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Topic: Power problem with Gammon's classic code (Read 582 times) previous topic - next topic


Hi Folks,

Maybe a stupid question but... I apply the great Nick Gammons code for AtTiny45.
Power consumption is round 400-500 nA if INT is NOT grounded. But, if grounded,
sleep power is round 100uA! I have a quicksilver switch, and it is ON or OFF: when
status is changed action should do. The problem is: if switch remains in ON position,
the power consumpition is round 100uA.

Please help!

// ATtiny85 sleep mode, wake on pin change interrupt demo
// Author: Nick Gammon
// Date: 12 October 2013

//                  +-\/-+
// Ain0 (D 5) PB5  1|    |8  Vcc
// Ain3 (D 3) PB3  2|    |7  PB2 (D 2) Ain1
// Ain2 (D 4) PB4  3|    |6  PB1 (D 1) pwm1
//            GND  4|    |5  PB0 (D 0) pwm0
//                  +----+

#include <avr/sleep.h>    // Sleep Modes
#include <avr/power.h>    // Power management

const byte LED = 3;  // pin 2
const byte SWITCH = 4; // pin 3 / PCINT4

ISR (PCINT0_vect)
 // do something interesting here
void setup ()
  pinMode (LED, OUTPUT);
  pinMode (SWITCH, INPUT);
  digitalWrite (SWITCH, HIGH);  // internal pull-up
  // pin change interrupt (example for D4)
  PCMSK  |= bit (PCINT4);  // want pin D4 / pin 3
  GIFR   |= bit (PCIF);    // clear any outstanding interrupts
  GIMSK  |= bit (PCIE);    // enable pin change interrupts
  }  // end of setup

void loop ()
  digitalWrite (LED, HIGH);
  delay (500);
  digitalWrite (LED, LOW);
  delay (500);
  goToSleep ();
  }  // end of loop
void goToSleep ()
  ADCSRA = 0;            // turn off ADC
  power_all_disable ();  // power off ADC, Timer 0 and 1, serial interface
  power_all_enable();    // power everything back on
  }  // end of goToSleep


Sounds about right.  a pullup resistor on a contact connected to ground consumes power.
The INPUT_PULLUP resistor is supposed to be about 40k.  5V/40K is about 100uA.
You can:
  • use a SPDT switch
  • use a higher-value external pullup or pulldown register.
  • Turn off the pullup EXCEPT when you actually need to detect interrupts.


Thanks westfw,

My idea is to trigger 1-2 minutes blinking period when quicksilver switch is going ON --> OFF or OFF-->ON.

The swicth is locating in dog's collar (to be seen in darkness when led is blinking). The dog is constantly moving around, and my device works perfectly when I walk with the dog.

Problem is only when I take off the dogs collar and quicksilver switch happens to be in ON mode --> 100uA for nothing!

Further ideas? I will try the solution you mentioned later this evening. -kari


To be continued...

Where (AtTiny45) should I place the higher value
external pull-up resistor? Gammon's code above.

2. use a higher-value external pullup or pulldown register.


Where (AtTiny45) should I place the higher value external pull-up resistor?
Between the pin and Vcc.


jremingon: thank you!

SOLVED, with 10M resistor between Vcc (+) and triggeg (physical pin #2)
in code above, the stand-by current is between 0.1 uA (open) and 0.5 uA (closed). This is
enough for me.

I'm not sure, can work both ways, but I changed line

digitalWrite (SWITCH, HIGH);  // internal pull-up

to digitalWrite(SWITCH, LOW);

and it works. Could also work with original code, I'm not sure.

BR, -kari

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