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Simple LED circuit design help

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SupaTreadz

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I have a simple request, but I am not too electronically inclined... yet.

I want to make a circuit with two LEDs, when the switch is on, one LED lights up, when the switch is off, the other LED lights up (and the first one goes off)

The only thing I could think of was maybe using logic gates, like an inverter gate. From a cursory reading on wikipedia, that sounded promising. I am open to all suggestions though.

Thanks in advance for any help!
 
Can you use a three-terminal Com-NO-NC (Form C) switch?
 
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If it comes to that yes, I guess. But the switch I'm currently using is a key switch, and I'd like to keep the same switch. So I may have been misleading, what I want is one LED on when the switch is in position one, and the other LED on in position two. I just want the position two connection to not experience the voltage drop associated with having that LED in the circuit (I'm trying to avoid having to account for the voltage drop by altering the power source). I know it may be overly complicated, I guess I just want to know if the inverter logic gate thing is a viable option.
 
Here is a simple current-steering circuit. It works by steering the current through either D1 or D2. For simulation, I'm modelling your switch using a LTSpice voltage-controlled switch, even though yours is manually controlled. The switch is open when the control voltage V(on) is -1V and closed when V(on) = +1V. Note the currents though the two LEDs, I(D1) and I(D2); they are mutually exclusive. The diode D3 is there to add to the forward drop of D1, so when the switch is closed, all of the current is diverted though D2.

Note that the voltage V(c) (the voltage at node C) doesn't change much. This circuit may not work if you using S1 to switch some other load at the same time as lighting the LEDs...
 

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Re MikeO's circuit, the LED on the left is always lit. Adding a Si Diode (1N914 type) , cathode pointing toward switch, in the horizontal wire between the anode of the right LED and the switch fixes it. Allows the switch to control another load, too.
 

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