What type of Thermowell for DS18B20

[cpearson88]

Does anyone know the best type of Thermowell to use with the DS18B20 temperature sensor? I am trying to make a built in temp monitor for my pool. Or if anyone has built their own using zwave as the protocol and communicating with HS have suggestions I would appreciate it. Thank you.

[ARA]

I'm using DS18B20 temperature sensors with some Fibaro sensors. They work quite well. They are inside, so I just have the bare DS18B20 wired into the sensor. I do recall seeing some DS18B20's that came with thermowells while shopping. I haven't tested any of them, but here are links to what I found.

https://www.adafruit.com/product/381
https://www.sparkfun.com/products/11050

One thing I thought would be interesting was creating a custom sensor using an Arduino and this Z-Wave add-on.

http://www.vesternet.com/z-wave-me-z...rd-for-arduino

Haven't gotten around to it yet though.

-Alex

[cpearson88]

Are you using the Fibaro Universal Sensor? What products are you using to get the sensor temperature into Homeseer? Thanks!

[ARA]

I'm using the Fibaro Door/Window Sensor (FKG101 from HomeSeer). It's basically a magnetic contact sensor, but it has space for an extra input - a DS18B20 temp sensor or an external button (momentary switch). I purchased the basic DS18B20 (TO-92 package - has 3 leads, easier for me to work with) from www.jameco.com (it's available elsewhere too). A little bit of trimming or bending and the DS18B20 can fit right into the Fibaro package - nothing showing. I did this before including it as a Z-Wave node.

Once I had the hardware all set, I included it into the HS3 system as normal. The Fibaro sensor shows Battery, Two Switches (Magnet, and Tamper) and Temperature. It's worth noting that the temperature and battery will show null or zero until there is a value change. They don't get polled, they only update when the sensor detects the change and sends it to the controller. I had trouble with one of the four I worked on. I excluded it, changed out the sensor with a spare, included it, and it was fine after. So, I'm not sure exactly where the problem was.

Fibaro has a decent manual for this at their website, and the promise of easy temperature sensing was what led me to buy it in the first place. It worked out pretty well.

Hope that helps,
-Alex

[BobSpen]

I'm using the Fibaro Door/Window Sensor (FKG101 from HomeSeer). It's basically a magnetic contact sensor, but it has space for an extra input - a DS18B20 temp sensor or an external button (momentary switch). I purchased the basic DS18B20 (TO-92 package - has 3 leads, easier for me to work with) from www.jameco.com (it's available elsewhere too). A little bit of trimming or bending and the DS18B20 can fit right into the Fibaro package - nothing showing. I did this before including it as a Z-Wave node.

Once I had the hardware all set, I included it into the HS3 system as normal. The Fibaro sensor shows Battery, Two Switches (Magnet, and Tamper) and Temperature. It's worth noting that the temperature and battery will show null or zero until there is a value change. They don't get polled, they only update when the sensor detects the change and sends it to the controller. I had trouble with one of the four I worked on. I excluded it, changed out the sensor with a spare, included it, and it was fine after. So, I'm not sure exactly where the problem was.

Fibaro has a decent manual for this at their website, and the promise of easy temperature sensing was what led me to buy it in the first place. It worked out pretty well.

Hope that helps,
-Alex

Alex,
A couple questions on this unit:
1) Are they z-wave+(the latest)?
2) What type battery do they use?
3) Have you had it long enough to observe battery life(and effect of temp changes and on/off activity)? Just looking for some "real" data verses their 2 year claim.....

Thanks much for the info,
BobSpen

[ARA]

A couple questions on this unit:
1) Are they z-wave+(the latest)?
2) What type battery do they use?
3) Have you had it long enough to observe battery life(and effect of temp changes and on/off activity)? Just looking for some "real" data verses their 2 year claim.....

1. No, I'm quite sure they are not Z-Wave+. They are running ZDK 4.55.
2. They use a single ER14250 (1/2AA) 3.6V Battery
3. I've only had them a few months. I suspect a two year battery life is a bit optimistic, but it's probably going to be pretty good. In three months, two sensors dropped from ~98% Battery to 93% & 90% respectively. A third one started with a bad battery, and it dropped from ~50% to 47%. Looking at my logs, I suspect that the temperature sensor adds a significant drain on the battery. They report the temp to the nearest tenth degree (66.5F) nearly once an hour. Although I have one that does it every two hours - not sure why it's different.

Thinking back to the original problem, they could be a transmitter for a pool thermostat, but they are not waterproof as they come. They could be made so with a bit of work though (this will probably void your warrantee). And so could potentially be used in damp locations. I would probably want to shelter them from too much direct weather - hurricanes, snow storms, that sort of thing. Fibaro claims you can use a DS18B20 with a 30 meter(!) cable. So you could have the sensor located where needed (outside, pool, roof) and run the cable to a more protected area where the sensor resides. Which still leaves us with the question of what type of temperature-well to use with the DS18B20...

-Alex

[cpearson88]

1. No, I'm quite sure they are not Z-Wave+. They are running ZDK 4.55.
2. They use a single ER14250 (1/2AA) 3.6V Battery
3. I've only had them a few months. I suspect a two year battery life is a bit optimistic, but it's probably going to be pretty good. In three months, two sensors dropped from ~98% Battery to 93% & 90% respectively. A third one started with a bad battery, and it dropped from ~50% to 47%. Looking at my logs, I suspect that the temperature sensor adds a significant drain on the battery. They report the temp to the nearest tenth degree (66.5F) nearly once an hour. Although I have one that does it every two hours - not sure why it's different.

Thinking back to the original problem, they could be a transmitter for a pool thermostat, but they are not waterproof as they come. They could be made so with a bit of work though (this will probably void your warrantee). And so could potentially be used in damp locations. I would probably want to shelter them from too much direct weather - hurricanes, snow storms, that sort of thing. Fibaro claims you can use a DS18B20 with a 30 meter(!) cable. So you could have the sensor located where needed (outside, pool, roof) and run the cable to a more protected area where the sensor resides. Which still leaves us with the question of what type of temperature-well to use with the DS18B20...

-Alex

How fast does the temp sensor update? I want to track the hot tub temp as it heats up. Once an hour is too long.

[ARA]

How fast does the temp sensor update? I want to track the hot tub temp as it heats up. Once an hour is too long.

Agreed, once an hour would be much too long for your application. So, I ran a bit of an experiment. I set the polling policy for the temperature part of the sensor to 3 minutes (Device Screen -> Device -> Z-Wave). After I did that, the sensor would report the temp every 4 minutes. So, then I tried setting the polling interval to 2 minutes. The sensor still reports every 4 minutes. Then I did a bit of reading. My understanding is that two things must happen for the sensor to report a reading. The polling interval must have elapsed - that is, 2 or 3 minutes must have passed - and the sensor must wake up and transmit the value (which seems to be the 4 minute interval). Additionally, if there is no temperature change, nothing is transmitted. I'm not sure if the sensor doesn't transmit at all, or if HS3 just ignores the data because it's the same as the current reading.

In brief:
- The DS18B20 can sample temperature quite fast - (I haven't read the whole data sheet, but I suspect several times per second at least).
- We can set the Z-Wave Polling Interval to 2 minutes,
- But the Fibaro Sensor only wakes up every 4 minutes.

So the best I can do with this combination is a reading every four minutes. And if there is no change, I don't get any new data (seemingly). I'm afraid I'll be time limited the next several weeks and won't be able to do further experiments.

I don't know all the internals for how HS3 and the Fibaro interact. There may be ways around these limitations. It's probably possible to connect a DS18B20 to an Arduino or the ADIO and use those plugins to get the same result. Although that would be hardwired, rather than Z-Wave.

- Alex

[cpearson88]

Thank for testing that for me Alex. Four minutes maybe ok for my situation.