A beginner needs help with electronics for a friend | 5 NeoPixel, 1Fan and a Arduino

Question

Hello Element14 Comunity, If you guys can help me, and I don't mean that you should give my a compleat circuit or code, I mean good practises or ideas and say what I have done wrong. I am pretty mutch a beginner and I want to learn. I'm building a costume for a friend and he wants LEDs and a Fan, this shouldn't be hard but I thought wrong. (I don't know if this is even possible with an Arduino....) So here is my idea. I have an Arduino that controls 5 NeoPixel LED strips and a fan, the LEDs should change colour or in the case of the fan the speed when he presses on of the 4 Buttons, in this case, FSRs (Force Sensitive Resistors). The first 3 controls the Colour with an effect of some sort. The last one has 2 modes to manage 1. when he holds the Button down the Fan should speed up, when he presses it and holds it down again in a very short amount of time the fan should slow down to a specific speed. 2. When he just press the button all LEDs should go off or on again. I have done the first idea in Fritzing and I don't know if this is good or the worst thing you guys have ever seen. I hope you guys can help me. 
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gadget.iom · Answer

I would start by building the circuit in stages. Start with a single neo-pixel and add some code to just flat some colour etc. Then add the rest of the pixels and check functionality. Then the motor. Keep building the circuit in steps, so that if it doesn't work for any reason you will have a better idea why. With respect to code, build the LED button control first, then add the motor control when you have the LEDs working. Paul

mcb1 · Answer

The neopixels come with some very good examples in the Adafruit library. You should be able to drive all 5 from a single regulator. https://learn.adafruit.com/adafruit-neopixel-uberguide/power gadget.iom is quite right ... build it in stages. Your diagram is a great start ... much better than a lot of other ones we see. Mark

niteowl12 · Answer

Don't forget to tie the 12v and 5v grounds together, otherwise the arduino will not be able to close that transistor.

mcb1 · Answer

niteowl12 Good spotting. The Sensing pin A0-A3 need to connect between the FSR and the pulldown resistor. Also PWM is only available on some pins. https://www.arduino.cc/en/Main/ArduinoBoardProMini You might want to change the Fan output to one to other pins (D3 will work) Mark

niteowl12 · Answer

You should only need one 5V regulator for the entire circuit not just the neopixel. Just make sure that the power dissipation isn't too high.For that you need to figure out how much current the whole circuit draws. From the looks of it the sense wire for the buttons is in the wrong place. To me it looks like the micro will always be sensing GND. I also don't know how the pin is configured in software.

mcb1 · Answer

I will use a 5V 3A PowerBank to run theNeoPixel and Arduino and the 12Vone to run the fan.

Sounds a much simplier way.

Your board layout has an error with Din and 5v swapped on the bottom left Neopixel, and obviously the track size needs to be much larger (never done a layout in Fritzing before)

Mark

niteowl12 · Answer

Here is a tool to help you calculate trace width. Very nice to have and its free. Saturn PCB Toolkit - Saturn PCB Design

mcb1 · Answer

I don't know how many I end up using. The only reason you are using 12v is the fan. You could use one of those 5v power banks, and a small 12v battery just for the fan. It might be an easier option than trying to regulate the neopixels. Mark

niteowl12 · Answer

Please make sure you account for power dissipation. You are looking at (12v - 5v) * 3.6A = 25.2W of power(ballpark) that needs to be dissipated by that regulator. my first experience figuring this out made a board get hot enough to boil water. I would suggest finding a way to use the 12v to power the neopixels by putting them in series if you can or finding a simple DC/DC buck regulator from sparkfun or adafruit. one that's already put together to make it easy for you.

mcb1 · Answer

I want a pretty long runtime for the circuit The first comment I'd make is the neopixels don't need to be run at 60mA (all three on). They are BRIGHT so unless it is in sunlight you may find you can get away with 30mA or less when it's running. If you're only using one colour it will be a third of whatever the figure is. The DC/DC converter is the best option to eliminate the heat component and save on energy wasted. You also gain a bit more run time using these. So using 85% efficiency 1.8A out is approx 0.92A in at 12v 0.92A = 920mA x 5 strips = 4600mA (ignore the fan) 19600 / 4600 = 4.2 hours at FULL BRIGHTNESS One thing to be aware of, most of the rated mA on these battery packs aren't. However I think considering it won't always be on white, you should get 4 hours easily. Mark

Superthin	8mil
Extra thin	12mil
Thin	2mil
Standard	24mil
Thick	32mil
Extra thick	48mil

A beginner needs help with electronics for a friend | 5 NeoPixel, 1Fan and a Arduino

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