87 lines
2.8 KiB
Python
87 lines
2.8 KiB
Python
from grove.adc import ADC
|
|
from time import sleep as delay
|
|
VoutArray = [ 0.0011498, 0.0033908, 0.011498, 0.041803,0.15199, 0.53367, 1.3689, 1.9068, 2.3]
|
|
LuxArray = [ 1.0108, 3.1201, 9.8051, 27.43, 69.545, 232.67, 645.11, 73.52, 1000]
|
|
|
|
|
|
|
|
class LuminanceSensorPI:
|
|
"""
|
|
Represents a luminance sensor created with an analog channel
|
|
In this projet, it is supposed to be exactly 2 LuminanceSensorPI for 1 PlantPI
|
|
"""
|
|
def __init__(self,channel):
|
|
self.channel = channel
|
|
|
|
def _readVout(self):
|
|
vout = ADC().read(self.channel) * (3.0 / 1023.0)
|
|
# Above 2.3V , the sensor value is saturated
|
|
return vout
|
|
|
|
def readLuminance(self):
|
|
# MeasuredVout = ADC Value * (Vcc / 1023) * (3 / Vcc)
|
|
# Vout samples are with reference to 3V Vcc
|
|
# The above expression is simplified by cancelling out Vcc
|
|
measuredVout = self._readVout()
|
|
luminance = self.FmultiMap(measuredVout, VoutArray, LuxArray, 9)
|
|
|
|
"""
|
|
|
|
The Luminance in Lux is calculated based on APDS9002 datasheet -- > Graph 1
|
|
( Output voltage vs. luminance at different load resistor)
|
|
The load resistor is 1k in this board. Vout is referenced to 3V Vcc.
|
|
|
|
The data from the graph is extracted using WebPlotDigitizer
|
|
http://arohatgi.info/WebPlotDigitizer/app/
|
|
|
|
VoutArray[] and LuxArray[] are these extracted data. Using MultiMap, the data
|
|
is interpolated to get the Luminance in Lux.
|
|
|
|
This implementation uses floating point arithmetic and hence will consume
|
|
more flash, RAM and time.
|
|
|
|
The Luminance in Lux is an approximation and depends on the accuracy of
|
|
Graph 1 used.
|
|
|
|
"""
|
|
return luminance
|
|
|
|
|
|
|
|
# This code uses MultiMap implementation from http://playground.arduino.cc/Main/MultiMap
|
|
|
|
def FmultiMap(self,val, _in, _out, size):
|
|
"""
|
|
The method wich convert the Tension VOut to an accurate corresponding value in Lux
|
|
"""
|
|
|
|
# take care the value is within range
|
|
# val = constrain(val, _in[0], _in[size-1])
|
|
if val <= _in[0]:
|
|
return _out[0]
|
|
if val >= _in[size-1]:
|
|
return _out[size-1]
|
|
|
|
# search right interval
|
|
pos = 1 # _in[0] allready tested
|
|
while val > _in[pos]:
|
|
pos += 1
|
|
|
|
# this will handle all exact "points" in the _in array
|
|
if val == _in[pos]:
|
|
return _out[pos]
|
|
|
|
#interpolate in the right segment for the rest
|
|
return (val - _in[pos-1]) * (_out[pos] - _out[pos-1]) / (_in[pos] - _in[pos-1]) + _out[pos-1]
|
|
|
|
|
|
def main():
|
|
sensor1 = LuminanceSensorPI(2)
|
|
while True:
|
|
print("[Tension capteur] {}".format(sensor1._readVout()))
|
|
print("[Lux] {}".format(sensor1.readLuminance()))
|
|
delay(1)
|
|
|
|
if __name__ == "__main__":
|
|
main()
|