Low power on Arduino Mega

Using Arduino Microcontrollers
1

Hi,

I intend to use Arduino Mega 2560 board for a project that needs to sleep most of the time. I need to achieve low power for a 2AA cell battery based application. So, I removed all the extra components from the board, like, mosfets, regulator, USB to UART, etc. Even the resistors are removed since all I need to do is to poll 20 GPIOs per second. Only the 16mhz XTAL and reset circuitry is retained. I hoped to achieve low power similar to pro mini. The consumption at startup is ~60mA and after entering sleep is ~3.3mA.

Can someone please help me figure out the reason for such high consumption? I believe the chip can hit a few uA in sleep mode. Attached is my sample code.

Regards,
WonderfulIOT

#include<avr/sleep.h>
#define SPEED_FACTOR 1.0
void setup() 
{
  // put your setup code here, to run once:

set_sleep_mode(SLEEP_MODE_PWR_DOWN);
sleep_enable();

  for(int i=2;i<=53;++i)
  {
    pinMode(i,OUTPUT);
    digitalWrite(i,0);  
  }
  
}

void loop() 
{
  // put your main code here, to run repeatedly:
  Serial.begin(9600*SPEED_FACTOR);
  Serial.print("Ok");
  delay(1000/SPEED_FACTOR);
  Serial.println(" Ok");
  delay(1000/SPEED_FACTOR);
  // __asm__  __volatile__("sleep");//in line assembler to go to sleep
  Serial.end();
  sleep_cpu();
}

20170314_124559.jpg
20170314_124559.jpg1632×918 623 KB

2

Before you hacked up your board it would have been a good idea to do some research beforehand. That way you could have seen this on the first page of the datasheet and not wasted your time.

screenshot.129.jpg

2 AA cells is far out of the required supply voltage spec for the ATmega2560, which requires a minumum of 4.5V no matter what. Even for the m2560V version, 2 cell operation requires reducing the oscillator speed to under 2 Mhz.

3

Thanks for the reply and pointing out that it will not run off 2AA cells.

However, my current sample code is using USB 5V supply and the current consumption is at that voltage. Any pointers as to whats wrong with my setup or code (or library)? I do see that the processor is indeed in sleep mode.

Regards,
WonderfulIOT

4

Have you removed the power regulators? The LDOs can have some high quiescent current.