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I am making an LED circuit for a Lobot (from star wars) costume headset that will not be on a PCB or stripboard. It will all be running inside the walls of the plastic shell I am making. Please see Gif of what I am hoping to do:

Gif of Lobot from the star wars in action

EDIT:

The LEDs will run through 4 different programs. Here is one program as an example:

-Far left and right led pairs will alternate on/off -Single LEDs will blink twice then off for a cycle -The (4) pairs on the left and right will rise and fall like a soundboard -The (3) pairs of white(blue in the demo) will chase bottom to top and back down again

I am new to electronics so I am a little nervous about running the ground wire for it. Here is my circuit:

EDIT 2:

Here is a reworked diagram based on the suggestions i received below: Circuit with resistors

The reds were switched to blue for the simulation but will actually be white. So they are 3v each but running in parallel will need 100ohm.

Now that we have that out of the way, is the ground wire run correctly?

The simulation runs perfectly, but I want to make sure that I am not overlooking something important before I try it on my arduino IRL. Is there a neater way to do this? Google searches availed me not. What is the accepted method for this type of circuit?

  • Hello and welcome. Most of your LEDs miss their current limiting resistor. I am not sure about the Arduinos digital outputs but typically that is not a safe thing to do. – Ghanima May 3 '17 at 19:28
  • Could you describe how you want it to behave, please? The circuit is unusual, but perhaps it makes sense when you know what you're trying to achieve. – Mark Smith May 3 '17 at 19:47
  • @MarkSmith I edited my original post with more details on the program i am running. I had to double-up the LEDs to slim down the circuit due to the limited number of pins on the nano. – Andrew Metzger May 3 '17 at 21:10
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The schematics is unfortunately somewhat complicated to read as one has to look at the pinout to understand it. When comparing it to the pinout however I find a few things that are odd, e.g. one of the green wires (top, fourth pin from the right) is connected to GND.

Note that the sum of the forward voltages of the LEDs connected in series need to be (significantly) lower than the supply voltage of the Arduino. This forward voltage is different for differing LEDs (depending on the colour). Blue LEDs have a higher voltage (typically 3.0 - 3.5 volts). Connecting two blue LEDs or some more red LEDs in series leads to a necessary forward voltage higher than what the Arduino can provide.

Be sure to add the current limiting resistor for the LEDs in the appropriate places. Due to the non-linear current-voltage characteristic of (light emitting) diodes those resistors are a must-have (unless driving them with a current source, which the Arduinos GPIO pins are not). Do use one resistor per LED or if LEDs are connected in series. Do not use only one resistor for LEDs wired in parallel. For more details on this topic see here.

Edit to add (revision of question):

Given 3 V forward voltage and 100 Ohm series resistor one LED presumably leads to a current of about 20 mA. But since you intent to drive two LEDs in parallel (so 40 mA) from each pin, you're well out of spec and hitting Absolute Maximum Ratings:

DC current rating, source:

DC Current per I/O Pin . . . . . . . . . . . . . . . . . . 20 mA

Absolute Maximum Rating, source

DC Current per I/O Pin . . . . . . . . . . . . . . . . . . 40.0mA

Furthermore you intend to connect 18 pairs of LEDs (give or take the red LEDs). This would be a total current of 720 mA which is significantly above the limits of the microcontroller. Consider that all the current flowing through the LEDs into the GPIO pins also needs to flow to VCC through the controllers power supply lines (just two pins!). Those have limits too:

Absolute Maximum Rating, source

DC Current VCC and GND Pins . . . . . . . . . . 200.0mA

You need an external driver (such as the ULN2803, as presented in this answer) or transistors.

  • I apologize for the confusing schematics. The Arduino i used in the fritz was a micro, not a nano. The major difference is the micro has two additional rows of pins that i am not using see image here: link – Andrew Metzger May 3 '17 at 21:20
  • @AndrewMetzger, Micro, Macro, Nano, Uno, Mega... It doesn't matter, all run at 5V. Your schematics won't work.Ghanima is giving you basic, but MUST components. Also i would suggest to use ULN2803 chips. Easy to use transistors. You won't need to calculate resistors for transistors :D – Martynas May 3 '17 at 21:32
  • As to the resistors, i have tested it on an uno without having any issues but I can add them onto the circuit. Based on a calculator i used online, i would need 30ohms of resistance for the reds and for the whites the current is too low, which i am fine with a lower output. – Andrew Metzger May 3 '17 at 21:32
  • Additional, your arduino will burn in first few seconds, because the current will be to big. you should not drive LEDs from Arduino – Martynas May 3 '17 at 21:34
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I am putting all comments here as answer. Micro, Macro, Nano, Uno, Mega... It doesn't matter, all run at 5V. Your schematics won't work.Ghanima is giving you basic, but MUST components. Also i would suggest to use ULN2803 chips. Easy to use transistors. You won't need to calculate resistors for transistors :D

Additional, your arduino will burn in first few seconds, because the current will be to big. you should not drive LEDs from Arduino.

To make it SUPER COOL i would suggest WS2812B LEDs. They need 5V, GND, and Data in. And you can make it any color you want and control all LEDs separately.

Some video about WS2812B

I would strongly recommend it.

  • Thank you so much for the advice. If I had not already programmed this using the Arduino I would definitely look into your suggestion of the alternate chip. Provided I add the resistors has everyone suggested comma would the circuit work with the ground wire the way it is? – Andrew Metzger May 3 '17 at 22:57
  • This chip does not require to change your code, and it is easiest to change few lines in your code, rather than make new pcb. When i will get back home i will make few hints for you. – Martynas May 4 '17 at 18:35

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