Dreaded 85 degrees C read from DS18B20 located outside

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Eloy Paris
On 03/02/2011 05:04 PM, nick wrote:

> Here are my water proof sensors using copper pipe and HMA, they have
> worked well so far.
>
> http://kiwi-hacker.blogspot.com/2011/01/new-soil-temperature-sensors.html

Cool stuff; thanks Nick. I've also bookmarked your blog in my
"Electronics" category :-)

Cheers,

Eloy Paris.-

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Mohclips
In reply to this post by scottjilek
"That's slick, but copper in aquariums is a big no-no.  High-end freshwater or saltwater reef aquarium inhabitants like corals and invertebrates can not tolerate copper. "

True, true.  then bic biro tube cut into 3 parts would be a good replacement for the copper. :)

On Wed, Mar 2, 2011 at 10:18 PM, Scott <[hidden email]> wrote:
That's slick, but copper in aquariums is a big no-no.  High-end freshwater or saltwater reef aquarium inhabitants like corals and invertebrates can not tolerate copper.

I encased my sensors in epoxy to avoid water contact.  Just solder up the sensor, mix up some 2-part epoxy, and smear it over the chip and any wire that will be in the water.  I put on 2 "coats" just to sure it's water proof.  I've found it works well for sensing temperature - they aren't pretty, but they track temps just fine.

http://bytality.com/gallery/1-wire_setup/

As far as 85°C, my temp collection script takes a series of readings and then tosses any that are outside a predefined distance from the average.   Granted, my aquarium should never hit anywhere near 85°C, but it got rid of my errant readings.

-Scott



On 3/2/2011 4:04 PM, nick wrote:
Here are my water proof sensors using copper pipe and HMA, they have worked well so far.

http://kiwi-hacker.blogspot.com/2011/01/new-soil-temperature-sensors.html



On Wed, Mar 2, 2011 at 9:57 PM, Mick Sulley <[hidden email]> wrote:
On Wed, 2011-03-02 at 09:18 -0600, Guil Barros wrote:
> > Hhmmm. Interesting. Tips like these is exactly what I am after, so thanks a
> > bunch for that.
> >
> > I like the idea of covering the sensor (or parts of the sensor and the PCB)
> > with silicone. Do you remember what specific product you used (was it a
> > spray, or just one of those tubes you buy at HomeDepot or Lowe's that you
> > apply with a gun)?
>
> Yes, I just got a tube of silicone I had laying around the house and
> encased the whole thing in it. If I remember the tech sheet correctly,
> the newer DS18b20's are entirely waterproof (old ones had issues) so
> you really only need to encase the leads. I did the whole thing as the
> sensor is pulling the temp read off of the ground wire anyways so
> might as well be safe.
>
I have several sensors out on the roof monitoring solar panels. I use 3
core 0.75mm high temperature cable, solder the DS18S20 to the end with
small heat shrink sleeves over the pins, then use another heat shrink
over the top and onto the outer of the cable, but filled it with epoxy
resin, squeeze the air out, refill, etc, then when I thought all the air
bubbles were out used a paint strip gun to shrink the sleeve.  It is
slow and very messy but I think I have got weather proof sensors as a
result.


> > I also like the idea of using wax. I obviously had not thought about it. I
> > suppose that in that case you melt the wax (like from a candle) in a pot and
> > then dip the PCB into it. Is that they way people would do it?
>
> I've seen it done for potting electronics on ROV's. In that case they
> had the electronics in a small plastic enclosure and just filled the
> enclosure with wax when done.
>
> > I also found about "conformal coating" while doing some searches last night.
> > Guess that is the official name of what I am after. There are products to do
> > conformal coating, although nothing you can find at your local hardware
> > store, which is why I'd prefer to go with one of the two methods you
> > mentioned.
>
> I think thats what Hobby-Boards uses, might be worth sending them an email.
>
> --------------------


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Re: Dreaded 85 degrees C read from DS18B20 located outside

Eloy Paris
In reply to this post by scottjilek
Hi Scott,

On 03/02/2011 05:18 PM, Scott wrote:

> That's slick, but copper in aquariums is a big no-no. High-end
> freshwater or saltwater reef aquarium inhabitants like corals and
> invertebrates can not tolerate copper.
>
> I encased my sensors in epoxy to avoid water contact. Just solder up the
> sensor, mix up some 2-part epoxy, and smear it over the chip and any
> wire that will be in the water. I put on 2 "coats" just to sure it's
> water proof. I've found it works well for sensing temperature - they
> aren't pretty, but they track temps just fine.
>
> http://bytality.com/gallery/1-wire_setup/

"Sorry, but you are not authorized to view this page". Even tried using
[hidden email] but no worky :-(

> As far as 85°C, my temp collection script takes a series of readings and
> then tosses any that are outside a predefined distance from the average.

I was thinking about implementing distance from previous reading but
distance from average works too.

I actually don't accept readings outside a range, and 85 is outside that
range, so my RRDs did not get messed up when I was getting 85 C
measurements for a while that day. And since 85 is outside the range I
don't think I'll have to come up with a fancy way of recognizing a true
85 C reading ;-)

Cheers,

Eloy Paris.-

> Granted, my aquarium should never hit anywhere near 85°C, but it got rid
> of my errant readings.
>
> -Scott
>
>
> On 3/2/2011 4:04 PM, nick wrote:
>> Here are my water proof sensors using copper pipe and HMA, they have
>> worked well so far.
>>
>> http://kiwi-hacker.blogspot.com/2011/01/new-soil-temperature-sensors.html
>>
>>
>>
>> On Wed, Mar 2, 2011 at 9:57 PM, Mick Sulley <[hidden email]
>> <mailto:[hidden email]>> wrote:
>>
>>     On Wed, 2011-03-02 at 09:18 -0600, Guil Barros wrote:
>>     > > Hhmmm. Interesting. Tips like these is exactly what I am
>>     after, so thanks a
>>     > > bunch for that.
>>     > >
>>     > > I like the idea of covering the sensor (or parts of the sensor
>>     and the PCB)
>>     > > with silicone. Do you remember what specific product you used
>>     (was it a
>>     > > spray, or just one of those tubes you buy at HomeDepot or
>>     Lowe's that you
>>     > > apply with a gun)?
>>     >
>>     > Yes, I just got a tube of silicone I had laying around the house and
>>     > encased the whole thing in it. If I remember the tech sheet
>>     correctly,
>>     > the newer DS18b20's are entirely waterproof (old ones had issues) so
>>     > you really only need to encase the leads. I did the whole thing
>>     as the
>>     > sensor is pulling the temp read off of the ground wire anyways so
>>     > might as well be safe.
>>     >
>>     I have several sensors out on the roof monitoring solar panels. I
>>     use 3
>>     core 0.75mm high temperature cable, solder the DS18S20 to the end with
>>     small heat shrink sleeves over the pins, then use another heat shrink
>>     over the top and onto the outer of the cable, but filled it with epoxy
>>     resin, squeeze the air out, refill, etc, then when I thought all
>>     the air
>>     bubbles were out used a paint strip gun to shrink the sleeve. It is
>>     slow and very messy but I think I have got weather proof sensors as a
>>     result.
>>
>>
>>     > > I also like the idea of using wax. I obviously had not thought
>>     about it. I
>>     > > suppose that in that case you melt the wax (like from a
>>     candle) in a pot and
>>     > > then dip the PCB into it. Is that they way people would do it?
>>     >
>>     > I've seen it done for potting electronics on ROV's. In that case
>>     they
>>     > had the electronics in a small plastic enclosure and just filled the
>>     > enclosure with wax when done.
>>     >
>>     > > I also found about "conformal coating" while doing some
>>     searches last night.
>>     > > Guess that is the official name of what I am after. There are
>>     products to do
>>     > > conformal coating, although nothing you can find at your local
>>     hardware
>>     > > store, which is why I'd prefer to go with one of the two
>>     methods you
>>     > > mentioned.
>>     >
>>     > I think thats what Hobby-Boards uses, might be worth sending
>>     them an email.
>>     >
>>     > --------------------
>>
>>
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>>     or in the cloud. Deliver compliance at lower cost and gain new
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Re: Dreaded 85 degrees C read from DS18B20 located outside

Patryk-6
In reply to this post by scottjilek
Dnia 02-03-2011 o 23:18:50 Scott <[hidden email]> napisał(a):

There are also special heat shrink tubes with glue.
They are much more expensive(~3 Euros) compared to regular ones but they  
could be better for very moist environments and easy to apply.


--
p4trykx

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Re: Dreaded 85 degrees C read from DS18B20 located outside

scottjilek
In reply to this post by Eloy Paris
Ooops!

I pulled the security off that gallery which should fix it.  Try it again.

-Scott


On 3/2/2011 4:29 PM, Eloy Paris wrote:

> Hi Scott,
>
> On 03/02/2011 05:18 PM, Scott wrote:
>
>> That's slick, but copper in aquariums is a big no-no. High-end
>> freshwater or saltwater reef aquarium inhabitants like corals and
>> invertebrates can not tolerate copper.
>>
>> I encased my sensors in epoxy to avoid water contact. Just solder up the
>> sensor, mix up some 2-part epoxy, and smear it over the chip and any
>> wire that will be in the water. I put on 2 "coats" just to sure it's
>> water proof. I've found it works well for sensing temperature - they
>> aren't pretty, but they track temps just fine.
>>
>> http://bytality.com/gallery/1-wire_setup/
> "Sorry, but you are not authorized to view this page". Even tried using
> [hidden email] but no worky :-(
>
>> As far as 85°C, my temp collection script takes a series of readings and
>> then tosses any that are outside a predefined distance from the average.
> I was thinking about implementing distance from previous reading but
> distance from average works too.
>
> I actually don't accept readings outside a range, and 85 is outside that
> range, so my RRDs did not get messed up when I was getting 85 C
> measurements for a while that day. And since 85 is outside the range I
> don't think I'll have to come up with a fancy way of recognizing a true
> 85 C reading ;-)
>
> Cheers,
>
> Eloy Paris.-
>
>> Granted, my aquarium should never hit anywhere near 85°C, but it got rid
>> of my errant readings.
>>
>> -Scott
>>
>>
>> On 3/2/2011 4:04 PM, nick wrote:
>>> Here are my water proof sensors using copper pipe and HMA, they have
>>> worked well so far.
>>>
>>> http://kiwi-hacker.blogspot.com/2011/01/new-soil-temperature-sensors.html
>>>
>>>
>>>
>>> On Wed, Mar 2, 2011 at 9:57 PM, Mick Sulley<[hidden email]
>>> <mailto:[hidden email]>>  wrote:
>>>
>>>      On Wed, 2011-03-02 at 09:18 -0600, Guil Barros wrote:
>>>      >  >  Hhmmm. Interesting. Tips like these is exactly what I am
>>>      after, so thanks a
>>>      >  >  bunch for that.
>>>      >  >
>>>      >  >  I like the idea of covering the sensor (or parts of the sensor
>>>      and the PCB)
>>>      >  >  with silicone. Do you remember what specific product you used
>>>      (was it a
>>>      >  >  spray, or just one of those tubes you buy at HomeDepot or
>>>      Lowe's that you
>>>      >  >  apply with a gun)?
>>>      >
>>>      >  Yes, I just got a tube of silicone I had laying around the house and
>>>      >  encased the whole thing in it. If I remember the tech sheet
>>>      correctly,
>>>      >  the newer DS18b20's are entirely waterproof (old ones had issues) so
>>>      >  you really only need to encase the leads. I did the whole thing
>>>      as the
>>>      >  sensor is pulling the temp read off of the ground wire anyways so
>>>      >  might as well be safe.
>>>      >
>>>      I have several sensors out on the roof monitoring solar panels. I
>>>      use 3
>>>      core 0.75mm high temperature cable, solder the DS18S20 to the end with
>>>      small heat shrink sleeves over the pins, then use another heat shrink
>>>      over the top and onto the outer of the cable, but filled it with epoxy
>>>      resin, squeeze the air out, refill, etc, then when I thought all
>>>      the air
>>>      bubbles were out used a paint strip gun to shrink the sleeve. It is
>>>      slow and very messy but I think I have got weather proof sensors as a
>>>      result.
>>>
>>>
>>>      >  >  I also like the idea of using wax. I obviously had not thought
>>>      about it. I
>>>      >  >  suppose that in that case you melt the wax (like from a
>>>      candle) in a pot and
>>>      >  >  then dip the PCB into it. Is that they way people would do it?
>>>      >
>>>      >  I've seen it done for potting electronics on ROV's. In that case
>>>      they
>>>      >  had the electronics in a small plastic enclosure and just filled the
>>>      >  enclosure with wax when done.
>>>      >
>>>      >  >  I also found about "conformal coating" while doing some
>>>      searches last night.
>>>      >  >  Guess that is the official name of what I am after. There are
>>>      products to do
>>>      >  >  conformal coating, although nothing you can find at your local
>>>      hardware
>>>      >  >  store, which is why I'd prefer to go with one of the two
>>>      methods you
>>>      >  >  mentioned.
>>>      >
>>>      >  I think thats what Hobby-Boards uses, might be worth sending
>>>      them an email.
>>>      >
>>>      >  --------------------
>>>
>>>
>>>      ------------------------------------------------------------------------------
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>>>      data in
>>>      Real-Time with Splunk. Collect, index and harness all the fast
>>>      moving IT data
>>>      generated by your applications, servers and devices whether
>>>      physical, virtual
>>>      or in the cloud. Deliver compliance at lower cost and gain new
>>>      business
>>>      insights. http://p.sf.net/sfu/splunk-dev2dev
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>>>      [hidden email]
>>>      <mailto:[hidden email]>
>>>      https://lists.sourceforge.net/lists/listinfo/owfs-developers
>>>
>>>
>>>
>>> ------------------------------------------------------------------------------
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>>>
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>>
>>
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>>
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Re: Dreaded 85 degrees C read from DS18B20 located outside

Paul Alfille-2
In answer to a couple of the questions:

1. 85C will be reported in whatever temperature scale units are requested.
2. OWFS rechecks all 85C readings 3 times automatically, but finally
will report 85C if the sensor reads 85C consistently.
3. The wine cellar uses a DS18S20 in a plastic drinking straw with
some GE RTV silicone sealant (from the hardware store) sealing the
end. It's been immersed and functioning for 6 years now.

Maybe some static charge in the Vcc lead confused the sensor in the
lightning storm?

Paul Alfille

On Wed, Mar 2, 2011 at 5:36 PM, Scott <[hidden email]> wrote:

> Ooops!
>
> I pulled the security off that gallery which should fix it.  Try it again.
>
> -Scott
>
>
> On 3/2/2011 4:29 PM, Eloy Paris wrote:
>> Hi Scott,
>>
>> On 03/02/2011 05:18 PM, Scott wrote:
>>
>>> That's slick, but copper in aquariums is a big no-no. High-end
>>> freshwater or saltwater reef aquarium inhabitants like corals and
>>> invertebrates can not tolerate copper.
>>>
>>> I encased my sensors in epoxy to avoid water contact. Just solder up the
>>> sensor, mix up some 2-part epoxy, and smear it over the chip and any
>>> wire that will be in the water. I put on 2 "coats" just to sure it's
>>> water proof. I've found it works well for sensing temperature - they
>>> aren't pretty, but they track temps just fine.
>>>
>>> http://bytality.com/gallery/1-wire_setup/
>> "Sorry, but you are not authorized to view this page". Even tried using
>> [hidden email] but no worky :-(
>>
>>> As far as 85°C, my temp collection script takes a series of readings and
>>> then tosses any that are outside a predefined distance from the average.
>> I was thinking about implementing distance from previous reading but
>> distance from average works too.
>>
>> I actually don't accept readings outside a range, and 85 is outside that
>> range, so my RRDs did not get messed up when I was getting 85 C
>> measurements for a while that day. And since 85 is outside the range I
>> don't think I'll have to come up with a fancy way of recognizing a true
>> 85 C reading ;-)
>>
>> Cheers,
>>
>> Eloy Paris.-
>>
>>> Granted, my aquarium should never hit anywhere near 85°C, but it got rid
>>> of my errant readings.
>>>
>>> -Scott
>>>
>>>
>>> On 3/2/2011 4:04 PM, nick wrote:
>>>> Here are my water proof sensors using copper pipe and HMA, they have
>>>> worked well so far.
>>>>
>>>> http://kiwi-hacker.blogspot.com/2011/01/new-soil-temperature-sensors.html
>>>>
>>>>
>>>>
>>>> On Wed, Mar 2, 2011 at 9:57 PM, Mick Sulley<[hidden email]
>>>> <mailto:[hidden email]>>  wrote:
>>>>
>>>>      On Wed, 2011-03-02 at 09:18 -0600, Guil Barros wrote:
>>>>      >  >  Hhmmm. Interesting. Tips like these is exactly what I am
>>>>      after, so thanks a
>>>>      >  >  bunch for that.
>>>>      >  >
>>>>      >  >  I like the idea of covering the sensor (or parts of the sensor
>>>>      and the PCB)
>>>>      >  >  with silicone. Do you remember what specific product you used
>>>>      (was it a
>>>>      >  >  spray, or just one of those tubes you buy at HomeDepot or
>>>>      Lowe's that you
>>>>      >  >  apply with a gun)?
>>>>      >
>>>>      >  Yes, I just got a tube of silicone I had laying around the house and
>>>>      >  encased the whole thing in it. If I remember the tech sheet
>>>>      correctly,
>>>>      >  the newer DS18b20's are entirely waterproof (old ones had issues) so
>>>>      >  you really only need to encase the leads. I did the whole thing
>>>>      as the
>>>>      >  sensor is pulling the temp read off of the ground wire anyways so
>>>>      >  might as well be safe.
>>>>      >
>>>>      I have several sensors out on the roof monitoring solar panels. I
>>>>      use 3
>>>>      core 0.75mm high temperature cable, solder the DS18S20 to the end with
>>>>      small heat shrink sleeves over the pins, then use another heat shrink
>>>>      over the top and onto the outer of the cable, but filled it with epoxy
>>>>      resin, squeeze the air out, refill, etc, then when I thought all
>>>>      the air
>>>>      bubbles were out used a paint strip gun to shrink the sleeve. It is
>>>>      slow and very messy but I think I have got weather proof sensors as a
>>>>      result.
>>>>
>>>>
>>>>      >  >  I also like the idea of using wax. I obviously had not thought
>>>>      about it. I
>>>>      >  >  suppose that in that case you melt the wax (like from a
>>>>      candle) in a pot and
>>>>      >  >  then dip the PCB into it. Is that they way people would do it?
>>>>      >
>>>>      >  I've seen it done for potting electronics on ROV's. In that case
>>>>      they
>>>>      >  had the electronics in a small plastic enclosure and just filled the
>>>>      >  enclosure with wax when done.
>>>>      >
>>>>      >  >  I also found about "conformal coating" while doing some
>>>>      searches last night.
>>>>      >  >  Guess that is the official name of what I am after. There are
>>>>      products to do
>>>>      >  >  conformal coating, although nothing you can find at your local
>>>>      hardware
>>>>      >  >  store, which is why I'd prefer to go with one of the two
>>>>      methods you
>>>>      >  >  mentioned.
>>>>      >
>>>>      >  I think thats what Hobby-Boards uses, might be worth sending
>>>>      them an email.
>>>>      >
>>>>      >  --------------------
>>>>
>>>>
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Re: Dreaded 85 degrees C read from DS18B20 located outside

Eloy Paris
In reply to this post by scottjilek
On 03/02/2011 05:36 PM, Scott wrote:

> Ooops!
>
> I pulled the security off that gallery which should fix it.  Try it again.

That worked; thanks!

Eloy Paris.-

>>> I encased my sensors in epoxy to avoid water contact. Just solder up the
>>> sensor, mix up some 2-part epoxy, and smear it over the chip and any
>>> wire that will be in the water. I put on 2 "coats" just to sure it's
>>> water proof. I've found it works well for sensing temperature - they
>>> aren't pretty, but they track temps just fine.

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Mick Sulley
In reply to this post by Paul Alfille-2
Sorry Paul,  just to clarify your first point, could I detect an error
by -

if temp = 85
        change to degree F and read again
        if temp = 85 report error
        else
        change to degree C and return 85

or will both error 85 and genuine 85 return 185 when set to degree F

Thanks
Mick

On Wed, 2011-03-02 at 17:49 -0500, Paul Alfille wrote:
> In answer to a couple of the questions:
>
> 1. 85C will be reported in whatever temperature scale units are requested.
> 2. OWFS rechecks all 85C readings 3 times automatically, but finally
> will report 85C if the sensor reads 85C consistently.
> 3. The wine cellar uses a DS18S20 in a plastic drinking straw with
> some GE RTV silicone sealant (from the hardware store) sealing the
> end. It's been immersed and functioning for 6 years now.



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Re: Dreaded 85 degrees C read from DS18B20 located outside

Doug Collinge-2
In reply to this post by Paul Alfille-2
I use DS18B20s to monitor the temperatures in my still. The 85C issue is a real pain because that's right around the temperatures I have to measure. Fortunately my system is pretty much 100% reliable so I never see 85C error readings.

Hot 96% ethanol vapour is pretty aggressive so I came up with a nice little package. I cut some slots and closed the end of a piece of 1/4" refrigeration tube with silver solder. The leads on the chip are soldered to some cable with heatshrink for insulation. The chip goes into the tube with some heatsink compound for thermal conductivity. The cable comes out the end of the tube and is sealed to the tube with some special shrink tubing with gooey resin on the inside. It all works reliably (so far) and seems to be utterly watertight.

I also have nice fitting made out of a brass compression fitting. I get a compression union, throw away the compression rings, cut it in half, and drill it out to 1/4". Now the 1/4" tubing goes straight through. Connect it somehow to the housing you want the sensor inside - I silver soldered it to the copper still but you could thread it and use a gasket or whatever. Now I put the compression nut on the sensor tube and follow it with a little O-ring. Put the tube into the fitting and tighten the nut, which squeezes the O-ring making a perfect and reliable seal. It's really an excellent scheme.

For less demanding situations (e.g. boiling beer) I have another one that is basically a sensor epoxied into the end of a stainless tube with the end of the package sticking out, otherwise similar to the copper one. It works really well too and would also fit into the compression fitting thing.

Copper is not only permitted inside a still but it has a positive chemical function!



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Re: Dreaded 85 degrees C read from DS18B20 located outside

Nathan Hurst-4
In reply to this post by Eloy Paris
On Wed, Mar 02, 2011 at 09:59:45AM -0500, Eloy Paris wrote:

> I like the idea of covering the sensor (or parts of the sensor and the
> PCB) with silicone. Do you remember what specific product you used (was
> it a spray, or just one of those tubes you buy at HomeDepot or Lowe's
> that you apply with a gun)?

You can use caulking silicone, but be warned that many are cured by
acetic acid, which reacts readily with copper (to form verdigris as it
happens).  The standard approach at a former workplace was to put some
neutral cure silicone in a heatshrink tube with the wire, and heat
shrink it to force the silicone into all the gaps.

exterior urethane caulks might be a better choice, though I have no
experience with them personally.  They are solvent cured (and thus
stink).

Wax is intriguing, and there are non-curing water sealing compounds
available too (I use one, tacgel, for stopping ants climbing fruit
trees - even after 5 years outside it's still water repelling and tacky)

njh

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Eloy Paris
In reply to this post by Paul Alfille-2
Hi Paul,

On 03/02/2011 05:49 PM, Paul Alfille wrote:

[...]

> 3. The wine cellar uses a DS18S20 in a plastic drinking straw with
> some GE RTV silicone sealant (from the hardware store) sealing the
> end. It's been immersed and functioning for 6 years now.

Wow, that's great! I wasn't too lucky with my first attempt (it got wet
inside). I'll keep trying, though.

By the way, related question: is heat shrink supposed to be waterproof?
I mean, if I heat-shrink a tube, can I leave it submerged?

> Maybe some static charge in the Vcc lead confused the sensor in the
> lightning storm?

You know what, I want to get to the bottom of this so I have decided to
do nothing now to try to fix the problem I experienced a couple of
nights ago when we had lots of rain and thunderstorms. Allow me to explain:

Whatever happened a couple of nights ago surely will happen again. When
that happens I'll go outside and start with the simple stuff, i.e.
grounding Vcc. I am hoping that the problem was caused by either high
humidity, or by some weird electric problem caused by not having Vcc
grounded. If it is the later I will be able to confirm it by grounding
Vcc when the problem is happening. As I said, I have not had a single 85
degree reading since that night, so I have no need to try to fix things
right.

I'll report back as soon as I know more.

By the way, thanks to everybody that have provided useful links and
shared their war stories; it's been a very enlightening discussion.

Cheers,

Eloy Paris.-

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Re: Dreaded 85 degrees C read from DS18B20 located outside

jerry scharf
Eloy,

Neither shrink wrap or standard cat 5 jackets or insulators are
impervious in general. This is generally measured with water at
pressure. Impervious jacket cables are available, and many of them also
have goo inside to prevent lateral moisture travel in the cable.

IMO, the easiest thing to do is put the whole cable in a PE
(polyethylene) or PEX tube and stick the senor out the end. There are
lots of options for sealing, but I put my vote with alcohol cure RTV
(silicone.) As said before, I stay away from the acetic acid curing RTV
that you get in the hardware store. If you want, I can find you a Dow
part number for an example.

For protecting the sensors, I really like the stainless steel tubes with
one end rolled closed. You cut them to length, stick the sensor inside
with some thermal paste and back fill with RTV the best you can (if you
can get a very large gauge syringe and needle, it works great.) The
thermal conductance of stainless is not that great, but the walls are so
thin it doesn't matter. If it's an air measurement, clip a heat sink on
the outside of the stainless tube.


If you are going to use conformal coating, you need to clean ALL the
flux and dirt off first. The stuff comes in cans and sticks to
everything, so gloves and lots of old newspaper are recommended. I have
used this to go through environmental testing where water was running
off the boards (the dummies did the cold test first and then the
humidity test...)

just my $.02.

jerry


On 03/02/2011 06:49 PM, Eloy Paris wrote:

> Hi Paul,
>
> On 03/02/2011 05:49 PM, Paul Alfille wrote:
>
> [...]
>
>> 3. The wine cellar uses a DS18S20 in a plastic drinking straw with
>> some GE RTV silicone sealant (from the hardware store) sealing the
>> end. It's been immersed and functioning for 6 years now.
>
> Wow, that's great! I wasn't too lucky with my first attempt (it got wet
> inside). I'll keep trying, though.
>
> By the way, related question: is heat shrink supposed to be waterproof?
> I mean, if I heat-shrink a tube, can I leave it submerged?
>
>> Maybe some static charge in the Vcc lead confused the sensor in the
>> lightning storm?
>
> You know what, I want to get to the bottom of this so I have decided to
> do nothing now to try to fix the problem I experienced a couple of
> nights ago when we had lots of rain and thunderstorms. Allow me to explain:
>
> Whatever happened a couple of nights ago surely will happen again. When
> that happens I'll go outside and start with the simple stuff, i.e.
> grounding Vcc. I am hoping that the problem was caused by either high
> humidity, or by some weird electric problem caused by not having Vcc
> grounded. If it is the later I will be able to confirm it by grounding
> Vcc when the problem is happening. As I said, I have not had a single 85
> degree reading since that night, so I have no need to try to fix things
> right.
>
> I'll report back as soon as I know more.
>
> By the way, thanks to everybody that have provided useful links and
> shared their war stories; it's been a very enlightening discussion.
>
> Cheers,
>
> Eloy Paris.-
>
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> generated by your applications, servers and devices whether physical, virtual
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Re: Dreaded 85 degrees C read from DS18B20 located outside

Paul Alfille-2
There are a number of commercially available temperature probes,
constructed much as Jerry has described.

https://www.embeddeddatasystems.com/OW-TEMP-B3-12xA--Temperature-Probe_p_40.html

http://www.datanab.com/Sensors/1Wire_8SSP3_RGD.htm

As well as a number of sealed moisture resistant preparations.

On Thu, Mar 3, 2011 at 12:45 AM, Jerry Scharf
<[hidden email]> wrote:

> Eloy,
>
> Neither shrink wrap or standard cat 5 jackets or insulators are
> impervious in general. This is generally measured with water at
> pressure. Impervious jacket cables are available, and many of them also
> have goo inside to prevent lateral moisture travel in the cable.
>
> IMO, the easiest thing to do is put the whole cable in a PE
> (polyethylene) or PEX tube and stick the senor out the end. There are
> lots of options for sealing, but I put my vote with alcohol cure RTV
> (silicone.) As said before, I stay away from the acetic acid curing RTV
> that you get in the hardware store. If you want, I can find you a Dow
> part number for an example.
>
> For protecting the sensors, I really like the stainless steel tubes with
> one end rolled closed. You cut them to length, stick the sensor inside
> with some thermal paste and back fill with RTV the best you can (if you
> can get a very large gauge syringe and needle, it works great.) The
> thermal conductance of stainless is not that great, but the walls are so
> thin it doesn't matter. If it's an air measurement, clip a heat sink on
> the outside of the stainless tube.
>
>
> If you are going to use conformal coating, you need to clean ALL the
> flux and dirt off first. The stuff comes in cans and sticks to
> everything, so gloves and lots of old newspaper are recommended. I have
> used this to go through environmental testing where water was running
> off the boards (the dummies did the cold test first and then the
> humidity test...)
>
> just my $.02.
>
> jerry
>
>
> On 03/02/2011 06:49 PM, Eloy Paris wrote:
>> Hi Paul,
>>
>> On 03/02/2011 05:49 PM, Paul Alfille wrote:
>>
>> [...]
>>
>>> 3. The wine cellar uses a DS18S20 in a plastic drinking straw with
>>> some GE RTV silicone sealant (from the hardware store) sealing the
>>> end. It's been immersed and functioning for 6 years now.
>>
>> Wow, that's great! I wasn't too lucky with my first attempt (it got wet
>> inside). I'll keep trying, though.
>>
>> By the way, related question: is heat shrink supposed to be waterproof?
>> I mean, if I heat-shrink a tube, can I leave it submerged?
>>
>>> Maybe some static charge in the Vcc lead confused the sensor in the
>>> lightning storm?
>>
>> You know what, I want to get to the bottom of this so I have decided to
>> do nothing now to try to fix the problem I experienced a couple of
>> nights ago when we had lots of rain and thunderstorms. Allow me to explain:
>>
>> Whatever happened a couple of nights ago surely will happen again. When
>> that happens I'll go outside and start with the simple stuff, i.e.
>> grounding Vcc. I am hoping that the problem was caused by either high
>> humidity, or by some weird electric problem caused by not having Vcc
>> grounded. If it is the later I will be able to confirm it by grounding
>> Vcc when the problem is happening. As I said, I have not had a single 85
>> degree reading since that night, so I have no need to try to fix things
>> right.
>>
>> I'll report back as soon as I know more.
>>
>> By the way, thanks to everybody that have provided useful links and
>> shared their war stories; it's been a very enlightening discussion.
>>
>> Cheers,
>>
>> Eloy Paris.-
>>
>> ------------------------------------------------------------------------------
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>> Real-Time with Splunk. Collect, index and harness all the fast moving IT data
>> generated by your applications, servers and devices whether physical, virtual
>> or in the cloud. Deliver compliance at lower cost and gain new business
>> insights. http://p.sf.net/sfu/splunk-dev2dev
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[SOLVED] Dreaded 85 degrees C read from DS18B20 located outside

Eloy Paris
In reply to this post by Eloy Paris
Hi list,

I am happy to report that this problem is solved! Please see below
(inline) for the details...

On 03/02/2011 09:49 PM, Eloy Paris wrote:

> On 03/02/2011 05:49 PM, Paul Alfille wrote:
>
>> Maybe some static charge in the Vcc lead confused the sensor in the
>> lightning storm?
>
> You know what, I want to get to the bottom of this so I have decided to
> do nothing now to try to fix the problem I experienced a couple of
> nights ago when we had lots of rain and thunderstorms. Allow me to explain:
>
> Whatever happened a couple of nights ago surely will happen again. When
> that happens I'll go outside and start with the simple stuff, i.e.
> grounding Vcc. I am hoping that the problem was caused by either high
> humidity, or by some weird electric problem caused by not having Vcc
> grounded. If it is the later I will be able to confirm it by grounding
> Vcc when the problem is happening. As I said, I have not had a single 85
> degree reading since that night, so I have no need to try to fix things
> right.
>
> I'll report back as soon as I know more.

It happened again last night. It started around 11:45 PM. The forecast
indicated that we were going to have some rain but the 85 degree
readings started even before rain started. When I woke up this morning I
had lots of emails, 5 minutes apart, indicating that my outside DS18B20
was reporting 85 degrees (I read temperatures every 5 minutes and have
the polling script email me if a sensor reports a temperature outside a
range). It seems like we had some rain overnight because the ground was
wet. However, it did not seem like it was a heavy rain, and we did not
have any thunderstorms.

So, with these perfect conditions, and knowing that the problem was
occurring, I decided to take a first stab at fixing the problem. As I
mentioned before, the easiest thing to try first was going to be to
ground Vdd, which I've had floating since I installed this sensor the
last week of November.

And that was it! I've been running for 9 hours now and have not received
another 85 degree reading. Furthermore, about 30 minutes ago we had a
big thunderstorm with strong winds and heavy rain, and that did not
cause the sensor to report 85 degrees.

So there you have it, grounding Vdd is what fixed the 85 degree
readings. I think I won't be needing fancy conformal coating after all
-- the sensor is not directly exposed to the elements and it seems to be
performing great now that I grounded Vdd.

Regarding the root cause, I think some of you mentioned something about
increased capacitance when humidity is high? It must have been something
related to increased humidity since we did not have lightning when the
problem started last night.

I am not rushing to ground Vdd in all my other sensors right now,
though, since they have not reported a single 85 degree reading in
several months of operation. I guess it does not get that humid inside,
although now that summer is close (and it gets really humid where I
live) that may happen, so I shall see. In any case, the minute I get an
85 degree reading from a sensor I am grounding that sensor's Vdd.

Guess DS18B20 sensors make for cheap high humidity detectors when Vdd is
left floating ;-)

Anyway, thanks to all for all the great comments and help. It's
definitely been a very interesting thread.

Cheers,

Eloy Paris.-

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