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Topic: Outside sensor for humidity (Read 17346 times) previous topic - next topic



I just started with Arduino, and started to buy sensors and equipment. So far loving it.
I have 2 DHT22 / AM2302 sensors.

I plan to build a little project that measures temp + humidity inside and outside. I am sure inside is fine, but I have heard that he DHT22 might not make it outside long term. I live in Canada, and temp ranges are from -35 to 35 deg C.

What kind of temp/ humidity sensor can I use that will last a reasonable amount of time with the clement (gasp) weather of Canada?
(will condensation ruin it long term?)

How do I protect it?

(If I can't find a suitable sensor, I will put a sealed DS18B20 outside...so not humidity).

Best wishes!


Also, the temperature will not be accurate if you sealed it using a plastic cover or something. Because of the plastic stopping the temperature (non conductor or temperature).

I say you use a water proof temperature sensor which also even if immersed in water.

Here is one http://www.adafruit.com/products/381

Here is one that can also detect moisture or humidity. It is meant for soil monitoring but I'm sure it'd work for air too. http://www.adafruit.com/products/1298
If you want to meet a beautiful nurse you must be patient.


A sealed DS18B20 will give the same temperature as an metal encapsulated DS18B20 of Sparkfun.
The DS18B20 doesn't produce heat, so it will no influence the temperature.

The soil moisture sensor with SHT10 is not ment for freezing temperatures. The DHT22 / AM3202 is better.

Freezing condensated moisture will destroy the sensor for sure.
You should protect it from wind and fog.

Is there a place that is always dry ? Under a tree of even in a shed ? Perhaps the humidity in a shed is not the same, but it gives some protection for the sensor.

With a box made of a few porous bricks, you have good protection.
As long as the bricks are in the air, protected from rain and not touching the wet ground.

You could use both sensors. Thay way you can compare the temperatures. I think the DS18B20 is still more accurate. Why not add a light sensor ? An Arduino is also capable to measure it's own voltage, so you can measure that. And a motion detector. You could even use three DHT22 / AM3202 sensors, and replace them if only one is working.
With an Ethernet Shield or Wifi Shield, you can upload it to www.thingspeak.com

The Arduino itself might stop working with freezing temperatures. The crystal is the first thing that stops working.


Thanks for the replies.

The DS18B20  I have is the metal encapsulated that sparkfun sells. It seems perfect.

What about this one: AM2315?
It seems to have a good case around it.

My plan is to use a protected area around my house. There is a little overhang in the front of my house where the second story is, it is about 20 cm long. I could suspend it there, and I could put a 'cup' around it that would protect it against the worst of the rain, the sides would have holes around it, but no holes around the top where the sensor is, but below enough to circulate the air in the sensor area. There could be a couple of vent holes on the top to circulate air, but not in an area where rain could get in.

The AM2302 seems great, but I heard the PCB might not be protected and sealed, so it could fail soon.

I intend to have the outside sensors wired to the Arduino inside.
- DS18B20 sealed
- AM2302 or similar if it can survive.

I plan on having INSIDE
- Barometer BMP05 (i2c)
- Temp /humidity ( AM2302)
- Smoke sensor MQ-2
- CO sensor MQ-7
- real time clock  (i2c)
- SD card logger (SPI)
- wifi, ethernet or 433mhz link. (SPI I presume)
- display (i2c)
- active buzzer for alarms
- power from the grid with battery backup as the MQ sensors operate on small heaters and are relatively demanding in terms of power.

I plan on using an Arduino mini that I already use. SO far I am not running out of input/outputs.
The Mq2 and MQ7 will pose challenges, but it will be fun.

This would be my first 'real' Arduino project.


Jul 16, 2013, 05:40 pm Last Edit: Jul 16, 2013, 06:28 pm by pwillard Reason: 1
Here is what I did...

I used a standard plastic conduit junction box... water tight kind.  I used a step drill open a small hole for a tiny "outound" blowing fan (with an insect screen) and a hole at the top for a water tight gland and a black air intake tube.  This moves the air through the enclosure allowing it to be sampled for temperature and humidity. (I use a Honeywell sensor and have a small cotton sock around it)

It has survived 2 Georgia winters (down to 22 degrees F) and summers (Up to 100+ degrees with 99% humidity) so far.

EDIT:  I wanted to add that I use automotive silicone grease in the RJ45 (cat-5) connectors to prevent corrosion of the delicate pins in the connector.


For ethernet, use the Ethernet Shield with W5100. You could try a cheap clone if you want to take the risk for cheap components.
Some try to be even cheaper than that, but the ENC28J60 is not officially supported. Don't do it.

Start with a few sensors, and add more along the way.

For my remote sensor, I found a dry place under the conifers. It has no direct sun or rain, and has some protection against wind. The box is open at the bottom and resting on a brick. That way any moisture is absorbed by the brick. The brick itself can not get wet by rain. I don't use a fan, because I don't care if my readings are slow and behind. I only update it every 10 minutes.

The trick is not to place the remote sensor in sunlight or rain, not to make the case very open and not to make it very closed, and an insect screen is a good idea.


Pwillard: Nice setup indeed, sturdy, rugged. I don't think I want to put the Arduino outside though as I want to check indoor and outdoor temps + humidity. If cabling to the outside sensors turns out to be an issue, I will put a tiny type atmel chip or a mini arduino with an RF link or similar.

If I go that route, I think that the board itself would be in a smaller sealed box with silica gel (it would eliminate any condensation in winter). I would put connectors on the box for the sensors that I can somehow seal. The small box with the arduino would go in an enclosure similar to yours, where the sensors would be protected from the direct elements. Does that sound reasonable to you?

According to specs the atmel chips should be -40degC to 125degC operating range, I will check the rest of the components too to make sure.

Erdin, thanks on the suggestion for the ethernet shield. My understanding is that the ENC28J60 does not have a firmware TCP IP stack, so taxes the Arduino uC. I did not see yet a smaller board with the W5100. I bought and ENC28J60  and an arduino ethernet shield clone with W5100. The first one is to play with and experiment.

Sheltering the box among conifers sounds like a mighty good idea to me.

Thanks... More comments? I am an avid learner :)


You are already thinking about 2 Arduino boards. What about 3 or 4 or more ?

My setup is this:
Arduino Mega with Ethernet Shield. My website is on a microSD card.
An Arduino Uno was quickly too small, so I had to use the Arduino Mega 2560.
The website is only available on my home network, but the Mega uploads the data to ThingSpeak.com.
The Mega has a 5V I2C bus and 3.3V I2C bus (using a level shifter). That is all for the Mega.

Connected to the I2C bus are other Arduino board (standalone ATmega8 or Pro Mini clones of 5 dollars or I2C sensors). One of them has a barometer, the atmospheric pressure is the same indoors as outdoors. Another is dedicated to a 433MHz receiver with VirtualWire.

Once I had that setup, I can place remote Arduino boards with transmitter and VirtualWire everywhere. They transmit once per 10 minutes without repeating the message.
I even added XTEA encryption to VirtualWire.

Next step is a few humidity sensors in the house and UVA and UVB sensors outdoors, and a wind speed and direction meter without moving parts, and a receiver for time signal and a FM radio controlled by a webpage.


Jul 16, 2013, 10:24 pm Last Edit: Jul 16, 2013, 10:37 pm by olof_n Reason: 1

I have a homemade weatherstation outside. I am using the DHT22 and BMP085 sensors.
The DHT22 sensor is placed in a plastic pipe which is attached under the box where the other components (MCU, BMP085, radio module etc.) is. The open side of the pipe is pointing down which protects the sensor from rain.

I live in Sweden where the temperatures are shifting between -25 and 30 degrees celsius.
The sensors (and everything else in the weatherstation) have survived 1 year now.

The weatherstation is placed in an open area. There is nothing that stopps the wind and snow.
Check it out :) http://kullen.dyndns.org/
Click on the about meny to view a "not so great picture" :)

The web site is hosted on a Cubieboard that also stores the weatherdata in a Sqlite database.



You are giving me many ideas. The wind speed and direction I wanted as I fly R/C planes and want to know from inside if the conditions are right :) Will have to research... Do you have suggestions?
UV sensors are another good idea.
For time signal, are you talking about staying synced up with 'real' time? If so why not use the net from your Mega?
I will have to read up on Virtual wire.

Olof: Very nice weather station indeed. Wow. I live in eastern Ontario, Canada. The coldest I have seen here is -36 degC, hottest about 37degC. So if yours lasts, then it is promising.
What sensor does the wind vane use? Do you use an encoder for the wind speed?



DroidDr, I bought Sparkfuns "Weather Meters".
They are a bit expensive but I bought them for the documentation. Cheaper to buy a lowprice Weatherstation and harvest the sensors.

The wind sensor uses magnetic reed switches that gives pulses when it rotates. The pulses triggers a interrupt function that counts them.
Really easy to use the sensor.

The wind wane is a bit harder to use, it gives different analog values for the direction of the wind.

Indoor I have a small LCD-screen where the up to date weather data is shown.



Lots of learning in perspective!


I bought a used Dallas 1-wire weather instrument on ebay (the version #2 made my AAG and sadly, no longer produced) for windspeed and direction.

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