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I am looking for a LED that I can use on my first underwater ROV so that I have enough light to record video under water. I am using a 12V battery so I am looking for a bright LED chip around 9-12V / around 400 lumens.

I am trying to figure out whether LEDs need a separate driver or whether they have a built in driver. I have a hard time figuring this out. What are the things to look for?

for example, I've read that there are different technologies like SMB, Cree, COB. Do any of these "by definition" include the LED driver?

Or is it regardless of the LED, and do I always need a separate driver for these small LED chips?

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    \$\begingroup\$ If it looks like they don't have a built-in driver, they don't have a built in driver. Which they won't unless it is an end-user product like an LED lamp. At least you have plenty of cooling in your application \$\endgroup\$
    – DKNguyen
    Commented Feb 21, 2021 at 18:57
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    \$\begingroup\$ You do not "need" a driver. A simple resistor will work. You need to ensure the current through the LED doesn't get so high the LED melts. A driver will let you set this to a specific value and will be more efficient. The resistor will drop some amount of power...maybe 20-30% of total LED power. The brightness of the LED will change with battery voltage. With a good driver the efficiency might become 90-95%. In an ROV application efficiency may be very important to you. \$\endgroup\$
    – Kyle B
    Commented Feb 21, 2021 at 19:08
  • \$\begingroup\$ Ah that's very helpful! \$\endgroup\$
    – bas
    Commented Feb 21, 2021 at 19:14
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    \$\begingroup\$ You may consider the Samsung SPHWHTL3D50CE4TMQF for the LED. It's 2 watts and 370 lumens. They're current $1.80 ea from au.element14.com/samsung/sphwhtl3d50ce4tmqf/… and out of stock(at $0.406 ea) at digikey: digikey.com/en/products/detail/samsung-semiconductor-inc/… \$\endgroup\$
    – enhzflep
    Commented Feb 21, 2021 at 19:27
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    \$\begingroup\$ I've never seen a DC-fed LED module of any sort that includes it's own driver. That's very common in AC, we call them "bulbs", but not DC. It's either going to be setup for a specific voltage using built-in resistors (ala LED strip, USB lamps) or be current-operated (SMD, COB, CREE) and need a driver or matched external resistor (if your voltage is stable). A cheap buck+boost DC-DC converter with CC can convert your battery voltage to a constant current for one of the latter categories of LEDs. \$\endgroup\$
    – dandavis
    Commented Feb 21, 2021 at 19:30

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As a shortcut solution, (from a personal experience), it is much better to buy a driver integrated in the LED with it, in my ROV I used a LED that's designed for Motorcycles, it'll probably take some time to find it on the internet or at some vehicle-parts shops but it's powerful and you can use as many as you want.

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