Author Topic: Fan speeds  (Read 995 times)

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Online Old Tele man

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Re: Fan speeds
« Reply #25 on: September 29, 2017, 08:48:08 PM »
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

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.?
« Last Edit: September 29, 2017, 08:52:26 PM by Old Tele man »
SYS: Davis VP2/WL-IP & Envoy8X/WL-USB
CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
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Offline ct

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Re: Fan speeds
« Reply #26 on: September 29, 2017, 09:23:16 PM »
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.

Online Old Tele man

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Re: Fan speeds
« Reply #27 on: September 29, 2017, 09:32:59 PM »
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?
« Last Edit: September 29, 2017, 09:35:57 PM by Old Tele man »
SYS: Davis VP2/WL-IP & Envoy8X/WL-USB
CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
WU - KAZTUCSO202, Countryside

Offline ct

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Re: Fan speeds
« Reply #28 on: September 29, 2017, 11:12:10 PM »
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.

Offline azchrisf

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Re: Fan speeds
« Reply #29 on: September 30, 2017, 05:23:31 AM »
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 :)

Offline Phil23

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Re: Fan speeds
« Reply #30 on: September 30, 2017, 06:14:04 AM »
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.

Offline Phil23

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Re: Fan speeds
« Reply #31 on: September 30, 2017, 06:46:57 AM »
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


Offline ValentineWeather

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Re: Fan speeds
« Reply #32 on: September 30, 2017, 11:38:16 AM »
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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Offline ValentineWeather

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Re: Fan speeds
« Reply #33 on: September 30, 2017, 11:48:55 AM »
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.
Randy, the Aviator is my father in 1963 with his Indian bike

Offline benay ra'am

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Re: Fan speeds
« Reply #34 on: September 30, 2017, 12:54:11 PM »
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
« Last Edit: September 30, 2017, 01:01:35 PM by benay ra'am »




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Online Old Tele man

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Re: Fan speeds
« Reply #35 on: September 30, 2017, 01:29:30 PM »
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.
SYS: Davis VP2/WL-IP & Envoy8X/WL-USB
CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
WU - KAZTUCSO202, Countryside

Offline SLOweather

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Re: Fan speeds
« Reply #36 on: September 30, 2017, 02:49:30 PM »

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

Quote
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:

Quote
Typically, the motor found on a drone is triple-phase, but this basic principle remains the same.
« Last Edit: September 30, 2017, 02:51:52 PM by SLOweather »

Offline CW2274

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Re: Fan speeds
« Reply #37 on: September 30, 2017, 03:12:43 PM »
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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Offline ct

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Re: Fan speeds
« Reply #38 on: September 30, 2017, 04:35:23 PM »
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.

Offline Phil23

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Re: Fan speeds
« Reply #39 on: September 30, 2017, 05:50:30 PM »
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.