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433Mhz module problems
#11
(06-02-2017, 23:18)uncle_bob Wrote: Apparently it's a major consideration with PCB's on spacecraft.


This is a problem to all PCBs, especially to those used in places where air moisture is high.
Unfortunately most people think dendrites only occur in very special conditions...


Certainly this is not a board used on a spacecraft...

[Image: D4sji.jpg]
MeteoCercal - Air Quality Data
Click here to watch at my ThingSpeak channel



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#12
(06-02-2017, 23:23)AllanG Wrote: ... this kind of situation is unlikely to arise but it's good to know the potential problems that can arise.

That is exactly the point... being aware of that possibility, and take precautions.
MeteoCercal - Air Quality Data
Click here to watch at my ThingSpeak channel



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#13
(06-02-2017, 23:32)Werk_AG Wrote: Regarding the use of sockets for the RF modules (both RX and TX) personally I only use them in test units, and never on production units. I do it not only because of the possible problems with the connections on the socket, but mainly because the path of the RF signal increases and change. Ideally the path between the RF output (or input) of the module and the antenna should be as short as possible.

I agree completely, Werk_AG, and certainly in the future if I'm using wifi tx modules I *will* mount them directly on the board. In the past I have constructed pcb's for use at microwave frequencies and would never even *think* of using any sockets!!

I used them on this project only because originally I wasn't sure the wifi modules I ordered were the correct ones and would work. In that case it's a lot easier to unplug than to unsolder... Confused 

Allan.
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#14
Looks like I was getting them confused with Tin Whiskers
https://nepp.nasa.gov/Whisker/background/index.htm#q4
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#15
(07-02-2017, 01:37)uncle_bob Wrote: Looks like I was getting them confused with Tin Whiskers
https://nepp.nasa.gov/Whisker/background/index.htm#q4

Hi my friend,
It seems so! Smile

From that page:
"Dendrites" are NOT "Whiskers"
MeteoCercal - Air Quality Data
Click here to watch at my ThingSpeak channel



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#16
Yep, that gave it away Smile
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#17
Hi,
When I used to do electronics for a living  in Gw labs we used to conformal coat all our finished pcbs to prevent this happening

I cannot post the Url, but have a look at the Electrolube website, they still sell numerous conformal coat products, paint on and spray can.

Maybe a worthwhile Exercise.?

Cheers

Patrick
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#18
Hi

Further.  thought about external electronics.

You can either hermetically seal them into a waterproof box, or put the pcbs into a vented enclosure with the vent being a breathing dessicator, expensive though!

It would be good to include a sachet of silica  gel crystals in the box.

We built electronic ground equipment fot use at Woomera range. One box of electronics failed after a week, it was full of water from condensation from the box -pumping air in and out due to the temperature changes day to night.in the dessert. Completely overcame the dessicator.i

Cheers

P
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#19
In the past, I also have had the TX module become intermittent and ultimately fail. It would not transmit for long periods of time, producing graphs similar to the one on the first page. Then it simply stopped working. I attempted to resolder individual components on transmitter module in hope to revive it, but without success.

Replacing it was my only option and needed to wait for shipping. Now I hold one TX module in reserve in case it happens again. When I build my second WeatherDuino TX Board up in the coming weeks, I will make it more modular, so I can easily plug in and unplug the TX module for replacement. This will save having to unsolder the module off the WeatherDuino TX board and make for quicker repair.

In the past I have also had reception problems and I have narrowed it down to when I place the RX unit on my desk, next to my computer monitor or on my cabinet next to my TV. When these monitors are on and working, my data I get becomes very unreliable. I can watch the receiver's receiving LED flash away as it should but as soon as a monitor is turned on, it will flash very irregular. The data stream shows this too on the computer. Solution, I have to have my RX unit half a metre away from my monitors.
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#20
I can safely say I too have, or am experiencing the same. I noticed about a month ago all external sensors jammed. When I looked at the graphs discovered the long period of no transmission and then it would just start again.
Initially I found one of the antenna wires had broken so made perfect sense. I replaced the whole fly lead and socket since I purchased extras. No problem for two weeks and then noticed again periods of no transmission, yet much shorter intervals.
It is very intermittent. 
I will replace the module.
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