Thanks!
Just for my understanding, I'd love to learn as I am building this, how did you know to use a 86k Ohm resistor, because it's 86% of the current?
Directly from the Meanwell datasheet. There were other options, too, such as using a 0-10V control signal. You should definitely read it... (RTFM
)
I was using guides on the internet (using Ohm's law) and came to a 12.66 Ohm (or 13 Ohm) resistor rated at 30 watts. To find that I used 19 volts of unused voltage divided by 1.5 amps to get 12.66 (or 13 Ohms). And then multiplied 19volts by 1.5A to get a resistor rated for 28.5 (or 30) watts. Can you please help me understand why that isn't correct?
Because this is not a voltage source at all -- it's a proper LED driver, already internally doing what you are wanting to DIY here, but in a modern, efficient, and more stable manner. Basically, it will guarantee that it only gives out the current you tell it, never more. (It can give
less current if it runs out of voltage - that's why it's good to have some excess in the rating, as you do!)
If you had a voltage source and needed to use a power resistor to dissipate excess voltage, then those calculations would be correct. Now you don't need one - 30 watts ridiculous power wasting saved!
OTOH, you won't be learning much about electronics, since you are just using a commercial product that does everything you want internally, as is. You only need to
configure the current as instructed in the manual. (That 86k resistor.)
But building the LED chain will teach you about thermal design. Be sure to google about that. It's not trivial. These LEDs will require significant effort for cooling design at 1500 mA. Consider driving them at 1000 mA. Even then the cooling must be right.