Arduino fried

[Omega1806]

Hi, i tried the project. Did the PCB's at pcbway, and started the project. I just wanted the classic, potentiometer RGB controller. First try, put the program with effects on the arduino. After starting it, i couldn't connect to the board any more, or upload any code. Secound try, bought another Arduino. Test no.1: with 1m LED strip and 12v 2A power supply, SUCCESS! it worked. Test no 2: swaped the 1m strip with 4m, same power supply. Arduino started smoking. Burned the 5v regulator on it. Test no 3: swaped the Arduino board with a new one. after starting i got green colour flashing + no reaction on the potentiometers + Arduino started to heat up.

What could be the issue? i'm kind of runnin' out of ideas and money for this project (getting to expensive).

Please help!

Thanks 😄

PS: tested every soldering for shortcircuits. the tests from the secound arduino were made with a new pcb. and new components.

[dbrgn]

Are you using the same components as in our v2 schema here? https://raw.githubusercontent.com/coredump-ch/rgb-led/master/v2/export/v2/schema.png (i.e. MOSFETs and not transistors, and an appropriate power supply and fuse?)

[Omega1806]

Hi, Thanks for the answer! The only thing that was different was that i didn't have a 6A power supply, just a 2A power supply. Wich worked just fine until i tried the 4m LED strip...After that the 5V regulator in the Arduino started smoking. That i might fried it with the "too small power supply", i don't argue. What i don't understand is why doesn't it work with another Arduino. Are there other components fried? I messured the mosfets, everything seems fine.

[dbrgn]

I don't quite understand how it could fry the Arduino. The LED strips are powered directly by the power supply, and the Arduino simply switches the MOSFETs on and off.

The only thing I could imagine based on the schematic is that the LED strips could try to source current from the Arduino's VIn pin if the power supply does not provide enough power. However, I assume that the Arduino prevents that.

(Maybe @rnestler has another idea...)

[Omega1806]

the problem is why isn't it working after swiching the arduino? i mean before switching the 1m strip with the 4m one, everything worked fine... This is my third try with the project. At the first try, i loaded the program with effects, but i wanted just the simple one with the potentiometers, but i couldn't load any program on the Arduino, comunication error. bought everything for the second try, worked just fine before i switched the 1m strip with the 4m one. Now i buy a 6A power supply, new arduino, new mosfets, new potentiometers, everything, and try again...

Ps: this is for my son, he is 4 years old, and i have done a plexiglass, wallmounted "lego ninjago" sign, wich i planned to light up with LED strip, wich he can adjust via potentiometers, so he can learn to mix colours.

[rnestler]

If the LEDs draw so much current, that the voltage of the 2A supply drops below 5V, current may start to flow in reverse for a short period. Then the Arduino may reset and thus turning the LEDs off, which will stabilize the the voltage again, but then will immediately drop again since the Arduino turns the LEDs on again. (This would explain the color flashing)

This oscillating may then break the power supply of the Arduino.

But this is a very hand wavy explanation :wink:

[rnestler]

The only protection the board has is the fuse, which of course needs to be rated below the maximum current the power-supply can deliver, since otherwise it is useless.

Theoretically one could add a software monitoring of the 12V supply and go in a fail state if the voltage ever drops below 10V or something (but this is hard to achieve, since measuring the voltage that powers your device is hard and it would also need to react extremely fast to handle a quasi short circuit from too many LEDs)

[rnestler]

What we probably should do is to have pull down resistors for the FET driver outputs (D3, D5, D6) since depending on the Arduino boards these outputs may be floating when starting up and thus will enable the LEDs while booting.

[dbrgn]

If the LEDs draw so much current, that the voltage of the 2A supply drops below 5V, current may start to flow in reverse for a short period. Then the Arduino may reset and thus turning the LEDs off, which will stabilize the the voltage again, but then will immediately drop again since the Arduino turns the LEDs on again. (This would explain the color flashing)

This oscillating may then break the power supply of the Arduino.

But this is a very hand wavy explanation wink

Ah yeah, that makes sense!

[Omega1806]

Hi guys, thank you all for the feedback! The LED strip says on the specs that it consumes 14,5 W per meter. I connected 4m.

I will try again next week with a new arduino and a 5-6A power supply and get back to you with the results.

Have a nice weekend!!

[rnestler]

The LED strip says on the specs that it consumes 14,5 W per meter. I connected 4m.

With a Voltage of 12V this gives you 4.83A: (14.5W/m * 4m) /12V = 4.833A. So a 5-6A power supply should be sufficient.