Tag: chinese

Please welcome my latest programming tool, the Arduino Power Cutter:

The BTE13-010 is a cheap Chinese clone of the Arduino Pro Mini, manufactured by Baite, which can be found from their Aliexpress store (among other places). The internets and the producer are unfortunately lacking much documentation about it.

Today I was trying to achieve a very low power consumption on the BTE13-010. You might already have had a look to popular pages when it comes to power saving on the Arduino, two popular ones being Power saving techniques for microprocessors on Gammon Forum and Arduino sleep mode basics on EngBlaze.

However, at first I struggled to achieve the promised great savings, possibly because I was using the BTE13-010 instead of rebuilding a circuit from scratch, like many of them suggest?

To make a long story short, after browsing everywhere, I came up with these two subroutines that will cut (no pun intended) through your power consumption:

	#include <avr/sleep.h>
	#include <avr/power.h>
	#include <avr/wdt.h>
	// watchdog interrupt
	ISR (WDT_vect)
	{
	wdt_disable(); // disable watchdog
	}
	void
	power_saving_sleep()
	{
	// disable ADC
	byte old_ADCSRA = ADCSRA;
	ADCSRA = 0;
	power_all_disable();
	PCIFR |= bit (PCIF0) | bit (PCIF1) | bit (PCIF2); // clear any outstanding interrupts
	PCICR = 0;
	TWCR = bit(TWEN) | bit(TWIE) | bit(TWEA) | bit(TWINT);
	digitalWrite (A4, LOW);
	digitalWrite (A5, LOW);
	// clear various "reset" flags
	MCUSR = 0;
	// allow changes, disable reset
	WDTCSR = bit (WDCE) | bit (WDE);
	// set interrupt mode and an interval
	WDTCSR = bit (WDIE) | bit (WDP3) | bit (WDP0); // set WDIE, and 8 seconds delay
	wdt_reset(); // pat the dog
	set_sleep_mode (SLEEP_MODE_PWR_DOWN);
	noInterrupts (); // timed sequence follows
	sleep_enable();
	// turn off brown-out enable in software
	MCUCR = bit (BODS) | bit (BODSE);
	MCUCR = bit (BODS);
	interrupts (); // guarantees next instruction executed
	sleep_cpu ();
	// cancel sleep as a precaution
	sleep_disable();
	power_all_enable();
	ADCSRA = old_ADCSRA;
	}
	void
	power_saving_init()
	{
	for (byte i = 0; i &lt;= A5; i++) {
	pinMode (i, OUTPUT);
	digitalWrite (i, LOW);
	}
	}

view raw power_saving.ino hosted with by GitHub

The power_saving_init() should be the first thing to be called at setup(), it will initialize all your pins to LOW. power_saving_sleep() will put everything to sleep, and wake up every 8 seconds. With these two, with the regular board (no bootloader modifications, with the power regulator on, etc) when sleeping I was able to achieve 3.24mA of power consumption, which is already pretty good considering it was draining about 10.2mA when fully powered on in the first place.

(I also tried to change the board internal clock with avrdude options, but that didn’t seem to be possible on this board. I also tried to clock it down via clock_prescale_set(), but nothing was gained).

But it doesn’t end here! That’s were the Power Cutter comes in. Thanks to Talpa PCB retrace of the BTE13-010 I was able to elaborate an evil power saving plan:

[Credits for this picture to Talpa, with a few corrections/additions by me]

With a cutter, I was able to cut (pun intended) thru power consumption by cutting the two traces in the picture (in light blue in the upper right), thus phisically cutting out the power LED and the regulation circuit (I wasn’t using that regulator anyway, both USB power and my batteries bypass it). The LED and the regulator were draining about 0.47mA and 2.44mA respectively. Note to adventurers: always check with a multimeter before and after attempting to cut traces.

Without those two components, my power consumption went down to 4uA.

For best results, use batteries with low self-discharge rates, like coin cell! AA batteries can have discharge rates up to 30 mA, it’s a lot!

Let me know your thoughts in the comments!