0.3.6 ACS712

libraries/ACS712/ACS712.cpp

@@ -1,7 +1,7 @@
 //
 //    FILE: ACS712.cpp
 //  AUTHOR: Rob Tillaart, Pete Thompson
-// VERSION: 0.3.6
+// VERSION: 0.3.7
 //    DATE: 2020-08-02
 // PURPOSE: ACS712 library - current measurement
 //     URL: https://github.com/RobTillaart/ACS712
@@ -133,7 +133,7 @@ float ACS712::mA_AC_sampling(float frequency, uint16_t cycles)
   if (cycles == 0) cycles = 1;
   float sum = 0;
 
-  // float noiseLevel = _noisemV/_mVperStep;
+  //  float noiseLevel = _noisemV/_mVperStep;
 
   for (uint16_t i = 0; i < cycles; i++)
   {
@@ -151,11 +151,11 @@ float ACS712::mA_AC_sampling(float frequency, uint16_t cycles)
       }
       float current = value - _midPoint;
       sumSquared += (current * current);
-      // not adding noise squared might be more correct for small currents.
-      // if (abs(current) > noiseLevel)
-      // {
-      //   sumSquared += (current * current);
-      // }
+      //  not adding noise squared might be more correct for small currents.
+      //  if (abs(current) > noiseLevel)
+      //  {
+      //    sumSquared += (current * current);
+      //  }
     }
     sum += sqrt(sumSquared / samples);
   }
@@ -416,7 +416,7 @@ uint16_t ACS712::getMaximum(uint16_t milliSeconds)
 {
   uint16_t maximum = _analogRead(_pin);
 
-  //  find minimum
+  //  find maximum
   uint32_t start = millis();
   while (millis() - start < milliSeconds)
   {
@@ -444,11 +444,11 @@ void ACS712::setADC(uint16_t (* f)(uint8_t), float volts, uint16_t maxADC)
 //
 uint16_t ACS712::_analogRead(uint8_t pin)
 {
-  //  if extern ADC is defined use it.
+  //  if external ADC is defined use it.
   if (_readADC != NULL) return _readADC(pin);
   return analogRead(pin);
 }
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
 

libraries/ACS712/ACS712.h

@@ -2,7 +2,7 @@
 //
 //    FILE: ACS712.h
 //  AUTHOR: Rob Tillaart, Pete Thompson
-// VERSION: 0.3.6
+// VERSION: 0.3.7
 //    DATE: 2020-08-02
 // PURPOSE: ACS712 library - current measurement
 //     URL: https://github.com/RobTillaart/ACS712
@@ -13,7 +13,7 @@
 
 #include "Arduino.h"
 
-#define ACS712_LIB_VERSION        (F("0.3.6"))
+#define ACS712_LIB_VERSION        (F("0.3.7"))
 
 
 //  ACS712_FF_SINUS == 1.0/sqrt(2) == 0.5 * sqrt(2)
@@ -133,5 +133,5 @@ class ACS712
 };
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
 

libraries/ACS712/CHANGELOG.md

@@ -6,12 +6,17 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.3.7] - 2023-05-20
+- add example **estimateMidPointAC.ino** #37
+- update readme.md (sampling trick #38).
+- minor edits.
+
+
 ## [0.3.6] - 2023-04-19
 - add **autoMidPointDC(cycles)** see issue #35
 - add rounding to **autoMidPoint()**
 - update README.md
 
-
 ## [0.3.5] - 2023-01-18
 - fix #33 failing build => issue 345 created @ arduino-ci
 - redo **setADC()**

libraries/ACS712/examples/ACS712_20_AC/ACS712_20_AC.ino

@@ -19,6 +19,9 @@ ACS712  ACS(A0, 5.0, 1023, 100);
 //  ACS712  ACS(25, 3.3, 4095, 185);
 
 
+uint32_t start, stop;
+
+
 void setup()
 {
   Serial.begin(115200);
@@ -27,6 +30,10 @@ void setup()
   Serial.print("ACS712_LIB_VERSION: ");
   Serial.println(ACS712_LIB_VERSION);
 
+
+  //  use simulation
+  ACS.setADC(signal, 5, 1024);
+
   ACS.autoMidPoint();
   Serial.print("MidPoint: ");
   Serial.print(ACS.getMidPoint());
@@ -37,13 +44,27 @@ void setup()
 
 void loop()
 {
-  int mA = ACS.mA_AC();
+  delay(100);
+  start = micros();
+  //  int mA = ACS.mA_AC();
+  int mA = ACS.mA_AC_sampling();
+  stop = micros();
   Serial.print("mA: ");
   Serial.print(mA);
   Serial.print(". Form factor: ");
-  Serial.println(ACS.getFormFactor());
+  Serial.print(ACS.getFormFactor());
+  Serial.print("  time: ");
+  Serial.println(stop - start);
+  delay(5000);
 }
 
 
-// -- END OF FILE --
+//  simulated 50 Hz signal
+uint16_t signal(uint8_t p)
+{
+  return 512 + 400 * sin((micros() % 1000000) * (TWO_PI * 50 / 1e6));
+}
+
+
+//  -- END OF FILE --
 

libraries/ACS712/examples/ACS712_20_AC_simulation/ACS712_20_AC_simulation.ino

@@ -0,0 +1,66 @@
+//
+//    FILE: ACS712_20_AC_simulation.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: demo AC measurement with point to point
+//     URL: https://github.com/RobTillaart/ACS712
+
+
+#include "ACS712.h"
+
+
+//  Arduino UNO has 5.0 volt with a max ADC value of 1023 steps
+//  ACS712 5A  uses 185 mV per A
+//  ACS712 20A uses 100 mV per A
+//  ACS712 30A uses  66 mV per A
+
+
+ACS712  ACS(A0, 5.0, 1023, 100);
+//  ESP 32 example (might requires resistors to step down the logic voltage)
+//  ACS712  ACS(25, 3.3, 4095, 185);
+
+
+uint32_t start, stop;
+
+
+void setup()
+{
+  Serial.begin(115200);
+  while (!Serial);
+  Serial.println(__FILE__);
+  Serial.print("ACS712_LIB_VERSION: ");
+  Serial.println(ACS712_LIB_VERSION);
+
+  //  select simulated signal
+  ACS.setADC(signal, 5, 1024);
+
+  ACS.autoMidPoint();
+  Serial.print("MidPoint: ");
+  Serial.print(ACS.getMidPoint());
+  Serial.print(". Noise mV: ");
+  Serial.println(ACS.getNoisemV());
+}
+
+
+void loop()
+{
+  delay(100);
+  start = micros();
+  //  int mA = ACS.mA_AC();
+  int mA = ACS.mA_AC_sampling(50);
+  stop = micros();
+  Serial.print("mA: ");
+  Serial.print(mA);
+  Serial.print("  time: ");
+  Serial.println(stop - start);
+  delay(5000);
+}
+
+
+//  simulation.
+uint16_t signal(uint8_t p)
+{
+  return round(512 + 400 * sin((micros() % 1000000) * (TWO_PI * 50 / 1e6)));
+}
+
+
+//  -- END OF FILE --

libraries/ACS712/examples/estimateMidPointAC/estimateMidPointAC.ino

@@ -0,0 +1,89 @@
+//    FILE: estimateMidPointAC.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: experimental 
+//     URL: https://github.com/RobTillaart/ACS712/issues/37
+//
+//  Estimates the midpoint by taking many (short-blocking) samples
+//  instead of many samples in a long blocking period.
+//  The function adjusts the confidence (or quality) of the midpoint 
+//  depending on the value read.
+//  This code is experimental and meant to investigate a non-blocking
+//  way to find the midPoint for the ACS712 when measuring AC currents.
+//
+//  It will not be included in the library
+//
+//  Use with care.
+
+
+#include "Arduino.h"
+
+
+uint32_t start, stop;
+int _pin = A0;
+uint32_t count = 0;
+volatile uint16_t mp;
+float conf = 0;
+
+
+uint16_t estimateMidPointAC(float &confidence, bool reset = false)
+{
+  static bool _firstCall = true;
+  static float _minimum, _maximum, _confidence;
+
+  int value = analogRead(_pin);
+  if (_firstCall || reset)
+  {
+    _firstCall = false;
+    _minimum = _maximum = value;
+    _confidence = 0;
+    confidence = _confidence;
+    return _minimum;
+  }
+  if (value > _maximum)
+  {
+    _maximum = value;
+    _confidence /= 2;
+  }
+  else if (value < _minimum)
+  {
+    _minimum = value;
+    _confidence /= 2;
+  }
+  else if (_confidence < 100)
+  {
+    _confidence += 1;
+  }
+  confidence = _confidence;
+  return (_minimum + _maximum) / 2;
+}
+
+
+void setup()
+{
+  Serial.begin(115200);
+  while (!Serial);
+  Serial.println(__FILE__);
+}
+
+
+void loop()
+{
+  count++;
+  start = micros();
+  mp = estimateMidPointAC(conf, true);
+  stop = micros();
+  Serial.print(millis());
+  Serial.print("\t");
+  Serial.print(count);
+  Serial.print("\t");
+  Serial.print(conf);
+  Serial.print("\t");
+  Serial.print(mp);
+  Serial.print("\t");
+  Serial.print(stop - start);
+  Serial.println();
+  delay(random(100));
+}
+
+
+//  -- END OF FILE --

libraries/ACS712/library.json

@@ -21,7 +21,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/ACS712.git"
   },
-  "version": "0.3.6",
+  "version": "0.3.7",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*",

libraries/ACS712/library.properties

@@ -1,5 +1,5 @@
 name=ACS712
-version=0.3.6
+version=0.3.7
 author=Rob Tillaart <rob.tillaart@gmail.com>, Pete Thompson <pete.thompson@yahoo.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=ACS712 library for Arduino.

libraries/ACS712/readme.md

@@ -112,6 +112,11 @@ Not tested, but looks compatible - same formula as above
 
 ## Interface
 
+```cpp
+#include ACS712.h
+```
+
+
 #### Base
 
 - **ACS712(uint8_t analogPin, float volts = 5.0, uint16_t maxADC = 1023, float mVperAmpere = 100)** constructor.
@@ -141,6 +146,23 @@ A negative value indicates the current flows in the opposite direction.
   - 0.2.8 the parameter samples allow to average over a number of samples.
 
 
+#### mA_AC_sampling performance trick.
+
+A trick to sample faster is to set the frequency to 2 times the actual frequency so to 100 or 120 Hz.
+This results in sampling only half a period and the same current will be measured.
+Advantage is that the function only blocks for ~10 ms @ 50Hz (8.5 @ 60Hz).
+The drawback is about 4x as many variation.
+So only use if the performance (or less blocking) is needed.
+
+In a similar way one can increase the accuracy (reducing the variation) 
+by setting the frequency a factor 2 lower (25 and 30 Hz).
+Drawback is a far longer blocking time.
+
+Use with care!
+
+See - https://github.com/RobTillaart/ACS712/issues/38
+
+
 #### Midpoint
 
 The midpoint is the (raw) zero-reference for all current measurements.
@@ -153,7 +175,7 @@ Since 0.3.0 all midpoint functions return the actual midPoint.
 Parameter must be between 0 and maxADC/2, otherwise midpoint is not changed.
 - **uint16_t getMidPoint()** read the value set / determined.
 - **uint16_t incMidPoint()** manual increase midpoint, e.g. useful in an interactive application.
-Will not increase if midpoint equals macADC.
+Will not increase if midpoint equals maxADC.
 - **uint16_t decMidPoint()** manual decrease midpoint.
 Will not decrease if midpoint equals 0.
 - **uint16_t resetMidPoint()** resets the midpoint to the initial value of maxADC / 2 as in the constructor.