Ask Slashdot: How Would You Suggest Making Rugged, Weather-Resistant ARM Systems?

New submitter pecosdave writes: I need suggestions for commercially-made ARM systems that will work in temperature ranges from -35F to 140F (-37C to 60C) for an engineering project. These things are going to be in metal boxes on the side of Texas Highways. The existing Intel systems we're using in other areas are all fan-less, but I'm not going to rule out systems with fans. Considering the extremes of Texas temperatures I'm actually contemplating putting fans on top of our fan-less systems anyways. Almost everything I can find pre-made with ARM is a bare board, or something not nearly as temperature tolerant as some Intel systems I can find. The very nature of an ARM processor should be more tolerant simply because they produce less heat, but I can't seem to find any manufacturers exploiting that fact. Slashdot reader pecosdave added more details in a comment: "It's more closely related to speed cameras, but it's not a speed camera. It's for a toll road, and its main job is to take pictures of a sign at about 10 FPS, though less is probably fine, with a time-stamp so if someone runs the toll we have a separate picture of the current price. If there's a problem with the sign it shows up as well. They just want something local to store it I guess in case the fiber link goes down. We're going to run it rather low-res too to keep the CPU and storage overhead low. I figure 640x480@10FPS is reasonable, but that's not set in stone."

Comments

Talk to an engineer

[guruevi]

There are plenty of industrial manufacturers that will get you a custom chip in an IP65 enclosure. My company does these things all the time, but it's a bit more complicated than just putting something in a box. You have to spec the comms, peripherals, serviceability, lifetime, support, software, updates, ...

Fans on top of fan-less design is a bit weird partially because you're going to sacrifice your IP rating and your fan shorting out or seizing up could bring the power and thus the system down. Also a fan is for moving hot air out and cooler air in. An ARM chip in most data collection circumstances won't get as hot as an asphalt highway in summer so you're just exchanging hot air for hot(ter) air, what's the point of a fan?

Re:Talk to an engineer

[Darinbob]

We stick stuff into a metal box, no fans, enamel coating. But the parts are all rated to +85c at 85% humidity (and also -40c?). Ie, they are industrial rated and not commercial rated; which has a drawback that there aren't as many suppliers and you won't find pre-made boards on the web for this.

As an FYI, if you have anything mounted high on poles then don't have any blinking LEDs on the outside. This tends to attract bullets from those looking for some target practice.

paint it white

[arsenix]

A lot of ARM systems (even raspberry PI) will live life fine at 60C. You will need a nice passive heatsink inside your box (if it is large) or thermally couple the device to the box wall and put a passive heatsink on the outside. You'll need an active heater of some kind in order to operate reliably below 0C, but that is easy. Paint your box white too... that will help keep it cool in the sun. Good luck! Also post to an appropriate reddit rather than slashdot!

Re:paint it white

[AmiMoJo]

Posted something similar in the firehose. A bit of heating would also help with the camera and is probably the easiest option.

60C isn't a problem, most ARM hardware is at least "industrial" temperature range which is up to 85C.

Seal it up to keep dust and moisture out.

There is probably an off-the-shelf CCTV option for this. They have CCTV in cold countries.

Re:paint it white

[bob4u2c]

Think outside the box. Mount your camera at the top of a simple pole mount, then run the wires down to a box at the bottom where the cpu and guts are. Then dig a hole in the ground a few feet deep and bury the box. A few feet down it should stay cool/warm year round with no active cooling/heating.

That is what we use to do with water pipes to keep them from freezing over in winter in the colder climates.

Re:paint it white

[Darinbob]

But now the box will possibly be wet or moist all year round which has its own problems. By the side of a road means you'll get some odd toxic stuff there too so you need to make sure things are resistant to corrosion. Even if above ground you can often get a lot of salt corrosion if you're closer to the ocean.

Beware of people intent on tampering. And animals. We had one product where we were considering a more expensive armored cable just to avoid problems with rodents.

I literally work on this kind of thing.

[Anonymous Coward]

This is my industry. I've worked with super ruggedized military grade ARM boards. I would go fanless, and for your application you shouldn't need much power. Products end up as metal boxes with fans if they even need that.
You've gotta find vendors which make automotive and military/aerospace grade chips, so the usual Samsung and TI OMAP chips won't always work. NXP is bigger into this space with IMX.6 chips and similar. As much as tons of developers dislike Freescale/NXP, they have a huge presence in military and embedded products for this reason.

Re:Stupid idea

[dgatwood]

Just put it in a box and fill the whole thing with epoxy. Use a big enough heat sink that the tips of the fins are exposed. Then mount it upside down so that if it gets wet, the water runs down the fins. :-)

Re:my raspberry pi & 3D printer says

[thegarbz]

What a silly suggestion. The raspberry pi 3 is thermally challenged at room temperature. Adding 40C to that would put it well above Tjmax

A few suggestions

[jrnvk]

You absolutely do not want any fans. Fans circulate air, which will only draw in dust, moisture, bugs and other foreign materials that will exponentially increase the rate of failure on your hardware. Remind yourself that most ARM manufacturers are tailored to one market: mobile devices. You will likely find the price of hardened components (the term you should be looking for) to be quite more expensive than off-the-shelf devices like a Raspberry Pi. The operating range for most of those common devices is well outside your requirements, not to mention the durability factor (dust, vibration, etc). For such a simple project, a dedicated construction or outdoor security camera with integrated storage and networking will probably tick all of your boxes. You won't find much gain in reinventing the wheel here.

The cold will get you too

[stevenm86]

I'm more worried about the -30C temperature. Worked for an unnamed ARM manufacturer for a while and we had some problems of our PLLs failing to lock below -25C. An environmental chamber is your friend. I wonder if a peltier unit with a heatsink would help. You could run it in reverse if it gets cold.

Texas Records

[srwood]

The record high in Texas was 120 F in Seymour, TX in 1936 and -23 F in Tulia, TX in 1899. The range is considerably less along MO-PAC.

Re:Fuckoff, police state enabler.

[Aighearach]

I'm pro-government, and I probably hate toll roads even more than the other guy! LOL

But the more serious answer to the question is, if it is an "engineering project" then your engineer should be telling us, you shouldn't be asking slashdot.

Are you going to need cooling? Yes, you're going to need cooling. Assuming that you have money, since you don't have an engineer you must still have the money, so you should buy a refrigerated water cooling system, and you're done asking about that part.

Since you're in Texas, you definitely want a TI-based ARM SOC, like from Octavio.

Or just buy a BeagleBone and put AC in the case, and done. That uses the Octavio.

It is all about the case, not the computer.

Re:Fuckoff, police state enabler.

[Aighearach]

This isn't true. Check out Texas Instruments. For example, all their Sitara processors are available up to 105C.

http://www.ti.com/processors/s...

I didn't even look at other lines, I just clicked the first product lines that would do the stuff in the question, eg push 32 bits around moderately fast.

Automotive or milspec line. Or te Zach to call Ray

[raymorris]

Thanks for getting this back on topic.

TI and others make units designed for automotive use which are speced for those kinds of temperatures. They are expected to work under the hood of a car, in Texas.

Just Google automotive micros or socs as needed, or call any manufacturer.

Milspec parts are similar temperatures plus a higher reliability rating.

Or, submitter could ask Zach, who works in signaling, which would then text Ray. :)

Re:Fuckoff, police state enabler.

[Immerman]

Cool! (or Hot!, I suppose)

So is that typical, or is TI an exception?

I know I still love my TI-85 calculator - I must have a first-year 1992 model as I think of the timing. That sucker has taken almost 30 years of abuse and is still going strong. I just have to remember to replace the AAs every couple of years when I cant crank the screen darkness high enough any more.

Anyway - I recall them being quite proud of the durability of the thing in their marketing, and could easily see them being an outlier in the "durable-products" category.

Re:Not just enabler. Conspiring traitor.

[GameboyRMH]

You heard it first on Slashdot folks, toll road payment checking system = war crimes.

My company makes one of these

[chendricks1]

My company makes an arm device that is packaged, hardened, and certified for long term outdoor use in Texas. It's widely deployed at drilling sites. See here for details https://www.detechtion.com/hub... We are located in Houston and happy to talk in person if you're interested...