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I'm attempting to make a 12v blinking light that turns off with a high signal and since I've got some 5v arduino pro minis I though I might do it with them. So I put together a program and a plan

enter image description here

My idea was, that when the switch is closed, 3-4.6v is applied to pin 3 (logic level high) and my program stops the blinking. Testing this with 5v without a voltage divider just pulling pin 3 high or low seemed to work. So I hooked up the voltage divider and tested it with a 12V-14V source. All seemed well until I connected the voltage divider (R1) to 12V (while monitoring the voltage it was outputting) even though I saw only 3V on pin 3 the micro-controller went pop. I'm not really sure why it popped, sorry if this is a stupid question but I'm not the best at this stuff. Any help is appreciated, thanks.

Edit: Genuine question, why do some of my questions get voted down? Am I using this site wrong or formatting my questions wrong? I've been trying to learn electronics, but so far this site hasn't been of much help. I don't really understand why some people vote down questions without telling the asker what they are doing wrong. If you could explain what they're doing wrong it can help them to not make the same mistake in the future (E.g. formatting wrong, not site applicable etc).

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    \$\begingroup\$ So may I gather that supplying 12V to "RAW" is okay for your pro mini? (It sounds like a regulator input pin, so the answer might be yes.) \$\endgroup\$ – jonk Jul 17 '18 at 3:58
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    \$\begingroup\$ Stream of logic: 12V is fine on RAW. Internal regulator produces 5V as Vcc. All I/O pins should be capable of accepting input voltages from 0V to 5V without involving the protection diodes. You have a divider that divides 12V by 3 to get 4V out, with a series resistance of about 67k. On paper, there is no possibility that 4V with a series Thevenin resistance of 67k should cause any harm. Therefore, something else is the problem. (Such as directly connecting 12V to an I/O pin.) \$\endgroup\$ – jonk Jul 17 '18 at 4:03
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    \$\begingroup\$ all seemed well until I connected the voltage divider .... this statement makes me wonder what you actually did ..... you show a push button switch .... why did you not say all seemed well until I pressed the button? \$\endgroup\$ – jsotola Jul 17 '18 at 6:00
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    \$\begingroup\$ What do you mean when you say 'pop'. \$\endgroup\$ – HandyHowie Jul 17 '18 at 7:11
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    \$\begingroup\$ Your schematic doesn't appear to have Vcc connected nor does it show any supply voltage decoupling. There is also a GND connecttion missing. Please show precisely your full circuit and describe in more detail how you made Vcc. \$\endgroup\$ – Andy aka Jul 17 '18 at 8:17
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Per OP's comment, the voltage regulator had failed and was passing all 12 volts on to the microcontroller.

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  • \$\begingroup\$ "tested it with a 12V-14V source" sounds like it could be automotive, and automotive power busses are notoriously nasty. Or perhaps the source is an unregulated wall wart. At any rate, until identified it should be considered an area of suspicion. Also even a clean 12v source puts a fair thermal load on a linear regulator. \$\endgroup\$ – Chris Stratton Aug 24 '18 at 14:28

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