I want to build a circuit that turns 3 LEDS (L1,L2,L3) on if the button isn't pressed and turns a different set of 3 LEDS (L4,L5,L6) on when the button is pressed. Only 1 of the sets of LEDS should be able to be lit up at a time though so pressing or releasing the button will turn off the currently lit up set. I built and assembled this schematic: enter image description here

When I don't press the button L1,L2,L3 light up properly. When I press the button L4,L5,L6 light up, but L1,L2,L3 don't turn off. How can I go about getting L1,L2,L3 to turn off when the button is pressed?


Simplest way is to use a 1PDT push button..

Otherwise you probably need another transistor \$Q2\$ that is normally biased on and is turned off when the original one \$Q1\$ turns on.


simulate this circuit – Schematic created using CircuitLab

You CAN tie \$Q1\$ to \$R2\$ via a diode \$D7\$, but then \$R2\$ needs to be 1/2W and \$Q1\$ needs to dump a lot more current than you need.


simulate this circuit

  • \$\begingroup\$ That Power waster version will have all LEDs turned on at the same time when the button is not pressed. \$\endgroup\$ – 12Lappie Apr 13 '17 at 19:22
  • \$\begingroup\$ @lappie oops..good point... That's what I get for rushing.. Fixed. \$\endgroup\$ – Trevor_G Apr 13 '17 at 19:24
  • \$\begingroup\$ Wow, big detailed schematics, good stuff...you can tell you've recently started working from home again, Trevor :-) :-) \$\endgroup\$ – TonyM Apr 13 '17 at 19:42
  • \$\begingroup\$ @TonyM.. OH YES... Working!... I knew I was supposed to be doing something else... LOL ;-) \$\endgroup\$ – Trevor_G Apr 13 '17 at 19:44
  • \$\begingroup\$ You're contributing good stuff to society's up and coming new generation, you can't get a more valuable use of time than this :-) (don't try telling the client that when they check in on things) \$\endgroup\$ – TonyM Apr 13 '17 at 20:02

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