Running an LED off a 120v wall outlet

[CocaCola]

What kind of wall wart would i need? like how many volts would it need to cut the power down to?

For the most efficiency choose your LEDs first, then pick a suitable wall wart... You can get them for a buck or two on Ebay or you likely have one laying around from something else that could be made to work...

 

[raultiger]

Im not really sure whether i need a high power led or not.... roughly how many lumens does one produce? and what about just normal leds

 

[BobK]

Doesn't everyone have an entire bin full of old wall warts? It's one of the few things I guard againt my anti-pack-rat wife!

Bob

 

[raultiger]

Coca Cola,
thanks ill do that. Now comes the question of what kind of LED....

 

[BobK]

What was the original light, that would give us some idea of what you would need to replace it?

A typical indicator LED running at 20ma puts out less than a lumen. I have some white high brightness LEDS that put out 8 lumens at 30ma. I use one for a book (actually kindle) light, and it is about minimal. Would the old light put out enough to use as a booklight? Much more?

Bob

 

[CocaCola]

roughly how many lumens does one produce?

Talk about a loaded question, I would defer you to a Google search for that... And afterward you still likely will not have a solid answer

As for what kind of LED, it will likley be a little trial and error... If it was me I would hit up Ebay and pick up a few different highly rated 'white' mcd 5mm LEDs and start playing around and see what I liked... You can vary the overall brightness with the series resistor... Also you might find that a certain color 'white' is more appealing then another... Most 'white' LEDs are really WHITE and have a slight blueish cast to them, but there are what they call 'warm white' LEDs that have a softer yellow/orange cast to them that you are likely more accustomed to with most incandescent bulbs...

The good thing is you can pick up several different LEDs for only a few bucks on Ebay and test away... Or you can hit up a domestic supply house but you will pay exponentially more usually...

 

[raultiger]

bob thanks for the ballpark on the lumens. Its been a while since ive had the old light working... but if i remember, i was more than a book light. I just found an a random LED booklight sitting in one of my drawers. It doesnt seem very bright, but I just held it in place at the bottom of the microscope and it was actually visible. This led in the booklight is running on 6v. Something 2 or 3 times as bright would be good.

 

[raultiger]

ok im going to look around on ebay for some leds. I think the almost blueish white would be the best (maybe will make things look clearer and sharper). I would need a different resistor for each LED right?

 

[KJ6EAD]

The original system doesn't seem very good... it uses some special kind of light bulb and it only has a mount for that specific kind.

Does this "special" bulb have a number on it like 222?

 

[raultiger]

Sorry i don't have the bulb anymore. I wish i could look at it

 

[CocaCola]

ok im going to look around on ebay for some leds. I think the almost blueish white would be the best (maybe will make things look clearer and sharper). I would need a different resistor for each LED right?

For testing most white LEDs will be similar enough that you can just use a 'safe' value resistor for all them... The blueish 'bright white' LEDs would be my first choice but due to their color certain things might fluoresce...

And do note that you can't really just compare an LED based on another... When looking at white LEDs you will soon find that some are rated in the low 1000s of mcd while others are in the 10s or even 100s of thousands of mcd there is a huge difference from one end to the other... Also pay close attention to the angle of the LED vs the mcd rating, just because an LED has a larger mcd rating doesn't necessarily mean it's brighter the viewing angle comes into play... Again I differ you to Google to study this relationship between viewing angle and mcd further...

 

[raultiger]

ok so now i just found a pen-light things sitting around somewhere in my house. It is running on a single 1.5v AAA battery. It is incredibly bright and i can still clearly see a large bright spot on the wall from 15 or 20 feet away.... maybe it uses a lens? i dont see how it could be this bright.

 

[raultiger]

Ok im going to do some google researching...

 

[KJ6EAD]

I have I fairly high quality microscope...

Does it have a brand name and model #?

 

[raultiger]

It is a National Microscope Exchange Discovery series 9000 Model 9020CM

 

[BobK]

Just looking at some micrscopes for sale. The better ones seem to have something like a 20W halgen bulb. Looking these up I got 350 lumens. You are going to need about a 3W to 5W LED. These take 1A or more of current at about 3.6V. And they need heat sinking.

Bob

 

[CocaCola]

Just looking at some micrscopes for sale. The better ones seem to have something like a 20W halgen bulb. Looking these up I got 350 lumens. You are going to need about a 3W to 5W LED. These take 1A or more of current at about 3.6V. And they need heat sinking.

On that note I offer that the directional focused light out of an LED comes into play when you are only lighting a small confined space or area... It's truly a different type of illumination and there really isn't a direct comparison, just like comparing a 100watt spot light to a 100watt flood light... I'm willing to bet a 5mm white super bright directly under the slide aimed into the lens would almost certainly render the microscope useless as you won't be able to look at it... But positioned/diffused or reflected correctly it might be more then enough... Same with even a key chain white LED, they are painful to look at directly even from several feet away, while I can stare at a 25 watt incandescent from a few feet away without any discomfort...

 

[BobK]

The LED ones I found were also in the hundreds of lumens. The professional grade lights have columnators.

What you are seeing in the microsope is a microsopic part of the beam coming out of the light, blown up to look like it is several inches across. It is not equivalent to looking at the LED.

Bob

 

[raultiger]

What about something like this?

http://www.ebay.com/itm/10pcs-3W-wa...=251081769565&ps=63&clkid=9089210449149550155

 

[BobK]

That looks good, but you might want to try something less powerful to start with in case Coca Cola is right an I am wrong. I would hate to think that my advice burned a hole in your eyes!

Bob