How do i light up these led

[janey]

Hey everyone..
I looked every where online and saw a few vids but i don't still get it. I have these Bulb led i bought online and i want to light up about 10 of them for this project i'm doing. It say to use a 12V DC . I found a 12vdc 300ma and i cut the ends and tied up about 4 of them black to black and Red tot Red and wired it to the plug and no lights ??
What am i doing wrong ???
Thanks Janet

 

[Mark Bianco]

Have you tested the output of the power supply you are using? Did you hook them up to the correct positive to positive and negative to negative polarity? If not hooking them up incorrectly you may just have toasted the lights. The last what is the ma rating for each light. 4 may exceed the output of the power supply doubt it but you never know.

Mark

 

[RAG_83]

You need to see what the amperage is on each led and get a power supply that can handle the amperage the 12 volt power supply you have is only .3 amps

 

[janey]

The lights work I tested each with 4 AA battery.
How do i test to see how much amp on each led . I do have a Multimeter.
Not sure how to test the amp with multimeter though..
Janet

 

[Ronic]

If I read that right you probably don't have enough amperage to run them that way. You will need to run them in series. red-led-black-red-led-black-red-led-black-red-led-black. Also if that is the wrong type of power supply (constant current or constant voltage) things can get toasted. Im no expert on led drivers and only have a small grasp on them so I could be totaly wrong.

 

[janey]

Or can someone tell me what kind of 12v adpater do i need then ????

 

[trzabka]

go red to black red to black and make sure you connect the positive the red and the negative to the black should work

 

[Mike31154]

Or can someone tell me what kind of 12v adpater do i need then ????

Can only guess without knowing what power each LED requires. They don't look very powerful, but evidently 'about 4' of them hooked up to a 300mA supply are too much. Test them one at a time with the 300mA supply you have to make sure they still work, then try hooking up 2 and if those light up, try 3. To run them all you may need a power supply of at least 1000mA & probably larger than that. 300mA x 12volts means your power supply is only capable of providing about 3 watts safely.

 

[janey]

Thanks everyone.. OK. gonna purchase the 12v 1000ma

 

[hllywd]

Really I doubt you need a 1A power supply for those LEDs. If they're .5W LEDs they draw about 40mA or.04A. Try a single with the supply you have. Of the wires coming from the supply, one will usually have a stripe, or raised ridges along it's length. That wire *should* go to the black wire on the LED. You can easily test the polarity of the supply if you have a volt meter, just hook it up to the leads. You may be surprised by the voltage you see, it's likely to be high in my experience, but if you have it connected + to + and - to - you'll get a positive reading. If its connected + to - and - to + you'll see a negative reading. If you don't get a reading the receptacle doesn't work, or the power supply is bad. You normally can hook an LED up backwards with no harm, it's a diode and only allows current to flow one way.

 

[janey]

ok, hllywd .
will do . I'll be back ....

 

[frogspawn74]

go red to black red to black and make sure you connect the positive the red and the negative to the black should work

+1. You need to chain them

 

[janey]

Ok i was able to hook up 5 led red to red and black tot black. tested with a 9v vattery and they all turn on.
But when i hook up to that power supply pictured above nothing.
and i chain them to black to red and still no light.

 

[janey]

This is the multimeter i have . How do i test the led with it ? and how do i test the power supply if it working ???

 

[Mike31154]

No need to test the LEDs with the meter if they work with the 9 volt battery. For the power supply, your photo shows the multimeter with the dial set to check Volts DC. Simply touch the meter leads to the power supply leads & you should see somewhere between 12 & 14 volts. Polarity shouldn't matter, the meter will show the voltage as either negative - or positive + depending on which meter lead is on which power supply wire. This will also confirm which power supply lead is positive/negative. If you see a positive voltage on the meter, the red meter lead will be on the positive power supply lead. If it's negative, the black meter lead is on the positive power supply lead.