Hello All,
I have a project I am working on that involves using an Arduino to read environmental conditions (i.e. ambient temp, %RH, etc). I am looking for an explosion proof enclosure to house the Arduino and components in. Obviously the sensors will have to access to outside of the enclosure in order to obtain the environmental readings. Any ideas?!?!?!?
I am so following this thread! I can't wait to hear where the explosions fit in.
@RuggedCircuits --
I hate to dissapoint, but my reason for needing an explosion proof enclosure is not to protect the Arduino from an explosion (which would be totally Rambo :)) but rather to prevent the circutry from being in contact with a potentially hazourdous environment. I need to make the Arduino and all related electrical components intrinsically safe.
I do agree with you though, we need some fireball Arduino projects!!!!
we need some fireball Arduino projects
I've had one or two that smoked :
Oh...bummer. I wanted big boom.
Well, what are the details? Temperature extremes, etc.? You know the Arduino is not going to work at certain temperatures. What other hazards are you trying to guard against? moisture? dust? vibration?
The temp won't get to what I would call "extreme", so that shouldn't be a problem. I need to be able to take readings for RH, ambient temp, substrate temp (the substrate is metal - so some sort of probe that will make contact with the steel), and dew point.
I would like to have this data streamed via the internet in real time (thinking about using pachube.com for this interface). A wi-fi shield won't work b/c the point of data collection will be out of wi-fi reach. What sort of shield do I need?
Thanks for the help
And there was me thinking you were a member of the Taliban wanting to use the Arduino to trigger IED's!
In my youth I used to go caving, when carrying a camera underground it needs to be protected from wet and knocks. Standard practice was to use an ammunition box from army surplus. You could try one of these.
P.S. There is a story of when I went caving in Ireland in the early 70s and my car was searched by the army. I was asked to open the back of the car and when they saw the ammunition box they all took a step back and raised and cocked their rifles. I was asked very politely to open it, relieving my camera. It was "one of those" moments. 
Presumably you are talking about the normal use for an explosion proof box which in the case of an explosion inside the case, the resulting gases upon exit are cooled to the point that they will not ignite the surrounding atmosphere? There are various classes depending on what the surrounding atmosphere is.
There are boxes designed for this purpose and so rated and they are plumbed up to the various sensors through similarly rated conduits and maybe smaller boxes for the sensors.
You can buy various types of sensors with explosion proof ratings and they almost always have threaded fittings. Everything just mentioned always comes with a healthy price tag.
Now you mentioned intrinsically safe and that is something altogether different. I won't go into a lot of detail unless that was what you meant instead.
I have designed and had approved both kinds of systems.
Intrinsic Safety is what I need for this project. The overall goal is to "shield" (not arduino shield) the electrical components from the atmosphere they will be recording. Think a miner flashlight that has to be intrinsically safe in the mine. Is this making sense??
Perfect sense. In layman terms, because you need to get a product certified before you can claim it is Intrinsically Safe, any currents entering or leaving your product that can somehow produce a spark must do so in such a way that the spark doesn't contain enough energy to ignite the surrounding atmosphere. Again, there are classes.
If you get more specific about the exact types of sensors you will be using, I can make some suggestions. I can tell you up front that no Arduinos that I am aware of are IS and cannot be made so without a complete redesign so that part will have to reside in an explosion proof box.
I can tell you up front that no Arduinos that I am aware of are IS and cannot be made so without a complete redesign so that part will have to reside in an explosion proof box.
And if I'm not mistaken if any individual components are not certified for the required electrical area classification requirements there must to a 3rd party inspection/certification performed to verify compliance for I.S. installations. I use to work in a oil refinery and complying with all the electrical area classifications was an expensive time consuming task. Because the Arduino most likely lacks any electrical standards listing (UL, CSA, etc) there are probably hurdles to get one blessed for installation is a I.S. installation.
Lefty
Lefty
It's best to hire a consultant to review the design at all stages before you submit to Factory Mutual, etc. for certification. It's a real racket and you're not likely to get approval unless you jump through the hoops in just the right order.
Micajah, search on zener barriers and intrinsic safety. You can place your Arduino in an explosion proof box and protect the inputs and outputs through certified barriers. There are severe voltage and current restrictions when using the barriers as they are basically resistors and zener diodes.
If the current/voltage requirements of your sensors and processor meet the restrictions imposed by the barriers then you have a chance. Otherwise, you'll have to find or design/invent some that do.
If you are to be held accountable for the design, you would do well to get a PE to consult with you on the job. Having to pay for a refinery or such will really cut into your profit margin.
In my past history as a network solutions architect, I've had to come up with enclosures that work in inviromeents like breweries (where you really don't want beer in your Ethernet switch) to paper plants where you need to have network components in close proximity to wonderful things like Chlorine (in large quantities).
You want to research NEMA enclosures: http://www.nema.org/prod/be/enclosures/upload/NEMA_Enclosure_Types.pdf
You can find a lot of them at mouser for example: http://www.mouser.com/Search/Refine.aspx?N=254149&Keyword=nema&FS=True
pete
pwillard, I believe the issue here is to protect the location, i.e. an explosive environment, not the instrumentation, although an explosion proof enclosure will certainly keep the hardware safe.
Nema enclosures are designed to protect their contents and are definitely not rated explosion proof in the sense of this thread.
Sorry: This was my understanding...
..to prevent the circutry from being in contact with a potentially hazourdous environment.
Which seemed to me to be very similar to my need to protect Ethernet gear from chlorine and beer... sorry again if I sent us astray with NEMA information.
I agree it was easy to interpret that the way you did. Plus, beer is a lot more fun especially if you get to blow something up.
Which seemed to me to be very similar to my need to protect Ethernet gear from chlorine and beer... sorry again if I sent us astray with NEMA information.
Well it's not really astray, as proper NEMA enclosures can be used in many I.S. installations, provided the internal components all carry the proper I.S. ratings and approvals. Lacking that, then explosion proof enclosures are a different way of meeting IS requirements. It can be quite complex, hard to interrupt and as EJ said, boarders on being a racket at times.
There were several times is the refinery that we had to wait a year or more before using some new technology instrumentation, having to wait for the instrument company to obtain FM approval of their new product.
Lefty
To everybody who has replied ---
I am very grateful to all the helpful input. Keep it coming!!!
As a newbie to not only the Arduino but to microprocessors in general I am realizing I have a long road of learning ahead of me. With the help of these communities I think I stand a chance.
I am going to keep researching intrinsic safety as I really want to get this project of environmental monitoring off the ground.
Peace & Love to all
Just remember, avoid all liability. At all costs. No matter what.