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Old January 23rd, 2018, 06:58 AM   #1
rguimond
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Disposable (cheap) wireless temperature probe

I'm trying to predict when a peat moss pile is likely to undergo spontaneously combustion. Currently, it's a full-time job for someone to punch holes in piles and insert probes to take periodic temperature readings. In addition to being cumbersome and time-consuming, the holes introduce oxygen, which tends to escalate temperature increase.

I was hoping to find a source of cheap wireless temperature transmitters. During processing, it's likely that most will be recovered, but it's also likely that a lot could be damaged.

These could be inserted as deep as 10' into piles of harvested sphagnum moss. Bluetooth would probably work, but 433MHz could also work.

Something like a AcuRite 06002RM Wireless Temperature and Humidity Sensor would be OK, but it will be expensive to have them in 1000+ piles and there's also a possibility that the reader will pick up signals from adjacent piles.

Something that could be assigned a unique address would be ideal.

I was thinking that whatever we use could be inserted into a sealed PVC pipe for protection from the elements and to allow easy retrieval before the pile is transferred by simply pulling out the pipe.
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Old January 23rd, 2018, 08:57 AM   #2
RDS
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I have heard of temperature sensors that are embedded in concrete to monitor the cure temperature, obviously throwaways. Try here for a start:
http://www.madgetech.com/data-logger.../concrete.html
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Old January 23rd, 2018, 09:36 AM   #3
boneless
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I think you need to define cheap? $20 bucks for a wireless sensor is pretty cheap imo, but if you multiply that by 1000, you are looking at a $20,000 bill.

If you need that many, I think you could be developing (having developed) your own sensors.

At my home I am using Xiaomi sensors using Zigbee (2.4GHz I believe). They work great. They daisy-chain wirelessly. They are made for the Chinese market, but I got them working in my home automation system.

They don't seem to have any IP rating, but pretty sure they would still work in an ABS box.

Not the perfect solution, but I think it would be worth a try?
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Old January 23rd, 2018, 02:05 PM   #4
arlenjacobs
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Quote:
Originally Posted by rguimond View Post
I was hoping to find a source of cheap wireless temperature transmitters. During processing, it's likely that most will be recovered, but it's also likely that a lot could be damaged.

These could be inserted as deep as 10' into piles of harvested sphagnum moss. Bluetooth would probably work, but 433MHz could also work.

Something like a AcuRite 06002RM Wireless Temperature and Humidity Sensor would be OK
My guess is that you'll have a tough time finding the right wireless sensor; if any could work at 10' (3 metres) deep.
  • RF frequency
  • power of the transmitter
  • how wet is the moss
  • depth of the transmitter

Is the moss wet? Water kills RF very quickly. Within 1/2 meter depth you'll get high loss of signal. I doubt that AcuRite could transmit very far through wet moss; too low of power. Who knows if 433MHz is the best frequency.


You may be best off with your manual temperature readings.
Or, could you leave a 10' pole there? Sensor at one end and the transmitter at the other?

Don't know. Sounds like a tough problem.
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Old January 23rd, 2018, 02:27 PM   #5
DBLD99
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We have used these for grain piles. Can't remember price though.

https://www.extrongrain.com/wireless...rature-probes/
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Old January 23rd, 2018, 02:28 PM   #6
mk42
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If that Acurite sensor is too expensive at $13 bucks a pop, I don't think you'll find what you're looking for. Maybe you can get massive discounts for buying 1000 at a time, but I dunno. I think you'll fail at the funding stage, before it even makes sense to worry about the engineering problems like wireless signal strength.
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Old January 23rd, 2018, 02:50 PM   #7
spaderkung
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Is the purpose to save the one pile that burns or the rest of them?
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Old January 23rd, 2018, 06:37 PM   #8
rguimond
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Quote:
Originally Posted by spaderkung View Post
Is the purpose to save the one pile that burns or the rest of them?
Actually, the purpose is to predict when a pile will likely ignite so that it can be selected for immediate processing.

I guess saving adjacent piles will be a side benefit
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Old January 23rd, 2018, 06:45 PM   #9
rguimond
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Quote:
Originally Posted by arlenjacobs View Post
My guess is that you'll have a tough time finding the right wireless sensor; if any could work at 10' (3 metres) deep.
  • RF frequency
  • power of the transmitter
  • how wet is the moss
  • depth of the transmitter

Is the moss wet? Water kills RF very quickly. Within 1/2 meter depth you'll get high loss of signal. I doubt that AcuRite could transmit very far through wet moss; too low of power. Who knows if 433MHz is the best frequency.


You may be best off with your manual temperature readings.
Or, could you leave a 10' pole there? Sensor at one end and the transmitter at the other?

Don't know. Sounds like a tough problem.
I expect this will be a challenge, but definitely worth it if it'll work.

I'll be testing various devices in an actual pile in a couple weeks. 2.4GHz and higher will undoubtedly be affected considerably if the moss is wet (it's never "sloppy-wet", and it's harvested when fairly dry) or if it's sheathed in an icy layer (like it is now). I have a 433MHz temperature and wind speed transmitter that I'll bury in a pile to see if the receiver will pick it up. I suspect it will, but I'll be sure to share the results. The problem with the 433MHz devices is that there are limited "channels".

Interestingly, we had a fire yesterday in a pile that was covered with 6-8" of ice and the ambient temperature was about -15C.
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Old January 23rd, 2018, 06:47 PM   #10
rguimond
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Quote:
Originally Posted by DBLD99 View Post
We have used these for grain piles. Can't remember price though.

https://www.extrongrain.com/wireless...rature-probes/
Could be feasible.
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Old January 23rd, 2018, 06:49 PM   #11
rguimond
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Quote:
Originally Posted by boneless View Post
I think you need to define cheap? $20 bucks for a wireless sensor is pretty cheap imo, but if you multiply that by 1000, you are looking at a $20,000 bill.

If you need that many, I think you could be developing (having developed) your own sensors.

At my home I am using Xiaomi sensors using Zigbee (2.4GHz I believe). They work great. They daisy-chain wirelessly. They are made for the Chinese market, but I got them working in my home automation system.

They don't seem to have any IP rating, but pretty sure they would still work in an ABS box.

Not the perfect solution, but I think it would be worth a try?
Probably worth a shot, but I'd have to come up with a way to provide power to the gateways they require. We're looking at several 200+ acre sites...
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Old January 24th, 2018, 04:28 AM   #12
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Is the high temperature noticeable from the surface? I know you say you have to stick the probe in, but what about using thermal imaging?

Still a manual job, but someone could just walk around with the camera scanning for a high temp.

Although if this happens under a layer of ice...

Canada sounds dangerous! Exploding frozen moss is not a hazard I've encountered before
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Old January 24th, 2018, 05:33 AM   #13
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Following on from what Saffa said. If the stuff is under a pile of snow you won't see a high temperature, but I would expect that there would be a differential between the too hot pile and a normal pile. Look for the ones that are different.

Otherwise, as detecting from the top is an issue, how about embedding permanent sensors underneath the piles. No need for disposable and they should see the too hot temperatures whatever the weather.
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Old January 24th, 2018, 08:20 AM   #14
lfe
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Time ago I worked with a kiln that served to determine the fire resistance of walls, doors and various materials.
The system recorded the temperature in several points and the test ended when some probes reached a certain temperature.
Many 3mm diameter thermocouple probes were used similar to this one. in both sides of the test wall. They were reused until they broke and it did not take much effort to mount the experiment.

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Old January 24th, 2018, 12:55 PM   #15
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That seems at least partly feasible to me: stick this in a 10' PVC or metal pipe, add some glue to keep moist and dirt out and you are done. One could make a few hundred in a single day. Only downside: it is not wireless. If wireless is a hard requirement, then a battery powered transmitter would have to be added to the connector end of the PVC pipe to sit outside of the pile. With a transmitter the complexity goes up, and with that required time and thus costs.
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