14 sensors on a stick

[Winfield Hill]

This is a stick of 14 sensors on six ICs, that's
meant to go into the middle of a beehive. But it
could be interesting for other uses. It runs on
low-power 3.3V, and uses a single I2C data bus.

https://www.dropbox.com/sh/97gj51p03554cii/AAAk8W8yaLS7W_bp_JWde5W5a?dl=0

WRT to the choice of sensors, there's redundancy
for the T + RH sensors, because we've had so much
trouble with RH sensors (it's a test platform).
It has a barometric-pressure sensor, a CO2 sensor,
and two volatile organic gas sensors. The latter
use miniature hot plates, briefly drawing up to
75mA. An 800M:1 dynamic-range light sensor is to
help explore interesting night-time hive activity
(but we didn't add proximity detectors). (I also
resisted temptation to add a lightning detector.)

As far as the bewildering array of IO connectors
is concerned, that's to handle a variety of uses.



--
Thanks,
- Win

 

[Winfield Hill]

Winfield Hill wrote...

This is a stick of 14 sensors on six ICs, that's
meant to go into the middle of a beehive. But it
could be interesting for other uses. It runs on
low-power 3.3V, and uses a single I2C data bus.

https://www.dropbox.com/sh/97gj51p03554cii/AAAk8W8yaLS7W_bp_JWde5W5a?dl=0

WRT to the choice of sensors, there's redundancy
for the T + RH sensors, because we've had so much
trouble with RH sensors (it's a test platform).
It has a barometric-pressure sensor, a CO2 sensor,
and two volatile organic gas sensors. The latter
use miniature hot plates, briefly drawing up to
75mA. An 800M:1 dynamic-range light sensor is to
help explore interesting night-time hive activity
(but we didn't add proximity detectors). (I also
resisted temptation to add a lightning detector.)

As far as the bewildering array of IO connectors
is concerned, that's to handle a variety of uses.

Anyone who wants to play with one of these
sticks, I may have extras in a month or so.


--
Thanks,
- Win

 

[mpm]

On Sunday, June 2, 2019 at 9:31:03 AM UTC-4, Winfield Hill wrote:

Winfield Hill wrote...

This is a stick of 14 sensors on six ICs, that's
meant to go into the middle of a beehive. But it
could be interesting for other uses. It runs on
low-power 3.3V, and uses a single I2C data bus.

https://www.dropbox.com/sh/97gj51p03554cii/AAAk8W8yaLS7W_bp_JWde5W5a?dl=0

WRT to the choice of sensors, there's redundancy
for the T + RH sensors, because we've had so much
trouble with RH sensors (it's a test platform).
It has a barometric-pressure sensor, a CO2 sensor,
and two volatile organic gas sensors. The latter
use miniature hot plates, briefly drawing up to
75mA. An 800M:1 dynamic-range light sensor is to
help explore interesting night-time hive activity
(but we didn't add proximity detectors). (I also
resisted temptation to add a lightning detector.)

As far as the bewildering array of IO connectors
is concerned, that's to handle a variety of uses.

Anyone who wants to play with one of these
sticks, I may have extras in a month or so.


--
Thanks,
- Win

I don't have a need for one, but might be interested if it comes conformal coated in honey.

Nice looking design. Hope it works out for you!

 

[Rick C]

On Sunday, June 2, 2019 at 10:00:14 AM UTC-4, mpm wrote:

On Sunday, June 2, 2019 at 9:31:03 AM UTC-4, Winfield Hill wrote:
Winfield Hill wrote...

This is a stick of 14 sensors on six ICs, that's
meant to go into the middle of a beehive. But it
could be interesting for other uses. It runs on
low-power 3.3V, and uses a single I2C data bus.

https://www.dropbox.com/sh/97gj51p03554cii/AAAk8W8yaLS7W_bp_JWde5W5a?dl=0

WRT to the choice of sensors, there's redundancy
for the T + RH sensors, because we've had so much
trouble with RH sensors (it's a test platform).
It has a barometric-pressure sensor, a CO2 sensor,
and two volatile organic gas sensors. The latter
use miniature hot plates, briefly drawing up to
75mA. An 800M:1 dynamic-range light sensor is to
help explore interesting night-time hive activity
(but we didn't add proximity detectors). (I also
resisted temptation to add a lightning detector.)

As far as the bewildering array of IO connectors
is concerned, that's to handle a variety of uses.

Anyone who wants to play with one of these
sticks, I may have extras in a month or so.


--
Thanks,
- Win


I don't have a need for one, but might be interested if it comes conformal coated in honey.

Or one at the bottom of the jar of honey like the worm in Tequila.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[Winfield Hill]

mpm wrote...

Nice looking design. Hope it works out for you!

Thank you! Yes, I enjoyed working on this design,
and admired the amazing sensors, but in the end,
I just selected simple sensors that can be drawn
as a box with four pins, and wired up supply and
ground, along with the two I2C pins in parallel.
Two 1.8-volt sensors added a hint of complexity.
There was quite a bit of mucking around, finding
various small parts, making weird PCB footprints,
learning about FFC flat flexible cables, etc.
And the Institute mathematician has spent several
weeks working on software to talk to the sensors.
Tomorrow we'll power one up and see what happens.


--
Thanks,
- Win

 

[glen walpert]

On Sat, 01 Jun 2019 18:47:48 -0700, Winfield Hill wrote:

This is a stick of 14 sensors on six ICs, that's
meant to go into the middle of a beehive. But it could be interesting
for other uses. It runs on low-power 3.3V, and uses a single I2C data
bus.

https://www.dropbox.com/sh/97gj51p03554cii/AAAk8W8yaLS7W_bp_JWde5W5a?
dl=0

WRT to the choice of sensors, there's redundancy for the T + RH
sensors, because we've had so much trouble with RH sensors (it's a test
platform). It has a barometric-pressure sensor, a CO2 sensor,
and two volatile organic gas sensors. The latter use miniature hot
plates, briefly drawing up to 75mA. An 800M:1 dynamic-range light
sensor is to help explore interesting night-time hive activity (but we
didn't add proximity detectors). (I also resisted temptation to add a
lightning detector.)

As far as the bewildering array of IO connectors is concerned, that's
to handle a variety of uses.

What is it you are looking for with these sensors? I kept a hive for 5
years, temporarily retiring it two years ago for lack of time but
planning to get two hives going again in a couple of years - we are
running low on honey . If I were to monitor my hives electronically
the first thing I would want is a scale and means for daily hive weight
logging to an MQTT broker which I could check from computer or phone, the
second might be a microphone and logging of a few FFT bins for swarm
prediction:

https://www.sciencedirect.com/science/article/pii/S0168169908001385
https://www.beeculture.com/arnia-remote-hive-monitoring-every-beekeeper/
https://igor.crew.c-base.org/1-s2.0-S0168169908001385-main.pdf

While looking for this I found a note on honeybee hearing which I
probably posted somewhere before:

Honeybees hearing is also sensitive to displacement rather than
pressure. For many years it was a mystery how an insect with no ears
could respond to the sound of the wingbeat of guide bees preforming the
"dance" which communicates direction to food source (by direction of the
central tail-waggle portion of the dance), distance (by the speed of tail
waggle), and quality (by wingbeat frequency). It was eventually
determined that hearing was done with an organ within a joint of the
antennae, and by testing in a standing wave tube shown that honeybees can
hear at the displacement maxima (pressure nodes) and not at the
displacement nodes (pressure maxima). This hearing is limited to a few
hundred Hz by the size of the antennae, which is much larger than the MEMS
displacement microphones.

My source of this information, The ABC-XYZ of Bee Culture, references
Towne, W.F. and W.H. Kirchner, Hearing in honey bees: detection of air
particle oscillations. Science 244: 686-688, 1989

Glen

 

[Joerg]

On 2019-06-02 09:41, glen walpert wrote:

[...]

While looking for this I found a note on honeybee hearing which I
probably posted somewhere before:

Honeybees hearing is also sensitive to displacement rather than
pressure. For many years it was a mystery how an insect with no ears
could respond to the sound of the wingbeat of guide bees preforming the
"dance" which communicates direction to food source (by direction of the
central tail-waggle portion of the dance), distance (by the speed of tail
waggle), and quality (by wingbeat frequency). It was eventually
determined that hearing was done with an organ within a joint of the
antennae, and by testing in a standing wave tube shown that honeybees can
hear at the displacement maxima (pressure nodes) and not at the
displacement nodes (pressure maxima). This hearing is limited to a few
hundred Hz by the size of the antennae, which is much larger than the MEMS
displacement microphones.

My source of this information, The ABC-XYZ of Bee Culture, references
Towne, W.F. and W.H. Kirchner, Hearing in honey bees: detection of air
particle oscillations. Science 244: 686-688, 1989

A few hundred Hz? The bees might enjoy some rap or didgeridoo music

After all, Kobe cattle is listening to Mozart I believe.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Rich S]

On Sunday, June 2, 2019 at 10:56:25 AM UTC-4, Winfield Hill wrote:

mpm wrote...

Nice looking design. Hope it works out for you!

Thank you! Yes, I enjoyed working on this design,
and admired the amazing sensors, but in the end,
I just selected simple sensors that can be drawn
as a box with four pins, and wired up supply and
ground, along with the two I2C pins in parallel.
Two 1.8-volt sensors added a hint of complexity.
There was quite a bit of mucking around, finding
various small parts, making weird PCB footprints,
learning about FFC flat flexible cables, etc.
And the Institute mathematician has spent several
weeks working on software to talk to the sensors.
Tomorrow we'll power one up and see what happens.


--
Thanks,
- Win

Great work and great sharing. The fraternal sharing of
experience, lessons learned, is precious. Engineering
-like life- should be a continuing education. Too much
of our industry is closed off, sensitive to competition,
separated by "oceans" - so places like S.E.D. our vital.
I hope our younger peers keep it going.
Cheers, Rich S.

 

[Winfield Hill]

glen walpert wrote...

On Sat, 01 Jun 2019, Winfield Hill wrote:

This is a stick of 14 sensors on six ICs, that's
meant to go into the middle of a beehive. ...

What is it you are looking for with these sensors?
I kept a hive for 5 years ...

Thanks for your comments.

This sensor stick plugs into our bee-hive monitor,
which has about 60 other sensors, including weight,
all bee trips in/out, temp, RH, and two microphones.
Running this last summer on seven hives, I learned
a lot, but I'm not sure how valuable it would be to
experienced bee-hive operators. We're still feeling
our way along, including this summer improving rapid
reporting, easy data visualization, analysis, etc.

As far as sound is concerned, we can make detailed
recordings, do FFTs, etc., but mostly we just save
minimum sound intensity every 10 minutes.

We only got one set of recordings on a hive abscond
event. The hive seemed healthy and things looked
pretty normal, up to just before the event. But we
had seen the unusual markers before, and without a
follow-on abscond event. One thing that we saw the
night before was guarding level suddenly way down,
virtually stopped. It's possible the absconding
had already started, and took two days. That's
what the weight and bee-trip data implied.

After the abscond, within a day or two, robber bees
arrived. But robbers never bothered to guard the
hive. One night about 60 bees were trapped in the
hive (they didn't know well how to navigate any of
the 24 counting-channel tunnels in the dark), but
they all escaped in a rush at 3am, into driving
rain and pitch black storm. Dunno what happened.


--
Thanks,
- Win

 

On Sunday, 2 June 2019 03:48:10 UTC+2, Winfield Hill wrote:

This is a stick of 14 sensors on six ICs, that's
meant to go into the middle of a beehive. But it
could be interesting for other uses. It runs on
low-power 3.3V, and uses a single I2C data bus.

https://www.dropbox.com/sh/97gj51p03554cii/AAAk8W8yaLS7W_bp_JWde5W5a?dl=0

WRT to the choice of sensors, there's redundancy
for the T + RH sensors, because we've had so much
trouble with RH sensors (it's a test platform).
It has a barometric-pressure sensor, a CO2 sensor,
and two volatile organic gas sensors. The latter
use miniature hot plates, briefly drawing up to
75mA. An 800M:1 dynamic-range light sensor is to
help explore interesting night-time hive activity
(but we didn't add proximity detectors). (I also
resisted temptation to add a lightning detector.)

As far as the bewildering array of IO connectors
is concerned, that's to handle a variety of uses.

Very interesting project

I was just checking out the schematics, you have 2 sensors that monitor gases/VOC

For a private project, I am looking for a sensor that would detect mold, so I could have a sensor that could track/detect where the mold origin is. As far I can see PM2.5 sensors (more or less dust sensors), are the preferred solution, but that said, I am not fully into the subject yet

Why did you decide for VOC and not PM2.5 sensors?

Also, how do you calibrate the sensors. From what I gather, the VOC sensors are difficult to use if they are not calibrated to a known reference first

Cheers

Klaus

 

[Phil Hobbs]

On 6/1/19 9:47 PM, Winfield Hill wrote:

This is a stick of 14 sensors on six ICs, that's
meant to go into the middle of a beehive. But it
could be interesting for other uses. It runs on
low-power 3.3V, and uses a single I2C data bus.

https://www.dropbox.com/sh/97gj51p03554cii/AAAk8W8yaLS7W_bp_JWde5W5a?dl=0

WRT to the choice of sensors, there's redundancy
for the T + RH sensors, because we've had so much
trouble with RH sensors (it's a test platform).
It has a barometric-pressure sensor, a CO2 sensor,
and two volatile organic gas sensors. The latter
use miniature hot plates, briefly drawing up to
75mA. An 800M:1 dynamic-range light sensor is to
help explore interesting night-time hive activity
(but we didn't add proximity detectors). (I also
resisted temptation to add a lightning detector.)

As far as the bewildering array of IO connectors
is concerned, that's to handle a variety of uses.

We're doing some high-Z optical sensors for detecting sparks in cotton
harvesting equipment. There's a 200 Mohm TIA in there, so we care quite
a lot about water inside the box, which leads us to put T/RH sensors
inside to give early warning of water ingress.

Could you tell us more about your RH sensor experience?

Thanks

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Winfield Hill]

Phil Hobbs wrote...

Could you tell us more about your RH sensor experience?

WE had only one brand that failed (one you wouldn't use);
I can tell you more after working with our four new brands.


--
Thanks,
- Win

 

[artie]

Very nice!

If you have extras in a moth or so, I have a chicken coop that needs
instrumented!

--bob


In article <qd0j2402gv@drn.newsguy.com>, Winfield Hill
<hill@rowland.harvard.edu> wrote:

Winfield Hill wrote...

This is a stick of 14 sensors on six ICs, that's
meant to go into the middle of a beehive. But it
could be interesting for other uses. It runs on
low-power 3.3V, and uses a single I2C data bus.

https://www.dropbox.com/sh/97gj51p03554cii/AAAk8W8yaLS7W_bp_JWde5W5a?dl=0

WRT to the choice of sensors, there's redundancy
for the T + RH sensors, because we've had so much
trouble with RH sensors (it's a test platform).
It has a barometric-pressure sensor, a CO2 sensor,
and two volatile organic gas sensors. The latter
use miniature hot plates, briefly drawing up to
75mA. An 800M:1 dynamic-range light sensor is to
help explore interesting night-time hive activity
(but we didn't add proximity detectors). (I also
resisted temptation to add a lightning detector.)

As far as the bewildering array of IO connectors
is concerned, that's to handle a variety of uses.

Anyone who wants to play with one of these
sticks, I may have extras in a month or so.

--

 

[Clifford Heath]

On 3/6/19 10:37 am, artie wrote:

Very nice!
If you have extras in a moth or so, I have a chicken coop that needs
instrumented!

I don't think it's small enough to be in a moth.

 

[Winfield Hill]

artie wrote...

Very nice!

If you have extras in a month or so, I have a
chicken coop that needs instrumented!

OK, Bob, send me an email to hold a place.


--
Thanks,
- Win

 

[glen walpert]

On Sun, 02 Jun 2019 10:59:47 -0700, Winfield Hill wrote:

glen walpert wrote...

On Sat, 01 Jun 2019, Winfield Hill wrote:

This is a stick of 14 sensors on six ICs, that's meant to go into the
middle of a beehive. ...

What is it you are looking for with these sensors?
I kept a hive for 5 years ...

Thanks for your comments.

This sensor stick plugs into our bee-hive monitor, which has about 60
other sensors, including weight, all bee trips in/out, temp, RH, and
two microphones.
Running this last summer on seven hives, I learned a lot, but I'm not
sure how valuable it would be to experienced bee-hive operators. We're
still feeling our way along, including this summer improving rapid
reporting, easy data visualization, analysis, etc.

As far as sound is concerned, we can make detailed recordings, do FFTs,
etc., but mostly we just save minimum sound intensity every 10 minutes.

We only got one set of recordings on a hive abscond event. The hive
seemed healthy and things looked pretty normal, up to just before the
event. But we had seen the unusual markers before, and without a
follow-on abscond event. One thing that we saw the night before was
guarding level suddenly way down, virtually stopped. It's possible the
absconding had already started, and took two days. That's what the
weight and bee-trip data implied.

After the abscond, within a day or two, robber bees arrived. But
robbers never bothered to guard the hive. One night about 60 bees were
trapped in the hive (they didn't know well how to navigate any of the
24 counting-channel tunnels in the dark), but they all escaped in a
rush at 3am, into driving rain and pitch black storm. Dunno what
happened.

Thanks for the details, sounds fascinating. I am in no way a bee expert,
my last two hives absconded without me noticing, and I have decided not
to try again until I can be around to take care of the 2 hives rather
than one, doubling my odds of making it through the winter. I trust you
will let us know of any interesting findings from your research.

Thanks,
Glen

 

[amdx]

On 6/2/2019 12:59 PM, Winfield Hill wrote:

glen walpert wrote...

On Sat, 01 Jun 2019, Winfield Hill wrote:

This is a stick of 14 sensors on six ICs, that's
meant to go into the middle of a beehive. ...

What is it you are looking for with these sensors?
I kept a hive for 5 years ...

Thanks for your comments.

This sensor stick plugs into our bee-hive monitor,
which has about 60 other sensors, including weight,
all bee trips in/out, temp, RH, and two microphones.
Running this last summer on seven hives, I learned
a lot, but I'm not sure how valuable it would be to
experienced bee-hive operators. We're still feeling
our way along, including this summer improving rapid
reporting, easy data visualization, analysis, etc.

As far as sound is concerned, we can make detailed
recordings, do FFTs, etc., but mostly we just save
minimum sound intensity every 10 minutes.

We only got one set of recordings on a hive abscond
event. The hive seemed healthy and things looked
pretty normal, up to just before the event. But we
had seen the unusual markers before, and without a
follow-on abscond event. One thing that we saw the
night before was guarding level suddenly way down,
virtually stopped. It's possible the absconding
had already started, and took two days. That's
what the weight and bee-trip data implied.

After the abscond, within a day or two, robber bees
arrived. But robbers never bothered to guard the
hive. One night about 60 bees were trapped in the
hive (they didn't know well how to navigate any of
the 24 counting-channel tunnels in the dark), but
they all escaped in a rush at 3am, into driving
rain and pitch black storm. Dunno what happened.

A short beekeeper blog about two hive abscondings.
> https://honeybeesuite.com/absconding-swarms-leave-an-empty-hive/

Mikek

 

[George Herold]

On Sunday, June 2, 2019 at 7:37:23 PM UTC-4, Phil Hobbs wrote:

On 6/1/19 9:47 PM, Winfield Hill wrote:
This is a stick of 14 sensors on six ICs, that's
meant to go into the middle of a beehive. But it
could be interesting for other uses. It runs on
low-power 3.3V, and uses a single I2C data bus.

https://www.dropbox.com/sh/97gj51p03554cii/AAAk8W8yaLS7W_bp_JWde5W5a?dl=0

WRT to the choice of sensors, there's redundancy
for the T + RH sensors, because we've had so much
trouble with RH sensors (it's a test platform).
It has a barometric-pressure sensor, a CO2 sensor,
and two volatile organic gas sensors. The latter
use miniature hot plates, briefly drawing up to
75mA. An 800M:1 dynamic-range light sensor is to
help explore interesting night-time hive activity
(but we didn't add proximity detectors). (I also
resisted temptation to add a lightning detector.)

As far as the bewildering array of IO connectors
is concerned, that's to handle a variety of uses.




We're doing some high-Z optical sensors for detecting sparks in cotton
harvesting equipment. There's a 200 Mohm TIA in there, so we care quite
a lot about water inside the box, which leads us to put T/RH sensors
inside to give early warning of water ingress.

Could you tell us more about your RH sensor experience?

I'd be interested too. (though I have no project in mind) I went looking
for info on how humidity sensors work, and found precious little.
this,
https://en.wikipedia.org/wiki/Hygrometer
and this,
https://www.sensorsmag.com/components/choosing-a-humidity-sensor-a-review-three-technologies

talked about how they work.

I found nothing about how they work in the vendors data sheets.

George H.

Thanks

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[George Herold]

On Monday, June 3, 2019 at 12:16:02 PM UTC-4, Jan Panteltje wrote:

On a sunny day (Mon, 3 Jun 2019 08:28:55 -0700 (PDT)) it happened George
Herold <gherold@teachspin.com> wrote in
e0383d1d-1917-4a7e-beb0-5af0097c9b3a@googlegroups.com>:


Could you tell us more about your RH sensor experience?
I'd be interested too. (though I have no project in mind) I went looking
for info on how humidity sensors work, and found precious little.
this,
https://en.wikipedia.org/wiki/Hygrometer
and this,
https://www.sensorsmag.com/components/choosing-a-humidity-sensor-a-review-three-technologies

talked about how they work.

I found nothing about how they work in the vendors data sheets.

George H.

Here in detail explained:
https://www.electronicshub.org/humidity-sensor-types-working-principle/

Thanks Jan. I guess I always want to know more. Why do these things
measure RH (relative humidity) so well? I'd think they some how
would measure the amount of water in the air. (absolute humidity)
Which changes dramatically with temperature.
https://en.wikipedia.org/wiki/Relative_humidity#Other_important_facts

I have 2 humidity sensors logging 24/7.
the first one is a variant of this one, and uses a DHT11 resistive sensor:
http://panteltje.com/panteltje/pic/humidity_pic_udp/
DHT11 resistance decreases when moisture increases.

The other one
https://www.ebay.com/itm/323089603357
uses a cheap Chinese wireless indoor / outdoor sensor
an USB DVB-T stick as receiver and some software to decode 433 MHz signals:
panteltje12: ~ # rtl_433 -d 0 -R 19 | weather_sensor_to_xgpspc -xy
Registering protocol [1] "Nexus Temperature & Humidity Sensor"
Registered 1 out of 101 device decoding protocols
Found 1 device(s)

trying device 0: Realtek, RTL2838UHIDIR, SN: 00000001
Found Rafael Micro R820T tuner
Using device 0: Generic RTL2832U OEM
Exact sample rate is: 250000.000414 Hz
Sample rate set to 250000.
Bit detection level set to 0 (Auto).
Tuner gain set to Auto.
Reading samples in async mode...
Tuned to 433920000 Hz.
...
2019 06 03 17:29 t 31.0 / rh 17.0 \ t_min 16.8 at 07:00 t_max 31.0 at 17:29 rh_min 17.0 at 17:28 rh_max 88.0 at 06:44
...
been hot here outside.

I opened it up (modified for li-ion battery (it sucks current) and it seems a very similar sensor to the DHT11.

rtl_433 is a nice program (written by somebody else) that decodes many 433 MHz device protocols.
weather_sensor_to_xgpspc just processes the output and then forwards it via ethernet to a Raspberry Pi, I wrote that.

I once worked with capacitive humidity sensors used to measure humidity of grain in silos, that was long ago,
big and expensive units, do no remember who made thsose.


Bees no...
Very few insects here this year, flowers bloom, but hardly any insects.

Yeah we had some wild bee hives in our woods, but they died off,
and now no honey bees at my house. :^(
(fewer apples on the trees.)

George H.

 

[Jan Panteltje]

On a sunny day (Mon, 3 Jun 2019 08:28:55 -0700 (PDT)) it happened George
Herold <gherold@teachspin.com> wrote in
<e0383d1d-1917-4a7e-beb0-5af0097c9b3a@googlegroups.com>:

Could you tell us more about your RH sensor experience?
I'd be interested too. (though I have no project in mind) I went looking
for info on how humidity sensors work, and found precious little.
this,
https://en.wikipedia.org/wiki/Hygrometer
and this,
https://www.sensorsmag.com/components/choosing-a-humidity-sensor-a-review-three-technologies

talked about how they work.

I found nothing about how they work in the vendors data sheets.

George H.

Here in detail explained:
https://www.electronicshub.org/humidity-sensor-types-working-principle/


I have 2 humidity sensors logging 24/7.
the first one is a variant of this one, and uses a DHT11 resistive sensor:
http://panteltje.com/panteltje/pic/humidity_pic_udp/
DHT11 resistance decreases when moisture increases.

The other one
https://www.ebay.com/itm/323089603357
uses a cheap Chinese wireless indoor / outdoor sensor
an USB DVB-T stick as receiver and some software to decode 433 MHz signals:
panteltje12: ~ # rtl_433 -d 0 -R 19 | weather_sensor_to_xgpspc -xy
Registering protocol [1] "Nexus Temperature & Humidity Sensor"
Registered 1 out of 101 device decoding protocols
Found 1 device(s)

trying device 0: Realtek, RTL2838UHIDIR, SN: 00000001
Found Rafael Micro R820T tuner
Using device 0: Generic RTL2832U OEM
Exact sample rate is: 250000.000414 Hz
Sample rate set to 250000.
Bit detection level set to 0 (Auto).
Tuner gain set to Auto.
Reading samples in async mode...
Tuned to 433920000 Hz.
....
2019 06 03 17:29 t 31.0 / rh 17.0 \ t_min 16.8 at 07:00 t_max 31.0 at 17:29 rh_min 17.0 at 17:28 rh_max 88.0 at 06:44
....
been hot here outside.

I opened it up (modified for li-ion battery (it sucks current) and it seems a very similar sensor to the DHT11.

rtl_433 is a nice program (written by somebody else) that decodes many 433 MHz device protocols.
weather_sensor_to_xgpspc just processes the output and then forwards it via ethernet to a Raspberry Pi, I wrote that.

I once worked with capacitive humidity sensors used to measure humidity of grain in silos, that was long ago,
big and expensive units, do no remember who made thsose.


Bees no...
Very few insects here this year, flowers bloom, but hardly any insects.