so I'm trying to make a large-format, lightweight light-table, and my plan is to poke around 300 little white LEDs through a sheet of coroplast, then build a lightweight frame around it with a semi-opaque acrylic sheet over the top for the work-surface.

My question is, what kind of adapter/regulator/whatevs do I need to be able to plug my 300ish LEDs into (US) household current?

I'm aiming to have this stupidly simple when it's finished so that I can just drop it on a table or floor anywhere and plug it into the wall without any fussing.

 

Can I point out No. 6 on the following Terms of Service. Restricted topics include: LEDs to Mains.

 

Hello,

To stay within the ToS, you will need an isolating power supply.
A power supply upto 30 Volts may work.
You can calculate the needed resistor as followed:
Series_Resistor = (V_power_supply - ( Number_of_leds * voltage_drop_of_leds )) / Wanted_current_through_the_leds
There should be at least 2 volts accross the Series_Resistor for good regulation.

Bertus

 

There is nothing "stupidly simple" about 300 LED's.. stupid maybe
There are just so many better ways to produce an LED light fixture without using small gumdrop LED's.

Of course a 48VDC power supply and tons of parallel strings (like 20 strings of 15 LED's each) each with their own current limiting resistor is fairly simple...after hours and hours of soldering.
Or just buy a few off the shelf LED Edison base type bulbs and appropriate Edison base socket for each all simply wired to AC.

 

To stay within the ToS, you will need an isolating power supply.

I'm not trying to raise a stink, but does this mean that even a string of Christmas lights can not be offered as a solution? It'd be easy to get a half dozen strings of 50 LEDs and just plug them in. Maybe not an elegant solution, but cheap and easy and - IMHO - not as unsafe as some things we read here.

 

I'm not trying to raise a stink, but does this mean that even a string of Christmas lights can not be offered as a solution? It'd be easy to get a half dozen strings of 50 LEDs and just plug them in. Maybe not an elegant solution, but cheap and easy and - IMHO - not as unsafe as some things we read here.

We do not allow in case LEDs connected directly to mains on this forum. Using transformer or an approved wall wart is OK then. It is a major difference between the latter and directly mains connection do you not agree?

 

I'm a little confused by the rule then, "mains" in this context means household current or plug-in power as opposed to batteries? So then, are we not allowed to talk about any kind of LED fixture that runs off of AC?

I wasn't talking about just hooking the LEDs up directly to land-power, I was asking what kind of regulator I would need between the LEDs and the plug to hook it up safely, that's why I was posing the question, I know well enough how to stick two wires together, but I also know well enough that that would be really stupid; what I need to know is how to regulate the right amount of power to the LEDs without frying them or myself.

 

... do you not agree?

I do, and I'm absolutely not trying to argue against the TOS here. But I have trouble drawing arbitrary lines. And putting a bunch of christmas light strings in a box sounds a lot safer to me than "forcing" a newbie to wire up some controller.

There's no need to hijack this thread for my diversion. I was just thinking out loud.

Sand3, you should search for "LED power supply". You'll find all sorts of stuff. In general, higher voltage (such as the 48V mentioned above) simplifies construction because you can put more LEDs in series, and have less strings in parallel.

 

..., are we not allowed to talk about any kind of LED fixture that runs off of AC?

It's not the source of power that is the issue, AC is just fine, it's the presence or lack of isolation from the source that is important. The power at the wall is almost "unlimited" relative to what a project typically needs, and bad things can happen without isolation, a way to limit the power at the project. A car battery can deliver a whopping amount of power also, but the safety hazard is dramatically reduced at 12v.

 

it's the presence or lack of isolation from the source that is important.

So then my question is okay because I was asking specifically about a way to regulate the power, right?

 

Okay, cool, I think I'm going to go with flex-strip, and I've found some useful video tutorials.

 

Sand3: Here's the rub: my hands down most effieient inexpensive way to run a bunch of LEDs would be direct to line, but unfortunately, we can't talk about that here due t the TOS.

Someone might put their eye out and we can't have that.

 

So then my question is okay because I was asking specifically about a way to regulate the power, right?

Your question is OK because you are asking how to make the circuit (comparatively) safe from death quality errors that a beginner might make.

 

LED strip sounds good to me. You can buy it on eBay for very cheap prices including 12V wall warts and even wireless IR controllers to go with them all in one package. Not fiddling about with mains and no chance of electrocution. Just make sure you get the waterproof ones if you're planning on using them outside.