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I made this exact build on my Arduino, with the following differences:

  • I'm using Arduino Nano
  • Transistors I use are 2N2222A
  • I'm running everything on 12V except Arduino, I use LM317 to feed Arduino 6v

Here's the build: enter image description here

Here's what happened. First, it started to get strange voltage, arduino would light up even when disconnected from power. After that, Arduino kind of got fried, when I connect it to USB, nothing happens. I can give it 6v to VIN and ground it with the rest, but turning potentiometers only dims the onboard LED of the Arduino and that's it.

Now I'm going to go and pick up a new nano, however, I'd prefer not to fry that one, so figuring out why this one burned would be nice.

PS. The image shows RGB LED instead of RGB LED Strip because 123d doesn't have strip component.

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    No base resistors? – Majenko Apr 24 '16 at 15:15
  • Nothing according to the original build, should there be any? – Predrag Beocanin Apr 24 '16 at 15:18
  • Yes, otherwise the transistors can draw too much current for the Arduino to handle. – Majenko Apr 24 '16 at 15:18
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    So i did try the resistor and arduino keeps burning up. One thing i noticed: if i wire pots directly to + arduino gets really hot really fast. If i wire them to arduino 5v pin, it gets hot slower, but still does. Im confused – Predrag Beocanin Apr 25 '16 at 3:55
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    Then you must have something seriously messed up with your wiring. – Majenko Apr 25 '16 at 8:28
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First, as Majenko said, you need resistors between the arduino output pins and the transistor bases. Start at something like 330 Ohm. Second, what is the value of the potentiometers? If it is too low you would be drawing too much current from the 5V pin to the ground. Third, you should power the arduino with at least 7V, assuming you power it through the Vin pin or the power jack. 6V is considered too low. I assume the pins connected to the potentiometers are initialised as inputs. Otherwise, it would be possible to burn your arduino by having them source/sink too much current (i.e. by turning the potentiometers to one end or the other).

  • I just figured 6v safe, but I'll increase it to 7. I did start with 330 and went all the way up to 1k resistors without results. The pots are 4.7k trimmers, original design said 10k, but I had none at hand. They are hooked to A5 and A6 which are initialised as inputs yes – Predrag Beocanin Apr 25 '16 at 13:58
  • Although 6V is generally considered too low (you are applying it to pin Vin or the power jack, right?) this would not explain the arduino burning, so pls don't try with another arduino unless you find a plausible explanation for this. It may seem a silly question, but have you double- and triple-checked all your connections? – Alphonsos_Pangas Apr 25 '16 at 14:04
  • The trimmers are fine. At 5V they will draw around 1 mA each, which is really unimportant toward the 200mA limit. – Alphonsos_Pangas Apr 25 '16 at 14:06
  • Yeah vin is connected to 6v and gnd to power supplu ground. I did, only thing left is to recheck the wires for broken ones (i had one that beep on continuity test but didnt work) and breadboard itself i see nothing else that can be an issue, since my circuit is correct – Predrag Beocanin Apr 25 '16 at 14:10
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Looking at the datasheet for the 2N2222A at http://www.onsemi.com/pub_link/Collateral/2N2222A-D.PDF The 2N2222A base will draw 50 ma at 2volt. You are giving them more than that. The maximum allowed output from the Arduino is 40ma. So check the 2N2222A's they are probably burnt out as well as the Arduino. Next time put in a limit resistor of 1k to the 2N2222A bases. Try pulling out the 2N2222A's and see if your Arduino powers up ok.

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