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Long distance sensing techniques?


#1

What opinions do people have about remote sensing? I have assumed that i would be using 1 wire for any remote sensing like temperature, switches but how do i do remote ADC of sensors? It appears 1wire ADC are obsolete now?

What other wire techniques can i use? CAN BUS(isn’t this for cars?)

Ethernet is overkill…need something in between.


#2

Can you provide more details, please?

What sensor? What distance?


#3

Well to be exact…i want to create a garden system that measures temperatures, humdity, ground moisture and be able to turn on/off a tap.

The main unit(g120 based) will be about 20metres away and controls other things as well.

CAN BUS looks good…is my only option? I want to make the sensing part cheap and easy ie do not want to incorporate another uP


#4

A Cerberus main board with sensors and Justin’s Rfpipe would be cheap a freaking easy!


#5

LIN and RS485 are other options.


#6

How about wireless sensors with solar power?

This module from Seeed works well. I use it myself to record analog sensor data with a G120 based Cobra 2 board. I have some more in development for a commercial project now that I know it works.

You can use the IO ports to switch remotely too. No processor needed unless you want remote calculation of some sort but the G120 receiving side can do all that.

You can add the battery and solar panel to suit. :slight_smile:

This can talk to the G120 if you get the XBee carrier board (Assuming you are using the G120HDR or you can add it to your custom board if that’s the route you are taking)

Wired would of course work and be a little cheaper but you then have the hassle of running the cable and getting power to it. You can then use either CAN bus or RS485 etc. This assumes you will have a processor at either end of course.


#7

I will defintely use xbee for wireless but want a wired technique as well. What is LIN?


#8

#9

Local Interconnect Network. A low cost alternative to CAN for short distance communications. Not multi-master like CAN but more poll and response like RS485 master/slave type network.


#10

thanks people…great knowledge as usual…


#11

anthonys, I know you said Ethernet was overkill, and it could be, but don’t forget PoE (power over ethernet). It sounds like you will need some processing and power at the control end.
You can get an ethernet Gadgeteer board like the FEZ Cerbuino Net.

You could use off the shelf Ethernet power injectors to send the 12vdc or 24vdc down the line. (http://tinyurl.com/ken7ysr)
Direct burial ethernet cable is also available.

You could do the same thing with RS485. But there is no processor boards with RS485 already on board.

Of course wireless would be the best. There are quite a few solar panel, charger and battery kits out there.


#12

Hmm, for garden purposes this one might fit http://www.seeedstudio.com/depot/seeeduino-stalker-waterproof-solar-kit-p-911.html?cPath=84_13

An rfbee from Seeed or another Bee on top?


#13

A other option is modbus.

Modbus over RS485 1200 meters
Modbus over TCP 100 meters

See

It is a very often used industrial bus.

More information:
https://www.ghielectronics.com/community/forum/topic?id=6563


#14

The link to the library is certainly interesting as I work with a number of devices that use Modbus and was in the process of creating a driver for this. I do need serial RTU though so would have to look at adding this protocol.