Light sensor - checking when to turn On/off lights

Using Arduino Sensors
1

Light sensor - checking when to turn On/off lights

Hi!

I am looking for light sensor to check when to turn on/off the lights..
I am interesting in measuring values between 40-200 LUX but I have totally no idea
which one I should use. Are there sensors which are focusing to measure only this range
or approximately this range of LUX? So us Arduino analog inputs have 10 bits I get very
precise device..

I think to measure in this range -2/+2 LUX accuracy will be ok but would rather prefer to
read with -1/+1 accuracy.

The sensor will work in normal conditions: 20-25 celsius under roof.
If anyone could recommend me some light sensors for my requirements or give me any tips I would
appreciate.

2

You may want to look at the TAOS TSL256x range, it provides an accurate digital output using I2C and you can find arduino code for this using google

http://www.taosinc.com/getfile.aspx?type=press&file=tsl2562-e40.pdf

3

Thank You for Your reply.

Haven't known about such solution.. If that works also with long distance - approx. 50 meters?

I am looking rather for light sensor 4-20mA connecting to analog input using resistor 250 ohm..
Maybe You could recommend me something for this also?

4

50 meters is too long for I2C and you may find it difficult to eliminate noise on analog signal running over that length.

Does your application really need an accuracy of 1 or 2 lux?

It will be easier for people to suggest solutions if you can say more about what you are building.

5

I would like to control lights above tables in production hall using light sensor. I will have 3 modes: lights OFF, half lights ON, lights ON.
So I need to choose correct value for this. I think I don't need so good accuracy as 2 LUX but thought it is possible with that kind of sensors.
Tables are not for graphics designers just for simple works so I think -5/+5 LUX or maybe more will be also good...
Thank You for Your reply.

6

one of these could possibly work using a 250 ohm resistor. I don't have direct experience with these, perhaps someone else can suggest a better solution.

7

I found this one - I think will be ok..

8

Consider...

$5

Three pins:

Gnd
Vcc... 3v3 or 5v okay (Up to 7v okay)
Output

"Output" is an analog signal... but you're using an Arduino, so no hassle.

"Tuned" to respond like human eye... an issue with some
Uses log scale, so, in effect, can deal with a broader range of light levels... also an issue with some sensors.

9

Thank You tkbyd

I think it is not what I am looking for but it is always good to know that something like that exist :slight_smile:
55000/10 bit ADC (1024) = 53,7 . If I am right that will be my accuracy so quite not good considering fact that I am interesting in 40-200 LUX. Second thing is that I don't think so it will work on 50 meters distance.. or maybe I am wrong? Does somebody know what is the max distance to work with such sensors?

The sensor which I mentioned has got two versions: 4-20mA and 0-10V. As I know it's better to use 4-20mA.
0-10V for long distance isn't good choice because of wires resistance but I am not sure about that. If I decide for 4-20mA version do I need to connect it via 250/220 ohm resistor or it's possible to connect it directly to analog Arduino pin?

10

use an optic fiber to guide some light to the sensor ... ? just an alternative..