Problem interfacing GYML8511 UV Sensor an offset is always present

[GM0000]

Hello!

I have followed these instructions for connecting GYML8511 to my Arduino UNO R3.
But I always read some voltage even when the sensor is kept covered so that UV can not hit the photosensitive area.

From the serial log it seems a voltage of 1.02 Volt.

MP8511 output: 204 MP8511 voltage: 1.02 UV Intensity (mW/cm^2): 0.22

I was wondering how is it possible, and if there are better way to have a more accurate measurment?

[TomGeorge]

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This link may help explain, it includes a graph of output voltage vs UV level.

https://learn.sparkfun.com/tutorials/ml8511-uv-sensor-hookup-guide/all

As you are not reading form the sensor directly, but through an amplifier.
An offset on the output for zero UV, is probably due to the fact that most OP-amps cannot drive their outputs to gnd potential.

So a fixed offset is programmed into the sensor module to make sure all modules output the same calibrated levels.

The example given in the above link, compensates for that offset.

Tom..

[GM0000]

Hi Tom, thanks a lot for your quick reply! I saw that guide however my GYML8511 UV Sensor should have this extra pin with the reference and also a voltage regulator that the basic ML8511 doesn't have and this should solve the issue.

The sparkfun example requires a breadboard to make all the connection I would like to avoid this using the GYML8511 version. I was wondering if anybody found an easy fix, I was thinking that because it is linear to take the dark current and subtract it...

[TomGeorge]

Hi,
So you want to use the raw IC rather than the module.
The site you link in post #1 gives you a schematic of what is on the module.
All you need to do is incorporate those components into your design.
If you already have a 3V3 supply then you don't need the 3V3 LDO.

@GM0000

however my GYML8511 UV Sensor should have this extra pin with the reference and also a voltage regulator that the basic ML8511 doesn't have and this should solve the issue.

What extra pin?
The offset can be taken care of in the software.
You cannot bypass the Op-Amp in the IC.

Tom...

[GM0000]

Hi Tom,
sorry for coming back only now and thanks for your help, this is how the GYML8511 looks like:

The 3V3 pin seems connected to a voltage regulator.
Yes, I think I will introduce a function to record the dark current and subtract the value to the reading.

Thanks for your help!