[Rajendra Bhatt] wrote in to share the latest in a series of PIC tutorials, which covers the microcontroller’s Sleep mode – a very useful tool for limiting current consumption in battery-powered applications.
He discusses how to put the PIC in sleep mode, as well as some common mistakes to watch out for, such as accidentally allowing I/O pins to sink or source current while sleeping. [Rajendra] also walks through the various ways a PIC can be brought out of sleep mode, focusing the majority of his tutorial to the mcu’s watchdog timer.
Using a PIC16F628A, he constructs a test circuit which allows him to demonstrate the power savings gained by using sleep mode rather than the microcontroller’s built-in delay function. The circuit simply blinks an LED every 4.3 seconds, using the watchdog timer for the first 2.3 seconds, and a delay() call for the rest of the time.
The power savings are quite substantial, similar to the results we saw using AVR microcontrollers a few weeks ago. [Rajendra] found that using the sleep function limited current consumption to about 4.5% of the current used when calling the mcu’s delay function – a huge savings.