lux sensor value

[astrojetson8]

fyi: looks like the default value for lux from gateway is around 360lux even when it's pitch dark.
https://msdn.microsoft.com/en-us/library/windows/desktop/dd319008(v=vs.85).aspx

[sendorm]

Someone has pointed out the fact from a xiaomi document that the lux sensor gives values between 300-1300. I went ahead and subtracted 300 from the reported value. Now it shows between 0-1000. Which for me is a better representation.

[sendorm]

Here is the link

lazcad/homeassistant#46

[astrojetson8]

@sendorm oh cool, thanks, and it make sense. are you manually subtracting 300 ?
@YinHangCode
option 1. update this in code?
option 2. add default start lux value via config
option 3. i don't know

[sendorm]

Yeah, I am directly subtracting 300 in the code. So the reported value is between 0-1000. But still they are not good values. I tried to find a multiplier using the mi flora sensor (which seems to have a much better represantation). The relation might even be quadratic, I might check into that.

But in the end it is not necessary, just get the values for your normal usage and create automations accordingly.

[astrojetson8]

@YinHangCode thanks for adding this to your latest release.

[YinHangCode]

@astrojetson8 @sendorm It looks like -300 is not a good value.

[sendorm]

yeah some users on the home assistant site also reported that 300 offset is not working for them too. 279 was the least reported as I recall.
Final solution was to add:

            # Workaround negative values for a few gateways which has a range of 279-1279 for unknown reason.
             if value < 0:
                value = 0

[YinHangCode]

@sendorm maybe -279 is the most suitable value.

[sendorm]

Maybe but the document here states that the values are between 300-1300.
https://github.com/louisZL/lumi-gateway-local-api/blob/master/网关.md

Some one else can say that his values goes down to 275 for instance, so a zero check is a must.
But of course it is your decision. You can make it 279 and put a negative check. That way no one will get an erroneous negative lux value.

[YinHangCode]

@sendorm yes, the document description is between 300-1300, but In fact, this is not the case.
following code should be better:
var illumination = data['illumination'] / 1.0 - 279;
and
illCharacteristic.updateValue(illumination > 0 ? illumination : 0);

[sendorm]

Yes, good solution. Thank you.

[astrojetson8]

@YinHangCode sounds good.