
This is one of the things that will help keep your project(s) going. I find it very strange that when you receive the UNO by default it is set to trigger the brownout at 2.7 volts. According to the specs the processor is / should be running at 10 Mhz at that voltage which makes no sense to me as apparently it runs at 16Mhz out of the box (correct me if I am wrong). Quite confusing if you ask me. However the idea behind this (BOD) is that when the voltage drops under a specified threshold the code execution is being stopped (reset state) until the voltage recovers. I would strongly suggest to program the arduino to trigger the brown out detector at 4.3 volts. You can have a look at the official arduino spec sheet to see what I am talking about:

#define CH1 3 // Digital Pin 3 on Arduino to CH1 on Relay Module void setup(){ //Setup all the Arduino Pins pinMode(CH1, OUTPUT); //Turn OFF any power to the Relay channels digitalWrite(CH1,HIGH); pinMode(LED_BUILTIN, OUTPUT); } void loop(){ digitalWrite(LED_BUILTIN, LOW); delay(500); digitalWrite(CH1, LOW); delay(3000); digitalWrite(CH1, HIGH); delay(3000); digitalWrite(LED_BUILTIN, HIGH); delay(500); }