I am planning to build a high luminosity lamp to act as a growth lamp during winter for my plants.
For this, I manage to recycle (upcycle?) a big LED bulb with the following inscription:
LED Corn Light E40 Volt: AC 35-265V CC1: 6000K Power: 54W
The bulb was not matching my needs as is (especially since it was providing an almost 360 degree light, while I need a directional light source), so I took it apart.
I saved 8 nice aluminium strips with 19 SMD LEDs each. I plan to power these from an ATX power supply, so I have a 12V 15A (probably I should say something like 10-12A to be safe) source.
The problem is that I can't identify these LEDs (I couldn't find a datasheet), so I'm not sure how much power they need. Based on similar LEDs I've seen around, I think 3V and 250 mA per LED would be a good guesstimate. Which means I should form groups of 4 LEDs in series and add a 3/0.25 = 12 ohm resistor per pair, everything nicely stuck to a solid piece of aluminum for cooling.
Are my calculations correct?
Side question: I was measuring the LEDs with a diode meter and it seems they very dimly light up. Also, when touching them in certain conditions, they produce a very dim light (the LEDs being disconnected from any circuitry). Is there any explanation for this?