# Not gate with 3 LEDS attached after NPN transistor

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:

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

• That Power waster version will have all LEDs turned on at the same time when the button is not pressed. – 12Lappie Apr 13 '17 at 19:22
• @lappie oops..good point... That's what I get for rushing.. Fixed. – Trevor_G Apr 13 '17 at 19:24
• Wow, big detailed schematics, good stuff...you can tell you've recently started working from home again, Trevor :-) :-) – TonyM Apr 13 '17 at 19:42
• @TonyM.. OH YES... Working!... I knew I was supposed to be doing something else... LOL ;-) – Trevor_G Apr 13 '17 at 19:44
• 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) – TonyM Apr 13 '17 at 20:02