 #define SERVO_HORZ_MIN 700
 #define SERVO_PIN_HORZ_POWER 8 // PB0
 
+#define DARK_THRESHOLD 500 // too dark below this
 
 // When the last move was attempted.
 unsigned long move_last = 0; 

// The transmit interval.
const long tx_interval = 2000; 

byte ledState = HIGH;
byte msgId = 0;


        
        // Move the panels if needed.
        tkr_move();
        
        if (light_level < DARK_THRESHOLD) {
          //goToSleep();
          //TODO connect PIN_LDR_LEFT to INT0
        }
        
    }
    
    if (now - tx_last >= tx_interval) {
