Hello everybody,
I'm failry new in electronics. I wanted to install RGB LED strips for secondary lighting in my room, but with the ability to control each color seperately and manually with a slider potentiometer (for each). I have gotten a pca9685, N-channel logic-level mosfet transistors (IRLB8743) and a step down converter to 5v to power my circuit. I'm thinking of doing it on two perfboards, one for the control board ( potentiometers and buttons) and one for the rest of the circuit ( arduino nano, transistors). I will 3d print 2 boxes to put them in, one will be visible and one hidden away. I will get a 14.4 Watt/m 24v ip65 rgb led strip (7,15m). I would really appreciate advice on how to do the connections on the perfboard, what extra components, actions, or general precaution measures might be useful that I haven't thought of and advice on the coding. It is my first time working on an actual application that will have a real life use, so any warning or advice you want to give is very welcome. Thank you for your time!
14.4 Watt/m * 7.15 m ~ 103W ~ 20A
Here is, what 2A did to my breadboard in few moments:
So power need to be done way better way (solder, use good dimensioned switch etc.)
Also divide power into LEDs and into Arduino and put therebig capacitor for Arduino, otherwise larger change on LED (especially turn on from black) may restart the Arduino, or do other confusion to it.
For normal Neopixels LEDs (or similar) you use one pin (+ground), all other pins you may use for controlling colors etc.
(I would probabelly use LCD + rotary encoder (with button), so I could increase internal logic how much I would like later, and would it fit on one (universal) PCB, but that is my approach)
Not at 24V.
but the arduino itself wont handle the current that will go to the led strip directly, but will control the transistors that will allow the current to flow. is that a problem?
yeah, indeed, it is calculated below 4,5 A.
The most important advice, always, is ask the forum before you spend your money.
WS2812 led strips may be a little more expensive but when you count up the cost of the additional components and building the circuit to use conventional RGB LEDs, the WS2812 strips are around the same total price, or cheaper. Plus, they give you much more flexibility to create impressive animated patterns, if you want to do that later.
Why would you need an IP65 strip in your room? Is there a leak in the roof? You should spend your money fixing that, not adding secondary lighting! 
Hahahaha, fair enough for both of them.
Firstly, from what i found and understand, ws2812 are addresible leds that can be controlled with the arduino i have. It would be cool to have such a feature, but it is more important to me that i have the analog feeling of the faders (and i could still do both, but the 8-bit pwm of the led strip is not enough for the lower brightnesses of the leds, due to gamma correction making many low values repeating)
Secondly, no, thankfully there is no leak in my room. i was thinking ip65 mainly for dust buildup.
Ok. But there are addressable strips that give more control over lower brightness levels, such as APA102 or SK9822 strips. In addition to the same 8-bit control over the red, blue and green channels, these strips have a 5-bit master brightness channel which allows the brightness to be reduced without loosing the colour resolution.
Even with ws2812, it is possible to effectively achieve greater than 8-bit resolution, by grouping LEDs into groups of 2, 3 or 4 and making small adjustments to the LEDs within each group. For example if you group ws2812 LEDs into pairs, you can effectively achieve 9-bit of resolution in each colour channel. With groups of 4 LEDs you can achieve 10-bit resolution.
Dust buildup doesn't harm LED strips. IP65 rating would give no advantage in exchange for the extra cost.
If you are thinking about the transparent tubes you can get for them, they do make them easier to wipe down with a damp cloth. I have used them on strips that go outside for decorative purposes that get pretty dusty after a while. If you seal the ends with silicone sealant they are pretty weather safe as well although I haven't submerged any.
A practical starting point is to test one short section first and measure its actual current before wiring the full run, since that makes the power supply choice much clearer. Keep the strip power separate from the Nano supply, share a common ground, and switch the strip with a suitably rated MOSFET or driver rather than powering it from a Nano pin. For smooth low brightness, an addressable strip or a small fade routine with gamma correction usually looks better than jumping straight between fixed brightness steps.
How so, please explain including the math.
Do you need a circuit diagram of how to build the circuit?
I see what you mean. It is a nice idea, but it makes it a bit more complicated than i can handle at the moment. I will have it in mind for future projects though.
For the protection, it is 6ā¬ higher and i think it's worth it if i want to clean it up from time to time
That is an alternative choice. Either pre built ip65 or outside plastic protection. Although the second option comes with aluminium support that might work as coolingfor the strip, if i have trouble with heat. That's another issue I'm considering
You should focus on the connections/wires/tracks that will sink the high currents from the strip. If you use stripboard, for example, the weak points are where the holes are. Here, the width of the copper strip is at its narrowest and most likely to "pop" with high current. You can lay bare metal wire along these vulnerable parts of the strip and apply a think layer of solder over the top. With perfboard, you will likely be using connector wires between the components that will carry the high current. Use suitably thick wire for those connections and solder the connections with extra solder.
You may also want to attach some kind of heatsink to the MOSFETs. Try without heatsinks to begin and test the strip at max brightness for several hours. If the MOSFETs remain cool enough to keep your finger on, you probably don't need the heatsinks. However, putting the circuit in a box will probably increase the temperatures.
Most of it looks ok. But the buttons won't work like that. You would need to add pull down resistors to the input pins, but...
It would be better to connect the buttons between the Arduino input pins and ground, not to 5V, and use INPUT_PULLUP mode.
What will these buttons do?
If not for those buttons and their unknown function, I suspect you could probably build this circuit with no Arduino or PCA chip, just using 3x 555 timer chips to create the PWM signals.
Doing it the way you suggest is just as easy so why not. Because it's not clear however, remind me how to code it. Do you put the Arduino pins at output or input mode? And how does the Arduino read it?
The use of the buttons will be to control the LEDs. I'm thinking of adding several different modes (fully off, fully on, rgb, hsb, color saving, etc) and to so all that you need three buttons
I will be extra careful on the high amps connections, thanks for the notice.
The MOSFETs are rated for 30 amps i think so they probably won't have an issue with overheating. Am i thinking it correctly?