4 replies to this topic

[Franva]

Dear all, I am new to here, please help me. I need to control a light sensor so when strength of illumination reaches a certain level, it will automatically open a sunroof on a green house. But I haven't found any light sensor on the Netduino platform. So could someone help me about where to buy a light sensor and how to integrate it onto the Netduino platform? Many thanks

[carb]

Dear all,

I am new to here, please help me.
I need to control a light sensor so when strength of illumination reaches a certain level, it will automatically open a sunroof on a green house.

But I haven't found any light sensor on the Netduino platform.
So could someone help me about where to buy a light sensor and how to integrate it onto the Netduino platform?

Many thanks

Franva,

Welcome to the Netduino Forum.

There are a couple of good sources, Adafruit.com or Sparkfun.com.

Which one you pick may depend on your code skill (SPI interface or simple photocell in a voltage divider network).

Another posibility would to use a temperature sensor also to determine if the roof vent should be opened.

Hope this helps,
Chuck

[baxter]

Hi Franva, The TAOS TSL235R is very easy to interface by measuring frequency output to get uW/cm^2 (irradiance). Frequency is directly proportional to irradiance. The TSL230R has has programmable sensitivity select and frequency scaling. There is some C# code for the TSL230R here, http://www.tinyclr.c...share/entry/252 and here is some really good information, http://jethomson.wor...l230r-articles/ You just need to convert irradiance to illuminance, http://en.wikipedia.org/wiki/Lux Baxter

[Gutworks]

Hi Franva,

Welcome to the Netduino community! I have the Adafruit TSL2561 digital luminosity sensor from Nwazet, and have been loving it. It allows you to separately measure infrared, full-spectrum or human-visible light. I looked over the math from the Adafruit tutorial and it was way over my head to create a Netduino driver for this module, which I suspect would be similar for other light sensors. Luckily Nwazet has done all the heavy lifting and created a .Net MF driver to be used with their Netduino Go DAQ module. I haven't tried it yet, but I'm sure with a few modifications you would be able to use the driver on the Netduino Plus.

Cheers,
Steve

[Dan Olson]

Hi Franva,
The TAOS TSL235R is very easy to interface by measuring frequency output to get uW/cm^2 (irradiance). Frequency is directly proportional to irradiance. The TSL230R has has programmable sensitivity select and frequency scaling. There is some C# code for the TSL230R here,
http://www.tinyclr.c...share/entry/252
Baxter

I'm actually a big fan of the TAOS sensors due to their very-linear response and high dynamic range. It can be difficult to interface the TAOS (now AMS) light-to-frequency converters directly to a Netduino because the TAOS sensors can output very high frequencies (1MHz or so) depending on the model. There are several ways to get around this problem.

1. Buy a light to voltage sensor. I've used the TSL257T in a PIC project (should work the same in a Netduino, though). You can find a few other options here http://www.ams.com/e...ght-to-Voltage. It combines the linearity of the TAOS sensors with the ease of using one of the built-in analog-to-digital converters (ADC). The downside is that your resolution (number of different brightness levels) is limited by the resolution of your ADC. Netduinos come with built-in 10-bit ACD, so you get 1,023 brightness levels.

2. Use one of the TAOS sensors that has a frequency divider (TSL230RD for example). With 100-fold reduction in output frequency, you would have a 10 kHz signal in bright light that would be fairly easy to measure, but you would have a 0.001 Hz signal in dark light, which means you might have to wait for 100 seconds (possibly longer depending on whether you're planning to measure pulse period or frequency). If you don't need to take fast measurements, but you do need to be able to distinguish between subtly different light levels, this is a good option. You get about 1,000,000 different brightness levels.

3. Use one of the TAOS sensors with built-in digital signal conversion (http://www.adafruit.com/products/439). This gives you the full resolution of the device (1,000,000 brightness levels), but the digital signal interface is more complicated. Adafruit has a good tutorial posted on the order page, though.

Hope this helps you decide which light sensor to use.

-Dan