Penn Electric / LinearAnalogSensors

This library is designed to work with devices like the LM335 temperature sensor. There are only two requirements for compatibility: 1) The device must be a sensor device that has an analog voltage output. 2) The physical quantity measured must vary linearly with the analog voltage. The LM335 creates an analog voltage proportional to temperature. It can work very well with this library using the nominal multiplier of 0.0050354 and offset of -273.15 or by providing two user defined calibration points to the constructor. It uses a median filter to remove unwanted noise from ADC readings.

Dependents:   mbed_measuring_temperature

LinearTemp.h@1:7ce89c2ecf05, 2012-12-23 (annotated)

Committer:
PennElectric
Date:
Sun Dec 23 07:29:42 2012 +0000
Revision:
1:7ce89c2ecf05
Parent:
0:d84ef842074b
Child:
2:989048937c77
updated auto doc

Who changed what in which revision?

UserRevisionLine numberNew contents of line
PennElectric 0:d84ef842074b 1 /* Copyright (c) <2012> <P. Patel>, MIT License
PennElectric 0:d84ef842074b 2 *
PennElectric 0:d84ef842074b 3 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
PennElectric 0:d84ef842074b 4 * and associated documentation files (the "Software"), to deal in the Software without restriction,
PennElectric 0:d84ef842074b 5 * including without limitation the rights to use, copy, modify, merge, publish, distribute,
PennElectric 0:d84ef842074b 6 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
PennElectric 0:d84ef842074b 7 * furnished to do so, subject to the following conditions:
PennElectric 0:d84ef842074b 8 *
PennElectric 0:d84ef842074b 9 * The above copyright notice and this permission notice shall be included in all copies or
PennElectric 0:d84ef842074b 10 * substantial portions of the Software.
PennElectric 0:d84ef842074b 11 *
PennElectric 0:d84ef842074b 12 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
PennElectric 0:d84ef842074b 13 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
PennElectric 0:d84ef842074b 14 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
PennElectric 0:d84ef842074b 15 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
PennElectric 0:d84ef842074b 16 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
PennElectric 0:d84ef842074b 17 */
PennElectric 0:d84ef842074b 18
PennElectric 0:d84ef842074b 19 // --------------------- Median Filtered Linear Temperature Sensor Reader ------------------------
PennElectric 0:d84ef842074b 20
PennElectric 0:d84ef842074b 21 #ifndef LINEAR_TEMP
PennElectric 0:d84ef842074b 22 #define LINEAR_TEMP
PennElectric 0:d84ef842074b 23
PennElectric 0:d84ef842074b 24 #include "mbed.h"
PennElectric 0:d84ef842074b 25 /** This library is designed to work with devices like the LM335 temperature sensor. There are only
PennElectric 0:d84ef842074b 26 * two requirements for compatibility of a device with this library: 1) It must be a sensor device
PennElectric 0:d84ef842074b 27 * that has an analog voltage output. 2) The physical quantity measured must vary linearly with
PennElectric 0:d84ef842074b 28 * the analog voltage. The LM335 which creates an analog voltage proportional to temperature
PennElectric 0:d84ef842074b 29 * can work very well with this library using the nominal multiplier of 0.0050354 and offset of
PennElectric 0:d84ef842074b 30 * -273.15 or by providing two calibration points to the constuctor to generate a linear response. It
PennElectric 0:d84ef842074b 31 * samples the sensor 9 times and uses the median to minimize the effect of poor ADC readings and sudden
PennElectric 0:d84ef842074b 32 * changes.
PennElectric 0:d84ef842074b 33 *
PennElectric 0:d84ef842074b 34 * Example:
PennElectric 0:d84ef842074b 35 * @code
PennElectric 0:d84ef842074b 36 * LinearTemp mysensor(p20, 0.0050354, -273.15); // Setup a LM335 temp sensor on pin 20
PennElectric 0:d84ef842074b 37 * DigitalOut myled(LED1);
PennElectric 0:d84ef842074b 38 *
PennElectric 0:d84ef842074b 39 * int main() {
PennElectric 0:d84ef842074b 40 * while(1) {
PennElectric 0:d84ef842074b 41 * // Light LED if filtered temperature is greater than 45 degrees Celsius
PennElectric 0:d84ef842074b 42 * if (mysensor > 45) myled = 1;
PennElectric 0:d84ef842074b 43 * else myled = 0;
PennElectric 0:d84ef842074b 44 * }
PennElectric 0:d84ef842074b 45 * }
PennElectric 0:d84ef842074b 46 * @endcode
PennElectric 0:d84ef842074b 47 */
PennElectric 0:d84ef842074b 48 class LinearTemp {
PennElectric 0:d84ef842074b 49 public:
PennElectric 0:d84ef842074b 50 /** Create a calibrated temperature sensor object connected to an Analog input pin
PennElectric 0:d84ef842074b 51 * @param pin Analog input pin to which an LM335 or comparable linear temp sensor is connected
PennElectric 0:d84ef842074b 52 * @param temp1 Temperature (float in degrees C or F) of first calibration point
PennElectric 0:d84ef842074b 53 * @param read1 Mbed ADC reading (unsigned short) of first calibration point
PennElectric 0:d84ef842074b 54 * @param temp2 Temperature (float in degrees C or F) of second calibration point
PennElectric 0:d84ef842074b 55 * @param read2 Mbed ADC reading (unsigned short) of second calibration point
PennElectric 0:d84ef842074b 56 */
PennElectric 0:d84ef842074b 57 LinearTemp(PinName pin, float temp1, unsigned short read1, float temp2, unsigned short read2);
PennElectric 0:d84ef842074b 58 /** Create a calibrated temperature sensor object connected to an Analog input pin
PennElectric 0:d84ef842074b 59 * @param pin Analog input pin to which an LM335 or comparable linear temp sensor is connected
PennElectric 0:d84ef842074b 60 * @param multiplier Conversion multiplier to go from ADC reading as unsigned short to temperature (change in degrees / change in unsigned short)
PennElectric 0:d84ef842074b 61 * @param offset Conversion offset (positive or negative)
PennElectric 0:d84ef842074b 62 */
PennElectric 0:d84ef842074b 63 LinearTemp(PinName pin, float multiplier, float offset);
PennElectric 1:7ce89c2ecf05 64 /** Returns a new median-filtered, converted reading from the sensor
PennElectric 1:7ce89c2ecf05 65 * @returns New temperature (float) in degrees C or F as designated by the calibration points
PennElectric 1:7ce89c2ecf05 66 */
PennElectric 0:d84ef842074b 67 float readTemp();
PennElectric 0:d84ef842074b 68 /** Return the last calculated and stored temperature
PennElectric 0:d84ef842074b 69 * @returns Last stored temperature (float) in degrees C or F as designated by the calibration points
PennElectric 0:d84ef842074b 70 */
PennElectric 0:d84ef842074b 71 float getTemp();
PennElectric 0:d84ef842074b 72 #ifdef MBED_OPERATORS
PennElectric 0:d84ef842074b 73 /** An operator shorthand for readTemp() to calculate filtered temperature
PennElectric 0:d84ef842074b 74 */
PennElectric 0:d84ef842074b 75 operator int() {
PennElectric 0:d84ef842074b 76 return readTemp();
PennElectric 0:d84ef842074b 77 }
PennElectric 0:d84ef842074b 78 #endif
PennElectric 0:d84ef842074b 79 private:
PennElectric 0:d84ef842074b 80 AnalogIn _pin;
PennElectric 0:d84ef842074b 81 unsigned short _tempArr[9];
PennElectric 0:d84ef842074b 82 float _temp;
PennElectric 0:d84ef842074b 83 float _multiplier;
PennElectric 0:d84ef842074b 84 float _offset;
PennElectric 0:d84ef842074b 85 };
PennElectric 0:d84ef842074b 86 #endif