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https://github.com/RobTillaart/Arduino.git
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57 lines
1.4 KiB
C++
57 lines
1.4 KiB
C++
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//
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// FILE: ACS712.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.1.1
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// DATE: 2020-03-17
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// PURPOSE: ACS712 library - current measurement
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//
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// HISTORY:
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// 0.1.0 2020-03-17 initial version
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// 0.1.1 2020-03-18 first release version
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//
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// Released to the public domain
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//
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#include "ACS712.h"
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ACS712::ACS712(uint8_t analogPin, float volts, uint16_t maxADC, uint8_t mVperA)
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{
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_pin = analogPin;
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// 1x 1000 for V -> mV
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_mVpstep = 1000.0 * volts / maxADC;
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_mVperAmpere = mVperA;
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_formFactor = 0.70710678119; // 0.5 * sqrt(2); TODO: should be smaller in practice 0.5 ?
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_midPoint = maxADC / 2;
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}
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int ACS712::mA_AC()
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{
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uint32_t start = micros();
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int _min, _max;
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_min = _max = analogRead(_pin);
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while (micros() - start < 20000) // UNO ~180 samples...
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{
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int val = analogRead(_pin);
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if (val < _min) _min = val;
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if (val > _max) _max = val;
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}
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int p2p = (_max - _min);
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// TODO determine _formFactor
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// two counters, a threshold and math is needed
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// D = (1.0 - #samples close to zero ) / #samples
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// FF = D * 0.5 * sqrt(2);
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// math could be partially precalculated
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return 1000.0 * 0.5 * p2p * _mVpstep * _formFactor / _mVperAmpere;
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}
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int ACS712::mA_DC()
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{
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// read twice to stabilize...
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analogRead(_pin);
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int steps = analogRead(_pin) - _midPoint;
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return 1000.0 * steps * _mVpstep / _mVperAmpere;
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}
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// END OF FILE
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