Very newbie LED light project

Ok, so the plan is to make a light strip for the underside of my bed. I have a loft bed, and my desk is under it, so this led strip will be used a actual lighting.

The whole programming part of this project is no problem for me, but i am hopelessly bad at electronics. I have searched a lot, but i have not been able to find good answers to thing i feel are very basic, so i am sorry if some of my questions are kind of stupid.

The strip will be approximately 7m. I think i would like to have a 5050 RGB strip with 60led/m. The plan is to be able to dimm the strip, change the color, and turn it off. I would prefer to be able to control this with some buttons connected to an Arduino Nano.

Controlling the colors i think i know how to do. I follow this guide: Ultimate Guide to Connecting LED Light Strips to Arduino

I would like to make different colors, but mostly i would like to make different levels of "warm" white light. Is this possible with RGB strips?

And now for my main problem. How do i power an 7m RGB strip? Is this no problem, or do i need to wire it differently or get a big power supply?

Also what would be the best way of dimming the lights?

Please make yours answers very pedagogical. As said before, you would be surprised of how incredibly bad i am at electronics.

Yes, you can make sort of “warm” whites, I’ve done it. No, you can not power 420 Neopixels from an Arduino. Almost every practical tutorial on the internet talks about power and power connections. Dimming is done by sending smaller control values to the LEDs.

aarg:
Yes, you can make sort of "warm" whites, I've done it. No, you can not power 420 Neopixels from an Arduino. Almost every practical tutorial on the internet talks about power and power connections. Dimming is done by sending smaller control values to the LEDs.

I don't know if i makes a difference, but i don't plan on using individually addressable LEDs. I also don't want to power it from the Arduino. I want to do the approach in the link, that uses transistors.

These things usually come with their own controller and if the LEDs are designed to be dimmable, the controller usually has that feature built in.

lapiki:
I don't know if i makes a difference, but i don't plan on using individually addressable LEDs. I also don't want to power it from the Arduino. I want to do the approach in the link, that uses transistors.

It will still use a similar amount of power. Except, those are usually 12V not 5V.

bluejets:
These things usually come with their own controller and if the LEDs are designed to be dimmable, the controller usually has that feature built in.

I know, but i would like to make my own system at a little project.

aarg:
It will still use a similar amount of power. Except, those are usually 12V not 5V.

Okay. But then how do i power 7m is led strip? It must be possible.

And now for my main problem. How do i power an 7m RGB strip? Is this no problem, or do i need to wire it differently or get a big power supply?

You need a big power supply at the same voltage as your strip needs.
Each LED on a 5V strip requires 0.06 Amps, so multiply this by the number of LEDs you have to get the maximum current, your power supply must be capable of more than this value.

For a 12V strip use a figure of 0.02 Amps.

Grumpy_Mike:
You need a big power supply at the same voltage as your strip needs.
Each LED on a 5V strip requires 0.06 Amps, so multiply this by the number of LEDs you have to get the maximum current, your power supply must be capable of more than this value.

For a 12V strip use a figure of 0.02 Amps.

Alright. I am looking at 60LED/m strips. Since i think this would look the best. So 7 * 60 is 420 LEDs. 0.02 * 420 = 8.4A. So i would need a 9A power supply?

I expect that i will never be using the LEDs a full power. If i go with a 5A power supply for example. Will the only negative effect of using a 5A power supply be the LEDs not being able to light up completely, or will i break the power supply/LEDs?

So i would need a 9A power supply?

Yes, although you would not be able to get one and you would have to go with a 10A supply.

Will the only negative effect of using a 5A power supply be the LEDs not being able to light up completely, or will i break the power supply/LEDs?

It depends on the way the power supply responds to over current. It could shut down the system, overheat the power supply and make the colours go off.

The good news is if you use the fast LED library you can set a current limit and if this is exceeded then the colours will be turned down. Mind you I don’t know if this is for 60mA per led or the 20mA calculation or if you can control this.

Grumpy_Mike:
It depends on the way the power supply responds to over current. It could shut down the system, overheat the power supply and make the colours go off.

Ahhh. Thanks for the great answer. I think i will go with a 10A then to be sure. I just have some last few questions.

I don't know if 9A at 12v is a lot. I will be using IRLZ44N mosfets, and regular resistors. Can they handle this?

Also what is a good calculator to find out how thick my wires for the 9A has to be?

Also also, i have heard that the brightness of the LEDs can diminish for longer strips. Is this a problem for 7m? If yes, how do i solve/minimize it?

I will be using IRLZ44N mosfets, and regular resistors. Can they handle this?

Well any one FET will only need to handle one third of this so you are looking at 3A per FET so that should be fine.

Also what is a good calculator to find out how thick my wires for the 9A has to be?

Any on line calculator should work,

i have heard that the brightness of the LEDs can diminish for longer strips. Is this a problem for 7m? If yes, how do i solve/minimize it?

Yes it is, the thin foil strips that drop a lot of voltage when the current is high.
You get round this by wiring thicker wire for power and ground every meter or so, including at the far end.

Grumpy_Mike:
Yes it is, the thin foil strips that drop a lot of voltage when the current is high.
You get round this by wiring thicker wire for power and ground every meter or so, including at the far end.

Ok last question. And this might be a really stupid one. If i have to wire wires to the far end of the strip. What do i connect the wires to? Positive to positive, and negative to negative, or do i switch it?

" or do i switch it?" - Only if you want to smoke test your Power Supply.

I ran 320 RGB LEDs for a Christmas display using this wire.

SteveMann:
I ran 320 RGB LEDs for a Christmas display using this wire.

Ahh thanks. That's about the size i was planning to use. Good to know.

Anyone know the answer to my last question?

lapiki:
Ok last question. And this might be a really stupid one. If i have to wire wires to the far end of the strip. What do i connect the wires to? Positive to positive, and negative to negative, or do i switch it?

Positive to positive and negative to negative. Always.