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I have 15 IR LEDs that I would like to use as a floodlight for my exterior cameras. The thing is I have no idea how to calculate the total voltage and amperage needed. A single LED is rated for 1.7V-2.2V and 700ma.

What type of power supply do I need? Would it make a difference if I wire them in parallel or in series?

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  • \$\begingroup\$ Hi there! Since you're new to this, give the model and datasheet of your LED. Are they pre mounted on little star shaped aluminum boards and do they have/have you planned any enclosure for them? The current control drivers frog has recommended will keep them from burning out but to get the best performance and life out of them you may want some cooling. \$\endgroup\$
    – K H
    Jan 30, 2021 at 3:00
  • \$\begingroup\$ They definitely do not have their own cooling so that's something I'm gonna have to look into. What do you suggest I mount them on? I don't have the datasheet, just these details: Item No.: 3W-IR-850 Power: 3W Emitting Color: Infrared IR Wavelength: 850nm Forward Current: 700mA Voltage: 1.8-2.2V View Angle: 60°/120° \$\endgroup\$
    – Alex Lab
    Jan 30, 2021 at 19:20
  • \$\begingroup\$ Are they pre mounted on little star shaped(or other shape) aluminum boards? \$\endgroup\$
    – K H
    Jan 31, 2021 at 2:02
  • \$\begingroup\$ If they're not already on aluminum heat sink boards you'll need to mount them. For low power applications with decent air flow the star boards are enough, but for better efficiency at 3W you mount the star board on a small additional heat sink. For outdoor lights often an aluminum casing is used. If you build your own casing make sure you don't trap the heat sink in insulating materials or it can't do it's job, so in a wooden or plastic(3d printed) box for example you can build the heat sink into the back of the box so it's exposed to outside air. \$\endgroup\$
    – K H
    Jan 31, 2021 at 2:14
  • \$\begingroup\$ Price varies insanely wide for heat sinks, but if you look on aliexpress you can find 300mm bars for ~4 currency units that will do about 10 LEDs if you cut them into pieces. Be aware aliexpress can be a risky place to buy electronics parts, but there is little risk here as it's hard to counterfeit or screw up a block of aluminum. You could 3d model a simple casing on tinkercad(EZ PZ free program for beginners) and contact local maker shops(almost all cities have these now) to get them 3d printed. For a batch of 15 you'd save a lot of labour. \$\endgroup\$
    – K H
    Jan 31, 2021 at 2:23

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Definitely put them in series, this guarantees they'll all draw the same current. You'll need a power supply capable of 33V and 700mA. Power supplies designed specifically as LED drivers are constant current rather than constant voltage, although they still have a maximum voltage, often around 40V. You should be able to get an off-the-shelf driver from your favourite LED lighting supplier.

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