Lighting LEDs PLEASE HELP

[SofaKing01]

Hi Gang,

As many of you know I am part of a team that is building a 1:1 scale of the Millennium Falcon and I am very close to finishing the cockpit console.

Well... I'm at the point where I am ready to light the console with various colored and flashing LEDs. I have searched the internet for wiring diagrams and videos on how to connect "prewired / flashing" 12V LEDs not only to each other, but then have the ability to plug everything into a wall socket. And... I've had ZERO luck.

Can anybody help me figure out not only what I need, but create / show a diagram of how all this works? I know I'll need resistors and I do know how to solder. I've seen LED light strings and christmas light strings so I know it's possible.

Basically, I would like to have the ability to plug the console into the wall and flip some toggle switches and the LEDs come to life.

I understand this isn't a simple request, but any help would be greatly appreciated.

Thanks!

G

 

[Rebelscum]

Are you sure your LEDs don't already have a resistor?

 

[jackdoud]

Easy option for a wall plug would be to get a 12v "wall wart" from Radio Shack. That way you don't have to solder together a transformer yourself, you can just buy a socket that will fit the plug and build off of that.

 

[SofaKing01]

Are you sure your LEDs don't already have a resistor?

I know prewired with resistirs are available But i didn't order those. I'm still trying to figure out the equation for which resistor I would need for a 12v LED going to a 120v wall.

 

[SofaKing01]

Easy option for a wall plug would be to get a 12v "wall wart" from Radio Shack. That way you don't have to solder together a transformer yourself, you can just buy a socket that will fit the plug and build off of that.

A "Wall Wart". I've never even heard of that. I'll look that up!

Thanks!

 

[XRobots]

You need a mains transformer to bring the outlet power to a lower voltage DC - a plug in the wall / universal one will do (called a wall wart because they are cheap in Wallmart).

If the output voltage matches the LEDs then great, otherwise you need a resistor on each, or on a combination of each. However if your transformer is unregulated, the voltage will be higher until you put it on load, which means that you will likely destroy a small number of LEDs by connecting them directly even if the voltage ratings match.

I have a tutorial series just for you:

XRobots.co.uk - Electronics tutorials

Also you need to check that the total current draw from all your LEDs (if there are a lot) doesn't exceed the total current capability of the mains transformer

 

[DrewSmith007]

I thought they were called wall warts because they look like a wart on an otherwise smooth wall...

 

[Honus]

This is really easy to do. The thing to remember with LEDs is that they are more sensitive to current than voltage so you must use a resistor with each LED. Most small LEDs draw anywhere from 20mA to 40mA so a 5V cell phone wall charger will work if you want to power between 10 or 20 LEDs. Anything more than that I would use an old computer ATX power supply- that way you get a high power regulated 5V power line.

I can draw you a wiring diagram after I get home from work tonight if you like.

 

[SofaKing01]

This is really easy to do. The thing to remember with LEDs is that they are more sensitive to current than voltage so you must use a resistor with each LED. Most small LEDs draw anywhere from 20mA to 40mA so a 5V cell phone wall charger will work if you want to power between 10 or 20 LEDs. Anything more than that I would use an old computer ATX power supply- that way you get a high power regulated 5V power line.

I can draw you a wiring diagram after I get home from work tonight if you like.

Hi H,

That would be GREAT! Thank you so much. The console itself will probably have at least 100 LEDs - 27 rocker knobs, 35 flashing LEDs, 8-12 dome panel lights, 10 blue LEDs, view screen (LCD screen) etc... It's going to be quite a task.

I'm excited... I just dont know where to begin.

In my mind I see one master switch / button that turns everything on and then toggle switches that would activate all the LEDs. Make sense?

 

[Rebelscum]

The master switch I'd recommend is a simple power strip, into which you can plug multiple wall warts, larger transformers, or anything you might have that's high voltage into, and then switch that strip with a regular light switch. Bring power from your wall into the console and then into the switch, and then onto a regular power plug. Turning on the switch energizes the plug, which gives power to the strip.

 

[digital509]

... Anything more than that I would use an old computer ATX power supply- that way you get a high power regulated 5V power line.

This.

ATX power supplies are great for these type of projects. I use them for LED and servo projects when 12V and 5V are involved.

 

[Honus]

Hi H,

That would be GREAT! Thank you so much. The console itself will probably have at least 100 LEDs - 27 rocker knobs, 35 flashing LEDs, 8-12 dome panel lights, 10 blue LEDs, view screen (LCD screen) etc... It's going to be quite a task.

I'm excited... I just dont know where to begin.

In my mind I see one master switch / button that turns everything on and then toggle switches that would activate all the LEDs. Make sense?

So here you go- this basic diagram should give you an idea of how you would wire it up. The LEDs are wired in parallel so you can add as many LEDs as you want. It doesn't matter how many LEDs are turned on by each switch (as long as they are wired in parallel- each LED only sees 5V), as long as you don't exceed the current limit for the switch.

There is a LED resistor value calculator here-
http://led.linear1.org/led.wiz

Let me know if you have any more questions!

 

[SofaKing01]

Hi H,

Thanks so much for the diagram! My concern is this. The LEDs (flashing, pre-wired) are all 12v. Is the 100 Ohm resistor correct for this application?

Also, you have the LED switches for each LED. If I want to power, for example, 20 LEDs on a single switch I would remove 4 (going from lft to rt) of the switches and leave the remaining in place?

Now... say I wanted to dim some of the LEDs... LOL

This diagram is awesome! Thank you!

 

[DrewSmith007]

Hi H,

Thanks so much for the diagram! My concern is this. The LEDs (flashing, pre-wired) are all 12v. Is the 100 Ohm resistor correct for this application?

It's a little difficult to tell without info on the flashing LED's. You may not need a resistor at all if they have one built in to the flashing circut. Do you have a datasheet or link to where you got them?

Also, you have the LED switches for each LED. If I want to power, for example, 20 LEDs on a single switch I would remove 4 (going from lft to rt) of the switches and leave the remaining in place?

It might help you to think of the circuit as a system of water pipes. The switches are like valves, and the positive voltage source is like a water spigot. The negative voltage source is like a drain. Wires would be pipes. So, think about how you would have to set up a plumbing system to allow water (electric current) to flow where you want it by turning valves (switches) on and off.

Now... say I wanted to dim some of the LEDs... LOL

This diagram is awesome! Thank you!

If you want to dim an LED, just use a higher value resistor in place of the one recommended for full brightness. A potentiometer would allow you to adjust the brightness.

 

[DrewSmith007]

It gets a little more complicated, but you can wire more than one LED per switch and resistor set. It all depends on the characteristics of the LED's and the voltage used.

 

[Honus]

The ATX power supply puts out 12V so you're good to go if you need that. I would also get a ATX wiring connector like this one as it'll make things easier to hook up-
ATX Connector Breakout Board - SparkFun Electronics

The diagram is only meant to be a general guide to get you started. You can have each switch turn on as many LEDs as you want or have each switch turn on a flashing circuit- just make sure the switch can handle the current draw of however many LEDs will be connected to each switch.

The LED resistor values for individual LEDs are dependent on the specific LEDs you use but for most small LEDs I've found 100 Ohm 1/4 Watt resistors to be sufficient. Any flashing circuit would have current limiting resistors so it's generally not needed to add a resistor before the flashing circuit. Flashing circuits are pretty easy to make and there are tons of examples online. Dimming LEDs is a bit trickier but that can be done as well, with the best method is probably to use a $20 microcontroller. I can help with that as well.

 

[DrewSmith007]

The value of your resistor is dependent on the voltage you're using and the voltage drop or forward voltage of the LED.

In a 12 volt system, with a single 2.1fv LED, you'll have an effective voltage of 9.9v. That means using a 100ohm resistor will give you about 99mA of current, which is about 5 times more than the LED is probably rated for. At best you'll be limiting the life of the LED and wasting power, at worst it will simply.

 

[DrewSmith007]

Also, the resistor value is dependent on the number of LED's and what they're rated for.

 

[epilepticsquirl]

For about $5 you can wire up a PWM Dimmer using a 555 IC. No need for microcontrollers and extremely efficient; better than using just a pot. It's actually quite easy and fun to do! I'm using one for my Holograph build.

An LED Array PWM Dimmer with the 555 - YouTube
An LED Array PWM Dimmer with the 555

 

[Honus]

Also, the resistor value is dependent on the number of LED's and what they're rated for.

That's why I posted a link to the LED resistor calculator. Why would you supply an individual 2.1fV LED with 12V? An ATX power supply gives you 5V and 3.3V and using those with that LED you get resistor values of (ideally) 68 Ohms and 150 Ohms. High power LEDs (Luxeon, etc.) are a whole different issue...