Hello! A lamp fixture in my living room went bust recently and I cannot find replacements. So I have decided to convert it to LED. I plan on putting 12 1W leds into it. But constant current LED drivers ar a tad on the expensive side and I can't afford them right now. I know I can make some using the lm317 regulators but it would take up space inside the enclosure.
I have a 12V dc source. Can I run 4 of these 1W LEDs in series? What kind of lifetime can I expect from them? They feel warm to the touch after 10mins on 12.4V.
I know that this has been discussed here before but I still wanted to sure that this will work .
Regards

 

Guesseng Vf @ 2.8V, so 4 LEDs would cutting it a bit close, try 4 parallel strings of 3 LEDs in series with a 10Ω 1W resistor in each of the 4 strings. Around 50,000 hours.

 

Agreed, but use 2W or 5W resistors.

 

Vf is 2.8V? I thought it was around 3.2. I got the LEDs from a local store. No part number or anything. They came mounted on star shaped heatsinks.

 

If you have the LEDs, measure the Vf's, then match them so each string has about same total Vf. The LED's might be around 3.3 V @ 350 mA.

 

A simple jig will make measuring easier, Red is LED under test, blue , a white in series with one or 2 diodes like 1N4002. Resistor 25Ω, 5W.

 

Presumably the blue is just an indicator, probably best to give it its own series resistor, because if the DUT is removed with only a 25 ohm resistor it will let the magic smoke out.

 

If it smokes it wasn't a 1W white LED. Yhe white 1W LED in series with a diode is for reverse LED connection protection; reversed , pilot LED glows, LED under test - off, correct polarity - pilot off & DUT on & can then be measured. Connecting pilot LED in reverse on initial powerup = poof.