ACS712.h

00001 #include <mbed.h>
00002 /** A Hall-Effect sensor for measuring current levels in a given path
00003  *
00004  * Can be used as a current detector
00005  *
00006  * Example:
00007  * @code
00008  * // Periodically read current levels in a circuit and
00009  * // send output to PC terminal
00010  *
00011  * #include "mbed.h"
00012  * #include "ACS712.h"
00013  *
00014  * // Connect the sensor analog output pin to mbed's AnalogIn pin
00015  * ACS712 dev(p18);
00016  * // Connect mbed to pc's USB port
00017  * Serial pc(USBTX, USBRX);
00018  *
00019  * int main() {
00020  *      pc.printf("Sensor Log: \n\n\r");
00021  *      while (1) {
00022  *          // Read current from sensor and output to pc terminal
00023  *          pc.printf("Sensor Value: %2.2f A\n\r", dev);
00024  *          wait(0.200);
00025  *      }
00026  * }
00027  * @endcode
00028  */
00029  
00030 class ACS712 { 
00031     
00032     public:
00033         /** Create a hall-effect sensor of the specified type
00034          *
00035          * @param _pin mbed AnalogIn pin where the analog output of sensor is connected
00036          * @param voltDivRatio resistor voltage division ratio at output of the sensor
00037          * @param type type of ACS712 sensor used
00038          *
00039          * @note Supported types of sensors:
00040          */
00041         ACS712(PinName _pin, float voltDivRatio = 1, short type = 5);
00042         
00043         /** Read the value of the measured current in amps
00044          *
00045          * @return current value in amps
00046          */
00047         float read();
00048 
00049         
00050         /** Read the value of the measured current in amps
00051          *  Allows the ACS712 object to be used in a float context
00052          * 
00053          * @return current value in amps
00054          */
00055         operator float() { return read(); 
00056         
00057         
00058         ACS712& operator=(const ACS712&);
00059         }
00060         
00061     private:
00062         AnalogIn sensor;
00063         float translate(float);
00064         float ratio;
00065         short type;
00066 
00067 };
00068 
00069 ACS712::ACS712(PinName _pin, float voltDivRatio, short sensorType) : sensor(_pin){
00070     ratio = voltDivRatio;
00071     type = sensorType;    
00072 }
00073 
00074 float ACS712::translate(float val){
00075     switch(type){
00076         case 5: 
00077             return (val*ratio - 2.46*ratio)/(.185*ratio);
00078         case 20:
00079             return (val*ratio - 2.46*ratio)/(.1*ratio);
00080         case 30:
00081             return (val*ratio - 2.46*ratio)/(.066*ratio);
00082         default:
00083             return 999;
00084     }
00085 }
00086 
00087 
00088 float ACS712::read(){
00089     return ACS712::translate(sensor * 3.3);   
00090 }
00091 
00092 ACS712& ACS712::operator=(const ACS712& rhs){
00093     sensor = rhs.sensor;
00094     ratio = rhs.ratio;
00095     type = rhs.type;
00096     return *this;
00097 }