diff --git a/main.c b/main.c
index 959ac45..85babe6 100644
--- a/main.c
+++ b/main.c
@@ -58,6 +58,9 @@ volatile bool frame_flag = false; /**< flag set when a frame has passed */
 #define SQUARE_WAVE_PIN 0 /**< pin connected to RTC DS1307 square wave output */
 volatile uint8_t rtc_seconds = 0; /**< number of seconds passed incremented by the square wave */
 
+#define STANDBY_TIMEOUT 30  /**< number of seconds after last shake before going down */
+volatile uint16_t standby_timer = 0; /**< number of seconds since last wake-up/activity */
+
 #define FRAME_TIMER 1 /**< timer to count frame time */
 #define FRAME_RATE 25 /**< frame rate */
 volatile uint8_t frame_count = 0; /**< number of frames passed */
@@ -209,12 +212,20 @@ void main(void)
 	}
 #endif
 
+	// enable wake up
+	rcc_periph_clock_enable(RCC_PWR); // enable power domain clock
+	if (pwr_get_wakeup_flag()) {
+		printf("woke up from standby\n");
+	}	
+	pwr_enable_wakeup_pin();
+
 	// disable internal RTC
 	printf("disable internal RTC: ");
 	rcc_periph_clock_enable(RCC_PWR); // enable power domain clock
 	rcc_periph_clock_enable(RCC_BKP); // enable backup domain clock
 	pwr_disable_backup_domain_write_protect(); // enable write on backup domain (including RTC)
 	RCC_BDCR &= ~RCC_BDCR_RTCEN; // disable RTC
+	pwr_enable_backup_domain_write_protect(); // re-enable write protect
 	printf("OK\n");
 
 	// setup external RTC
@@ -357,6 +368,14 @@ void main(void)
 			action = true; // action has been performed
 			led_toggle(); // toggle LED (good to indicate if main function is stuck)
 			frame_count = 0; // resync frame counter to second
+			if (standby_timer>=STANDBY_TIMEOUT) { // standby timeout complete
+				// go into standby mode
+				printf("standing by\n");
+				led_max7219_off(0xff); // switch displays off
+				pwr_clear_wakeup_flag(); // clear flag
+				SCB_SCR |= SCB_SCR_SLEEPDEEP; // enable deep sleep
+				pwr_set_standby_mode(); // go to deep sleep
+			}
 			if (rtc_seconds>=60) { // one minute passed
 				rtc_ds1307_time = rtc_ds1307_read_time(); // get time/date from external RTC
 				if (rtc_ds1307_time==NULL) {
@@ -370,10 +389,14 @@ void main(void)
 				}
 			}
 		}
+		while (pwr_get_wakeup_flag()) { // someone is moving the clapperboard
+			pwr_clear_wakeup_flag(); // clear flag
+			standby_timer = 0; // restart standby timer
+		}
 		if (action) { // go to sleep if nothing had to be done, else recheck for activity
 			action = false;
 		} else {
-			__WFI(); // go to sleep
+			__WFI(); // go to sleep and wait for interrupt
 		}
 	} // main loop
 }
@@ -383,6 +406,9 @@ void EXTI_ISR(SQUARE_WAVE_PIN)(void)
 {
     exti_reset_request(EXTI(SQUARE_WAVE_PIN)); // reset interrupt
 	rtc_seconds++; // increment number of seconds passed
+	if (standby_timer<STANDBY_TIMEOUT) { // timeout countdown not complete
+		standby_timer++; // continue counting down
+	}
     rtc_tick_flag = true; // let main know a second passed
 }