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I am super rusty with circuits and I am just trying to find the simplest implementation for what I am looking for...

I want to turn on an LED strip that requires 12v input, using a pin that pushes out 3.3v from an arduino board. Ive seen many circuit designs, but so many seem extremely overwhelming. I am hoping I can make this as simple as possible, with as few parts as possible. I have NPN and PNP transistors, relays, etc.

Shown below, is the ideal setup I would want, but the obvious issue is the transistor (ignore the given model, thats just an autofill from the site I used) will not handle the voltage. Any advice is super welcomed.

Quick sketch of design

J-Mac
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  • Can you give a link to the led strip? Most of the time those led strips have built in resistors/ current limiting chips. If that's the case, just replace the bjt with a mosfet and you're done. If you use a mosfet, I would still probably use a small (10-100ohm) resistor between the Arduino and gate as common practice. – bunker89320 Jul 07 '21 at 14:28

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All you need to add is a resistor between the Arduino and the transistor's base.

Select a transistor that can support at least 12 V from collector to emitter (this should be easy). This transistor must also have a maximum collector current greater than the current needed by your LEDs.

The value of the base resistor should limit the current into the base to a safe value. This will depend on the transistor you use and the LED current. But, something around 330 \$\Omega\$ will probably be suitable.

Elliot Alderson
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  • Thank you for the quick response - so I tried something like this (and just checked again) and it kind of works. The issue is that the voltage drop across the LED strip goes from 12v to about 10.7v, lighting up only half the LED strip. Is this because of the Transistor I chose to use? – J-Mac Jul 07 '21 at 12:53
  • @J-Mac Which transistor did you use? – HandyHowie Jul 07 '21 at 13:13
  • Ive tried both 2n2222 (NPN) and the one I mentioned is having the issue above is BC327 (PNP) – J-Mac Jul 07 '21 at 13:16
  • I apologize if I have to tag you guys to notify you, and also when I say 'half-lit', I mean 'dimly lit' @HandyHowie – J-Mac Jul 07 '21 at 13:45
  • How much current does your strip draw? How long is the strip? – Elliot Alderson Jul 07 '21 at 13:46
  • When you say the "voltage drop...goes from 12 V to about 10.7 V" clarify exactly how and where you are making this measurement. – Elliot Alderson Jul 07 '21 at 13:47
  • @ElliotAlderson Im not sure how much current it draws, but Im using the smallest possible length of strip 3 LEDs) to test with. I will also add, I purchased some MOSFETs as Im told they work differently but I dunno how, so I will give that a try when they arrive as well. Here is the LEDs Im using: https://smile.amazon.com/gp/product/B01HRMP46S/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1 – J-Mac Jul 08 '21 at 05:33
  • Solved: Used a MOSFET in a similar way to this guide https://www.makeuseof.com/tag/connect-led-light-strips-arduino/ – J-Mac Jul 08 '21 at 14:20