Hi Sandy,
If you're using 3 seperate lights (or LEDs) for red, yellow and green, and you intend manual operation, you'll need a 3 position switch. These are normally a rotary type of switch. You just need 3 position single pole. Common one wire of each light together and connect it to your power supply. The other wire from each light goes to each of the three poles and the common from the rotary switch goes to your other power supply terminal (via a resistor if using LEDs). You can also use one of those 3 button switches they use for 3 different fan speeds. When you press one the other one pops out. Wiring is similar.
HTH
Automatic operation - well thats a whole different ballgame.
Alan Jones in Sunny Queensland (Oz)
That all depends on if it's a 2-lead bicolor LED or a 3-lead one. The 3-lead type you actually can do it with a switch, however you need at least a single pole triple throw (SP3T) switch - they DO make such beasts, in slide switch format only. You can actually do it with a SPDT center-off and some extra resistors - in the center postion it would be yellow and one way would be red and the other green.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
With a single bi-color LED, you would need more than a switch. Model Railroader has a circuit in the April 2001 issue on how to do this. Need an IC, couple transistors and some resistors, couple diodes.
AC is needed to make a bi-color LED yellow. DC for green or red.
Some do this with a couple 555 IC's.
Three target signals, appropriate bulbs or LED with resistors and a switch.
You did not specify bulbs, LED's?
Commercial products are available to do this with a single bi-color LED and some bi-color LED's are more orange with AC. You need to fine tune the series resistors for the green side and red side.
I have a link to someone who sells the PC board with with parts, without parts, built or just a kit.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
I'm trying to make my own colour searchlight signals - just simple red/yellow/green. What sort of electrical switch can I use for these? The ordnary DPDT won't do it.
Thanks
Sandy