Question regarding wall wart power supplies

Mirage_Man

Flashlight Enthusiast
Joined
Apr 2, 2006
Messages
2,170
Location
Florida
If a power suplly states 12V and 1A. Does that mean it will put out up to 1A at 12V?

If I were to connnect 4 LEDs in series that have a fV of 3.4v each the total would be 13.6V. What would the above power supply deliver to the 4 LEDs?
 

Norm

Retired Administrator
Joined
Jun 13, 2006
Messages
9,512
Location
Australia
Just keep in mind that most of the wall wart type power supplies aren't regulated and the voltage will vary with different loads. Measure the open circuit voltage and I think you'll find it's much higher than 12 Volts, so it makes it a bit more difficult to do the maths I'd just wire it up and then measure Voltage and current and go from there. Add a little resistance if you want to lower the current through the LEDs. Just remember that they can be AC or DC output.
Norm
 

nein166

Flashlight Enthusiast
Joined
Feb 16, 2006
Messages
1,579
Location
New York
I have a 12v 1A from radioshak that runs at 15v unloaded. Definately don't run directdrive.
 

ken2400

Enlightened
Joined
Oct 30, 2006
Messages
227
I like using power supples I get from the 99 cent store. They are for cell phones and put out around 5 V. As for your idea I would do that and add something like a 10 ohm resister to be safe. Use a multi meter to mesure the current being used. Try to get around 80 ma since 20 x 4 is 80. If it is higher then use more resistance. If lower then lower the resistance. Most 5 mm LED should do fine with 20 ma BUT check the specs on yours.

Good luck and keep us posted on your results.

Mirage_Man said:
If a power suplly states 12V and 1A. Does that mean it will put out up to 1A at 12V?

If I were to connnect 4 LEDs in series that have a fV of 3.4v each the total would be 13.6V. What would the above power supply deliver to the 4 LEDs?
 

r3d33m3r

Newly Enlightened
Joined
Feb 20, 2007
Messages
40
Is it a regulated power supply or just a rectifier and a electrolyte condensator ? Regulated is a no problem but at a lower light output than rated, and the unregulated one might be even better in your case becouse the Vout changes depending on the load. It would be nice if you had a Volt/Ampere meter and connect tem for a sec or two and see what is the current draw. Anyway if it is a decent power suply, you are safe to try without frying the LED-s, but LED-s have to be the same.
Regards.
 

Mirage_Man

Flashlight Enthusiast
Joined
Apr 2, 2006
Messages
2,170
Location
Florida
ken2400 said:
I like using power supples I get from the 99 cent store. They are for cell phones and put out around 5 V. As for your idea I would do that and add something like a 10 ohm resister to be safe. Use a multi meter to mesure the current being used. Try to get around 80 ma since 20 x 4 is 80. If it is higher then use more resistance. If lower then lower the resistance. Most 5 mm LED should do fine with 20 ma BUT check the specs on yours.

Good luck and keep us posted on your results.

I'm not planning on using 5mm LEDS.

I plan on using Cree LEDs in a Quad arrangement in a Mag head for a lathe work light :grin2:. I have a single LuxIII in a modded grill light now running off an 18650. It just doesn't put out enough light nor does the battery last long enough.

I had thought I would like to be able to vary the brightness with a Pot too.

Are there any plans online anywhere for something like what I'm wanting to build?
 

cdosrun

Enlightened
Joined
Sep 22, 2006
Messages
369
Location
West Sussex - England
MM,

you could use a Shark boost converter to regulate the current to the Crees. As long as the output of the adapter is below the Vf of the LEDs in series (about 16v?), the converter will be in boost mode and the current regulated. You can attach a pot to the Shark converter to adjust the current. Whilst more expensive than direct drive, you have more control over the LEDs and they would probably last longer.

Link to Shark converter at the Shoppe - http://theledguy.chainreactionweb.com/product_info.php?products_id=721

Andrew
 

Mirage_Man

Flashlight Enthusiast
Joined
Apr 2, 2006
Messages
2,170
Location
Florida
Ctechlite said:
Sounds like you need a fatman convertor with a potentiometer. http://www.taskled.com/techfatman.html

You can probably use a wall wart that is 9v or so, just make sure it has enough current capacity. George also has "flexi" kits http://www.taskled.com/flexiled.html
That may interest you as a work light.

Good luck Mirage Man!

Yeah I had the Fatman in mind too. In fact I have a potentiometer I bought from George awhile back sitting in my parts box.

I already bought a few feet of black Loc-Line and fittings from http://www.modularhose.com/ . Like I said I plan to use a Mag head though.
 

Weylan

Enlightened
Joined
Mar 2, 2005
Messages
356
Location
Fremont, CA
I think a cool thing would be the combination of

MAG head
Modamag pts2 for Cree xre
Reflectors for cree.
maxflex
1amp by 9V DC power supply wall transformer should work.

If you drill out the PTS for the CREE xre to handle the 1/8 NTP threads this would work really well I bet since you then can flex it and point it where ever you want!

It should be able to provide just the right amount of light that you need at any time.

If you build it and can drill and tap the 1/8 NTP heatsink, This is about the only thing I can't do. I have been thinking of a light like this that can be put into a pedistal light, that can be either portable or plugged into the wall for use as a regular light.

So when are you going to build it?
 

Ctechlite

Enlightened
Joined
Dec 7, 2004
Messages
750
Location
Philadelphia, PA
So use the mag head, just make an adapter that screws into the mag head and has the appropriate threads for the loc line....
 

Mirage_Man

Flashlight Enthusiast
Joined
Apr 2, 2006
Messages
2,170
Location
Florida
Ctechlite said:
So use the mag head, just make an adapter that screws into the mag head and has the appropriate threads for the loc line....

Yep, that was the plan. But I may explore the idea of making my own head too. :grin2:
 

Ctechlite

Enlightened
Joined
Dec 7, 2004
Messages
750
Location
Philadelphia, PA
Another idea...go to a hi end jewelry store and check out their display lighting. It's most likely incandescents or fibre optics but it will give you an idea of what's possible for small area lighting with a very minimal physical presence ie small, bright, unobtrusive.
 
Top