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.
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).
