Dreaded 85 degrees C read from DS18B20 located outside

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Dreaded 85 degrees C read from DS18B20 located outside

Eloy Paris
Hi list,

Apologies for the slightly off-topic message but I figured someone here
may have some suggestions for me on this non-owfs issue I am having...

I have a DS18B20 sensor located outside. It is in a location that is
safe from water (unless it rains horizontally). My bus master reaches
this sensor through a cat5 bus that has about 10 more sensors. The
sensor, its pins, and the small PCB the sensor is soldered to, are all
exposed (to wind and humidity, but not to direct water). Parasitic
powered, and Vcc pin is floating (not connected to ground). This setup
has been pretty stable (no 1-wire errors or bad temperature readouts in
6 months of operation).

Last night there was heavy rain and thunderstorms in the area and for a
period of about two hours I was getting the dreaded 85 degrees C from
this sensor. All other sensors were fine during this time and did not
report 85 degrees. The problem fixed itself a bit after rain and
thunderstorms passed.

I think it is humidity what causes the 85 degrees C readout since we've
had a few warm and humid days/nights recently (but no rain) and I've
gotten a few 85 degrees C readouts here and there from the same sensor.
But nothing like last night when I consistently got 85 degrees C
readouts for about two hours.

Next time this happens I plan on grounding Vcc to see if that helps, but
I also wanted to ask the list for theories on what could be causing
these 85 degrees C readouts when it is humid (or when there are
thunderstorms in the area).

If grounding Vcc does not help I think my next step should be to protect
from the elements the sensor, its pins, and the small PCB. Any ideas on
how to accomplish this; is there some coating I can spray on the
sensor's pins and on the PCB that will protect them from humidity?

Thanks in advance for any suggestions.

Cheers,

Eloy Paris.-

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Jan Chrillesen-2

On Tue, Mar 1, 2011 at 6:54 PM, Eloy Paris <[hidden email]> wrote:

I have a DS18B20 sensor located outside. It is in a location that is
safe from water (unless it rains horizontally). My bus master reaches
this sensor through a cat5 bus that has about 10 more sensors. The
sensor, its pins, and the small PCB the sensor is soldered to, are all
exposed (to wind and humidity, but not to direct water).

...
 
If grounding Vcc does not help I think my next step should be to protect
from the elements the sensor, its pins, and the small PCB. Any ideas on
how to accomplish this; is there some coating I can spray on the
sensor's pins and on the PCB that will protect them from humidity?

In my experience the 85 degrees issue can be caused by a number of issues.

- bad timing on the bus (especially when using bitbanging)
- reading high temperatures on a parasite powered bus
- very long busses with lots of sensors (picking up noise)
- capacitive issues on the wiring (often related to using shielded wiring)

Since your busmaster (and hence timing) didn't change and you're most likely not reading 80+ degrees C outside, I think the suspect here is the wiring. If water entered your CAT5 cabel it's electrical properties will change and the capacity of the cable will change. Make sure that everything outside is totally isolated from water.

- Jan

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Mick Sulley
In reply to this post by Eloy Paris
Hi Eloy,

I am using a mix of DS18B20 and DS18S20, my experience has been that
they will work reliably when powered and also in parasitic mode if you
link Gnd and Vdd, but if you don't they are a bit hit and miss on a
sensor by sensor basis, one may work fine but another reads 85.  Also
when floating they don't seem to be sure if they are powered or not,
some say they are and others say they are not.

My advice therefore is to link Vdd to Gnd.  Why it should be affected by
humidity or thunder storms I don't know, but given that they seem to be
a bit 'on the edge' with Vdd floating I guess it may change the
resistance or capacitance slightly and push it over the edge.  The
capacitance effect will also be influenced by objects and materials in
close proximity.

Also does anyone know if the 85 reading is irrespective of units?  My
setup is in degrees C, but if it was in F would the error still be 85 or
would it be 185F?  If it stays at 85 irrespective it is a way to
differentiate an error from a genuine 85 reading.

Best of luck
Mick

On Tue, 2011-03-01 at 12:54 -0500, Eloy Paris wrote:

> Hi list,
>
> Apologies for the slightly off-topic message but I figured someone here
> may have some suggestions for me on this non-owfs issue I am having...
>
> I have a DS18B20 sensor located outside. It is in a location that is
> safe from water (unless it rains horizontally). My bus master reaches
> this sensor through a cat5 bus that has about 10 more sensors. The
> sensor, its pins, and the small PCB the sensor is soldered to, are all
> exposed (to wind and humidity, but not to direct water). Parasitic
> powered, and Vcc pin is floating (not connected to ground). This setup
> has been pretty stable (no 1-wire errors or bad temperature readouts in
> 6 months of operation).
>
> Last night there was heavy rain and thunderstorms in the area and for a
> period of about two hours I was getting the dreaded 85 degrees C from
> this sensor. All other sensors were fine during this time and did not
> report 85 degrees. The problem fixed itself a bit after rain and
> thunderstorms passed.
>
> I think it is humidity what causes the 85 degrees C readout since we've
> had a few warm and humid days/nights recently (but no rain) and I've
> gotten a few 85 degrees C readouts here and there from the same sensor.
> But nothing like last night when I consistently got 85 degrees C
> readouts for about two hours.
>
> Next time this happens I plan on grounding Vcc to see if that helps, but
> I also wanted to ask the list for theories on what could be causing
> these 85 degrees C readouts when it is humid (or when there are
> thunderstorms in the area).
>
> If grounding Vcc does not help I think my next step should be to protect
> from the elements the sensor, its pins, and the small PCB. Any ideas on
> how to accomplish this; is there some coating I can spray on the
> sensor's pins and on the PCB that will protect them from humidity?
>
> Thanks in advance for any suggestions.
>
> Cheers,
>
> Eloy Paris.-




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Re: Dreaded 85 degrees C read from DS18B20 located outside

Patryk-6
In reply to this post by Eloy Paris
Dnia 2011-03-01, wto o godzinie 12:54 -0500, Eloy Paris pisze:

> If grounding Vcc does not help I think my next step should be to protect
> from the elements the sensor, its pins, and the small PCB. Any ideas on
> how to accomplish this; is there some coating I can spray on the
> sensor's pins and on the PCB that will protect them from humidity?

I soldered some wire(20cm) directly to DS18b20 pins with VCC and GND
together and put it in a heatshrink tube and placed the connector to the
rest of the network inside.

Maxim suggests connecting Vcc do GND when using parasite power. Maybe
you have DS18B20+PAR with Vcc and GND already connected internally.

--
p4trykx


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Re: Dreaded 85 degrees C read from DS18B20 located outside

Patryk-6
In reply to this post by Eloy Paris
Dnia 2011-03-01, wto o godzinie 12:54 -0500, Eloy Paris pisze:

> If grounding Vcc does not help I think my next step should be to protect
> from the elements the sensor, its pins, and the small PCB. Any ideas on
> how to accomplish this; is there some coating I can spray on the
> sensor's pins and on the PCB that will protect them from humidity?

I soldered some wire(20cm) directly to DS18b20 pins with VCC and GND
together and put it in a heatshrink tube and placed the connector to the
rest of the network inside.

Maxim suggests connecting Vcc do GND when using parasite power maybe you
have ds18b20par with Vcc and GND already connected internally.

--
p4trykx


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Re: Dreaded 85 degrees C read from DS18B20 located outside

Paul Alfille-2
In reply to this post by Eloy Paris
That's interesting that the humidity effects only one sensor, not the whole bus.

The HobbyBoards people used a special coating for their PCBs that
seems effective.

What is the design of your sensor -- what does the PCB do?

Paul

On Tue, Mar 1, 2011 at 12:54 PM, Eloy Paris <[hidden email]> wrote:

> Hi list,
>
> Apologies for the slightly off-topic message but I figured someone here
> may have some suggestions for me on this non-owfs issue I am having...
>
> I have a DS18B20 sensor located outside. It is in a location that is
> safe from water (unless it rains horizontally). My bus master reaches
> this sensor through a cat5 bus that has about 10 more sensors. The
> sensor, its pins, and the small PCB the sensor is soldered to, are all
> exposed (to wind and humidity, but not to direct water). Parasitic
> powered, and Vcc pin is floating (not connected to ground). This setup
> has been pretty stable (no 1-wire errors or bad temperature readouts in
> 6 months of operation).
>
> Last night there was heavy rain and thunderstorms in the area and for a
> period of about two hours I was getting the dreaded 85 degrees C from
> this sensor. All other sensors were fine during this time and did not
> report 85 degrees. The problem fixed itself a bit after rain and
> thunderstorms passed.
>
> I think it is humidity what causes the 85 degrees C readout since we've
> had a few warm and humid days/nights recently (but no rain) and I've
> gotten a few 85 degrees C readouts here and there from the same sensor.
> But nothing like last night when I consistently got 85 degrees C
> readouts for about two hours.
>
> Next time this happens I plan on grounding Vcc to see if that helps, but
> I also wanted to ask the list for theories on what could be causing
> these 85 degrees C readouts when it is humid (or when there are
> thunderstorms in the area).
>
> If grounding Vcc does not help I think my next step should be to protect
> from the elements the sensor, its pins, and the small PCB. Any ideas on
> how to accomplish this; is there some coating I can spray on the
> sensor's pins and on the PCB that will protect them from humidity?
>
> Thanks in advance for any suggestions.
>
> 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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Re: Dreaded 85 degrees C read from DS18B20 located outside

Guil Barros
In reply to this post by Eloy Paris
The sensor returns 85/185 at startup if it has not had a chance to do
a complete convert_t by the time you read_t on it. My guess is its
either shorting out somewhere and resetting or not getting enough
juice to handle the convert_t.

Are the other sensors ok? Are any of the other ones also outside?

I have my outside sensor covered in silicone. Its non-conductive,
waterproof, etc. It will delay temp changes slightly as it has a
higher specific heat capacity than air though, but not by much ;) I
have heard of other people using wax for this also as it is easier to
remove if needed but if you live in Texas it might melt off by itself
if left in the sun in summer.

Hope that helps.
-Guil

On Tue, Mar 1, 2011 at 11:54 AM, Eloy Paris <[hidden email]> wrote:

> Hi list,
>
> Apologies for the slightly off-topic message but I figured someone here
> may have some suggestions for me on this non-owfs issue I am having...
>
> I have a DS18B20 sensor located outside. It is in a location that is
> safe from water (unless it rains horizontally). My bus master reaches
> this sensor through a cat5 bus that has about 10 more sensors. The
> sensor, its pins, and the small PCB the sensor is soldered to, are all
> exposed (to wind and humidity, but not to direct water). Parasitic
> powered, and Vcc pin is floating (not connected to ground). This setup
> has been pretty stable (no 1-wire errors or bad temperature readouts in
> 6 months of operation).
>
> Last night there was heavy rain and thunderstorms in the area and for a
> period of about two hours I was getting the dreaded 85 degrees C from
> this sensor. All other sensors were fine during this time and did not
> report 85 degrees. The problem fixed itself a bit after rain and
> thunderstorms passed.
>
> I think it is humidity what causes the 85 degrees C readout since we've
> had a few warm and humid days/nights recently (but no rain) and I've
> gotten a few 85 degrees C readouts here and there from the same sensor.
> But nothing like last night when I consistently got 85 degrees C
> readouts for about two hours.
>
> Next time this happens I plan on grounding Vcc to see if that helps, but
> I also wanted to ask the list for theories on what could be causing
> these 85 degrees C readouts when it is humid (or when there are
> thunderstorms in the area).
>
> If grounding Vcc does not help I think my next step should be to protect
> from the elements the sensor, its pins, and the small PCB. Any ideas on
> how to accomplish this; is there some coating I can spray on the
> sensor's pins and on the PCB that will protect them from humidity?
>
> Thanks in advance for any suggestions.
>
> 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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>

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Eloy Paris
Hi Guil,

On 03/02/2011 09:42 AM, Guil Barros wrote:

> The sensor returns 85/185 at startup if it has not had a chance to do
> a complete convert_t by the time you read_t on it. My guess is its
> either shorting out somewhere and resetting or not getting enough
> juice to handle the convert_t.

That's what I thought too. Something to do with high humidity in the
air, perhaps?

> Are the other sensors ok? Are any of the other ones also outside?

All other sensors are (were, actually, for the duration of this event)
100% perfect, i.e. no errors, no 85 degrees C returned. The other
sensors are all inside.

I actually experienced 85 degrees returned by another sensor (every now
and then, not continuously for a period of time like in the case of this
outside sensor two nights ago), and it that case it turned out that
water had gotten inside the wire (this one was a sensor that was
monitoring water temperature in a fish tank. I insulated the wire but
didn't do a good job so water got in and caused 85 degrees readouts
every now and then. As soon as I took the sensor out of the tank and it
got dry the 85 degrees readouts stopped).

> I have my outside sensor covered in silicone. Its non-conductive,
> waterproof, etc. It will delay temp changes slightly as it has a
> higher specific heat capacity than air though, but not by much ;) I
> have heard of other people using wax for this also as it is easier to
> remove if needed but if you live in Texas it might melt off by itself
> if left in the sun in summer.

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)?

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 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.

> Hope that helps.

It does; thanks a lot for the insight :-)

Cheers,

Eloy Paris.-

> On Tue, Mar 1, 2011 at 11:54 AM, Eloy Paris<[hidden email]>  wrote:
>> Hi list,
>>
>> Apologies for the slightly off-topic message but I figured someone here
>> may have some suggestions for me on this non-owfs issue I am having...
>>
>> I have a DS18B20 sensor located outside. It is in a location that is
>> safe from water (unless it rains horizontally). My bus master reaches
>> this sensor through a cat5 bus that has about 10 more sensors. The
>> sensor, its pins, and the small PCB the sensor is soldered to, are all
>> exposed (to wind and humidity, but not to direct water). Parasitic
>> powered, and Vcc pin is floating (not connected to ground). This setup
>> has been pretty stable (no 1-wire errors or bad temperature readouts in
>> 6 months of operation).
>>
>> Last night there was heavy rain and thunderstorms in the area and for a
>> period of about two hours I was getting the dreaded 85 degrees C from
>> this sensor. All other sensors were fine during this time and did not
>> report 85 degrees. The problem fixed itself a bit after rain and
>> thunderstorms passed.
>>
>> I think it is humidity what causes the 85 degrees C readout since we've
>> had a few warm and humid days/nights recently (but no rain) and I've
>> gotten a few 85 degrees C readouts here and there from the same sensor.
>> But nothing like last night when I consistently got 85 degrees C
>> readouts for about two hours.
>>
>> Next time this happens I plan on grounding Vcc to see if that helps, but
>> I also wanted to ask the list for theories on what could be causing
>> these 85 degrees C readouts when it is humid (or when there are
>> thunderstorms in the area).
>>
>> If grounding Vcc does not help I think my next step should be to protect
>> from the elements the sensor, its pins, and the small PCB. Any ideas on
>> how to accomplish this; is there some coating I can spray on the
>> sensor's pins and on the PCB that will protect them from humidity?
>>
>> Thanks in advance for any suggestions.
>>
>> Cheers,
>>
>> Eloy Paris.-

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Guil Barros
> 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 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

Guil Barros
In reply to this post by Mick Sulley
> Also does anyone know if the 85 reading is irrespective of units?  My
> setup is in degrees C, but if it was in F would the error still be 85 or
> would it be 185F?  If it stays at 85 irrespective it is a way to
> differentiate an error from a genuine 85 reading.

I have found mine to show 185F and 85C.

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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 08:49 AM, Paul Alfille wrote:

> That's interesting that the humidity effects only one sensor, not the whole bus.

Yes, I also thought it was pretty interesting. Furthermore, I don't know
if this makes this more interesting, or if it has any relevance, but
this sensor that had the 85 degrees problem is not the last one on the
bus -- the bus has 12 DS18B20s, and the one that had problems is #8. The
7 sensors before, and the 4 sensors after, didn't have any problems
during the duration of the event.

> The HobbyBoards people used a special coating for their PCBs that
> seems effective.
>
> What is the design of your sensor -- what does the PCB do?

Oh, the PCB is just a convenience so I don't have to mess up with wires
(including soldering a sensor to the end of a cat5 cable) and so things
look a bit more tidy and neat. The PCB is 100% passive; just a DS18B20
sensor and a female RJ-45 jack soldered to the PCB (in most cases there
isn't even an RJ-45 since I just solder a short cat5 cable that ends in
the male RJ-45 that then connects to the RJ-45 jack in the wall). I
ordered the PCBs from BatchPCB using the Eagle and Gerber files from:

http://www.digitemp.com/dt1a.shtml

After reading p4trykx's reply (thanks p4trykx, BTW), though, I am
thinking that for this outside location (the actual location is
underneath the screened porch in the back of my house; that's why the
location is safe from rain) it is better to go without a PCB, and just
insulate a cat5 wire with heatshrink and some silicone, similar to what
this wine cellar monitoring project uses:

http://owfs.org/index.php?page=monitor-a-wine-cellar

I made a sensor like the one in that page to monitor water temperature
in a fish tank. The sensor got wet due to poor insulation on my part and
it is not currently measuring water temperature, but it should be
sufficiently protected to measure outside temperature at this location,
so I may just repurpose it and build another sensor for the fish tank.
That'll probably be the best solution.

Cheers,

Eloy Paris.-

> On Tue, Mar 1, 2011 at 12:54 PM, Eloy Paris<[hidden email]>  wrote:
>> Hi list,
>>
>> Apologies for the slightly off-topic message but I figured someone here
>> may have some suggestions for me on this non-owfs issue I am having...
>>
>> I have a DS18B20 sensor located outside. It is in a location that is
>> safe from water (unless it rains horizontally). My bus master reaches
>> this sensor through a cat5 bus that has about 10 more sensors. The
>> sensor, its pins, and the small PCB the sensor is soldered to, are all
>> exposed (to wind and humidity, but not to direct water). Parasitic
>> powered, and Vcc pin is floating (not connected to ground). This setup
>> has been pretty stable (no 1-wire errors or bad temperature readouts in
>> 6 months of operation).
>>
>> Last night there was heavy rain and thunderstorms in the area and for a
>> period of about two hours I was getting the dreaded 85 degrees C from
>> this sensor. All other sensors were fine during this time and did not
>> report 85 degrees. The problem fixed itself a bit after rain and
>> thunderstorms passed.
>>
>> I think it is humidity what causes the 85 degrees C readout since we've
>> had a few warm and humid days/nights recently (but no rain) and I've
>> gotten a few 85 degrees C readouts here and there from the same sensor.
>> But nothing like last night when I consistently got 85 degrees C
>> readouts for about two hours.
>>
>> Next time this happens I plan on grounding Vcc to see if that helps, but
>> I also wanted to ask the list for theories on what could be causing
>> these 85 degrees C readouts when it is humid (or when there are
>> thunderstorms in the area).
>>
>> If grounding Vcc does not help I think my next step should be to protect
>> from the elements the sensor, its pins, and the small PCB. Any ideas on
>> how to accomplish this; is there some coating I can spray on the
>> sensor's pins and on the PCB that will protect them from humidity?
>>
>> Thanks in advance for any suggestions.
>>
>> Cheers,
>>
>> Eloy Paris.-
>>

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Eloy Paris
In reply to this post by Patryk-6
Hi patyrk,

On 03/02/2011 05:09 AM, patyrk wrote:

> Dnia 2011-03-01, wto o godzinie 12:54 -0500, Eloy Paris pisze:
>
>> If grounding Vcc does not help I think my next step should be to protect
>> from the elements the sensor, its pins, and the small PCB. Any ideas on
>> how to accomplish this; is there some coating I can spray on the
>> sensor's pins and on the PCB that will protect them from humidity?
>
> I soldered some wire(20cm) directly to DS18b20 pins with VCC and GND
> together and put it in a heatshrink tube and placed the connector to the
> rest of the network inside.

Good suggestion. I built a cable like that for monitoring water
temperature in a fish tank. The sensor was actually submerged. It got
wet because of bad final insulation (silicone not being tight) but I
plan to try again.

As I mentioned in my previous message to Paul, I think I will re-purpose
this cable I am (was) using for the fish tank and use it outside instead.

> Maxim suggests connecting Vcc do GND when using parasite power. Maybe
> you have DS18B20+PAR with Vcc and GND already connected internally.

Yup, I am aware of the recommendation. My current 12 sensors do not have
Vcc grounded and they have been working fine so far, though. They are
regular 18B20s, not the -PAR version.

Related to this practice of not grounding Vcc when using parasitic
power, I found this in the manual for iButtonLink's T-Sense sensor
(http://www.ibuttonlink.com/pdf/manuals%20for%20t-sense%2005-22-08.pdf):

"NOTE: Important information

There is a small chance that the bus could become unstable when using
T-Sense units as the only sensor on the bus. This condition comes about
as a result of the new design of the T-Sense, using the DS18B20 sensor.
The third lead on the DS18B20, (Vdd) is left floating, (to allow design
flexibility for sophisticated networks) which leaves the possibility of
unpredictable performance. Our engineering department has not been able
to create this condition. Experiments with > 30 T-Sensors on the bus,
and a variety of interfaces, have shown all devices working properly.

In the unlikely event of unstable behavior on the bus, resolution can be
accomplished by simply connecting pin 2 (+5 volts) to pin 6 (Aux).
Alternately, any MS-xx product on the bus will provide the jumper
internally, or the use of a LinkHub as the interface."

Cheers,

Eloy Paris.-

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Eloy Paris
In reply to this post by Jan Chrillesen-2
Hi Jan,

On 03/02/2011 03:49 AM, Jan Chrillesen wrote:

> On Tue, Mar 1, 2011 at 6:54 PM, Eloy Paris <[hidden email]
> <mailto:[hidden email]>> wrote:
>
>     I have a DS18B20 sensor located outside. It is in a location that is
>     safe from water (unless it rains horizontally). My bus master reaches
>     this sensor through a cat5 bus that has about 10 more sensors. The
>     sensor, its pins, and the small PCB the sensor is soldered to, are all
>     exposed (to wind and humidity, but not to direct water).
>
>
> ...
>
> If grounding Vcc does not help I think my next step should be to protect
>
>     from the elements the sensor, its pins, and the small PCB. Any ideas on
>     how to accomplish this; is there some coating I can spray on the
>     sensor's pins and on the PCB that will protect them from humidity?
>
>
> In my experience the 85 degrees issue can be caused by a number of issues.
>
> - bad timing on the bus (especially when using bitbanging)
> - reading high temperatures on a parasite powered bus
> - very long busses with lots of sensors (picking up noise)
> - capacitive issues on the wiring (often related to using shielded wiring)
>
> Since your busmaster (and hence timing) didn't change and you're most
> likely not reading 80+ degrees C outside, I think the suspect here is
> the wiring. If water entered your CAT5 cabel it's electrical properties
> will change and the capacity of the cable will change. Make sure that
> everything outside is totally isolated from water.

I'll double check, but I am pretty sure that water did not enter the
cat5 cable -- for that to happen rain must have had to be horizontal and
with pretty strong winds.

Humidity is the only thing that was probably different when the event
occurred.

Cheers,

Eloy Paris.-

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Eloy Paris
In reply to this post by Mick Sulley
Hi Mick,

On 03/02/2011 04:41 AM, Mick Sulley wrote:

> Hi Eloy,
>
> I am using a mix of DS18B20 and DS18S20, my experience has been that
> they will work reliably when powered and also in parasitic mode if you
> link Gnd and Vdd, but if you don't they are a bit hit and miss on a
> sensor by sensor basis, one may work fine but another reads 85.  Also
> when floating they don't seem to be sure if they are powered or not,
> some say they are and others say they are not.
>
> My advice therefore is to link Vdd to Gnd.

I think this is sound advice even if things have worked well for me with
12 sensors that all have Vdd floating.

> Why it should be affected by
> humidity or thunder storms I don't know, but given that they seem to be
> a bit 'on the edge' with Vdd floating I guess it may change the
> resistance or capacitance slightly and push it over the edge.  The
> capacitance effect will also be influenced by objects and materials in
> close proximity.

Thanks for the insight! Good stuff in this thread; I'm glad I asked even
if it was a bit off-topic for owfs :-)

> Also does anyone know if the 85 reading is irrespective of units?  My
> setup is in degrees C, but if it was in F would the error still be 85 or
> would it be 185F?  If it stays at 85 irrespective it is a way to
> differentiate an error from a genuine 85 reading.

The 1820 only reports in degrees Celsius and it is owfs the one
providing degrees F capabilities, right? If that is the case then I
would expect 85 C to be reported by owfs in the equivalent degrees F.

So yes, that is a good question -- how does one tell the difference
between true 85 C and error 85 C? (not that I am expecting to read a
true 85 C, although I suspect things get pretty hot in an attic in the
summer).

Cheers,

Eloy Paris.-

>
> Best of luck
> Mick
>
> On Tue, 2011-03-01 at 12:54 -0500, Eloy Paris wrote:
>> Hi list,
>>
>> Apologies for the slightly off-topic message but I figured someone here
>> may have some suggestions for me on this non-owfs issue I am having...
>>
>> I have a DS18B20 sensor located outside. It is in a location that is
>> safe from water (unless it rains horizontally). My bus master reaches
>> this sensor through a cat5 bus that has about 10 more sensors. The
>> sensor, its pins, and the small PCB the sensor is soldered to, are all
>> exposed (to wind and humidity, but not to direct water). Parasitic
>> powered, and Vcc pin is floating (not connected to ground). This setup
>> has been pretty stable (no 1-wire errors or bad temperature readouts in
>> 6 months of operation).
>>
>> Last night there was heavy rain and thunderstorms in the area and for a
>> period of about two hours I was getting the dreaded 85 degrees C from
>> this sensor. All other sensors were fine during this time and did not
>> report 85 degrees. The problem fixed itself a bit after rain and
>> thunderstorms passed.
>>
>> I think it is humidity what causes the 85 degrees C readout since we've
>> had a few warm and humid days/nights recently (but no rain) and I've
>> gotten a few 85 degrees C readouts here and there from the same sensor.
>> But nothing like last night when I consistently got 85 degrees C
>> readouts for about two hours.
>>
>> Next time this happens I plan on grounding Vcc to see if that helps, but
>> I also wanted to ask the list for theories on what could be causing
>> these 85 degrees C readouts when it is humid (or when there are
>> thunderstorms in the area).
>>
>> If grounding Vcc does not help I think my next step should be to protect
>> from the elements the sensor, its pins, and the small PCB. Any ideas on
>> how to accomplish this; is there some coating I can spray on the
>> sensor's pins and on the PCB that will protect them from humidity?
>>
>> Thanks in advance for any suggestions.
>>
>> Cheers,
>>
>> Eloy Paris.-
>
>
>
>
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> 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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Re: Dreaded 85 degrees C read from DS18B20 located outside

Roberto Spadim
hum, i had the same problem, when i read 85 i read again, if two reads
are 85 i accept the 85 value (ok 1 lost 1 read, maybe 1 second per
sensor)

2011/3/2 Eloy Paris <[hidden email]>:

> Hi Mick,
>
> On 03/02/2011 04:41 AM, Mick Sulley wrote:
>
>> Hi Eloy,
>>
>> I am using a mix of DS18B20 and DS18S20, my experience has been that
>> they will work reliably when powered and also in parasitic mode if you
>> link Gnd and Vdd, but if you don't they are a bit hit and miss on a
>> sensor by sensor basis, one may work fine but another reads 85.  Also
>> when floating they don't seem to be sure if they are powered or not,
>> some say they are and others say they are not.
>>
>> My advice therefore is to link Vdd to Gnd.
>
> I think this is sound advice even if things have worked well for me with
> 12 sensors that all have Vdd floating.
>
>> Why it should be affected by
>> humidity or thunder storms I don't know, but given that they seem to be
>> a bit 'on the edge' with Vdd floating I guess it may change the
>> resistance or capacitance slightly and push it over the edge.  The
>> capacitance effect will also be influenced by objects and materials in
>> close proximity.
>
> Thanks for the insight! Good stuff in this thread; I'm glad I asked even
> if it was a bit off-topic for owfs :-)
>
>> Also does anyone know if the 85 reading is irrespective of units?  My
>> setup is in degrees C, but if it was in F would the error still be 85 or
>> would it be 185F?  If it stays at 85 irrespective it is a way to
>> differentiate an error from a genuine 85 reading.
>
> The 1820 only reports in degrees Celsius and it is owfs the one
> providing degrees F capabilities, right? If that is the case then I
> would expect 85 C to be reported by owfs in the equivalent degrees F.
>
> So yes, that is a good question -- how does one tell the difference
> between true 85 C and error 85 C? (not that I am expecting to read a
> true 85 C, although I suspect things get pretty hot in an attic in the
> summer).
>
> Cheers,
>
> Eloy Paris.-
>
>>
>> Best of luck
>> Mick
>>
>> On Tue, 2011-03-01 at 12:54 -0500, Eloy Paris wrote:
>>> Hi list,
>>>
>>> Apologies for the slightly off-topic message but I figured someone here
>>> may have some suggestions for me on this non-owfs issue I am having...
>>>
>>> I have a DS18B20 sensor located outside. It is in a location that is
>>> safe from water (unless it rains horizontally). My bus master reaches
>>> this sensor through a cat5 bus that has about 10 more sensors. The
>>> sensor, its pins, and the small PCB the sensor is soldered to, are all
>>> exposed (to wind and humidity, but not to direct water). Parasitic
>>> powered, and Vcc pin is floating (not connected to ground). This setup
>>> has been pretty stable (no 1-wire errors or bad temperature readouts in
>>> 6 months of operation).
>>>
>>> Last night there was heavy rain and thunderstorms in the area and for a
>>> period of about two hours I was getting the dreaded 85 degrees C from
>>> this sensor. All other sensors were fine during this time and did not
>>> report 85 degrees. The problem fixed itself a bit after rain and
>>> thunderstorms passed.
>>>
>>> I think it is humidity what causes the 85 degrees C readout since we've
>>> had a few warm and humid days/nights recently (but no rain) and I've
>>> gotten a few 85 degrees C readouts here and there from the same sensor.
>>> But nothing like last night when I consistently got 85 degrees C
>>> readouts for about two hours.
>>>
>>> Next time this happens I plan on grounding Vcc to see if that helps, but
>>> I also wanted to ask the list for theories on what could be causing
>>> these 85 degrees C readouts when it is humid (or when there are
>>> thunderstorms in the area).
>>>
>>> If grounding Vcc does not help I think my next step should be to protect
>>> from the elements the sensor, its pins, and the small PCB. Any ideas on
>>> how to accomplish this; is there some coating I can spray on the
>>> sensor's pins and on the PCB that will protect them from humidity?
>>>
>>> Thanks in advance for any suggestions.
>>>
>>> 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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>
>
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>
>



--
Roberto Spadim
Spadim Technology / SPAEmpresarial

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Eloy Paris
Hi Roberto,

On 03/02/2011 04:24 PM, Roberto Spadim wrote:

> hum, i had the same problem, when i read 85 i read again, if two reads
> are 85 i accept the 85 value (ok 1 lost 1 read, maybe 1 second per
> sensor)

I think a better algorithm would be to look at the delta between
consecutive readings -- your algorithm of doing a second read if the
first one is 85 C would have failed (returned 85 C) in the situation
that I had a couple of days ago since all readings from that sensor
during a two-hour period returned a consistent 85 C.

Making sure that the delta between current reading and previous reading
is reasonable would allow one to accept a real 85 C (if for example the
delta between current 85 reading and previous reading is, say 5
degrees), and to reject a false 85 C (if for example, the delta between
current 85 reading and previous reading is 65 degrees).

Cheers,

Eloy Paris.-

> 2011/3/2 Eloy Paris<[hidden email]>:
>> Hi Mick,
>>
>> On 03/02/2011 04:41 AM, Mick Sulley wrote:
>>
>>> Hi Eloy,
>>>
>>> I am using a mix of DS18B20 and DS18S20, my experience has been that
>>> they will work reliably when powered and also in parasitic mode if you
>>> link Gnd and Vdd, but if you don't they are a bit hit and miss on a
>>> sensor by sensor basis, one may work fine but another reads 85.  Also
>>> when floating they don't seem to be sure if they are powered or not,
>>> some say they are and others say they are not.
>>>
>>> My advice therefore is to link Vdd to Gnd.
>>
>> I think this is sound advice even if things have worked well for me with
>> 12 sensors that all have Vdd floating.
>>
>>> Why it should be affected by
>>> humidity or thunder storms I don't know, but given that they seem to be
>>> a bit 'on the edge' with Vdd floating I guess it may change the
>>> resistance or capacitance slightly and push it over the edge.  The
>>> capacitance effect will also be influenced by objects and materials in
>>> close proximity.
>>
>> Thanks for the insight! Good stuff in this thread; I'm glad I asked even
>> if it was a bit off-topic for owfs :-)
>>
>>> Also does anyone know if the 85 reading is irrespective of units?  My
>>> setup is in degrees C, but if it was in F would the error still be 85 or
>>> would it be 185F?  If it stays at 85 irrespective it is a way to
>>> differentiate an error from a genuine 85 reading.
>>
>> The 1820 only reports in degrees Celsius and it is owfs the one
>> providing degrees F capabilities, right? If that is the case then I
>> would expect 85 C to be reported by owfs in the equivalent degrees F.
>>
>> So yes, that is a good question -- how does one tell the difference
>> between true 85 C and error 85 C? (not that I am expecting to read a
>> true 85 C, although I suspect things get pretty hot in an attic in the
>> summer).
>>
>> Cheers,
>>
>> Eloy Paris.-
>>
>>>
>>> Best of luck
>>> Mick
>>>
>>> On Tue, 2011-03-01 at 12:54 -0500, Eloy Paris wrote:
>>>> Hi list,
>>>>
>>>> Apologies for the slightly off-topic message but I figured someone here
>>>> may have some suggestions for me on this non-owfs issue I am having...
>>>>
>>>> I have a DS18B20 sensor located outside. It is in a location that is
>>>> safe from water (unless it rains horizontally). My bus master reaches
>>>> this sensor through a cat5 bus that has about 10 more sensors. The
>>>> sensor, its pins, and the small PCB the sensor is soldered to, are all
>>>> exposed (to wind and humidity, but not to direct water). Parasitic
>>>> powered, and Vcc pin is floating (not connected to ground). This setup
>>>> has been pretty stable (no 1-wire errors or bad temperature readouts in
>>>> 6 months of operation).
>>>>
>>>> Last night there was heavy rain and thunderstorms in the area and for a
>>>> period of about two hours I was getting the dreaded 85 degrees C from
>>>> this sensor. All other sensors were fine during this time and did not
>>>> report 85 degrees. The problem fixed itself a bit after rain and
>>>> thunderstorms passed.
>>>>
>>>> I think it is humidity what causes the 85 degrees C readout since we've
>>>> had a few warm and humid days/nights recently (but no rain) and I've
>>>> gotten a few 85 degrees C readouts here and there from the same sensor.
>>>> But nothing like last night when I consistently got 85 degrees C
>>>> readouts for about two hours.
>>>>
>>>> Next time this happens I plan on grounding Vcc to see if that helps, but
>>>> I also wanted to ask the list for theories on what could be causing
>>>> these 85 degrees C readouts when it is humid (or when there are
>>>> thunderstorms in the area).
>>>>
>>>> If grounding Vcc does not help I think my next step should be to protect
>>>> from the elements the sensor, its pins, and the small PCB. Any ideas on
>>>> how to accomplish this; is there some coating I can spray on the
>>>> sensor's pins and on the PCB that will protect them from humidity?
>>>>
>>>> Thanks in advance for any suggestions.
>>>>
>>>> Cheers,
>>>>
>>>> Eloy Paris.-
>>>

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Roberto Spadim
no problem =] works too =]

2011/3/2 Eloy Paris <[hidden email]>:

> Hi Roberto,
>
> On 03/02/2011 04:24 PM, Roberto Spadim wrote:
>
>> hum, i had the same problem, when i read 85 i read again, if two reads
>> are 85 i accept the 85 value (ok 1 lost 1 read, maybe 1 second per
>> sensor)
>
> I think a better algorithm would be to look at the delta between consecutive
> readings -- your algorithm of doing a second read if the first one is 85 C
> would have failed (returned 85 C) in the situation that I had a couple of
> days ago since all readings from that sensor during a two-hour period
> returned a consistent 85 C.
>
> Making sure that the delta between current reading and previous reading is
> reasonable would allow one to accept a real 85 C (if for example the delta
> between current 85 reading and previous reading is, say 5 degrees), and to
> reject a false 85 C (if for example, the delta between current 85 reading
> and previous reading is 65 degrees).
>
> Cheers,
>
> Eloy Paris.-
>
>> 2011/3/2 Eloy Paris<[hidden email]>:
>>>
>>> Hi Mick,
>>>
>>> On 03/02/2011 04:41 AM, Mick Sulley wrote:
>>>
>>>> Hi Eloy,
>>>>
>>>> I am using a mix of DS18B20 and DS18S20, my experience has been that
>>>> they will work reliably when powered and also in parasitic mode if you
>>>> link Gnd and Vdd, but if you don't they are a bit hit and miss on a
>>>> sensor by sensor basis, one may work fine but another reads 85.  Also
>>>> when floating they don't seem to be sure if they are powered or not,
>>>> some say they are and others say they are not.
>>>>
>>>> My advice therefore is to link Vdd to Gnd.
>>>
>>> I think this is sound advice even if things have worked well for me with
>>> 12 sensors that all have Vdd floating.
>>>
>>>> Why it should be affected by
>>>> humidity or thunder storms I don't know, but given that they seem to be
>>>> a bit 'on the edge' with Vdd floating I guess it may change the
>>>> resistance or capacitance slightly and push it over the edge.  The
>>>> capacitance effect will also be influenced by objects and materials in
>>>> close proximity.
>>>
>>> Thanks for the insight! Good stuff in this thread; I'm glad I asked even
>>> if it was a bit off-topic for owfs :-)
>>>
>>>> Also does anyone know if the 85 reading is irrespective of units?  My
>>>> setup is in degrees C, but if it was in F would the error still be 85 or
>>>> would it be 185F?  If it stays at 85 irrespective it is a way to
>>>> differentiate an error from a genuine 85 reading.
>>>
>>> The 1820 only reports in degrees Celsius and it is owfs the one
>>> providing degrees F capabilities, right? If that is the case then I
>>> would expect 85 C to be reported by owfs in the equivalent degrees F.
>>>
>>> So yes, that is a good question -- how does one tell the difference
>>> between true 85 C and error 85 C? (not that I am expecting to read a
>>> true 85 C, although I suspect things get pretty hot in an attic in the
>>> summer).
>>>
>>> Cheers,
>>>
>>> Eloy Paris.-
>>>
>>>>
>>>> Best of luck
>>>> Mick
>>>>
>>>> On Tue, 2011-03-01 at 12:54 -0500, Eloy Paris wrote:
>>>>>
>>>>> Hi list,
>>>>>
>>>>> Apologies for the slightly off-topic message but I figured someone here
>>>>> may have some suggestions for me on this non-owfs issue I am having...
>>>>>
>>>>> I have a DS18B20 sensor located outside. It is in a location that is
>>>>> safe from water (unless it rains horizontally). My bus master reaches
>>>>> this sensor through a cat5 bus that has about 10 more sensors. The
>>>>> sensor, its pins, and the small PCB the sensor is soldered to, are all
>>>>> exposed (to wind and humidity, but not to direct water). Parasitic
>>>>> powered, and Vcc pin is floating (not connected to ground). This setup
>>>>> has been pretty stable (no 1-wire errors or bad temperature readouts in
>>>>> 6 months of operation).
>>>>>
>>>>> Last night there was heavy rain and thunderstorms in the area and for a
>>>>> period of about two hours I was getting the dreaded 85 degrees C from
>>>>> this sensor. All other sensors were fine during this time and did not
>>>>> report 85 degrees. The problem fixed itself a bit after rain and
>>>>> thunderstorms passed.
>>>>>
>>>>> I think it is humidity what causes the 85 degrees C readout since we've
>>>>> had a few warm and humid days/nights recently (but no rain) and I've
>>>>> gotten a few 85 degrees C readouts here and there from the same sensor.
>>>>> But nothing like last night when I consistently got 85 degrees C
>>>>> readouts for about two hours.
>>>>>
>>>>> Next time this happens I plan on grounding Vcc to see if that helps,
>>>>> but
>>>>> I also wanted to ask the list for theories on what could be causing
>>>>> these 85 degrees C readouts when it is humid (or when there are
>>>>> thunderstorms in the area).
>>>>>
>>>>> If grounding Vcc does not help I think my next step should be to
>>>>> protect
>>>>> from the elements the sensor, its pins, and the small PCB. Any ideas on
>>>>> how to accomplish this; is there some coating I can spray on the
>>>>> sensor's pins and on the PCB that will protect them from humidity?
>>>>>
>>>>> Thanks in advance for any suggestions.
>>>>>
>>>>> Cheers,
>>>>>
>>>>> Eloy Paris.-
>>>>
>
>



--
Roberto Spadim
Spadim Technology / SPAEmpresarial

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Re: Dreaded 85 degrees C read from DS18B20 located outside

Mick Sulley
In reply to this post by Guil Barros
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

Mohclips
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

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.

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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