partynoparty
Posts: 5
Joined: Tue Nov 18, 2014 1:06 pm

distributed network of sensors

Tue Nov 18, 2014 1:33 pm

Looking to start a project and I'm new to all this so I've got some questions. I am trying to plan out a project involving collecting environmental data from lakes and other bodies of water. The general idea would be to have several sensor nodes placed around a lake that would relay data to a central hub. I was planning on using Python messaging queues to relay the data between nodes. I'd like to get some idea of the equipment I might need for this type of project.

The first issue would be the communication. What are the different means of communication that might be available between the nodes? A wifi antenna seems like the most obvious choice, but I'm not sure what sort of range I might expect from that. Some of the lakes we'll be studying are close to a mile from end to end. I envisioned the sensor nodes would only be collecting data while the central hub would only be receiving data, but I feel like the large area might require some nodes to receive the data and then pass it along toward the central hub.

The other concern would be the power consumption. We were hoping to have these things solar powered. I'm not sure how much power the senors and communication would require. The sensors would be collecting probably every ten minutes or so, but the communication does not need to be continuous. I was thinking the nodes could temporarily store the data then then send it off once a day, or something to that effect.

Not sure how feasible any of this is, so all input is appreciated. Thanks!

-Mike

User avatar
DougieLawson
Posts: 37083
Joined: Sun Jun 16, 2013 11:19 pm
Location: Basingstoke, UK
Contact: Website Twitter

Re: distributed network of sensors

Tue Nov 18, 2014 2:40 pm

Take a look at http://mosquitto.org and http://MQTT.org, MQTT is the protocol for sensor networks.
Note: Having anything humorous in your signature is completely banned on this forum. Wear a tin-foil hat and you'll get a ban.

Any DMs sent on Twitter will be answered next month.

This is a doctor free zone.

rgrbic
Posts: 128
Joined: Thu Jun 12, 2014 1:07 pm
Contact: Website

Re: distributed network of sensors

Tue Nov 18, 2014 3:09 pm

You can go with microcontrollers paired with zigbee modules for communication.
At 127.0.0.1
Twitter: @rgrbic
IoT-projects.com

danjperron
Posts: 3440
Joined: Thu Dec 27, 2012 4:05 am
Location: Québec, Canada

Re: distributed network of sensors

Tue Nov 18, 2014 3:18 pm

I made a small module exactly for that.

Code: Select all

http://www.raspberrypi.org/forums/viewtopic.php?p=618006#p618006
This is a small cpu using the RS-485 protocol or the Xbee module. With the rs-485 you could wire up to 64 modules over 1000 meters. The cable could bring power to the devices and you only need to care about the server.

Each module has 10 IO and they can read Ds18b20 or dht22 temperature sensor or read 10 bits A/D values.

Or use the xbee pro which will give you long distance remote possibility.

The code and the gerber is available on the github. And nothing prevent you to modify the code to fit your needs. The cost in parts is around $20 per module, including the box. The most expensive parts is the dc converter but it should work very well with a standard lm7805 regulator.

b.t.w. interface is easy since it is base on modbus protocol.

partynoparty
Posts: 5
Joined: Tue Nov 18, 2014 1:06 pm

Re: distributed network of sensors

Tue Nov 18, 2014 9:16 pm

Thanks guys. Does anyone have any experience with waterproof housings for Raspberry Pi setups? I will have to run the cables from the solar panels into the enclosure, and will have to run the sensors out of the enclosure. Are there any enclosures that might be designed for this kind of setup, or would it be more of DIY kind of thing? Also, would the enclosure and the fact that the enclosure is submerged some distance (maybe a foot) below water affect the range of the wifi?

User avatar
joan
Posts: 14668
Joined: Thu Jul 05, 2012 5:09 pm
Location: UK

Re: distributed network of sensors

Tue Nov 18, 2014 9:33 pm

It might be sensible to have a Raspberry Pi as the central collator but surely there are better, less power hungry, devices to use for the remote sensors.

rgrbic
Posts: 128
Joined: Thu Jun 12, 2014 1:07 pm
Contact: Website

Re: distributed network of sensors

Wed Nov 19, 2014 11:35 am

partynoparty wrote:Thanks guys. Does anyone have any experience with waterproof housings for Raspberry Pi setups? I will have to run the cables from the solar panels into the enclosure, and will have to run the sensors out of the enclosure. Are there any enclosures that might be designed for this kind of setup, or would it be more of DIY kind of thing? Also, would the enclosure and the fact that the enclosure is submerged some distance (maybe a foot) below water affect the range of the wifi?
Do you really need to submerge the whole enclosure under the water? If you want to measure something, temperature for example, it is easier to submerge only temperature sensor. You can put the sensor in appropriate waterproof housing and connect it to the microcontroller or RPi which is in enclosure outside the water. You can use rubber rings on enclosure holes for cables. Also, put the enclosure below solar panel to prevent direct sunlight to enclosure since it get can pretty hot inside. See some examples on pictures. It is DIY electrical fence.
Attachments
cob01.jpg
cob01.jpg (60.47 KiB) Viewed 1647 times
cob4.jpg
cob4.jpg (47.02 KiB) Viewed 1647 times
cob03.jpg
cob03.jpg (37.2 KiB) Viewed 1647 times
At 127.0.0.1
Twitter: @rgrbic
IoT-projects.com

drgeoff
Posts: 10209
Joined: Wed Jan 25, 2012 6:39 pm

Re: distributed network of sensors

Thu Nov 20, 2014 11:40 am

Not sure if Wi-Fi through water was part of your thinking but it doesn't work well. Especially 2.4 GHz which is the band that microwave ovens use.

Even if aerial (antenna) is not underwater, Wi-Fi range will be reduced when its raining.

Return to “Networking and servers”