs you do not require the Dropping resistor)
Please note that this DP3T (Double Pole Triple Throw) has a special configuration on the inside of the switch (SW313) ,
a normal DPDT will not work, even though they look the same.
Due to the link between 3 & 5 it is advisable to use Heatshrink sleeving on the connecting wires, just to protect against
short circuits.
The following is another combination of the 3 Aspect signal Light, where the Yellow & Green are on at the same time.
In this sequence when the switch is in the Yellow position it also supplies power to the Green via a diode D1. This can be a signal diode such as a 1N4148, (DD120) or a power diode 1N4002 (DD102) (which you are more likely to have).
Please note the + of the diode must face the terminal 4. The 1N4148 has a black line to indicate the positive end, whereas the 1N4002 has a white line to indicate the positive end.

Again if you are using Wheat Germ of Filament lamps rated at 12 volts then the 1K Resistor is not required.