Hi Arduino community! I am excited to be working on my second project and have a few questions about using an LED strips, which I could not find answers for via Google.
My project is essentially lighting up a retro "on air" box, like you might see at a radio or TV station. I want the Arduino to light up one strip of LEDs, and then turn them off and light up a second strip. It is essentially a "traffic light" project, except it only has two lamps.
I have two short strips of non-addressable 5050RGB LEDs to provide the light. However, all the guides and tutorials I can find are for 12V LED strips. The ones I have are 5V.
Can I connect this 5V strip directly to the Arduino Nano?
All the 12V tutorials say I should use MOSFET transistors - is this necessary for a 5V strip?
Each strip has 14 LEDs, and I would only need to power on strip at a time. And does it matter which of the D-pins I solder to (as I can change my code accordingly)?
If you have a 5V supply the Arduino and LED strip can share the same power supply. That's the most common way to do it.
Or, if you are powering via USB you can get about 1 Amp (1000mA) out from the 5V pin.
But if you have a 12V power supply, you can't power the LED strip through the Arduino's 5V voltage regulator. (You might "squeak by" with 14 LEDs lit-up with one color.)
RGB LED strips usually require about 20mA per-LED per-color. Usually we design for "worst-case" of 60mA per LED (all LEDs at full-brightness white).
And does it matter which of the D-pins I solder to (as I can change my code accordingly)?
Any I/O pin will work.
All the 12V tutorials say I should use MOSFET transistors - is this necessary for a 5V strip?
You don't need a MOSFET with addressable LED strips. With addressable strips, each LED already has it's own driver chip (built into the LEDs). With non-addressable strips you need a higher-amperage driver circuit to handle the total current of all of the LEDs together.
Thank you all for your responses. I have so much to learn!
UKHeliBob:
Have you measured how much current each LED strip takes and did you omit a current limiting resistor from your schematic ?
I have measured the current with all 14 LEDs lit in red and it drew 0.26A. Lit only in blue it drew 0.24A. These are the only two states I would use.
There is no current limiting resistor on my schematic as I didn't know I would need one.
DVDdoug:
You don't need a MOSFET with addressable LED strips... with non-addressable strips you need a higher-amperage driver circuit to handle the total current of all of the LEDs together.
So with a non-addressable LED strip, the MOSFET is an essential piece of the circuit in order to be able to control the strip at all? There's no way for the Arduino itself to turn the LED strip on and off if it's wired to one of the digital pins?
look at the traces on your nano, then look at a fuse. if you try to run power through an arduino, you have created an intelligent programmable fuse
an arduino is a microcontroller, not an expensive fuse
use the microcontroller to send signals to an external solid state relay, which is a glorified namr for a MOSFET. switch the relay with the controller and switch the current with the relay
Thank you for this succinct explanation! I understand it much better now.
With a non-addressable LED strip, you need to put current through it and perhaps even vary that current in order to fade the strip in and out. A logic-level MOSFET receives its instructions from the Arduino and does the heavy lifting with the current.
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I realised last night that I was over-complicating things for myself, because the LED strips came with their own in-line microcontroller. For the purpose of my project I could just solder two LED strips to one controller (only connecting one of the RGB pins on each, so current-wise it is no different to it powering one strip). The microcontroller is pre-progammed with an RGB colour cycle, so it does the job perfectly.
