SafeDuino – Part 03: The goalposts change

Ok, I admit it… feature creep has officially set in on this project.

After doing the basic designs and working out I needed the EtherMega (from Freetronics) for the SafeDuino project, and consequently purchased some (I say some as I keep changing the design) of the components I decided that it was a “waste” of a mega to only use the small number of I/O’s I needed (but more than I could get from an ethernet connected UNO), and this is where the feature creep began.

So, now what I have is more of an environmental monitor not only for the cabinet it was to maintain originally, but also for the room/building it is housed in, this will allow me to do differential monitoring for parts of the building vs the areas I am going to monitor/control individually.

So far I have determined, that beyond the original cabinet it was going to monitor, the following are going to be monitored;

  • The building itself, this is to allow for differential comparisons and fluctuations in temperature and humidity to see if the things I am putting in place to control humidity are in fact working
  • Two other cabinets, including one humidor, just because I can 😀
    • Turn on/off humidification/dehumidification equipment and fans to allow for circulation in the closed environments based upon readings
  • Possibility of wine/beer fridges
  • External temperature/humidity
  • Solar Radiation (for estimating solar panel power generation)
  • Background radiation, this is more of another because I can thing, being able to monitor radiation (Alpha, Beta, Gamma) in the background of the environment long-term will be useful in the future just to see the changes over time, I will be connecting it to one of the sensor networks that have popped up after the Fukushima accident
  • Internal and External light sensors, again to see how it affects temperature/humidity in the closed environments/building
  • Same goes for door/window openings

I am sure there is more to come, in fact I know there is, I have 40 odd pins to fill up :D.

In addition to these added features, I have decided to add some protection to the arduino itself through the use of optocouplers/optoisolators to isolate the external electronics from the device itself, where possible anyway, this will also take some of the current loading of the arduino board. So far I have confirmed that the 4N25 optocouplers work, and I have tested those which I have purchased to ensure they operate correctly.

I am still to get a few linear optocouplers for use the with the voltage divider to allow me to monitor the voltage in the battery system.

Considering ultimately that the EtherMega will be powered via POE (supplied by the switch, so a proper 801.11af regulator, which is being done to ensure monitoring will continue even if the batteries for the lights etc fail) there will be no load on the batteries apart from a few mA for sensors and alike for the most part, but I will be configuring the reed switches for example to be Normally Open (NO) so that there is no power going through them when they are not activated (apart from what is used by the resistors to keep a proper ground) I should be able to maintain this for a long period with just the batteries, and with a solar charger, I should be able to maintain this use of the system indefinitely.

Written By Justin

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