I need to monitor approximately 25 sensors, none of which is greater than 80m from the monitoring device. The monitoring device will be a single board computer, e.g. beaglebone black, (yet to be decided).

I will be monitoring conditions such as temperature, lux, etc. It will be sufficient to take one sensor reading per minute, (i.e. 25 int total per minute). Because of the variable distance, I do not want to monitor potential noisy and attenuated analog sensor signals. I2C/ SPI are not suited for long distance so this leaves protocols such as CAN, RS485 or Onewire.

I am looking for a protocol that is support by CE marked sensors that can be plugged directly into the SBC. I don't want to have to build and certify each sensor we devise. For example, I could easily build a CAN sensor board but it would cost thousands to run such a sensor through compliance testing. If I negate compliance testing and the building burns down I will be at fault.

I have seen elsewhere a recommendation for CAN for use with wired sensor networks but I cannot find suitable sensors for sale.

So, any ideas for a communications protocol for wired sensors that has industry support?

  • \$\begingroup\$ So you need light and temperature sensors that are CE certified, and you need the protocols that they use. Did you include a shopping cart with those questions? This maybe OFF-TOPIC a bit, as it is mostly about us searching the web. Unless someone here has personal experience in those parts, it will be difficult to help you. How much searching have YOU done? \$\endgroup\$ – Sparky256 May 22 '16 at 22:06
  • \$\begingroup\$ You already mentioned it. RS-485. And I think there are LOADs of sensors that support it. \$\endgroup\$ – Claudio Avi Chami May 22 '16 at 22:09
  • \$\begingroup\$ @Sparky256 a lot of searching on Onewire & CAN. I'm not looking for a shopping list just an answer, e.g. rs485 is the appropriate protocol for your application. I am looking for a wired protocol that is used in buildings as described above. \$\endgroup\$ – SeanJ May 22 '16 at 22:10
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    \$\begingroup\$ Anyone who has gone to the trouble of properly CE marking this sort of sensor will be using a proprietary protocol, and charging a lot for the hub. This is O/T, without some major changes to the question. \$\endgroup\$ – Sean Houlihane May 22 '16 at 22:11
  • \$\begingroup\$ @SeanHoulihane I have changed to, "I am looking for a protocol that is support by CE marked sensors that can be plugged directly into the SBC". Hope that helps. \$\endgroup\$ – SeanJ May 22 '16 at 22:16

I know that RS-485 is a proper answer for your question, not only that, but I have personally used RS-485 networked sensors in several installations that worked for years. And there are lots of sensors using RS-485.

I learned the hard way that for noisy environments shielded conductors are important as is single point of connection of the shield to ground (close to the host). Avoid multiple ground connections for long networks.

Regarding CE, it is as simple as googling RS-485 CE certified sensors or something like that. I have already tried by myself and there are many hits.

  • \$\begingroup\$ Remember that the sensors have to be CE certified. RS-485 or CAN hardware and protocols would be the easy part. Do you know of actual sensor part numbers or a manufacturer? \$\endgroup\$ – Sparky256 May 22 '16 at 22:17
  • \$\begingroup\$ @Sparky256 I added a comment regarding CE, I think that providing lists of sensors is way beyond the scope of the answers we have to provide. \$\endgroup\$ – Claudio Avi Chami May 22 '16 at 22:19
  • \$\begingroup\$ Thanks for providing the basics so the OP has something to work with. \$\endgroup\$ – Sparky256 May 22 '16 at 22:24

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