Please see this following link.

enter image description here

That's exactly I want to make but with little change, In place of a single LED I want to place 2 LEDs (not combined). I mean let's say we have 2 LEDs - one red, one green

When I press switch once, red LED should glow and green LED should be off again.

When I press switch again, green LED should glow and red LED should be off.

I'm new to electronics so please don't suggest me any complex circuit designs, just keep it simple ;] friends

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  • \$\begingroup\$ In essence you are looking for an "inverter". When the 555 is high you want one high output and one low output. Thinking about the easiest way to do this. Er. You could use another 555 as an inverter! \$\endgroup\$ – carveone Aug 2 '13 at 15:38

The 555 can either source or sink quite a considerable amount of current (like 200mA). Thus the transistor shown in the circuit isn't necessary (IMHO) for something like an LED. You can connect one LED from + to the output and another from output to GND. Like this:

enter image description here

Note - I've a feeling that the 555 doesn't have a high value that's equal to Vcc but slightly less than it. Which means that when LED2 is on, LED1 might be a little on too (anyone?)

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  • \$\begingroup\$ As long as the high value is less than ~2V below VCC, LED1 should go off (voltage difference not high enough to forward bias diode) \$\endgroup\$ – pjc50 Aug 2 '13 at 15:55
  • \$\begingroup\$ Yes, of course! I was thinking 0.7V drop for some reason. It's an LED not a diode :-) The 555 is 1.7V below Vcc according to Wikipedia... \$\endgroup\$ – carveone Aug 2 '13 at 16:01
  • \$\begingroup\$ Hmm, that will probably still turn it on then. How about putting the transistor back and using it as an inverter? \$\endgroup\$ – pjc50 Aug 2 '13 at 16:18
  • \$\begingroup\$ Use a complementary pair of transistors. \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 2 '13 at 16:38

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