Powering 12v led

Hi...I'm Powering an arduino uno through usb from computer. It will be connected to addressable led string of 25 lights. Is an ULN2003A connected to Arduino pwm output pin and 12v power supply an acceptable way to power the lights? Do I need any other components?

No, with addressable leds, you just need to connect the power lines of the strip directly to your 12V power supply, and the data-in line of the strip to an Arduino pin using a resistor (e.g.330R). No pwm outputs or transistors/fets required, because these are provided by the chips in the strip. However a large cap (e.g. 1000uF) across the power lines is a good idea. You must also connect the grounds of the Arduino and the 12V supply.

Thanks! I'm a little unclear about when I would need a transistor or like. I thought (I'm brand new to this) that I needed something that would allow the 5v of arduino to "fire" the 12v leds... ?
So im clear, the cap would go across the + and - of the 12v power supply as close to the leds? And a 330 ohm resistor from the Arduino pin to data input of leds?
Thanks again for your input and help!

Or would I only need one if I was using single-colour led's that don't have a data-In wire?

The key thing is that your strip is addressable. Addressable strips have chips on the strip or built in to the leds themselves. These chips mean that you don't need transistors or pwm outputs from the Arduino. The 5V addressable strips usually have the chips built into the leds and you can individually control each led. On the 12V addressable strips you can usually see the chips on the strip and leds are controlled in groups of 3.

Ordinary single colour and non-adressable rgb strips don't have these chips built in, so then you need the transistors & pwm Arduino outputs.

If you post a link to the strip you have, or a close up picture of the end of the strip showing the connections and the first few leds, we can check what type you have. You say your strip is 12V but has 25 leds, which is not a multiple of 3, so I am concerned that you have not identified it correctly.

I'm awaiting delivery of the leds...this is the description:

WS2811Led Full Color character string matrix screen point source 12mm 5V/12V

Brand new, high quality
WS2811 IC Chip, Addressable Color, need for controller.
Identify IC every led light,
The note glue craft processing, IP68 waterproof
Lamp to Lamp Wire 7.5cm
Max current: 0.05A
Max power: 0.3w
Size: 12mm Round/Square
Working voltage: DC 5V/12V
Note: please note it's 50pcs pixel per string

Here’s a pic from eBay…I’m still awaiting delivery, so it’s the best pics I’ve got. I’m sure I opted for thev12v variety

Why not just post the link to the eBay page? Then we could see the description and the pics.
c949f0884655245b323d68aae57ab619e76408c5.jpg5d02ceed5028e1a27e729834e0a305a1c91dd456.jpg

bigsammy:
I’m sure I opted for thev12v variety

Well, you are a beginner and did not know that the 5V would have been better. Next time, ask here before you buy. The 12V will be OK, its just that they will waste more than half the power from your supply.

Would 5v be just as bright as the 12v ones? And would the Arduino deliver enough current to light them?

bigsammy:
Would 5v be just as bright as the 12v ones?

Yes. The amount of light is the same, but with the 12V type, the extra power is wasted as heat.

bigsammy:
And would the Arduino deliver enough current to light them?

No, you would still need an external power supply. But a 5V power supply would be more than twice as efficient as a 12V one for use with this type of led string.

12V strips don't simply just dump the 7V as heat compared to 5V strips -.-
But you already bought them so let's not bother correcting bad info given thus far.

Adafruit has some good guides for you to look through, remember that you're working with WS2811 leds.

INTP:
12V strips don't simply just dump the 7V as heat compared to 5V strips -.-
But you already bought them so let's not bother correcting bad info given thus far.

INTP, can you please explain to myself and bigsammy how the strips purchased avoid wasting the extra voltage as heat? Can you also be kind enough to list all the other bad advice I have given, as obviously I don't want to repeat any of it to others.

I am trying to boost the IR light in my vehicle so my dash cam will work better. I recently purchased:

Package Include: 10pcs 5W 940nm Infrared led
Emitted Color: Infrared IR Wave Length: 940nm
Viewing Angle: 120 degrees
DC Forward Voltage (VF): 1.5-1.7V DC Forward Current (IF): 1400mA

I would like to wire 2 of these together. I get the idea of how to calc for resistors. I.E. 12V-3.5V=8.5V resistor needed, but the 1400mA is throwing me. Not sure if I just need to connect the two lights together, put an 8.5V resistor between them and the power source and I will be good to go or not. Any help?

Thanks in advance!
Dax