What am I doing wrong??

Other Hardware General Electronics
1

Hey forum,

Basically my problem is, that I crashed my second bootloader today...
First of all I describe my circuit.
I have an Arduino Uno(R3) and I control 2 SMD-Led Strips via a photo-resistor.
I have connected the photo-resistor to A0, it's doing fine, I controlled it via serial monitor, it's not the problem.
When the voltage goes below 1 (I convert the value to "voltage" - 5V) the Arduino should turn on the 2 SMD-strips, connected to Pin5 and Pin6 via PWM. The 12V side of the strips are connected to a 12V power supply unit, the other sides of the strips go into Pin5 and Pin6. The other cable of the power supply goes into a "GND" of the arduino.
Before that I did it with only one SMD-strip and it worked fine for days. The botloader crashed today after connecting the second strip.
After installing the new circuit, I flashed the new sketch to the board and that crashed the bootloader. After that I changed the Atmel328 with a new one(with a preinstalled Bootloader) , and flashed it to the board with no problems. I changed some settings, still connected to the board, again no problems, the led-strips started after the voltage went below 1. Then I disconnected my laptop and had done some additional changes in the sketch. After reconnecting and flashing it to the board, the bootloader crashed again so it has something to do with the corcuit I suppose...
I don't know what I've done wrong in the circuit...Can you help me?
Greetings

2

Well, if it has something to do with the circuit, don't you think we need to see it too? A pencil sketch photographed with a smartphone is usually good enough.

"Other side of 12V strip plugged into Arduino" sounds bad. Like smoke and flames bad. There must be something else you're not telling us there.

3

You cannot pull 12V LED strips low directly, you need transistors in between. You are damaging your 328P chips.

4

Actually you probably damaged the pins through over current, not over-voltage - 12V LED strips don't start to
conduct till they have perhaps 8 or 9V across them, at which point the Arduino pin was within its comfort zone
voltage wise. However Arduino pins cannot tolerate 40mA or above.

However the point is you never use an Arduino pin to handle power, and never connect to anything that
goes out of voltage range - otherwise you'll be buying new chips again and again. Absolute maximum
ratings are called that for a very good reason.