[Circuit of MUC with cds photo problem]

Hi recently,I design a circuit.

Use a 10k resistor series to cds photo .

And I measure the Varible of cds by adc 10 bit channel to measure the value of resistor.[Fig 0]

the characteristics Cure is like fig 0.

My problem is that the rage is only show 1 Lux to 100 Lux.

and we also know the data of table from wiki.[Fig 1]

so my problem is that in normal Value of “Sunrise or sunset on a clear day.” maybe is 400 lux.

and we also look another picture.[Fig 2]

we can see this picture which is my sensor get a "clear day " of lux at Taiwan 1.00PM - 4.00PM

we can know the resistor range is that 2.5k ohm ~ 22 k ohm.

so that see fig 0 . we can convert the lux range is about 80 Lux ~ 30 Lux

so why the result is so difference between wiki and this curve?

It seems this cds sensor maybe also can measure 0~100 lux.

like to measure inside lux,it is not useful for outside?

so if i want to get outside lux ,how should i do?



Resistance continues to drop at higher illumination.

But for any halfway accurate measurement of light levels an LDR is of course one of the worst possible choices. Get a real light level sensor, like the TSL2591. It's giving you the light level from 188 uLux up to 88,000 Lux without the need of calibration.

So the LDR can’t to measure for outside illumination?

or maybe it is not Accurate??

because i don’t have the component Characteristic equation ,

I only have the curve. And See the Curve mean that the sensor suck suitable under 100 lux .

But I want to measure the 0~60000 LUX by LDR.

because some project is i design that i choice the low cost function to measure illumination

like the following picture.

It's very far from accurate or high resolution. You can measure those very high illuminations with it if you use a much lower value pull-up resistor, but then you get other problems such as excessive current, and you can't measure lower illuminations any more.

That you want to use it for the purpose doesn't mean it's suitable. A phototransistor (e.g. TEMT6000) is also cheap and will work a lot better, though 60k lux will handily saturate it as well.

OK, if the LDR is not suitable.

That , could u suggestion the sensor of the circle package?

I find this component


buy it seems only measure under 1000 lux.

because my machine of surface is remain the 20 Ø for the sensor position.

but it may be can change for under 20 Ø . i don't want square package.

Why does the package shape matter at all? Isn't it the window in front of it that matters? Or were you really planning of having an ugly CdS cell sitting smack in the middle of your device, instead of behind a pretty frosted window?