WIRING TWO LEDS FOR INDICATION


Ed
 

Need some help here. I am trying to wire a pair of 2mm red/green, 3 lead, common cathode LEDs together to indicate turnout position.  To prepare the LED sets,  I have soldered the anode of two 1N4148 diodes to the common cathode and the cathode of each diode to the anodes on each side of the LED.  I then checked these assemblies out using the diode test function of my multimeter and the green lights when the polarity is one way and the red when the polarity is the other way.  I then take 2 of these LED sets and solder them together so that the polarity of one set is the opposite of the other.  In this way, I should get the green of one to light when the red of the other lights and vice versa.  The problem is that only the red lights up on each LED.  When I check each individual LED set, the green lights one way and the red the other just as intended but when assembled, only the red lights. What am I doing wrong here?

Ed Robinson


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