Author Topic: How well does a Moteino hold up under heat?  (Read 8422 times)

WhiteHare

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How well does a Moteino hold up under heat?
« on: August 31, 2015, 03:23:37 PM »
Thinking of a quick hack to modify one of:

http://www.ebay.com/itm/2xSUPER-LED-SOLAR-POWER-RECHARGEABLE-PIR-MOTION-SENSOR-SECURITY-LIGHT-DOOR-WALLS-/252053834350?hash=item3aaf944a6e-SOLAR-POWER-RECHARGEABLE-PIR-MOTION-SENSOR-SECURITY-LIGHT-DOOR-WALLS-/252053834350?hash=item3aaf944a6e
to include a Moteino inside and thereby make an inexpensive outdoor motion sensor.  I like that it's solar powered, but if it were to get direct sunlight I suppose the sun might heat it up to 150F or maybe more inside. What's the practical upper limit for how hot a temperature it's safe to operate a moteino?

TomWS

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Re: How well does a Moteino hold up under heat?
« Reply #1 on: August 31, 2015, 05:46:10 PM »
if it were to get direct sunlight I suppose the sun might heat it up to 150F or maybe more inside. What's the practical upper limit for how hot a temperature it's safe to operate a moteino?
I'm not sure where you're located but it seems unlikely that the temperature would go that high given that the enclosure appears to be metal (shiny at that) and attached to a wall.  Maybe the wall is a super insulator, but most construction materials would act as a heatsink to some degree and only a portion of the enclosure is a solar collector.

I don't know the answer to your question, but I've had motes running in my Workshop loft when its reached 118 degrees during the heat of the day without failure.  I'd be more inclined to expect battery failure before the Mote fails and, since this is a commercial unit where presumably they'd be out of business if the batteries routinely fail, that further reinforces my suspicion that the temps don't reach a point of failure.  However, this is pure speculation on my part  ;)

Tom

kobuki

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Re: How well does a Moteino hold up under heat?
« Reply #2 on: August 31, 2015, 05:56:01 PM »
I was thinking of using a similar LED outdoor assembly with built-in solar panels earlier. It should be noted that this panel is only providing 2V and it seems to have a single 1.2V battery to hold the charge. I'd expect a direct connection between the 2 using a protection diode. This is not going to drive the Moteino without a step-up converter of some kind. But there are many kinds of similar LED nigt lights on the cheap...

WhiteHare

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Re: How well does a Moteino hold up under heat?
« Reply #3 on: August 31, 2015, 07:30:51 PM »
I'm in Texas, and the sun is truly fierce in July and August.

Looks as though for ATmega168/328 maximum ratings
Operating Temperature.................................. -55 C to +125

According to the RFM69 datasheet, the absolute maximum temperature it can tolerate is 115C.

So, aside from the battery, what else might fail?  Isn't it usually a capacitor?  Are they all ceramic on the Moteino?  I don't know enough to ID what they are made from or have a good guess as to what their upper temperature limit is for continuous use.

I picked 150F as a hopefully worst case, only because I've read that some asphalt roof shingles can get that hot under the sun, because that's the only top of mind reference that I have, imperfect though it is.  Polished metal isn't very emissive though, so it might get just as hot or maybe even hotter, so it's just a ballpark figure.

It's frustrating to shop for consumer gear.  For instance, I'm now realizing the picture I posted above probably doesn't even have PIR, even though it says it does.  I say that because I found what looks like the same thing on Amazon, and it makes no mention of PIR, and there's no obvious visual indication either that it might be there. 

I thought the metal would be preferable to plastic, despite the emissiveness problem, if only because I've seen plastic get yellower and yellower after hours of sun exposure accumulated on some expensive Optex PIR sensors I once had.  So, I could address the emissiveness by painting it, but then that's more work for me.  Or, I suppose I might just as well paint a plastic enclosure, and then it wouldn't yellow.  However, in both cases, that's me doing the work and not chinamation, which is where it should be done.    Furthermore, anything that isn't metal or painted will probably fog over under sun exposure, including the epoxy enclosing the solar cell itself, plastic lensing, etc., since it's not behind glass.  Argh, so often it seems there's just almost never any consideration whatsoever given to product longevity...

kobuki

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Re: How well does a Moteino hold up under heat?
« Reply #4 on: August 31, 2015, 07:47:46 PM »
Uh, yeah. I remember I was eyeing a variant of this one, exactly because its cover around the solar cells is made of aluminium alloy where the sun hits it the most.

TomWS

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Re: How well does a Moteino hold up under heat?
« Reply #5 on: August 31, 2015, 08:53:54 PM »
I wouldn't worry about emissivity.  It's conductivity that you care about.  You want the enclosure to conduct the heat into the mounting walls and away from the heat source. 

Texas?  Been there, done that.  I had moisture sensors installed 6" underground reach temperatures of 117 degrees by mid-day.   The WORST thing that happens, besides battery contacts corroding, is the PVC NEMA 4 enclosure edges curling up from the heat!  Aluminum?  Excellent.  Stainless?  Wow, if you can afford it. Plastic? NFW!

However, besides all that, do you really need to have a light that emits only 12lumens in the best case?  As a 'security' light?   Uh, I'll bet you could find SOME other power source for this application.  And I'll bet you can find a PIR sensor you can rely on.

Tom

WhiteHare

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Re: How well does a Moteino hold up under heat?
« Reply #6 on: August 31, 2015, 09:00:57 PM »
@Kobuki Not bad.  If mounted on a north facing fench wall,  it might be the best.  For a different direction, here's a stainless steel one that may be angled to catch a bit more energy: 

http://www.amazon.com/Wireless-Activated-Security-Lighting-Staircase/dp/B00N4L1VMS/ref=pd_rhf_gw_p_img_2?ie=UTF8&refRID=1D65EW5ZSC31X002TNB4

 I'd still prefer to know the heat risk, if any, to the capacitors though...


« Last Edit: August 31, 2015, 09:40:33 PM by WhiteHare »

WhiteHare

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Re: How well does a Moteino hold up under heat?
« Reply #7 on: August 31, 2015, 10:52:17 PM »
Uh, yeah. I remember I was eyeing a variant of this one, exactly because its cover around the solar cells is made of aluminium alloy where the sun hits it the most.

@kobuki
By chance I noticed a few reviews on youtube for it while I was looking for something else  :


kobuki

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Re: How well does a Moteino hold up under heat?
« Reply #8 on: September 01, 2015, 05:47:34 AM »
Yeah, thanks. Though my purpose was rather removing the light and hack some other electronics and a moteino inside. I didn't need a night light. But these have a solar panel + charger and plenty of space inside for so little money they're asking to be hacked. OTOH, you could even order one and tuck in any temperature sensor you can find to check the inside temperatures if that's your only fear.

WhiteHare

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Re: How well does a Moteino hold up under heat?
« Reply #9 on: September 01, 2015, 07:32:02 AM »
I had moisture sensors installed 6" underground reach temperatures of 117 degrees by mid-day. 
What part of Texas was that?  I don't think my soil temperatures ever exceed 80-85 degrees at that depth.  The "cold" city water comes out of the tap at about 80+F during the hottest part of the summer, which still seems freakish to me.

Nonetheless, that temperature would be cool compared to above ground, so for the longest time I've been thinking it would make sense to have just the solar panel and antenna and "peripherals" like LEDs or sensors above ground and plant the rest of it, especially batteries, into the ground.  For one thing, it would address my safety concern about using Lithium batteries in the heat because if, worst cast, it burst into flames, I don't know that it would cause any danger at all if it were buried.

That idea starts to fail though if your underground temperature reaches 117 degrees at 6 inches.  In such a case I guess you'd just have to dig deeper (not necessarily easy if your native soil is rocky) or else go for something shaded above ground.
« Last Edit: September 01, 2015, 07:38:25 AM by WhiteHare »

Felix

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Re: How well does a Moteino hold up under heat?
« Reply #10 on: September 01, 2015, 07:45:50 AM »
You should have no issues from -20 to 130 - FAHRENHEIT, tested by myself in various deployed nodes around the home.

TomWS

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Re: How well does a Moteino hold up under heat?
« Reply #11 on: September 01, 2015, 07:59:14 AM »
I had moisture sensors installed 6" underground reach temperatures of 117 degrees by mid-day. 
What part of Texas was that?  I don't think my soil temperatures ever exceed 80-85 degrees at that depth. 
Georgetown, just north of Austin. Yes, the 'soil' was very rocky (actually layers of limestone separating thin layers of some kind of sandy dirt). That particular sensor was in the middle of the sunny 'lawn' (if you can call burnt Buffalo grass that).  The temperature sensor type was an MCP9700 IIRC with a PIC processor and Linx 418MHz transmitter module 'tucked' away, in the shade of a tree, in one of those 4" PVC NEMA 4 boxes whose edges curled from the heat after 5 years...  Still the whole thing ran for years on two AA Lithium batteries.

Tom

WhiteHare

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Re: How well does a Moteino hold up under heat?
« Reply #12 on: September 01, 2015, 08:32:07 AM »
I had moisture sensors installed 6" underground reach temperatures of 117 degrees by mid-day. 
What part of Texas was that?  I don't think my soil temperatures ever exceed 80-85 degrees at that depth. 
Georgetown, just north of Austin. Yes, the 'soil' was very rocky (actually layers of limestone separating thin layers of some kind of sandy dirt). That particular sensor was in the middle of the sunny 'lawn' (if you can call burnt Buffalo grass that).  The temperature sensor type was an MCP9700 IIRC with a PIC processor and Linx 418MHz transmitter module 'tucked' away, in the shade of a tree, in one of those 4" PVC NEMA 4 boxes whose edges curled from the heat after 5 years...  Still the whole thing ran for years on two AA Lithium batteries.

Tom

That's interesting.  I'm in Austin, so I guess the temperature difference must be due to all that hyper-expensive water I'm foolishly dumping onto my mostly green St. Augustine lawn.  So, I guess the ground temperature difference is mainly, or at least partly,  due to cooling from evapotranspiration and the way living grass reflects IR and green wavelengths and the way dead grass doesn't reflect IR or (obviously) green wavelengths either.
« Last Edit: September 02, 2015, 11:46:17 AM by WhiteHare »

TomWS

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Re: How well does a Moteino hold up under heat?
« Reply #13 on: September 01, 2015, 11:48:05 AM »
So, I guess the ground temperature difference is mainly, or at least partly,  due to cooling from evapotranspiration and the way living grass reflects IR and green wavelengths and the way dead grass doesn't reflect IR or (obviously) green wavelengths either.
Yes, very likely.  The case that I cited occurred toward the end of a very long dry spell where no amount of watering would help so I simply gave up.  Buffalo grass can deal with that to some extent.  St. Augustine probably won't.

When I first deployed my moisture sensing units, I proudly told a colleague (who was born and raised in TX) at work about it.  His comment was, "What's it gonna tell ya?  That its dry?"

Yup, that's pretty much it.
Tom

luisr320

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Re: How well does a Moteino hold up under heat?
« Reply #14 on: September 01, 2015, 03:02:11 PM »
I have a moteino inside my car engine bay for months and nothing stopped working until now. I have made about 3 hours or continuous rides with it next to the 90ยบ Celsius engine and never stopped working.
As far as I know, there is a slight shift on the transmitting frequency when the crystal is heated but I still get a very good range out of it, even from inside the metal structure of the car.
Top notched peace of technology!!!  ;) ;) ;) ;)
Just go ahead with that project and don't forget to shows us some pics.