Multiple LEDs with Multiple Switches and one power source

[Hinokagutsuchi]

I'm sorry if the title doesn't accurately describe my point, and I'm sorry, but I don't really know how to phrase it.

Here's the thing. I'm planning a mod, and it calls for a panel with lots of switches. I'm tossing the idea around now, and it'll work out aesthetically in the end. My problem is with the LEDs that the switches control.

To be honest, I'm inexperienced with electricity, so I'll just describe what I want:

I have roughly 24 or so LEDs that these switches will control. There will be four switches for four banks of 3 LEDs, which leaves 12 LEDs and 12 switches. How can I wire these up? I know that I can use a one 12v rail from my PSU for each LED, but that's horribly inefficient and the wrong way to go.

What I was thinking of is a sort of box where one or two lines from the PSU are plugged in, then the power is split off to each LED. Then all I have to do is wire in a switch for each line. There has to be enough power to support having all the LEDs on at once.

What I have now are 5mm 4K~5K ultra bright blue LEDs from modsthatglow.com and they use 2.8-3.5v per LED. At least, that's what the slip that came with them says.

Hm... here's an example to clarify: I want to flip a switch and have a single LED come on that lights up a 5.25" bay. Another switch gets flipped to light up one of the case feet. Flip another switch, and an LED comes on inside the case. They all operate independently, that is, I don't have to have the inside LED on to have the foot LED come on.

I know it sounds like a horribly unpleasant thing to the eyes, but in the end it'll work out and be sweet.... I hope.

I know I suck at describing this, so if I need to clarify it further, then please ask.

Thanks!

 

[Fenris_Ulf]

Very simple. What you're talking about is called a "bus". Depending on how you want to do this aesthetically, it might be very easy, but it will definitely help if you have some soldering skills. The +12v will go to one of the switch leads. The other switch lead will have a small resisitor (about 450 ohms for a single LED, about 150 ohms for three LEDs in series, you may have to adjust based on desired brightness) attached and then a wire from the resistor to the positive lead of the LED. The other lead of the LED will have a wire going to the ground (black wire) bus.

 

[Hinokagutsuchi]

I can see that working for one LED or a series of LEDs wired to a single switch, but will I have to have a +12v lead for every switch? Is there any way to split it or ration it out to the other LEDs. I know I'll need more than one +12v lead to run the LEDs, but 24 LEDs(thereabouts) won't run more than 30v, will it?

Would I be better off getting a single 120w PSU(whatever a 1U is) to run this LED sub-assembly?

To give a better idea, I plan to be using a PSU in the neighborhood of 550w to power a 2.1ghz AMD, 2gb of ram, 1 Radeon AIW(agp), 1 Radeon 7000(pci), a dvd-rom drive, two HDs, and.. well, I'm probably forgetting something. It's looking like I'll need a small PSU to power the lighting.

It only has to look pretty on the panel that has the switches. Everything else will be hidden, and I have tons of rooms to work with to cram all this stuff in.

 

[Frank4d]

I drew up wiring schematics for the LEDs that you have "3mm & 5mm Mega Bright Blue 8~10k mcd" for 1, 2, and 3 LEDs. You need to have series resistors as shown which will keep the current through the LEDs between 17-18mA (assuming LEDs are about 3.3 volts) so brightness will be about the same for all three configurations. Note for 2-3 LEDs use 12 volts source, for 1 LED use 5 volts source. Off the shelf 1/4 watt resistors will work for all.

You could also power the single LED configuration from 12 volts using a 470 or 510 ohm resistor.

 

[Hinokagutsuchi]

Sorry it's been a while since I've replied.

If the yellow line in the molex carries 12v and the red line carries 5v, then can I run 2 LEDs per molex connector? For instance, have one LED on the 12v line and one on the 5v line.

I drew up a couple of diagrams to illustrate my next question, and they are drawn with two LEDs per molex connector, but if I can only do 1 per molex, the question is still relevant:

This is the first diagram:

I'm assuming I'll have to wire the LEDs similar to that, with each molex connector being wired to one or two LEDs.

I want to know if I can do it something like this:

I connect the PSU's molex to a splitter, then to each of the molexes on the splitter I wire my LEDs.

I know that I can't run all of this off of my main PSU, so I want to get a small PSU, something like a shuttle or rackmount PSU. What size would be best to run the 24 LEDs and about four cathodes?

Thanks, and I appreciate the diagram, Frank4d

 

[Top Nurse]

I'm sorry if the title doesn't accurately describe my point, and I'm sorry, but I don't really know how to phrase it.

Here's the thing. I'm planning a mod, and it calls for a panel with lots of switches. I'm tossing the idea around now, and it'll work out aesthetically in the end. My problem is with the LEDs that the switches control.

To be honest, I'm inexperienced with electricity...

There is a commercial product available called a Multiswitch that would do what you want to do. It is made by Aqua Computer. It can control I think eight switches and eight LED's. It can be configured for either manual or software control through the Aquasuite software. Try this link for more info.

 

[Mohonri]

You can hook up a whole lot of LEDs to just one 12V line. Do what Fenris_Ulf said. You should end up with something like this (the thing on the far left is a molex connector):

  |---12v   \_  <-switch
  |   |     [_]
]-|   |-----||---^^^^---|>|---|
]     |                       |
]-|   |     \_                |
] |   |     [_]               |
  |   |-----||---^^^^---|>|---|
  |                           |
   --------------------------GND

You can hook up pretty much as many LEDs as you want in parallel this way, with the same 12V line and the same ground wire from the PSU. One wire will be enough for everything you're planning on doing.

As an aside, what you're worried about is actually the current capacity of the wires. (basically the number of electrons going through the wires, as opposed to voltage, which is the energy each electron has) If you wire each LED with its own switch and resistor, you add the current ratings of all of them together. Since the current capacity of a single 12V lead is somewhere in the several-to-dozens of amps range and your LEDs are in the 20-30 milli-Amp range, it'll take more LEDs than you have to hit the limit of the power leads.

 

[Hinokagutsuchi]

You can hook up a whole lot of LEDs to just one 12V line. Do what Fenris_Ulf said. You should end up with something like this (the thing on the far left is a molex connector):

  |---12v   \_  <-switch
  |   |     [_]
]-|   |-----||---^^^^---|>|---|
]     |                       |
]-|   |     \_                |
] |   |     [_]               |
  |   |-----||---^^^^---|>|---|
  |                           |
   --------------------------GND

You can hook up pretty much as many LEDs as you want in parallel this way, with the same 12V line and the same ground wire from the PSU. One wire will be enough for everything you're planning on doing.

As an aside, what you're worried about is actually the current capacity of the wires. (basically the number of electrons going through the wires, as opposed to voltage, which is the energy each electron has) If you wire each LED with its own switch and resistor, you add the current ratings of all of them together. Since the current capacity of a single 12V lead is somewhere in the several-to-dozens of amps range and your LEDs are in the 20-30 milli-Amp range, it'll take more LEDs than you have to hit the limit of the power leads.

Hm, ok. Let me make sure I understand what you're saying. I can wire this up in parallel with one 12V line with the 20 or so LED and switch combinations(like the diagram you made) and it'll work. From what I understand, then, the current causes the LEDs to light, and wiring them in parallel gives an even current to each LED, meaning that they'll all light up properly.

Did I get that right?

 

[Hito Bahadur]

Close enough. You will have some LEDs in parallel and some in series. The size of the resistor (in series) with the LEDs is what is limiting the current and therefore the brightness. One of the reasons you were quoted different size resistors (for different #s of LEDs in series) was in order to maintain similar brightness.

Bottom line, like said above, one molex is fine for your usage.

 

[Mohonri]

Hm, ok. Let me make sure I understand what you're saying. I can wire this up in parallel with one 12V line with the 20 or so LED and switch combinations(like the diagram you made) and it'll work. From what I understand, then, the current causes the LEDs to light, and wiring them in parallel gives an even current to each LED, meaning that they'll all light up properly.

Did I get that right?

You probably don't want to wire the LEDs themselves in parallel with each other, since variations in manufacturing could land you with one LED that lights up and another that doesn't. You will, however, wire switch/resistor/LED strings in parallel (kinda like Frank4d's schematic or my ascii schematic). You can put more than one LED in each string, but I wouldn't put more than 3. If you're using blue LEDs, which are typically rated at ~3V, you'll use a 150Ohm resistor in a string with three LEDs, a 300 Ohm resistor in a string with two LEDs, and a 450Ohm resistor if there's one LED in the string.

 

[Hinokagutsuchi]

Er, yeah. I gotcha now. Thanks!

I can't wait to start building this thing.