Solar powered & other independent/remote projects

scribb · 2004-08-22 13:40

I'm just wondering·how many·of you people have used·a BASIC Stamp in a·solar powered·/ remotely located·/ marine project...
I want to know how well the stamp can withstand adverse weather conditions (temperature extremes, humidity, etc.).

Please, share your·stories·about any·projects like this.

Thanks,
Sheldon

Bruce Bates · 2004-08-22 13:56

Sheldon -

So long as your project or product is hermetically sealed, there shouldn't be any problems with outdoor, marine use. I've used PVC enclosures sealed with GE RTV compund or other similar sealants with great result. It's also reentrant by merely slicing through the sealant with a razor, if necessary, at a later point in time.

You may be interested in knowing that the BS-2 Stamp is available in and industrial version which has extended temperature capabilities: - 40C --> + 85C (-40F --> 185F). The Industrial BS-2 Module can be found here:
http://www.parallax.com/detail.asp?product_id=BS2I-IC

Regards,

Bruce Bates

Tracy Allen · 2004-08-23 00:21

As Bruce says, there are things you can do with the packaging that will make the Stamp run in adverse conditions along with the best of them. But the packaging is the key. If condensation forms on the circuit board (your carrier board or on the Stamp itself), bad things can happen. For example, the clock oscillator might stop, or refuse to wake from sleep. Wet powered circuits can corrode. These are no more issues with the Stamp than they would be with any electronics. "How well the stamp can withstand adverse weather conditions" will mostly depend on how well you keep it out of the rain!

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Tracy Allen
www.emesystems.com

KenM · 2004-08-23 00:57

Has anybody tried re-using·a small packet of silica gel that is commonly found in products where moisture is undesireable?

Tracy Allen said...
As Bruce says, there are things you can do with the packaging that will make the Stamp run in adverse conditions along with the best of them. But the packaging is the key. If condensation forms on the circuit board (your carrier board or on the Stamp itself), bad things can happen. For example, the clock oscillator might stop, or refuse to wake from sleep. Wet powered circuits can corrode. These are no more issues with the Stamp than they would be with any electronics. "How well the stamp can withstand adverse weather conditions" will mostly depend on how well you keep it out of the rain!

Tracy Allen · 2004-08-23 01:38

Yes, a desiccant can help. They can be reacitivated by heating to a specific dry temperature for a few hours.

It is not a cure-all, though, because one pack of desiccant can only absorb so much moisture. That is fine if the box is really sealed, or hermetically sealed as Bruce pointed out. The entry of water vapor should be nil or so slow that the desiccant can keep up.

If an enclosure is exposed to the elements, especially outdoors with direct exposure to sun and sky, pressure changes inside a sealed box can be tremendous as the box heats up in the direct sun and then cools off under the night sky. The seals on the box and on the entry points for cables connectors etc. have to be exceptional in order to keep the flow of air and moisture out. Moisture that enters the box at night in the vaccuum conditions may not escape in the daytime. Pressure dropping and temperature cooling at night => condensation. You may come back to a "sealed" enclosure and find a puddle of water in the bottom.

For that reason, some people eschew complete sealing of the enclosure and put a vent in the bottom so that the pressure cannot build up. Gore (as in Gortex) sells expanded teflon vents for this purpose. It is a good idea to use double roofs or other techniques to lessen the temperature extremes and rates of change.

There is another consideration in solar powered systems, because usually the solar panel will be charging a battery located inside the enclosure, and the battery may give off gases including H2O that have to be vented. A good sealed battery properly float charged will not vent much, but it is really touch and go if the system needs to do any fast charging. A vented enclosure is essential for that.

-- Tracy

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Tracy Allen
www.emesystems.com

SPENCE · 2004-08-23 01:46

Larry · 2004-08-23 01:58

Some dessicants need to be heated to a higher degree than others. Most common ones will do well at 300 F. for 20 min or so. Some, like Zorbit, only need 100 F. some even have crystals that change color when they are good or not.

Take a look at : http://science.howstuffworks.com/question206.htm

for info and links to other dessicants

Larry

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KenM · 2004-08-23 02:07

Correct me if wrong......the effects of pressure changes, (and hence vacuum when cooled off) due to delta temperature inside the vesseal can be minimized if a vacuum is pulled on the vessel and sealed. Obviously easier said than done, especially for the hobbyist.

Tracy Allen said...
Yes, a desiccant can help. They can be reacitivated by heating to a specific dry temperature for a few hours.

It is not a cure-all, though, because one pack of desiccant can only absorb so much moisture. That is fine if the box is really sealed, or hermetically sealed as Bruce pointed out. The entry of water vapor should be nil or so slow that the desiccant can keep up.

If an enclosure is exposed to the elements, especially outdoors with direct exposure to sun and sky, pressure changes inside a sealed box can be tremendous as the box heats up in the direct sun and then cools off under the night sky. The seals on the box and on the entry points for cables connectors etc. have to be exceptional in order to keep the flow of air and moisture out. Moisture that enters the box at night in the vaccuum conditions may not escape in the daytime. Pressure dropping and temperature cooling at night => condensation. You may come back to a "sealed" enclosure and find a puddle of water in the bottom.

For that reason, some people eschew complete sealing of the enclosure and put a vent in the bottom so that the pressure cannot build up. Gore (as in Gortex) sells expanded teflon vents for this purpose. It is a good idea to use double roofs or other techniques to lessen the temperature extremes and rates of change.

There is another consideration in solar powered systems, because usually the solar panel will be charging a battery located inside the enclosure, and the battery may give off gases including H2O that have to be vented. A good sealed battery properly float charged will not vent much, but it is really touch and go if the system needs to do any fast charging. A vented enclosure is essential for that.

-- Tracy

steve_b · 2004-08-23 17:06

The trick to using the dessicant, as someone already stated, is to be sure there is enough of it so that it can absorb humidity for a given area.
Don't use a 2'x2' box if you are just going to put the BOE in there.· Use a 3"PVC pipe cut short and capped at both ends with a small dessicant pack in it.

Something to note:· someone mentioned about daytime heating and nighttime cooling.· The pressure changes here create a "pumping" affect which if you have the slightest pinhole leak, can suck moisture in.· I can't go through and tell you all the physics of all this....but in the field we've opened NEMA rated boxes to find a couple inches of water in the bottom of the box.· (Those pinholes are good for drawing water in, but don't think for a second that the water will necessarily go back out the same hole!).

We had picked up a bunch of these boxes and were having problems with them all....mostly because they were used or had holes already predrilled (can't remember, but we tried sealing them as the holes were of no use to us).
Anyhow, sort of a novelty bandaide solution was to glue a balloon (used a condom at the time -- ribbed of course! I'm not selfish! haha) to the opening of the hole (glue the open edges to the inside of the box).
Now when the "pumping" would occur, there was enough relief with the balloon in the opening that no water was sucked in.· Kinda funny to watch the condom blow up in the middle of the day....Just remember they're not UV rated and there's no where near enough pressure change to blow it up!

I work with weather sensing equipment, so this obviously doesn't work on barometry boxes (you NEED an opening to the 'real world' in this case!).

Anyhow, if you are reusing old boxes that you find to be well oversized for what you need them for....try getting some 'cheese-cloth' (what old ladies wrap their herbs in to dry) and fill it will kitty litter or absorb-all or something like that (vermiculite??).· Leave it in the bottom of the box· and be sure to mount your electronics up out of the way (in case of a few inches of water getting in to the box that your electronics will not be sitting in it!).·
that's just a quick suggestion off the top of my head!·
I know people that put vaseline on their car battery terminals to stop oxidization....it's messy but not as perminant as silicon.

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·

Steve
http://members.rogers.com/steve.brady
http://www.geocities.com/paulsopenstage

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

K de Jong · 2004-08-23 17:43

Hi Steve and others on this thread,

I'm very impressed by the methods you describe to keep wate out of your equipment boxes. You seal everything!!

In contrast to your methods I deliberately leave a small hole (3 to 5 mm) open at the bottom of the box. So, no vacuum, no pumping water in and if some water comes in it can go out easily.

The little bit of heat the electronics produce gives a lower relative humidity inside the box. So, to my exprience, there is actually no problem with condensation.

It works fine for me, even with the very fast weather changes we have here in the Netherlands!!

Regards,

Klaus

Bean · 2004-08-23 18:56

Awhile ago we had thought of covering our circuit with wax. Then if we needed to we could heat it up and melt off the wax. But we never tried it.

I was wondering if anyone else had used this method ?

Terry

Beau Schwabe · 2004-08-23 19:58

Terry,

Seems like I have seen this method in old electronics... radios specifically, but not for keeping
out moisture (I don't think), but to stabilize a tuning coil or something. Many circuits I saw were
very liberal with the wax. Bottom line is that I don't think it would hurt anything, and it might
work to keep the moisture out...or in depending on how and when you applied the wax (grin)

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Beau Schwabe Mask Designer II

National Semiconductor Corporation
(Communication Interface Division)

500 Pinnacle Court, Suite 525
Mail Stop GA1
Norcross,GA 30071

steve_b · 2004-08-23 20:01

K de Jong said...
In contrast to your methods I deliberately leave a small hole (3 to 5 mm) open at the bottom of the box. So, no vacuum, no pumping water in and if some water comes in it can go out easily.

The little bit of heat the electronics produce gives a lower relative humidity inside the box. So, to my exprience, there is actually no problem with condensation.

It works fine for me, even with the very fast weather changes we have here in the Netherlands!!

We have equipment up in northern Canada (and lower arctic) that we don't worry about.· The relative humidity is so low (15%-ish) that the issues with non sealed equipment is that it heats up the inside air and pushes all the moisture out creating a vacuum.· We end up using a screwdriver to open the box next visit that wrecks the gasket.·
But we still like a good tight seal (insert favorite Walrus joke) so that we don't end up with bugs or even snow inside that melts from the equipment heat.

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·

Steve
http://members.rogers.com/steve.brady
http://www.geocities.com/paulsopenstage

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

K de Jong · 2004-08-23 21:12

Hi Steve,

Tja, arctic conditions is a special case, I would think.

But in more general

K de Jong · 2004-08-23 21:16

Hi Steve,

Tja, arctic conditions is a special case, I would think.

But in more general conditions it can sometimes be favorable to use a vent in stead trying to close a box as closed a box can be.

Try a small vent with a piece of pipe some inches downwards.

Regards,

Klaus

steve_b · 2004-08-23 21:59

I've seen some box vents made with goretex type membrane that will let air in and out but not moisture.

http://www.pmc1.com/Capability.asp?CapabilityID=223&Cat1ID=84&Cat2ID=107

this is a quick google result.·

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·

Steve
http://members.rogers.com/steve.brady
http://www.geocities.com/paulsopenstage

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

K de Jong · 2004-08-23 22:09

This could be an even better solution !!

With these GoreTex vents sealing of equipment will be unnescessary in many cases. Especially if you put some heat into the box abslolutely no condensation will take place.

Regards,

Klaus

Tracy Allen · 2004-08-23 23:39

Here is a photo of a Gore-tex vent on one of our Vinker enclosures. It screws into a standard PG7 opening:

The vent is the slotted object in the upper right hand corner.
...

Here is a link to a Gore descriptive data sheet: owlogic.com/pdfs/Gore-Membrane-vents.pdf
...

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Tracy Allen
www.emesystems.com

Tracy Allen · 2004-08-23 23:48

Silicone resin is one of the standard alternatives to wax. It is repairable, in that you can solder right through silicone resin. There are other conformal coatings (acrylic for example) that also protect the board from H2O, but are not as repairable.

We have worked with smoke detectors that are usually manufactured with a coating of wax, in particular over the high impedance electometer amplifier for the ionization chamber. As they are used in kitchens, they are otherwise quite sensitive to condensation from the humidity of cooking and other kitchen activities.

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Tracy Allen
www.emesystems.com

KenM · 2004-08-24 04:07

Just to add one point with regards to the wax method.

Have opened many vehicle wire harnesses (Korean) and they use wax to keep moisture out of wire harness splices. A typical splice might be 3 or more wires joined together with a brass crimp.

Ken

JKtech · 2004-08-25 03:23

We used hot glue to encase a circuit in a cube. It worked well but makes it unrepairable.

Sunflower · 2004-08-25 16:06

I have used Stamps outdoors for about ten years tracking solar dish
concentrators towards the sun +/- 0.008 degrees with photo resistors.
The high-intensity flux of 1000 suns increases photovoltaic power output
by 1000 times. This flux will melt steel.
http://www.harbornet.com/sunflower/pvdish.html

Outdoor DC devices can have galvanic corrosion problems after more than
five years. From experience, silicone sealer, plastic pipe, hot glue,
etc. do not make hermetic seals. Steel surplus ammunition boxes work
dry. So does vented heat. The Stamp and Motor Mind C produce a lot of
heat. I am considering combining the micros with the shadow band photo
resistor eyes to drive the morning moisture off of the eye windows.

Several eye boxes have been invaded by colonies of tiny ants. I plugged
and replaced drain holes with very fine faucet screens.

The next Stamp will use a clock DS1307 and EEPROM to track the sun
through the clouds with data stored from solar dish positions on
previous sunny days. Also Stamp controlled and monitored: water delta
pressure, flux temperature, power output, tracking accuracy with auto
correction, clock reset via sun position, and massive error checking
routines. The large solar dish is a dangerous autonomous robot that can
(and did) start fires, burn people, and self destruct. A daunting task
for an amateur Stamp programmer

Antz · 2004-08-30 04:41

If you REALLY want something to be weatherproof, put it in a plastic bag filled with silicone grease. Tape the bag closed around the cable with a self-vulcanising tape, and put the whole bag inside a solid container. Good for extreme wet climates, and also keeps all insects at bay. A bit messy for repairs, but they are still possible.

On the other hand, down here in Antarctica, even with close to no humidity, electronics will still corrode if snow or ice gets in through the tiniest hole, as the heat from working electronics will usually be just enough to let things corrode.
Sometimes a double-container system works well, the outer one as a general buffer against driven weather, the inner one to keep the electronics dry/free of snow etc.

KenM · 2004-08-30 04:53

Antz,

How about some pics from where you work/live?

Antz said...
If you REALLY want something to be weatherproof, put it in a plastic bag filled with silicone grease. Tape the bag closed around the cable with a self-vulcanising tape, and put the whole bag inside a solid container. Good for extreme wet climates, and also keeps all insects at bay. A bit messy for repairs, but they are still possible.

On the other hand, down here in Antarctica, even with close to no humidity, electronics will still corrode if snow or ice gets in through the tiniest hole, as the heat from working electronics will usually be just enough to let things corrode.
Sometimes a double-container system works well, the outer one as a general buffer against driven weather, the inner one to keep the electronics dry/free of snow etc.

Antz · 2004-09-02 00:45

Here's a couple of pics then...

Mount Erebus, Antarcticas only active volcano.
Aurora Australis, we get a lot of them in winter. We are only just getting to see the sun now for the first time in 4 months.

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Post Edited (Antz) : 9/2/2004 8:55:55 PM GMT

Jonny555 · 2004-09-02 01:17

I've also been concerned with environmental factors(cold weather). I've been researching methods and technology for increasing survivability. One very interesting technology right out of satellite research is the thin film heater. Electric goldmine sells em quite cheap and I've been considering using the thermostat feature ont this DS1620. I am however unfamiliar with the power requirements of these items...

http://sales.goldmine-elec.com/prodinfo.asp?prodid=3252

Post Edited (Jonny555) : 9/2/2004 1:23:30 AM GMT

Chris Savage · 2004-09-02 03:06

The pics didn't come out...

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Chris Savage

Knight Designs
324 West Main Street
P.O. Box 97
Montour Falls, NY 14865
(607) 535-6777

Business Page:·· http://www.knightdesigns.com
Personal Page:··· http://www.lightlink.com/dream/chris
·

Bruce Bates · 2004-09-02 07:22

Jonny555 -

The company mentioned in the Electronics Goldmine ad, Minco, has a web site here:
http://www.minco.com/

That might be a good place to start your research on poawer requirements.

Regards,

Bruce Bates

Antz · 2004-09-02 21:12

It's been my experience that most electronics will survive quite well to -40 deg. It does pay to have cold temperature rated components though.

Temperatures below -40 are going to cause all sorts of headaches eventually.

The main problem a lot of systems have is micro-fractures on the circuit boards or in components due to temperature changes. The transition from around freezing down to -40 is pretty hard on the gear. If things can be kept at a reasonably constant temperature they are usually ok once they settle in.

In terms of moving parts, it is oftem best to run them with no lubrication, as a lot of lubricants turn sticky when it gets really cold.

PS: I reloaded the pics on the previous post.

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Post Edited (Antz) : 9/3/2004 4:20:28 AM GMT

Jonny555 · 2004-09-04 00:08

Ya minco looks like they don't manufacture those anymore... they are surplus now. I suppose that a quick email to them would yield bountifull information but I've wandered away from them as other more important aspects of my project require indepth testing. Woah why did I wait so long to get into Basic Stamps.
Big thanks to parallax... man these guys offer so much help it makes me proud to incorporate their products into my vision hehe. I can just imagine the sick demented creations others may be conjuring up with these micros.

Which brings me to my next thought...
Solar Panels, epoxy coated(heavy) or flexible(can be rolled onto a 2" pipe).
I can picture neat mechanical devices to deploy panels from a hatch of some sort either way.
But how to protect panels from harsh temperatures and varying weather...

Antz · 2004-09-04 03:23

Don't know about the flexi ones, but the solid solar panels of varying types we pretty much never have a problem with down here, and we leave them out all year round at remote repeater sites etc, where the temperature can drop to -90F / -70C ambient during the winter.
Not sure how they do in extreme heat.

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Solar powered & other independent/remote projects

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