LED problems

[barend]

Trying to figure out a small problem with a LED light. I have power at the end of the wires, I have continuity across the LED poles, but I have no light??!!! Now I am no electrical wizard, but it seems that with those premises I should be illuminated. What's going on, do LED's not work the same way as a regular bulb?

 

Enlighten me please!!

[TDunc]

Read continuity twice, once with the red lead on one pole and then the second time with the red lead from the meter on the other pole. You should have continuity one way and nothing the other direction if the led is OK. ( this is a quick way to check any diode ).

 

Then you must make sure that the positive voltage is going to the positive pole of the diode for it to work. If this is done, and you don't have light... spend a few pennies and get a new LED.

[MiCarl]

Some meters will give funny results reading a diode unless the meter is set to the correct range.

 

If it's got one you should set the meter to the range that has a symbol like this:

http://t2.gstatic.com/images?q=tbn:ANd9GcTbeomuT59fVo0I6aLRbtlIl_8FpRef4Igcu8ZpeocWRJJrSpqb

 

Then do the test TD'sTD described.

 

Most leds are rated for under 3 volts. If you're not using one rated at 12V you'll cook it unless you have a properly sized resistor in series with it.

[Flyinfool]

LEDs are not like a regular bulb.

Unlike a regular bulb LEDs are polarity sensitive.

If you hook an LED up backwards nothing bad will happen, it just will not light.

Switch the wires around and see if that makes it light.

 

Also as TD'sTD said, make sure it is a 12V LED or it will only light for a VERY VERY short split second, once only.

[cimmer]

If you just replaced a regular bulb with a LED, you will need a resistor inline with the LED to create the current that is needed. LEDs operate on current more then voltage. You will need to determine the voltage you are presenting to the LED and then figure out the resistor that gives you the current that the LED needs to operate. You will need to know the current requirements for the LED to determine the correct resistor and the spec sheet for the LED will give you that value.

Here is a URL to a calculator for figuring out the resistor size that might help you out.

http://www.quickar.com/noqbestledcalc.htm

 

Good Luck..

Rick F.

[Flyinfool]

I think that what we need here is more info from Barend.

 

What kind of LED are you using and what are you trying to do with it?

 

There are a bunch of different answers that we can give depending on what you are doing.

[barend]

I'm trying to figure out why some LED walk path lights a have quit working. these things have a "ballast" (?) build into the wiring and the LED sits on a small disk with the connectors attached to it. As to what kind of LED, not sure what you mean and I don't want to be a smartass and say that it's a square one You simply slip the solid core wiring into them to hook them up. No way you can swap wires . the owner can't find the information on where he bought them so i can't call those guys.

 

So I am kind of lost on this one and figured to tap into the wealth of knowledge on here.

[Flyinfool]

Look at the "ballast" there should be info printed on it that lists both the input power and the output power.

Let us know what the output power is, We mainly need to know the voltage and whether it is AC or DC.

 

Did you check the LED with the continuity meter and then try reversing the leads and check it again?