UV sensor ML8511

[visnja30]

Hi to all and Happy New year.
Today I receive a UV sensor ML 8511.
Watching his datasheet the output voltage is linear to intensity of the UV light.
How to measured voltage convert into a UV index.
Supply voltage PIC and the sensor is 5.0V
AD conversion is 10 bit and I use 18F4520 chip




Code example to measure voltage:

' ** Setup the ADCIN Defines **

Define ADC_BITS 10 ' Set resolution of conversion
Define ADC_CLOCK 2 ' Set clock source (x/FOSC or FRC)
Define ADC_SAMPLEUS 50 ' Set sampling time (in uS)




' ** Declare the Variables **

AD_Raw Var Word ' 10-bit result of A/D conversion
AD_Result Var Word ' Quantasized ADC result
Average Var Word ' Variable for building up the average result
Samples Var Byte ' Amount of samples taken
Volts Var Byte ' Holds the Volts part of the result (only for display purposes)
Millivolts Var Word ' Holds the Millivolts part of the result (only for display purposes)



' quanta level = (5/1024) * 256 == 1250
Quanta Con 1250
' ** Define the bits within the ADCON1 register **

ADFM Var ADCON1.7 ' ADC result fotmat select bit
PCFG3 Var ADCON1.3 ' ADC port configuration bit
PCFG2 Var ADCON1.2 ' ADC port configuration bit
PCFG1 Var ADCON1.1 ' ADC port configuration bit
PCFG0 Var ADCON1.0 ' ADC port configuration bit




PCFG0=0
PCFG1=1
PCFG2=0
PCFG3=0 ' Configure for AN0-AN4 as analogue input
ADFM=1 ' Right justified result in ADRESL and ADRESH

' ** THE MAIN PROGRAM STARTS HERE **
main:

Average=0 ' Clear the Average variable befor use
For Samples=0 to 9 ' We will take 10 samples of the ADC
ADCIN 1,AD_Raw ' Place the conversion of channel0 into AD_RAW
Average=Average+AD_Raw ' Build up the Average result
Next ' Close the loop
Average=Average/10 ' Calculate the average by dividing by the number of samples taken
AD_Result=(Average) */ Quanta ' Quantasize the result

Volts= AD_Result/100 ' Calculate the Volts part of the result
Millivolts=AD_Result//100 ' Calculate the Millivolts part of the result


Lcdout $fe, 2 '
Lcdout "Napon = ", DEC volts, ".",dec Millivolts, "V" '

pause 100

goto main

[Gusse]

How to measured voltage convert into a UV index.
Supply voltage PIC and the sensor is 5.0V

UV Index is defined W/m2 --> 1 mW/cm2 = 10 W/m2 (10x)
From datasheet:
UV Index: 0 = 1.0V (typ), 100 = 2.2V (typ)
Make sure that supply voltage is very stable, 1mV = 0.833 UV index

Check operating voltage from datasheet!!

[visnja30]

On board is 3V3 voltage regulator so I think it must work with 5V input voltage.

[Scampy]

can you provide a link to the actual module you have. Most of the hits from Google suggest the unit is 3.3v, with a pull up resistor between EN and +3.3v and show no regulator... It would also suggest that the voltage out will be from 0 to +3.3v and not 5v that you might expect.

[visnja30]

http://www.ebay.com/itm/351494135550...%3AMEBIDX%3AIT

I know that the maximum voltage from the module is 3.3volts and my PIC AD module can measure 5 volt maximum.Is that problem?

[Gusse]

It seems that it is challenging to calculate accurate UV-Index (0-11+), as you would like to do.
Index is weighted using 3 different wavelengths and this broadband UV sensor covers all of them.
Problem is that there is just one output value for all of them.

Wavelenghts and weighting:
295 nm -> 1x , 305 nm -> 0.22x , and 325 nm -> 0.003x
How is the UV-Index Calculated?

Basically you could generate your own multiplier, based on above values and hands-on testing.

About operating voltages, even there is 3.3v LDO for chips itself, EN (enable pin) still need to be in spec. Put voltage divider between PIC and sensor.
ADC is not a problem, measure & scale result (1v -> 0, 3v -> 1023, 10-bit ADC)