WXforum.net
Weather Station Hardware => Davis Instruments Weather Stations => Topic started by: azchrisf on September 25, 2017, 03:45:25 AM
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I was going thru a document from Davis that states to use one battery for more daytime aspiration, and two for more nighttime aspiration, or something to that affect.
What I gather from this is that some of the power from the solar panel is diverted to recharge the batteries. So, the question would be, what kind of modifications can I make (do not want to do the AC fan mod), such as adding an additional solar panel, that will offer 24 hour same-level aspiration?
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I don't have the answer to your question, but too bad you won't or can't consider the a/c route, cause it'd be a hellofalot cheaper, easier, more reliable, and better performer than what you're looking for. GL.
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Adding additional solar panel wouldn't do anything for night speeds because it goes on batteries 1.2 volts vs 2.8 daytime with full sun. I also didn't see any daytime voltage or fan speed difference between 1 or 2 batteries contrary to what Davis manual says.
I played around with different combo's adding more solar cells and batteries bumping fan speed by wiring in series (doubling voltage) but in the end the system didn't work as well draining batteries before sunrise even when using bank of 8-1.2v batteries in series 2.4 volts won't make it until sunrise the next day.
I'm sure it can be made to work with the right battery solar panel combo but decided to stick with what Davis intended.
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That's quite interesting.
So what's with the 6V fan upgrade then?
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6 volt?
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Yes someone had mentioned replacing the 3V fan with a 6V fan, don't remember if that was part of a upgrade or not.
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I run a 6V motor in my FARS, replacing the Davis motor.
http://www.jameco.com/z/RF-500TB-14415-R-J-32-Nichibo-Taiwan-MOTOR-DC-6V-1-6V-RANGE-2755-RPM-164A-077-SOLDER_2230037.html
At 6v, I measure the fan rotation at 25% higher RPMs than the Davis motor at 3V.
I use my own circuitry for powering and battery charging. In fact I have replaced the entire ISS with my own concoction.
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ct can you give me a detailed writeup of what you did?
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ct can you give me a detailed writeup of what you did?
And, I will SECOND that request, thank you.
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This is my ISS replacement.
[ You are not allowed to view attachments ]
I'm quite a novice in electronics, just trying to learn what I can by reading online and watching Youtube videos.
From left to right the RJ12 connector are: Solar input, Fan power and speed monitoring, Temperature (SHT35), Wind, Rain.
The top battery powers the circuit, the bottom battery powers the fan.
There are 2 solar charge controllers next to the top switches. An adjustable voltage boost/buck converter regulates the output voltage (3.3v) for the fan during the night. During the day the fan is powered by solar (6V). When replacing the Davis motor I installed an Allegro A3213 hall effect sensor in the fan housing and a small magnet on the fan to record the fan rotation status.
The microcontroller is an ATmega 328p. The board also has a DS3231 real time clock and a BMP180 pressure sensor. An XBee transmitter transmits readings to an indoor XBee gateway. This gateway also receives data from other devices, such as roof mounted solar/UV station, letter box monitor etc. The gateway transmits data to a Davis console using an RFM69 transmitter.
The weather observations are transmitted in a single line of text. Eg.
ID=W3 SQ=355347 TS=20170930-083309 UT=1776735 ST=12.56 SH=64.08 WR=1790831 WS=7/7 WD=5 RC=1177 TC=0 TL=416538 BT=16.66 AP=1012.61 L1=4.21/88/18/ON L2=4.22/694/26/ON FS=6.02/2275 CK=203D45B2
ID = Device ID
SQ = Packet sequence
TS = Timestamp
UT = Uptime in seconds
ST = SHT35 temperature
SH = SHT35 humidity
WR = Anemometer wind rotation since last reboot
WS = Wind speed Gust/Average
WD = Wind direction
RC = Rain tip counter
TC = Time interval between rain tips
TL = Seconds since last rain tip
BT = BMP180 temperature
AP = BMP180 air pressure
L1 = Li-Ion battery 1 : voltage/charge current/controller temperature/charge status
L2 = Li-Ion battery 2 : voltage/charge current/controller temperature/charge status
FS = Fan status : Voltage/Rotations(RPM)
CK = Packet checksum
Currently the controller reports readings every 5 seconds, but this can be adjusted remotely as I have 2 way communications with the controller. This allows remote firmware updates.
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You have an SHT35 sensor already? Only the SHT31 is available from DAVIS and Sensirion officially, the SHT35 hasn't officially been implemented (yet) to our knowledge.
ADDENDUM: OOPS, I see that Mouser now has the surface-mount SHT35 in their catalog for sale...decent price, too.
P.S. -- Very neat component lay-out.
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I'm using this SHT35 board, which is the i2c version.
https://www.tindie.com/products/closedcube/sht35-d-digital-humidity-and-temperature-sensor/
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I see, you're using the I2C communication link...as yet, DAVIS isn't.
2 x 5200mA is a pretty stout battery pack...so, what size solar panel you using to power/charge it from?
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I'm using this SHT35 board, which is the i2c version.
https://www.tindie.com/products/closedcube/sht35-d-digital-humidity-and-temperature-sensor/
Clue us dumbasses in, is this something we normal users can incorporate without going to MIT? In other words, "plug n play"?
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The SHT35 is NOT (now) compatible with DAVIS at all because of its different I2C communication protocol...which DAVIS has apparently NOT embraced (yet).
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The SHT35 is NOT (now) compatible with DAVIS at all because of its different I2C communication protocol...which DAVIS has apparently NOT embraced (yet).
So I gather ct has made his own, completely separate from Davis?
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I know this is getting OT, but why would "whomever" make the 31 compatible, but not the 35?
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The SHT35 is NOT (now) compatible with DAVIS at all because of its different I2C communication protocol...which DAVIS has apparently NOT embraced (yet).
So I gather ct has made his own, completely separate from Davis?
No, he's using a mircochip that DOES use the "new" I2C communication protocol that the SHT35 has. DAVIS parts still use the "old" ANALOG data output.
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I know this is getting OT, but why would "whomever" make the 31 compatible, but not the 35?
My WAG is the SHT31 was the "last" of the "old" and the SHT35 the "first of the "new"...Sensirion 'pushing' the technology change, which Davis hasn't yet embraced.
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The SHT35 is NOT (now) compatible with DAVIS at all because of its different I2C communication protocol...which DAVIS has apparently NOT embraced (yet).
So I gather ct has made his own, completely separate from Davis?
No, he's using a mircochip that DOES use the "new" I2C communication protocol that the SHT35 has. DAVIS parts still use the "old" serial communication protocol.
I guess I'm not getting my question across properly. Is there a way to get this into my ISS without being a rocket surgeon?
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The SHT35 is NOT (now) compatible with DAVIS at all because of its different I2C communication protocol...which DAVIS has apparently NOT embraced (yet).
So I gather ct has made his own, completely separate from Davis?
No, he's using a mircochip that DOES use the "new" I2C communication protocol that the SHT35 has. DAVIS parts still use the "old" serial communication protocol.
I guess I'm not getting my question across properly. Is there a way to get this into my ISS without being a rocket surgeon?
Monosyllabic answer: NO.
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Harumph...
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Both SHT31-D and SHT35-D are the new i2C serial-DIGITAL protocol.
The SHT31-A is the old ANALOG protcol that our Davis ISS's use.
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To my knowledge, the Davis uses an SMBus version of the SHT31, which is a similar protocol to i2c but not the same. This makes it not possible to use the i2c SHT35 with a Davis ISS.
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2 x 5200mA is a pretty stout battery pack...so, what size solar panel you using to power/charge it from?
At the moment it is connected to a rather large panel (12V 200W) that I also use for various backyard solar projects.
A similar weather station at parents house charges the batteries with 2 x 6V 3W panels in parallel
https://www.seeedstudio.com/3W-Solar-Panel-138X160-p-954.html
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To my knowledge, the Davis uses an SMBus version of the SHT31, which is a similar protocol to i2c but not the same. This makes it not possible to use the i2c SHT35 with a Davis ISS.
As I understand it, SMB is a similar/but different incarnation of I2C, but it's not what DAVIS currently uses:
https://www.wxforum.net/index.php?topic=29500.0 (https://www.wxforum.net/index.php?topic=29500.0)
When tested with I2C communication, the "older" SHT31 (and SHT15) were silent.
Getting back "on-topic" how do you control the fan's DAY/NITE speed/voltage changes? Computer, time-of-day, daylight sensor, etc.?
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how do you control the fan's DAY/NITE speed/voltage changes? Computer, time-of-day, daylight sensor, etc.?
The adjustable voltage regular is set to around 3.6v. The solar input varies up to 6.4v. Both these connect to the fan load through diodes. Whichever has the highest voltage seems to supply the power. Taking into account the diode voltage drop the fan is powered at 6.1v in sunlight and 3.3v at night.
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how do you control the fan's DAY/NITE speed/voltage changes? Computer, time-of-day, daylight sensor, etc.?
The adjustable voltage regular is set to around 3.6v. The solar input varies up to 6.4v. Both these connect to the fan load through diodes. Whichever has the highest voltage seems to supply the power. Taking into account the diode voltage drop the fan is powered at 6.1v in sunlight and 3.3v at night.
So, during the sunlight of day, the solar cell (and regulator?) power the fan with 6.1Vdc...via...diode (Schottky?) "OR" gating such that at night only the remaining 3.6Vdc battery power is powering the fan. Correct?
Presumably, during the sunglight of day, the solar cell is powering BOTH regulators and their loads?
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During sunlight when the solar panel reaches a voltage higher than the set output of the regulator, only the solar panel will power the fan. This solar panel is effectively wired directly to the fan.
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It appears he has completely rebuilt the weather station from the ground up, not a simple mod.
Still shows what is possible but definitely not a "mod", per-se. Regardless, very interesting and shows a very intelligent owner :)
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My DFARs has been running 24/7 for the past 2 weeks.
Still design in progress, but at this stage it's just 3 simple modules involved; It will improve with planned changes.
Li-Ion charge module to charge a pair of 18650's in parallel with a 4.5W panel (6V & 165x165mm).
A "Juice Bank" module to boost the Li batts to a 5V output, which steps down again with an LM2596 Buck regulator.
Last 4 days have been overcast, but I have still not seen the battery's drop below about 75% charge of a morning.
Will see what to-morrow brings.
The regulator to the fan is set at 2.1V.
Cheers.
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Adding additional solar panel wouldn't do anything for night speeds because it goes on batteries 1.2 volts vs 2.8 daytime with full sun.....
So is 2.8V the daytime voltage to the fan in the 24 hour FARs?
Interesting, as the DFAR's never seems to see more than 2.2V in my case & in my current conversion to 24 hour I'm wondering what is the best voltage to use.
Wasn't thinking of different day night voltages, just possibly increasing it up to about 2.4
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Adding additional solar panel wouldn't do anything for night speeds because it goes on batteries 1.2 volts vs 2.8 daytime with full sun.....
So is 2.8V the daytime voltage to the fan in the 24 hour FARs?
Interesting, as the DFAR's never seems to see more than 2.2V in my case & in my current conversion to 24 hour I'm wondering what is the best voltage to use.
Wasn't thinking of different day night voltages, just possibly increasing it up to about 2.4
Yes going from memory was seeing 2.8v peak voltage. Running less voltage over 24 hour would be better on fan however because they don't tend to last long even going down to 1.2 volts on at night. Running higher voltage will shorten life of fan no doubt.
Davis used 3 volt power plug at one time but this design is no longer available.
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Phil I also read where someone was saying 2.5 volts was max for fans. One thing also the Dfars solar cell is much smaller than the cell that comes with 24 hr shield.
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Adding additional solar panel wouldn't do anything for night speeds because it goes on batteries 1.2 volts vs 2.8 daytime with full sun.....
So is 2.8V the daytime voltage to the fan in the 24 hour FARs?
Interesting, as the DFAR's never seems to see more than 2.2V in my case & in my current conversion to 24 hour I'm wondering what is the best voltage to use.
Wasn't thinking of different day night voltages, just possibly increasing it up to about 2.4
Yes going from memory was seeing 2.8v peak voltage. Running less voltage over 24 hour would be better on fan however because they don't tend to last long even going down to 1.2 volts on at night. Running higher voltage will shorten life of fan no doubt.
Davis used 3 volt power plug at one time but this design is no longer available.
I wonder what a DJI Drone Motor would work? Should have a Long MTBF life span. Or would the demensions be to large?
https://www.amazon.com/DJI-Phantom-Part-Motor-California/dp/B00LJOYB10/ref=sr_1_4?ie=UTF8&qid=1423258209&sr=8-4&tag=ifixitam-20
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Adding additional solar panel wouldn't do anything for night speeds because it goes on batteries 1.2 volts vs 2.8 daytime with full sun.....
So is 2.8V the daytime voltage to the fan in the 24 hour FARs?
Interesting, as the DFAR's never seems to see more than 2.2V in my case & in my current conversion to 24 hour I'm wondering what is the best voltage to use.
Wasn't thinking of different day night voltages, just possibly increasing it up to about 2.4
Yes going from memory was seeing 2.8v peak voltage. Running less voltage over 24 hour would be better on fan however because they don't tend to last long even going down to 1.2 volts on at night. Running higher voltage will shorten life of fan no doubt.
Davis used 3 volt power plug at one time but this design is no longer available.
I wonder what a DJI Drone Motor would work? Should have a Long MTBF life span. Or would the demensions be to large?
https://www.amazon.com/DJI-Phantom-Part-Motor-California/dp/B00LJOYB10/ref=sr_1_4?ie=UTF8&qid=1423258209&sr=8-4&tag=ifixitam-20
What's the normal operating RPMs? It might not want to run at low RPMs because of too low voltage.
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I wonder what a DJI Drone Motor would work? Should have a Long MTBF life span. Or would the demensions be to large?
https://www.amazon.com/DJI-Phantom-Part-Motor-California/dp/B00LJOYB10/ref=sr_1_4?ie=UTF8&qid=1423258209&sr=8-4&tag=ifixitam-20
Probably not without a lot of fancy electronics to drive it.
From https://forum.dji.com/thread-2908-1-1.html
looks like you're using a 400Hz 3-phase stepper drive, PWM modulated for speed control
And DJI says at http://www.dji.com/newsroom/news/inside-a-drone-brushless-motors:
Typically, the motor found on a drone is triple-phase, but this basic principle remains the same.
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I also read where someone was saying 2.5 volts was max for fans.
It's been a while, but I believe in full sun my multimeter had the panel output at ~2.45 volts. These are obviously rated to 3vcd.
https://www.jameco.com/z/RF-500TB-18280-R-Nichibo-Taiwan-3-Volt-Dc-Motor-2104-Rpm-1-3-Volt-Range_2158442.html
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Yes going from memory was seeing 2.8v peak voltage. Running less voltage over 24 hour would be better on fan however because they don't tend to last long even going down to 1.2 volts on at night. Running higher voltage will shorten life of fan no doubt.
In my ancient VP1 I have a Jameco 3V motor that runs at 3V during the day and 2.2V during the night. Still going strong after 16 months.
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I also read where someone was saying 2.5 volts was max for fans.
It's been a while, but I believe in full sun my multimeter had the panel output at ~2.45 volts. These are obviously rated to 3vcd.
https://www.jameco.com/z/RF-500TB-18280-R-Nichibo-Taiwan-3-Volt-Dc-Motor-2104-Rpm-1-3-Volt-Range_2158442.html
Think that rings a bell, 2.45V & from memory that was open circuit, vaguely recall 150mA short circuit. (Std Daytime panel).
Full sun & fan running was 2.05V @ 100mA, which seems a lot lower power than Nichibo above, using 350mA @ 2.0V.
I'd recheck now but it's overcast & raining.
At least the Test fan is still running, after a good 3 days of overcast weather.