Master switch to turn on and off independent lights

Question

i am adding some led lighting to a dolls house where each room can be turned on and off independently but i would like a master switch which turns all lights off(simple) but should turn on all lights even if they were off before. I just can't figure how to get this to work.

Example

• With 2 LEDs in the system.
• When the master switch is turned on all LEDs turn on.
• Led1 is switched off, led2 is kept on. -When the master switch is turned off all LEDs turn off.
• And then when the master switch is turned on all LEDs are turned on.

Answer 1

You will not be able to do the last step without resetting relays (costly, not easy to find), complex logic circuit (hardware intensive) or a microcontroller. A microcontroller solution with push buttons will be super easy. On/off switches will require slightly more code but pretty easy too.

The microcontroller solution can be cheap, and consist of nothing more than the switches and some resistor + Transistor pairs (and your leds of course). Depending on how many lights you could skip the transistors too. The internal Pull-Ups are enough for the inputs, but external ones can be used too.

^{simulate this circuit – Schematic created using CircuitLab}

Code would be simple:

Boot/Power On{
  turn all lights on, set inputs;
  Wait for button press{
    At button press toggle light;
    At master button turn all lights off;
    At second master button, go to boot.
  }
}

Or skip the master button and use a hard power switch turning the microcontroller off. When turned on it starts at boot. Cuts down on some of the coding.

^{simulate this circuit}

Answer 2

Your description is kind of vague, but I understand it to mean that you want a 3-position master switch: "All Off", "All On" and the third state in which all of the LEDs are controlled individually. You'll need some diodes:

^{simulate this circuit – Schematic created using CircuitLab}

Answer 3

Despite I'm using buttons rather than switches, you can achieve this using a 4013 dual D flip-flop with set and reset, where you have a flip-flop per LED configured as a T flip-flop to toggle the LED's state with a single button. But the main point we're using this is for the SET and RESET functions which can turn all LEDs on and off.

Note that I put debouncing circuitry to prevent accidental extra triggering of the clock. The SET and RESET do not need this.

Answer 4

If you're comfortable with each of your individual light switches being SPDT, and you're comfortable having separate master switches (or one center-off DPDT master switch), you can do this without any additional components.

^{simulate this circuit – Schematic created using CircuitLab}

In Figure 1, when the master-on switch is open, then each of the individual switches has one pole on and one pole off. When the master-on switch is closed, then each of the individual switches has both poles "on", effectively overriding the individual switches. Of course, the separate off switch prevents any current flowing, so it overrides everything (including the master-on switch).

Figure 2 uses a single center-off DPDT switch as the master. This works mostly the same way, where having the switch in the "up" position powers both terminals of each switch, "center" isolates ground and prevents all current from flowing, and "down" connects ground and exactly one pole of each individual switch (allowing for normal operation).