If your unit is to run things like turn signals and door lights, then you can just connect it to the power that gets turned off when that system is not running.Arduino Uno is a microcontroller board based on the ATmega328P ( datasheet). Just because you put the processor to sleep, it does not reduce your to near zero. The Arduino UNO or any of the manufactured boards will have multiple circuits that run all the time. What about arduino Mini, Micro, Nano? does they need less current to stay alive? (i think it's better to use a standby mode with Wake Up on PIN and use Arduino Uno, i see him as more strong) If i use arduino UNO with 12v power, and it doesnt give current on his PIN because everything is in INPUT mode, how much current does he need to stay alive? Are there some function to let it go in sleep mode, and then wake up when +5v goes to a pin? (a kind of standby mode) ? Obviously i have to create something low power or i will discharge car's battery quickly. I need to power it with 12v car battery, so i only can create another circuit with a 78L05 or something that can hold 0,6 Amp max current, let the Ground common to Arduino's ground (of course) and then i have all the power i need. I often use 1K resistors and find the newer LEDs to be very bright. You may find not much difference between 10mA and 20mA. To find a resistor value: (5V - Vf)/.02A = lowest resistor value to use, higher is ok.Įxample Vf = 2.2V for a typical Red LED: (5V - 2.2V)/.02A = 140 ohm, use a 150ohm standard value resistor.

LEDs have a forward voltage, Vf, that is the voltage you will measure across the leads when it starts to conduct.

LEDs typically have a max continuous current of 20mA, if more current is allowed they overheat and their lifetime is reduced, or they fail.A trimmer with one outer leg at 5V and the other at Gnd can have any wiper position.Uno regulator and the reverse polarity protection diode are only rated for 1A.ĥV regulator is NCP1117 is rated for 800mA - but the part will overheat and go into thermal shutdown will before that if the barrel jack voltage is over 7.5V.ADC output will be 0 to 1023 (0x00 to 0x3F).

Datasheet for arduino uno