Best sensor - Light and humidity

Well, i have another question, hope someone can help me :slight_smile:

I will buy a humidity and a light sensor, but i don't know which to buy (best is the one that has the better specifications and more tutorials).

First, the humidity sensor: it must have at least 1Hz update rate, this is, i want to read the data each second, at least.

From what i saw from the datasheets i didn't understood where i can see the rate of update, just appear response time.

http://inmotion.pt/documentation/sparkfun/SEN-09569/SEN-09569-HIH-4030-datasheet.pdf - don't know rate
http://inmotion.pt/documentation/sparkfun/SEN-10167/RHT03.pdf - website says 0.5Hz
http://inmotion.pt/documentation/others/INM-0627/DS_IM120628005_DHT11.pdf - website says 1Hz
http://inmotion.pt/documentation/sparkfun/SEN-12064/HTU21D.pdf - measuring time in datasheet 16ms (don't know if is this)
http://inmotion.pt/documentation/sparkfun/SEN-08257/Datasheet-humidity-sensor-SHT1x.pdf - don't know
https://www.sparkfun.com/datasheets/Sensors/Temperature/HH10D.pdf - don't know

So, which is the best humidity sensor (at least 1Hz update rate)? To me it seems the HTU21D.

Secondly, the light sensor, it must have an update rate of at least 1Hz.

What i come across were:

http://inmotion.pt/documentation/phidgets/PHD-1142_0/APDS-9002.pdf

http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/LightImaging/TSL2561.pdf - it says that has 2 channels, one for ir

Based on tutorials and specifications which is the best humidity sensor and light sensor? DO you think it would be HTU21D and TSL2561?

Grateful

Can you tell us how they will be used and what accuracy you want ?

Normally a humidity sensor can be updated every few seconds. Why do you need 1Hz, do you have a strong air flow ?
Or do you only want to display it and want to see if it is rising or falling ?
Some sensors can be 50% inaccurate, even if the specification tells otherwise. For example the DHT11 can show 30%, when the humidity is 80%.

The HIH-6100 series from HoneyWell seem to be much better (I have not bought one myself yet).
But I read that the response time is 6 seconds in 20 l/min minimum airflow.
I can't find how much time the ADC requires, since I can't find the document how to use the I2C registers.

I don't know if 1Hz is even possible for humidity.

What kind of light sensor do you want ?
A photo-transistor or photo-diode can be very fast, but some chips measure the ambient light in lux.
If you would only need some kind of raw indication, the 1Hz can be done.

Caltoa:
Can you tell us how they will be used and what accuracy you want ?

Normally a humidity sensor can be updated every few seconds. Why do you need 1Hz, do you have a strong air flow ?
Or do you only want to display it and want to see if it is rising or falling ?
Some sensors can be 50% inaccurate, even if the specification tells otherwise. For example the DHT11 can show 30%, when the humidity is 80%.

The HIH-6100 series from HoneyWell seem to be much better (I have not bought one myself yet).
But I read that the response time is 6 seconds in 20 l/min minimum airflow.
I can't find how much time the ADC requires, since I can't find the document how to use the I2C registers.

I don't know if 1Hz is even possible for humidity.

What kind of light sensor do you want ?
A photo-transistor or photo-diode can be very fast, but some chips measure the ambient light in lux.
If you would only need some kind of raw indication, the 1Hz can be done.

The dht11 it seems to have 1Hz. It will be used to show the relative humidity during a fall, this is, the object with the humidity will be droped and is to make a comparison between altitude and humidity. About accuracy as much as possible, i saw that some have 1% accuracy, so i think that 5-7% should do

About the light i don't know. It is to measure the wavelength of the ambient. If it could measure ir wevelength too, better.

Thanks for the help

The TLS2561 seems to have 400ms conversion time. It should be okay for you.
Here is a breakout board and libraries:

The Adafruit function getFullLuminosity() waits sometimes for 14 or 102 or 403 ms. That means you program stops during that delay, you might have to rewrite that.

I was serious about the inaccuracy. The DHT11 could return 30% while it is 80%. Even if the datasheet says it is accurate. The HIH-6100 seems to be a lot better.
When you use the DHT11 you don't know at all if the humidity is even near the actual humidity.

This one is made fast for wheater balloons, but it still needs 3 seconds and it could be 15 seconds at -20°C.

There are other fast humidity sensors, but it is hard to find how fast they respond to a change in humidity.

After searching the internet for a while, I think the HTU21D is the best option

But I suggest you also buy a Honeywell HIH-6100 series sensor to compare the values.

Thanks for all of your fast answers.

FInal question: The tls2561 just returns the lux? ALS-PT19 returns the wavelength? I wanted the light sensor to return which was the wavelength, isn't that possible?

Grateful

Yes, just the lux. The ALS-PT19 also returns the amount of light, not the wavelength.

Measuring the wavelenght is something else than measuring the RGB value.
Do you want a color sensor ?
I trust Adafruit that they picked a good one:

I don't understand the datasheet of the TCS34725 very well, but I think that maximum accuracy takes 700ms. So this should work for you.

So, the als-pt19 returns the lux also?

When i thought about a light sensor i thought it would return the wavelength of the ambient light. There isn’t a ir sensor that returns the amount of ir in ambient, like the uv sensor to arduino, that detects uv-a? Don’t know if it this: http://ptrobotics.com/opticos/1292-tsl235r-light-to-frequency-converter.html

The ALX-PT19 outputs an analog voltage, I think you can convert that to lux.
The TSL235R converts visible light (plus a portion of IR light) to a frequency. You can read that in the datasheet.

Simple light sensors also accept IR light, that is why some sensor detect the IR light, to be able to subtract that from the main sensor and get the visible light intensity a result.

When I think about a light sensor, I think about an LDR that changes value with light:
http://bildr.org/2012/11/photoresistor-arduino/

You want a lot, I don't understand what you want to measure.
Do you want to know the wavelength without knowing the intensity of the light ?
Or do you want to know the full RGB value for visible light ?
Or do you want to know the IR light intensity, or the UV-A and UV-B, or everything ?
If you want everything, you might need 4 sensors.

The dht11 it seems to have 1Hz. It will be used to show the relative humidity during a fall, this is, the object with the humidity will be droped

What do you mean, the object with the humidity will be dropped ? Objects don't normally have "humidity", air has humidity.

michinyon:

The dht11 it seems to have 1Hz. It will be used to show the relative humidity during a fall, this is, the object with the humidity will be droped

What do you mean, the object with the humidity will be dropped ? Objects don't normally have "humidity", air has humidity.

What i meant was the object with the humidity sensor will be droped.

You want a lot, I don't understand what you want to measure.
Do you want to know the wavelength without knowing the intensity of the light ?
Or do you want to know the full RGB value for visible light ?
Or do you want to know the IR light intensity, or the UV-A and UV-B, or everything ?
If you want everything, you might need 4 sensors.

Sorry if i'm confusing you. I will use a uv sensor (UV Sensor-DFRobot) and about the light sensor, i thought that from the data recovered we could make something like this: http://static.abdserotec.com/thumbnails/maximal1.jpg

Is this possible, from the sun light see something like this?

And when i talked about ir was something smiliar to the light sensor but with the different spectrum.

That is a sensor for UV-A. It is in sunlight.
You could add a UV-B sensor as well.
To get the ambient light and the wavelenght, you still need that RGB sensor.
And you want to measure IR light.
That is why I'm thinking of 4 sensors.

Caltoa:
That is a sensor for UV-A. It is in sunlight.
You could add a UV-B sensor as well.
To get the ambient light and the wavelenght, you still need that RGB sensor.
And you want to measure IR light.
That is why I'm thinking of 4 sensors.

And could you tell me the namoe of the components that i will be needing, if this isn't asking too much?

I don't know what sensors are good. There are so many sensors.

You can start with that TCS34725 RGB sensor that Adafruit sells.
And with the UV-A sensor you found.
Try to connect them to the Arduino and get proper values out of them.
Meanwhile you can look for UV-B and IR sensors.

ok, thanks