Condensation problem?

Bronson

Hi,

I just finished a project: connecting an electronic scale to LED display through RS-232 using BS2.
The BS-2 board is working properly on normal condition, but when it is used in the cold storage (temp: 10 C), after 1 hours the problem arises. The BS2 hangs.
Then the board has to put inside the heater cabinet for 5-10 mins to get it back to work.
Do you think it is the condensation problem? I have used the silicon coating to protect my board, it only helped up to 2 hours.
The scale and the LED display itself are working fine. Or maybe the BS2's IC cannot stand up to 10 C degree?

Pls help me, what should I do? The BS-2 board has to be used at least 3 hours non-stop.

Alan Bradford

Hi Bronson,

The stamp should be able to function @ 10c. Can you look at any of the I/O lines with a meter or scope to see if they are active?
When you say 'Hangs', does the display stay on, but no I/O functions, or does everything wink out?

If you think It may be a heat issue, put a small lamp in the enclosure, to keep it warm and see if the problem goes away.

I would suspect it is more like a poor (Cold) solder joint or bad connection. When it gets cold and contracts it opens a circuit and causes the problem. When you warm it up does it start running again. Can you warm it without shutting it off? Will it restart on its own, or do·you have to power it down and back up?

Check all the solder joints for 'Cold' connections. They will· be gray and dull, unlike a good solder connection that is shiny.

Good Luck,

Alan Bradford
Plasma Technologies
www.plasmatechnologies.com

allanlane5

How is it being powered? A frozen battery doesn't work very well.

Bruce Bates

Bronson -

You said: "I have used the silicon coating to protect my board ...". Can you provide a link or description to the coating you used? It should be what's known as a conformal coating, and I just want to make sure that it is just that.

Regards,

Bruce Bates

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stamptrol

Temperature of 10C (approx 50F ) should be no trouble. I've run Stamps at -30C hanging off the bottom of fuel delivery trucks.

I think Alan's suggestion of solder joint trouble is probably what you're seeing.

On some of our fish farm projects, we sprayed the boards with a silicone based varnish which takes care of any condensation issues. But, ordinary clear lacquer from an auto parts store works almost equally well.

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Tom Sisk

http://www.siskconsult.com
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Bruce Bates

Tom -

I'm not doubting what you said, one iota! However you said:

"On some of our fish farm projects, we sprayed the boards with a silicone based varnish which takes care of any condensation issues. But, ordinary clear lacquer from an auto parts store works almost equally well."

Could you expand on that and indicate the environment?

We may be spending WAY TOO MUCH on reasonably thick, silicone or "coal tar" conformal coatings, when a mere coat of decent sealing laquer might do. My father always told me I was an expert at building a BRICK outhouse

Thanks!

Regards,

Bruce Bates

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stamptrol

Hi Bruce,

At the risk of being moved to the Sandbox.....

The stamp controllers were a board based controllers of our own design ( the EnT ) which were mounted inside a fibreglas enclosure approx 12" x 12" x 8" deep. Inside was the board, solenoids, etc. These boards were in turn mounted on the railing of fish cages moored about a mile off-shore . Cabling for video, control, as well as the pneumatic source for the air cylinder ran back to the barge which contained the generators, air blowers, control room and 100 tons of fish feed. There was provision for, I think, 24 controllers on the network.

Our experience was, as long as the boards were mounted on edge, the condensation could be controlled with either the silicone or the lacquer spray. We did both sides of the board so the chip pins were also protected. Temperatures ran from almost +30C in summer to -30C in winter. Other than being messy, I think even a coat of WD-40 would keep condensation at bay.

It must be said that being able to survive condensation is NOT the same as being waterproof! The fibreglas box must seal absolutely tight!

Cheers

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Tom Sisk

http://www.siskconsult.com
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Bronson

Wow,

Thx for the response guys....
I am using silicon coating :TOSHIBA TSE399-W.
All the devices are powered by AC Power (no battery at all).

I would like to put a small lamp in the enclosure, to keep it warm as the suggestion from Alan. But I am afraid that other components can't stand with the heat inside the tight closure. What kind of lamp do you suggest?

Also, can anyone suggest which silicon coating I should use to provide better protection from condensation?

Regards,
Bronson

Alan Bradford

Hi,

I would try one thing at·a time. If you do 3 things and it works, you will not know what the problem was, and which fix, fixed it.
Thinking about 10C, as not being that cold, I would try the coatings first. (After looking for the cold solder joints.)

If you are running it from 120 VAC, what is your power supply? If you have a linear regulator, that could be your heat source.

I have Stamps working in the high heat of Phoenix, the humidity of Oakland, the freezing winters of New Hampshire, the coast of Maine, and lots of other places.·These are used in Plasma Cutting Machines with water tables. Sometimes the water in the tables freeze, but the stamps keep on Stampin. I use the plain old BS2 most of the time. I have never had any problems with condensation, heat·or humidity.· I do not coat any of my PC Boards. Some of the units are in sealed NEMA 12 enclosures, but the NH and Maine units are not in sealed enclosures. Both of them are in vented enclosures, inside industrial buildings that get real cold when the big doors are open and the winter winds fill the shops. The one right on the coast is at the US Navy Yard, and the doors to the ocean are open most of the time.

I still think it may be a connection problem. But thats my 2 cents worth.

Alan Bradford
Plasma Technologies
www.plasmatechnologies.com