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I need to design a circuit so that when a button is pressed, the red LED lights and starts an activate delay circuit so that when capacitor C2 (100uF) is charged it turns the red LED OFF and green LED on.

I tried this in a simulator and it's working fine, but i would like not to use two led diodes, just one bi-color red/green LED. What do I need to add to circuit to make it simple as is and to acheive above idea? (On toggles RED on, after capacitor in delay circuit is charged, turns off RED, and turn green ON.

Here is schematic:

enter image description here

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  • \$\begingroup\$ Are you talking about something like a common anode bicoloured LED? \$\endgroup\$ – DiBosco Feb 19 '18 at 11:47
  • \$\begingroup\$ It is not importanf if is common anode or common cathode or mix of them together...i need only to archive above idea so that only one led is lighting uppon pressing sw1 button. \$\endgroup\$ – Igor Petev Feb 19 '18 at 11:49
  • \$\begingroup\$ If red is off, should green be always on? \$\endgroup\$ – Andy aka Feb 19 '18 at 11:52
  • \$\begingroup\$ Yes...i im building softstart circuit using relays and i added led to make things simplier...idea is simple...when user push button RED led is on, after a few seconds RED led is off, GREEN is on. Simple and very useful..but need to be one led not two.. \$\endgroup\$ – Igor Petev Feb 19 '18 at 12:08
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If that circuit is working but you want to combine the LEDs then you need a common anode red/green LED. This will have three pins.

schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. Common anode RG LED with common resistor.

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  • \$\begingroup\$ Thanks..but using this RED will light and after some seconds GREEN will light too..i need only to light only one at same time..not two..above circuit i posted is working using two leds but two leds are on at same time...and i need to be on only one led at same time..i think i need one bi color led...two diodes in same package but anode conncted to cathode..but i don't know where i need to connect to circuit...scienceprog.com/bi-color-led-indication \$\endgroup\$ – Igor Petev Feb 19 '18 at 12:12
  • \$\begingroup\$ Your question says that the circuit is working fine. \$\endgroup\$ – Transistor Feb 19 '18 at 12:13
  • \$\begingroup\$ Circuit is working fine..but i don't want to use two led diodes...i would like to use only one bi-color diode...and on my schematic you see in simulation both diodes are on..and need to be only one led on. \$\endgroup\$ – Igor Petev Feb 19 '18 at 12:18
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    \$\begingroup\$ So the circuit is not working fine, then. Either it's working fine and there is just the matter of switching the two diodes with a common anode one, or the circuit is not working fine, and you need to change it to work as expected, i.e. only one LED lighting up at a time. \$\endgroup\$ – MrGerber Feb 19 '18 at 13:07
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I finally fixed it.

I just added PNP inverter transistor..so when SW1 button is pressed Q2 will connect drain-source to ground and Q4 inverter PNP will invert 0V to cca 12V and RED led will be on, after few seconds Q3 will be open and Q4 inverter will invert 12V from drain to 0V and switch RED led off, and GREEN led will be on. Used is common anode...i put two leds because i don't have in simulation program bi-color common anode..but it is the same package...

enter image description here

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