Driving XR-E from a AC power adapter

[mds82]

I have a few Nokia Phone chargers laying around the house, and they are all rated at 3.7 Volt, 300ma. I did a quick test the other night with this AC adapter and it did work fine. My question however, is it safe to use this as a driver with no other devices to control the current to the LED?

 

[65535]

Should work great actually.

 

[nutz_about_lights]

I have a few Nokia Phone chargers laying around the house, and they are all rated at 3.7 Volt, 300ma. I did a quick test the other night with this AC adapter and it did work fine. My question however, is it safe to use this as a driver with no other devices to control the current to the LED?

My sentiments too. I have a few adaptors that put out 12V and 300ma. Can I snip off the tip and connect bare wires to LEDs?

 

[W-c.Scenario]

I suggest u check it with a multimeter before you cut the wires, I use some of mine to drive leds, but some adapters I've checked is not providing what its dataspecs says.

 

[nein166]

If you trust the wall plug-in to function without spiking, it will work.
I have a Nokia 3.7v wall wart that puts out 9v, the battery wasn't happy after that happened I doubt an LED will be.
Theres always a risk with DD.

 

[LukeA]

One of these will work better.

 

[SafetyBob]

I also endorse the use of the MicroDriver for use in LED projects. Have one running beautifully on my undercounter lighting project. The wall wort will work, but if you want your project to be 99% reliable, I recommend using the MicroDriver for supperb regulation that you won't have to be wondering about.

If it's just a project to use for awhile or expermentation, then go for it. Save your money and use those old chargers! Been there doing that.

Bob E.

 

[matrixshaman]

Phone chargers are made for 3.6/3.7 volt batteries. That is standard Li-Ion battery voltage when under load. Most Li-Ions are charged to around 4.2 volts. That means the charger often puts out more than 4.2 volts and sometimes by quite a lot. Usually the phones have a circuit inside to cutoff the charging when it reaches around 4.2 or so. So while the charger is made for 3.6 volt batteries and it might sound just right for Vf of an LED it will in many cases overdrive it meaning short life or Phone chargers are actually a good start for an LED power supply but you want a voltage limiting circuit on most since most chargers are only current limiting and not voltage limiting. Basic charger construction only requires the voltage to be at or higher than the voltage that a battery will be charged up to.

 

[Mash]

I have used lots of Nokia (and other cellphone) chargers rated eg at 5.7V 800mA for direct driving single crees, after some knowledgable members here mentioned that they are current controlled PSUs. They mentioned that the newish lightweight ones (as opposed to the heavy old old stuff with coils etc inside) are the CC ones. If I didnt know this fact, I wouldnt use them since to my eyes, 5.7V would blow a cree, however as per their advice, they work great, and top out at 800mA and whatever voltage the cree needs at that current, I can also parrelel two crees for 400mA each.
However I want to know how can I tell (without relying on an empirical weighting!, and blowing LEDs) if a psu is really current controlled? Any tricks with a multimeter, resistor etc?

 

[kurri]

with a small resistor and multimeter you can measure the current that it puts out.. but resistor needs to be small enough not to limit current itself. (you could short circuit it too, but it or meter might go )

and that one in pic seems to have tri-wing screws.. it can be opened and examined