How do I build a master control?

I want to build a circuit that has several led groups. Each group has an on/off switch. I want there to be a master control switch that overrides the state of all other switches; i.e. when master control is on, circuit behaves normally, when off, all outputs are 0. How do I build this circuit? Are there any parts that can simplify the process? I thought of using a multiplexer but it only outputs one value and I'm not sure how multiple output multiplexers work. Thanks for the help!

sort by: active | newest | oldest
This is a case for diode isolation. Another "answer" asks a similar question, but in a slightly different situation, but is pertinent enough to visit.

The basic idea is that you take a wire from the output of each of the individual switches, put a diode in that new line, then a recalculated resistor (depending on the diode, you'll have from 0.3 to 0.7 volts less available to drive the LEDs), then tie all of them together to the output of the master switch. This way, you have isolation and current limiting for each branch. This is assuming you are running each group in parallel using 1 resistor for each group. If you are using 1 resistor per LED, then you need a resistor/diode combo for each LED. A schematic/drawing of your setup would help.

Let me know if you need a schematic/drawing or if the link in the other question is enough to get you there.

Qa
kaddyshack (author)  Quercus austrina5 years ago
My handwriting stinks but I'll upload it. I'm trying to make a light up sweatshirt. I want to be able to control which part of the shirt glows (inside of course) and have a master control for ease of access. I think I eventually want to incorporate this into a larger project involving a sweatshirt that can synchronize with touch, music, movement, sound, or a computerized light show in a room. That's way down the road. For now I'd just like an ominously glowing sweatshirt for parties.
simplified led hoody concept w master control.jpg
I have drawn a quick schematic for you. Note that there are no values because I don't have any info for your design. This is just a basic suggestion to get you started and can be expanded by adding extra zones and the corresponding isolation parts. There are many other questions and 'ibles here that you can look for in the search box to give you help on where to find LED/resistor calculators and design advice. Give it a try, look around and ask more questions if you have any.

Qa
kaddyshack (author)  Quercus austrina5 years ago
thank you so much. The project looks a lot simpler than I thought. I've needed this type of design for a couple of other projects. Again, I appreciate the help!
kaddyshack (author)  Quercus austrina5 years ago
I'm still a little confused. The diode is supposed to be allowing the current to flow from the switches depending on the state of the master control, correct?
You are quite welcome. I am glad to help.

Qa