diff --git a/libraries/Max44009/Max44009.h b/libraries/Max44009/Max44009.h
index 1e6ba37c..433d4188 100644
--- a/libraries/Max44009/Max44009.h
+++ b/libraries/Max44009/Max44009.h
@@ -2,7 +2,7 @@
 
 //    FILE: Max44009.h
 //  AUTHOR: Rob dot Tillaart at gmail dot com
-// VERSION: 0.5.1
+// VERSION: 0.5.2
 // PURPOSE: library for MAX44009 lux sensor Arduino
 // HISTORY: See Max440099.cpp
 
@@ -32,7 +32,7 @@
 #include "Arduino.h"
 
 
-#define MAX44009_LIB_VERSION                  (F("0.5.1"))
+#define MAX44009_LIB_VERSION                  (F("0.5.2"))
 
 #define MAX44009_DEFAULT_ADDRESS              0x4A
 #define MAX44009_ALT_ADDRESS                  0x4B
@@ -123,7 +123,7 @@ public:
   float   convertToLux(uint8_t datahigh, uint8_t datalow);
 
 
-private:
+protected:
   bool    setThreshold(uint8_t reg, float value);
   float   getThreshold(uint8_t reg);
 
diff --git a/libraries/Max44009/library.json b/libraries/Max44009/library.json
index d62c2bc9..7e4811e9 100644
--- a/libraries/Max44009/library.json
+++ b/libraries/Max44009/library.json
@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/Max44009.git"
   },
-  "version": "0.5.1",
+  "version": "0.5.2",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*",
diff --git a/libraries/Max44009/library.properties b/libraries/Max44009/library.properties
index fbe0b506..c74df425 100644
--- a/libraries/Max44009/library.properties
+++ b/libraries/Max44009/library.properties
@@ -1,5 +1,5 @@
 name=Max44009
-version=0.5.1
+version=0.5.2
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Library for MAX44009 I2C LUX sensor Arduino. 
diff --git a/libraries/Max44009/max44009.cpp b/libraries/Max44009/max44009.cpp
index f72e30f5..ec4cd237 100644
--- a/libraries/Max44009/max44009.cpp
+++ b/libraries/Max44009/max44009.cpp
@@ -1,18 +1,19 @@
 //
 //    FILE: Max44009.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.5.1
+// VERSION: 0.5.2
 // PURPOSE: library for MAX44009 lux sensor Arduino
 //     URL: https://github.com/RobTillaart/MAX44009
 //
 //  HISTORY
 //
+//  0.5.2   2022-01-05  minor edits after creating Max44007 library
 //  0.5.1   2021-12-21  update library.json, license, minor edits
 //  0.5.0   2021-06-04  fix exponent math.
-//  0.4.4   2021-05-27  arduino-lint
-//  0.4.3   2020-12-30  arduino-ci, unit test
+//  0.4.4   2021-05-27  Arduino-lint
+//  0.4.3   2020-12-30  Arduino-CI, unit test
 //  0.4.2   2020-06-19  fix library.json
-//  0.4.1   2020-03-21  #pragma, readme.nd, license.md
+//  0.4.1   2020-03-21  #pragma, readme.md, license.md
 //  0.4.0   2020-01-30  remove automatic mode from constructors;
 //                      added example code
 //  0.3.3   2020-01-27  issue #140 refactor constructors / configure
@@ -40,6 +41,10 @@
 
 #include "Max44009.h"
 
+// MAX44007 KEY VALUES
+#define MAX44009_MIN_LUX                       (0.045)
+#define MAX44009_MAX_LUX                       (188006.0)
+
 
 #if defined(ESP8266) || defined(ESP32)
 Max44009::Max44009(const uint8_t address, const uint8_t dataPin, const uint8_t clockPin)
@@ -216,7 +221,7 @@ float Max44009::convertToLux(uint8_t datahigh, uint8_t datalow)
 {
   uint8_t  exponent = datahigh >> 4;
   uint32_t mantissa = ((datahigh & 0x0F) << 4) + (datalow & 0x0F);
-  float lux = ((0x0001 << exponent) * 0.045) * mantissa;
+  float lux = ((0x0001 << exponent) * MAX44009_MIN_LUX) * mantissa;
   return lux;
 }
 
@@ -228,9 +233,9 @@ float Max44009::convertToLux(uint8_t datahigh, uint8_t datalow)
 bool Max44009::setThreshold(const uint8_t reg, const float value)
 {
   // CHECK RANGE OF VALUE
-  if ((value < 0.0) || (value > 188006)) return false;
+  if ((value < 0.0) || (value > MAX44009_MAX_LUX)) return false;
 
-  uint32_t mantissa = round(value * 22.2222222);     // was round(value / 0.045);  multiply is faster.
+  uint32_t mantissa = round(value * (1.0 / MAX44009_MIN_LUX));     //  compile time optimized.
   uint8_t exponent = 0;
   while (mantissa > 255)
   {
diff --git a/libraries/Max44009/readme.md b/libraries/Max44009/readme.md
index 351a6cf4..ef6c976c 100644
--- a/libraries/Max44009/readme.md
+++ b/libraries/Max44009/readme.md
@@ -18,6 +18,8 @@ a.k.a. GY-49
 The MAX44009 ambient light sensor is an I2C sensor, that has a 22 bit 
 dynamic range from 0.045 lux to 188,000 lux.
 
+relates to https://github.com/RobTillaart/Max44007 
+
 
 ## Schema breakout max44009 / GY-49
 
@@ -176,5 +178,10 @@ right address and sometimes not. (been there ;)
 ## Future
 
 - improve documentation
-- 
+- merge MAX44007 library in the future. (shared base class?)
 
+
+#### MAX44007
+
+The MAX44007 is an almost identical sensor that uses a step size of 0.025.
+That implies the library is not useable 1 to 1 for the MAX4007, however some