diff --git a/Marlin/temperature.cpp b/Marlin/temperature.cpp
index 7acc5ffd87..8bdb7647f8 100644
--- a/Marlin/temperature.cpp
+++ b/Marlin/temperature.cpp
@@ -497,7 +497,7 @@ void manage_heater()
     SERIAL_ECHO(" iTerm ");
     SERIAL_ECHO(iTerm[e]);
     SERIAL_ECHO(" dTerm ");
-    SERIAL_ECHOLN(dTerm[e]);  
+    SERIAL_ECHOLN(dTerm[e]);
     #endif //PID_DEBUG
   #else /* PID off */
     pid_output = 0;
@@ -1221,68 +1221,311 @@ ISR(TIMER0_COMPB_vect)
   static unsigned char temp_state = 10;
   static unsigned char pwm_count = (1 << SOFT_PWM_SCALE);
   static unsigned char soft_pwm_0;
-  #if (EXTRUDERS > 1) || defined(HEATERS_PARALLEL)
+#ifdef SLOW_PWM_HEATERS
+  static unsigned char slow_pwm_count = 0;
+  static unsigned char state_heater_0 = 0;
+  static unsigned char state_timer_heater_0 = 0;
+#endif 
+#if (EXTRUDERS > 1) || defined(HEATERS_PARALLEL)
   static unsigned char soft_pwm_1;
-  #endif
-  #if EXTRUDERS > 2
+#ifdef SLOW_PWM_HEATERS
+  static unsigned char state_heater_1 = 0;
+  static unsigned char state_timer_heater_1 = 0;
+#endif 
+#endif
+#if EXTRUDERS > 2
   static unsigned char soft_pwm_2;
-  #endif
-  #if HEATER_BED_PIN > -1
+#ifdef SLOW_PWM_HEATERS
+  static unsigned char state_heater_2 = 0;
+  static unsigned char state_timer_heater_2 = 0;
+#endif 
+#endif
+#if HEATER_BED_PIN > -1
   static unsigned char soft_pwm_b;
-  #endif
+#ifdef SLOW_PWM_HEATERS
+  static unsigned char state_heater_b = 0;
+  static unsigned char state_timer_heater_b = 0;
+#endif 
+#endif
   
-  #if defined(FILWIDTH_PIN) &&(FILWIDTH_PIN > -1)
-   static unsigned long raw_filwidth_value = 0;  //added for filament width sensor
-  #endif
+#if defined(FILWIDTH_PIN) &&(FILWIDTH_PIN > -1)
+  static unsigned long raw_filwidth_value = 0;  //added for filament width sensor
+#endif
   
+#ifndef SLOW_PWM_HEATERS
+  /*
+   * standard PWM modulation
+   */
   if(pwm_count == 0){
     soft_pwm_0 = soft_pwm[0];
     if(soft_pwm_0 > 0) { 
       WRITE(HEATER_0_PIN,1);
-      #ifdef HEATERS_PARALLEL
+#ifdef HEATERS_PARALLEL
       WRITE(HEATER_1_PIN,1);
-      #endif
+#endif
     } else WRITE(HEATER_0_PIN,0);
-	
-    #if EXTRUDERS > 1
+    
+#if EXTRUDERS > 1
     soft_pwm_1 = soft_pwm[1];
     if(soft_pwm_1 > 0) WRITE(HEATER_1_PIN,1); else WRITE(HEATER_1_PIN,0);
-    #endif
-    #if EXTRUDERS > 2
+#endif
+#if EXTRUDERS > 2
     soft_pwm_2 = soft_pwm[2];
     if(soft_pwm_2 > 0) WRITE(HEATER_2_PIN,1); else WRITE(HEATER_2_PIN,0);
-    #endif
-    #if defined(HEATER_BED_PIN) && HEATER_BED_PIN > -1
+#endif
+#if defined(HEATER_BED_PIN) && HEATER_BED_PIN > -1
     soft_pwm_b = soft_pwm_bed;
     if(soft_pwm_b > 0) WRITE(HEATER_BED_PIN,1); else WRITE(HEATER_BED_PIN,0);
-    #endif
-    #ifdef FAN_SOFT_PWM
+#endif
+#ifdef FAN_SOFT_PWM
     soft_pwm_fan = fanSpeedSoftPwm / 2;
     if(soft_pwm_fan > 0) WRITE(FAN_PIN,1); else WRITE(FAN_PIN,0);
-    #endif
+#endif
   }
   if(soft_pwm_0 < pwm_count) { 
-      WRITE(HEATER_0_PIN,0);
-      #ifdef HEATERS_PARALLEL
-      WRITE(HEATER_1_PIN,0);
-      #endif
-    }
-  #if EXTRUDERS > 1
+    WRITE(HEATER_0_PIN,0);
+#ifdef HEATERS_PARALLEL
+    WRITE(HEATER_1_PIN,0);
+#endif
+  }
+#if EXTRUDERS > 1
   if(soft_pwm_1 < pwm_count) WRITE(HEATER_1_PIN,0);
-  #endif
-  #if EXTRUDERS > 2
+#endif
+#if EXTRUDERS > 2
   if(soft_pwm_2 < pwm_count) WRITE(HEATER_2_PIN,0);
-  #endif
-  #if defined(HEATER_BED_PIN) && HEATER_BED_PIN > -1
+#endif
+#if defined(HEATER_BED_PIN) && HEATER_BED_PIN > -1
   if(soft_pwm_b < pwm_count) WRITE(HEATER_BED_PIN,0);
-  #endif
-  #ifdef FAN_SOFT_PWM
+#endif
+#ifdef FAN_SOFT_PWM
   if(soft_pwm_fan < pwm_count) WRITE(FAN_PIN,0);
-  #endif
+#endif
+  
+  pwm_count += (1 << SOFT_PWM_SCALE);
+  pwm_count &= 0x7f;
+  
+#else //ifndef SLOW_PWM_HEATERS
+  /*
+   * SLOW PWM HEATERS
+   *
+   * for heaters drived by relay
+   */
+#ifndef MIN_STATE_TIME
+#define MIN_STATE_TIME 16 // MIN_STATE_TIME * 65.5 = time in milliseconds
+#endif
+  if (slow_pwm_count == 0) {
+    // EXTRUDER 0 
+    soft_pwm_0 = soft_pwm[0];
+    if (soft_pwm_0 > 0) {
+      // turn ON heather only if the minimum time is up 
+      if (state_timer_heater_0 == 0) { 
+	// if change state set timer 
+	if (state_heater_0 == 0) {
+	  state_timer_heater_0 = MIN_STATE_TIME;
+	}
+	state_heater_0 = 1;
+	WRITE(HEATER_0_PIN, 1);
+#ifdef HEATERS_PARALLEL
+	WRITE(HEATER_1_PIN, 1);
+#endif
+      }
+    } else {
+      // turn OFF heather only if the minimum time is up 
+      if (state_timer_heater_0 == 0) {
+	// if change state set timer 
+	if (state_heater_0 == 1) {
+	  state_timer_heater_0 = MIN_STATE_TIME;
+	}
+	state_heater_0 = 0;
+	WRITE(HEATER_0_PIN, 0);
+#ifdef HEATERS_PARALLEL
+	WRITE(HEATER_1_PIN, 0);
+#endif
+      }
+    }
+    
+#if EXTRUDERS > 1
+    // EXTRUDER 1
+    soft_pwm_1 = soft_pwm[1];
+    if (soft_pwm_1 > 0) {
+      // turn ON heather only if the minimum time is up 
+      if (state_timer_heater_1 == 0) { 
+	// if change state set timer 
+	if (state_heater_1 == 0) {
+	  state_timer_heater_1 = MIN_STATE_TIME;
+	}
+	state_heater_1 = 1;
+	WRITE(HEATER_1_PIN, 1);
+      }
+    } else {
+      // turn OFF heather only if the minimum time is up 
+      if (state_timer_heater_1 == 0) {
+	// if change state set timer 
+	if (state_heater_1 == 1) {
+	  state_timer_heater_1 = MIN_STATE_TIME;
+	}
+	state_heater_1 = 0;
+	WRITE(HEATER_1_PIN, 0);
+      }
+    }
+#endif
+    
+#if EXTRUDERS > 2
+    // EXTRUDER 2
+    soft_pwm_2 = soft_pwm[2];
+    if (soft_pwm_2 > 0) {
+      // turn ON heather only if the minimum time is up 
+      if (state_timer_heater_2 == 0) { 
+	// if change state set timer 
+	if (state_heater_2 == 0) {
+	  state_timer_heater_2 = MIN_STATE_TIME;
+	}
+	state_heater_2 = 1;
+	WRITE(HEATER_2_PIN, 1);
+      }
+    } else {
+      // turn OFF heather only if the minimum time is up 
+      if (state_timer_heater_2 == 0) {
+	// if change state set timer 
+	if (state_heater_2 == 1) {
+	  state_timer_heater_2 = MIN_STATE_TIME;
+	}
+	state_heater_2 = 0;
+	WRITE(HEATER_2_PIN, 0);
+      }
+    }
+#endif
+    
+#if defined(HEATER_BED_PIN) && HEATER_BED_PIN > -1
+    // BED
+    soft_pwm_b = soft_pwm_bed;
+    if (soft_pwm_b > 0) {
+      // turn ON heather only if the minimum time is up 
+      if (state_timer_heater_b == 0) { 
+	// if change state set timer 
+	if (state_heater_b == 0) {
+	  state_timer_heater_b = MIN_STATE_TIME;
+	}
+	state_heater_b = 1;
+	WRITE(HEATER_BED_PIN, 1);
+      }
+    } else {
+      // turn OFF heather only if the minimum time is up 
+      if (state_timer_heater_b == 0) {
+	// if change state set timer 
+	if (state_heater_b == 1) {
+	  state_timer_heater_b = MIN_STATE_TIME;
+	}
+	state_heater_b = 0;
+	WRITE(HEATER_BED_PIN, 0);
+      }
+    }
+#endif
+  } // if (slow_pwm_count == 0)
+  
+  // EXTRUDER 0 
+  if (soft_pwm_0 < slow_pwm_count) {
+    // turn OFF heather only if the minimum time is up 
+    if (state_timer_heater_0 == 0) { 
+      // if change state set timer 
+      if (state_heater_0 == 1) {
+	state_timer_heater_0 = MIN_STATE_TIME;
+      }
+      state_heater_0 = 0;
+      WRITE(HEATER_0_PIN, 0);
+#ifdef HEATERS_PARALLEL
+      WRITE(HEATER_1_PIN, 0);
+#endif
+    }
+  }
+    
+#if EXTRUDERS > 1
+  // EXTRUDER 1 
+  if (soft_pwm_1 < slow_pwm_count) {
+    // turn OFF heather only if the minimum time is up 
+    if (state_timer_heater_1 == 0) { 
+      // if change state set timer 
+      if (state_heater_1 == 1) {
+	state_timer_heater_1 = MIN_STATE_TIME;
+      }
+      state_heater_1 = 0;
+      WRITE(HEATER_1_PIN, 0);
+    }
+  }
+#endif
+  
+#if EXTRUDERS > 2
+  // EXTRUDER 2
+  if (soft_pwm_2 < slow_pwm_count) {
+    // turn OFF heather only if the minimum time is up 
+    if (state_timer_heater_2 == 0) { 
+      // if change state set timer 
+      if (state_heater_2 == 1) {
+	state_timer_heater_2 = MIN_STATE_TIME;
+      }
+      state_heater_2 = 0;
+      WRITE(HEATER_2_PIN, 0);
+    }
+  }
+#endif
+  
+#if defined(HEATER_BED_PIN) && HEATER_BED_PIN > -1
+  // BED
+  if (soft_pwm_b < slow_pwm_count) {
+    // turn OFF heather only if the minimum time is up 
+    if (state_timer_heater_b == 0) { 
+      // if change state set timer 
+      if (state_heater_b == 1) {
+	state_timer_heater_b = MIN_STATE_TIME;
+      }
+      state_heater_b = 0;
+      WRITE(HEATER_BED_PIN, 0);
+    }
+  }
+#endif
+  
+#ifdef FAN_SOFT_PWM
+  if (pwm_count == 0){
+    soft_pwm_fan = fanSpeedSoftPwm / 2;
+    if (soft_pwm_fan > 0) WRITE(FAN_PIN,1); else WRITE(FAN_PIN,0);
+  }
+  if (soft_pwm_fan < pwm_count) WRITE(FAN_PIN,0);
+#endif
   
   pwm_count += (1 << SOFT_PWM_SCALE);
   pwm_count &= 0x7f;
   
+  // increment slow_pwm_count only every 64 pwm_count circa 65.5ms
+  if ((pwm_count % 64) == 0) {
+    slow_pwm_count++;
+    slow_pwm_count &= 0x7f;
+    
+    // Extruder 0
+    if (state_timer_heater_0 > 0) {
+      state_timer_heater_0--;
+    } 
+  
+#if EXTRUDERS > 1
+    // Extruder 1
+    if (state_timer_heater_1 > 0) 
+      state_timer_heater_1--;
+#endif
+    
+#if EXTRUDERS > 2
+    // Extruder 2
+    if (state_timer_heater_2 > 0) 
+      state_timer_heater_2--;
+#endif
+    
+#if defined(HEATER_BED_PIN) && HEATER_BED_PIN > -1
+    // Bed   
+    if (state_timer_heater_b > 0) 
+      state_timer_heater_b--;
+#endif
+  } //if ((pwm_count % 64) == 0) {
+  
+#endif //ifndef SLOW_PWM_HEATERS
+  
   switch(temp_state) {
     case 0: // Prepare TEMP_0
       #if defined(TEMP_0_PIN) && (TEMP_0_PIN > -1)