From 36fb16274bc34bba794a3f0d537d5d890794ea1f Mon Sep 17 00:00:00 2001
From: "J.M. Dana" <jmdana@gmail.com>
Date: Fri, 2 Oct 2015 21:50:43 +0100
Subject: [PATCH 1/3] DHT::computeHeatIndex has been modified so it uses both
 Rothfusz and Steadman's equations. As a result, it allows a larger range of
 temperatures and more accurate results for extreme conditions.

---
 DHT.cpp | 36 +++++++++++++++++++-----------------
 1 file changed, 19 insertions(+), 17 deletions(-)

diff --git a/DHT.cpp b/DHT.cpp
index c2257d0..6431f1c 100644
--- a/DHT.cpp
+++ b/DHT.cpp
@@ -88,23 +88,17 @@ float DHT::readHumidity(bool force) {
 
 //boolean isFahrenheit: True == Fahrenheit; False == Celcius
 float DHT::computeHeatIndex(float temperature, float percentHumidity, bool isFahrenheit) {
-  // Adapted from equation at: https://github.com/adafruit/DHT-sensor-library/issues/9 and
-  // Wikipedia: http://en.wikipedia.org/wiki/Heat_index
-  if (!isFahrenheit) {
-    // Celsius heat index calculation.
-    return -8.784695 +
-             1.61139411 * temperature +
-             2.338549   * percentHumidity +
-            -0.14611605 * temperature*percentHumidity +
-            -0.01230809 * pow(temperature, 2) +
-            -0.01642482 * pow(percentHumidity, 2) +
-             0.00221173 * pow(temperature, 2) * percentHumidity +
-             0.00072546 * temperature*pow(percentHumidity, 2) +
-            -0.00000358 * pow(temperature, 2) * pow(percentHumidity, 2);
-  }
-  else {
-    // Fahrenheit heat index calculation.
-    return -42.379 +
+  // Using both Rothfusz and Steadman's equations
+  // http://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml
+  float hi;
+
+  if (!isFahrenheit)
+    temperature = convertCtoF(temperature);
+
+  hi = 0.5 * (temperature + 61.0 + ((temperature - 68.0) * 1.2) + (percentHumidity * 0.094)); 
+
+  if (hi > 79) {
+    hi = -42.379 +
              2.04901523 * temperature +
             10.14333127 * percentHumidity +
             -0.22475541 * temperature*percentHumidity +
@@ -113,7 +107,15 @@ float DHT::computeHeatIndex(float temperature, float percentHumidity, bool isFah
              0.00122874 * pow(temperature, 2) * percentHumidity +
              0.00085282 * temperature*pow(percentHumidity, 2) +
             -0.00000199 * pow(temperature, 2) * pow(percentHumidity, 2);
+
+    if((percentHumidity < 13) && (temperature >= 80.0) && (temperature <= 112.0))
+      hi -= ((13.0 - percentHumidity) / 4.0) * sqrt((17.0 - abs(temperature - 95.0))/17.0);
+
+    else if((percentHumidity > 85.0) && (temperature >= 80.0) && (temperature <= 87.0))
+      hi += ((percentHumidity - 85.0) / 10.0) * ((87.0 - temperature)/5.0);
   }
+
+  return isFahrenheit ? hi : convertFtoC(hi);
 }
 
 boolean DHT::read(bool force) {

From 51a8b814acb4ecf0f851fa89e2f480ac3672f1dd Mon Sep 17 00:00:00 2001
From: "J.M. Dana" <jmdana@gmail.com>
Date: Sat, 3 Oct 2015 13:42:09 +0100
Subject: [PATCH 2/3] Divisions have been replaced by multiplications.

---
 DHT.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/DHT.cpp b/DHT.cpp
index 6431f1c..bdd8161 100644
--- a/DHT.cpp
+++ b/DHT.cpp
@@ -109,10 +109,10 @@ float DHT::computeHeatIndex(float temperature, float percentHumidity, bool isFah
             -0.00000199 * pow(temperature, 2) * pow(percentHumidity, 2);
 
     if((percentHumidity < 13) && (temperature >= 80.0) && (temperature <= 112.0))
-      hi -= ((13.0 - percentHumidity) / 4.0) * sqrt((17.0 - abs(temperature - 95.0))/17.0);
+      hi -= ((13.0 - percentHumidity) * 0.25) * sqrt((17.0 - abs(temperature - 95.0)) * 0.05882);
 
     else if((percentHumidity > 85.0) && (temperature >= 80.0) && (temperature <= 87.0))
-      hi += ((percentHumidity - 85.0) / 10.0) * ((87.0 - temperature)/5.0);
+      hi += ((percentHumidity - 85.0) * 0.1) * ((87.0 - temperature) * 0.2);
   }
 
   return isFahrenheit ? hi : convertFtoC(hi);

From c57f0c8c290cb3d882fecb454df7cdb52d85ce01 Mon Sep 17 00:00:00 2001
From: Tony DiCola <tony@tonydicola.com>
Date: Mon, 5 Oct 2015 17:54:59 -0700
Subject: [PATCH 3/3] Bump version to 1.2.1

---
 library.properties | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library.properties b/library.properties
index 49c992d..9e77fc5 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=DHT sensor library
-version=1.2.0
+version=1.2.1
 author=Adafruit
 maintainer=Adafruit <info@adafruit.com>
 sentence=Arduino library for DHT11, DHT22, etc Temp & Humidity Sensors