Solar power percentage of charge control ??????

On 6/19/2021 3:05 PM, Jeff Liebermann wrote:
> On Sat, 19 Jun 2021 14:03:20 -0400, bitrex <user@example.net> wrote:
> 
>> We can assume they're properly licensed I guess, this is only an
>> intellectual exercise at the moment and that stuff is their problem.
>> 100 watts is the minimum for a licensed LPFM station that's good for
>> several miles with an ordinary portable FM radio or car stereo.
> 
> <https://www.fcc.gov/media/radio/lpfm-frequently-asked-questions>
> Q:  How far will the signal go?
> A:  LPFM stations are limited to 100 watts and a service range of 5.6
> kilometers (3.5 mile radius).  This does not mean that the station
> cannot be heard beyond a 3.5 miles radius.  It&rsquo;s an approximation of
> the expected average coverage.
> 

Ope, 100 watt is the minimum for a standard FM station, not LPFM

On 6/19/2021 4:36 PM, Don Y wrote:
> On 6/19/2021 5:05 AM, bitrex wrote:
> 
> [You know, it wouldn't kill you to trim posts -- including your
> own -- in stead of just appending to something that has already been
> seen!]
> 
>> You can get inverters with adjustable low-voltage 
>> disconnect/hysteresis threshold on the primary side, off the shelf.
> 
> You can also directly power kit from batteries without the need
> for an inverter.
> 
>> Dunno why the OP wants to use a laptop, mixer, audio compressor and 
>> all that. If the station is just to play pre-recorded audio files you 
>> can batch compress/limit them all ahead of time, put 'em on an SD 
>> card, and low-power SBC can just spit them out to the transmitter 
>> setting the levels appropriately, never gonna change.
> 
> Or a cell phone running a tiny app -- with or without "service".
> 
>> Anyway the FCC limit without a LPFM license is 250 microvolts/meter at 
>> 3 meters; with appropriate choice of SBC and micro-power transmitter 
>> you probably charge up and lug one battery up there a year and it run 
>> for a year, particularly if you just run off the low voltage directly.
>>
>> Need a LPFM license for broadcasting with more power than that in the 
>> US, but can't get 'em no mo...
> 
> huh?  Local makerspace set up a 50W LPFM station just a year or two
> ago.  Scraping together the money for the antenna and tower was their
> last hurdle.
> 
> As it is located "in town", they figure ~300K pairs of ears in its
> listening area.
> 
> A more remote station (OP's?) might have a greater geographical coverage
> area -- with fewer ears.

Says there hasn't been a filing window since 2013:

<https://www.fcc.gov/media/radio/lpfm>

"No LPFM application filing window period is presently scheduled.

When a new filing window period is scheduled, it will be announced via 
Public Notice and posted on the FCC's web site, in several locations, 
including this web page, at least 30 days before the start of the filing 
period.  We regret that we are not able to provide personal or advance 
notice to interested parties.  All applications must be electronically 
filed.  [The last filing period as in October 2013.]"

On 6/19/2021 2:09 PM, bitrex wrote:
> On 6/19/2021 4:36 PM, Don Y wrote:
>> On 6/19/2021 5:05 AM, bitrex wrote:
>>
>> [You know, it wouldn't kill you to trim posts -- including your
>> own -- in stead of just appending to something that has already been
>> seen!]

>>> Anyway the FCC limit without a LPFM license is 250 microvolts/meter at 3 
>>> meters; with appropriate choice of SBC and micro-power transmitter you 
>>> probably charge up and lug one battery up there a year and it run for a 
>>> year, particularly if you just run off the low voltage directly.
>>>
>>> Need a LPFM license for broadcasting with more power than that in the US, 
>>> but can't get 'em no mo...
>>
>> huh?  Local makerspace set up a 50W LPFM station just a year or two
>> ago.  Scraping together the money for the antenna and tower was their
>> last hurdle.

So, it was likely more than a "year or two".   The pandemic has created a
gap in my sense of time...

>> As it is located "in town", they figure ~300K pairs of ears in its
>> listening area.
>>
>> A more remote station (OP's?) might have a greater geographical coverage
>> area -- with fewer ears.
> 
> Says there hasn't been a filing window since 2013:

The Makerspace's facebook page shows a video ANTICIPATING the
first broadcast -- *5* years ago.  And, fundraisers for the
tower, transmitter, etc. in the same time period.

I recall there was an issue with their application possibly
"expiring" before they scraped together the necessary funding
to emit first signal.  I recall their assigned frequency
changing -- possibly as a result of their slowness to get
their shit together.

> <https://www.fcc.gov/media/radio/lpfm>
> 
> "No LPFM application filing window period is presently scheduled.
> 
> When a new filing window period is scheduled, it will be announced via Public 
> Notice and posted on the FCC's web site, in several locations, including this 
> web page, at least 30 days before the start of the filing period.  We regret 
> that we are not able to provide personal or advance notice to interested 
> parties.  All applications must be electronically filed.  [The last filing 
> period as in October 2013.]"

On 6/19/2021 2:07 PM, Jeff Liebermann wrote:
> On Sat, 19 Jun 2021 13:37:52 -0400, bitrex <user@example.net> wrote:
> 
>> On 6/19/2021 12:36 PM, Jeff Liebermann wrote:
>>> On Sat, 19 Jun 2021 01:25:47 -0500, Unlisted <unlisted@nomail.com>
>>> wrote:
>>>
>>>> However, one problem. When the sun comes back and the batteries begin
>>>> recharging, I dont want the equipment to turn on until the batteries are
>>>> up to at least 20% charge, or the equipment will begin cycling on and
>>>> off. (Bad for the equipment).
>>>>
>>>> What can I use to sense percent of charge and delay turning on the
>>>> equipment until that (pre set) % of charge is achieved? Im sure it can
>>>> be done, but I have no clue how.....
>>>
>>> Without hysteresis, that could make an interesting oscillator.  Power
>>> goes down to below the threshold at night.  Sun comes up in the
>>> morning and starts charging the battery.  Circuit detects that's it's
>>> over your threshold and applies power to the transmitter.  That
>>> immediately draws enough current to run the battery down below the
>>> threshold, which turns off the transmitter.  The transmitter remains
>>> off the air until the sun charges the battery above the threshold.
>>> Transmitter goes on and off all day because the solar panel would need
>>> to charge the battery *AND* power the transmitter when the sun is up.
> 
>> I have a cheap LED nightlight that works just like that
> 
> Not quite.  The FM transmitter needs to operate during the day and
> turn off at night.  The night light (or garden light) needs to operate
> during the night, and turn off during the day.  The night light has
> the advantage of charging while there's no load.  The solar panels in
> the FM transmitter need to both charge the battery AND power the
> transmitter during the day.
> 
> Incidentally, most such small lights use a single NiMH cell.
> <https://www.electronicsforu.com/electronics-projects/garden-solar-light>
> <https://watergreat.com/reference/CL0116.pdf>
> The cell lasts about 1.5 years or 500 charge cycles.  That's what I
> would expect from a commodity NiMH cell (although better cells might
> live to 2000 charge cycles).
> 
> In 2006, our local radio club was looking into a solar powered
> repeater.  So, I threw together a spreadsheet to help with the
> calculations.  The main question was how many panels are necessary to
> insure 24 hr functionality.
> <http://www.learnbydestroying.com/jeffl/rf-calc/solar-repeater-207.xls>
> There are a few mistakes and bad guesses in the spreadsheet, so please
> be careful when using it.  What it demonstrated was that the solar
> panels had to provide sufficient power to replace what was consumed by
> the repeater on a daily basis.  If the panels produced less each day,
> the stored charge level of the battery will decrease each day, until
> the battery is depleted.  Winter sun is the worst.
> 
> Spreadsheed for doing the same with a WRT54G wireless router:
> <http://www.learnbydestroying.com/jeffl/rf-calc/solar-wrt54g-v101.xls>
> I built this and found the predicted charge cycles to be too
> optimistic because I didn't include multiple sources of battery and
> solar panel deterioration with age, weather and data sheet creativity.
> I also screwed up and assumed that the charge/discharge
> characteristics of a gell cell beattery were similar to a wet cell.
> 

I got my technician license late last year cuz I figured at age 40 it 
was probably something I should do and might be useful to have at some 
point, my "rig" so far is an N-75 transceiver:

<http://www.4sqrp.com/n-75.php>

and MFJ tuner:

<https://mfjenterprises.com/collections/tuners/products/mfj-971>

Unfortunately haven't had a lot of time to get deep into it due to work 
and family commitments and the general excitement of the past year but 
should have more time this summer

On 2021-06-19, Ed Lee <edward.ming.lee@gmail.com> wrote:
> On Saturday, June 19, 2021 at 1:26:30 AM UTC-7, Rheilly Phoull wrote:
>> On 19/06/2021 2:25 pm, Unlisted wrote: 
>> > Im setting up a low powered FM radio station transmitter to play 
>> > continuous music 24/7 from a remote off grid location. The entire setup 
>> > will run from solar panels and batteries. The station will consist of 
>> > the transmitter, a small mixer board, audio compressor, and a laptop 
>> > computer filled with MP3 music. 
>> > 
>> > The station should run 98% of the time without human intervention. But 
>> > many cloudy days in a row, or snow on the solar panels may cause a 
>> > battery drain and shutdown of the station. 
>> > 
>> > When the sun comes back the station transmitter and controls should 
>> > restart on their own. However I am working on a system using relays, to 
>> > reboot the computer. 
>> > 
>> > However, one problem. When the sun comes back and the batteries begin 
>> > recharging, I dont want the equipment to turn on until the batteries are 
>> > up to at least 20% charge, or the equipment will begin cycling on and 
>> > off. (Bad for the equipment). 
>> > 
>> > What can I use to sense percent of charge and delay turning on the 
>> > equipment until that (pre set) % of charge is achieved? Im sure it can 
>> > be done, but I have no clue how..... 
>> > 
>> > Most of the time no persons will be there to manually flip switches. But 
>> > I have thought of sending charge data to my smartphone, where I can 
>> > manually turn things on via my phone. But I have no knowledge of 
>> > smartphone controls. I just know its possible...... 
>> > 
>> > 
>> Perhaps a micro like Arduino would suit the task. It could for instance 
>> measure the battery voltage and charging current and deduce battery 
>> state from that data. Amongst the many other things you may want to 
>> monitor or control.
>
> And a usb host micro (STM32F411 black pill, for example) can send
> data via 4G with a stick (T-mobile web-connect, for example).  That's
> what i am working on.  Unfortunately, there is no example driver for
> it, exact hidden deep inside Linux. 


At low data rates something like swarm (swarm.space) might be worth
considering, the hardware is more expensive but the subscription is
less.

-- 
  Jasen.

On 2021-06-19, Unlisted <unlisted@nomail.com> wrote:
> Im setting up a low powered FM radio station transmitter to play
> continuous music 24/7 from a remote off grid location. The entire setup
> will run from solar panels and batteries. The station will consist of
> the transmitter, a small mixer board, audio compressor, and a laptop
> computer filled with MP3 music.  

https://www.theverge.com/2019/11/26/20981630/raspberry-pi-pirate-radio-fm-station-35-dollars-diy

it uses a software defined transmitter, and it generates quite a few sidebands, 
but presumably they could be filtered out.

> However, one problem. When the sun comes back and the batteries begin
> recharging, I dont want the equipment to turn on until the batteries are
> up to at least 20% charge, or the equipment will begin cycling on and
> off. (Bad for the equipment).

> What can I use to sense percent of charge and delay turning on the
> equipment until that (pre set) % of charge is achieved? Im sure it can
> be done, but I have no clue how.....

That depends what sort of battery you use.  voltage sensing (to
determine state of charge) works well for lithium.  failry well for lead acid,
and very poorly for nickel chemistries.

> Most of the time no persons will be there to manually flip switches. But
> I have thought of sending charge data to my smartphone, where I can
> manually turn things on via my phone. But I have no knowledge of
> smartphone controls. I just know its possible......

For a device without a reachable IP address you'll probably have to
resort to SMS messaging, or use a cloud service like "ITTT".

-- 
  Jasen.

On Sat, 19 Jun 2021 17:03:24 -0400, bitrex <user@example.net> wrote:

>On 6/19/2021 3:05 PM, Jeff Liebermann wrote:
>> On Sat, 19 Jun 2021 14:03:20 -0400, bitrex <user@example.net> wrote:
>> 
>>> We can assume they're properly licensed I guess, this is only an
>>> intellectual exercise at the moment and that stuff is their problem.
>>> 100 watts is the minimum for a licensed LPFM station that's good for
>>> several miles with an ordinary portable FM radio or car stereo.
>> 
>> <https://www.fcc.gov/media/radio/lpfm-frequently-asked-questions>
>> Q:  How far will the signal go?
>> A:  LPFM stations are limited to 100 watts and a service range of 5.6
>> kilometers (3.5 mile radius).  This does not mean that the station
>> cannot be heard beyond a 3.5 miles radius.  It&#4294967295;s an approximation of
>> the expected average coverage.

>Ope, 100 watt is the minimum for a standard FM station, not LPFM

The page I cited above is specifically for LPFM stations.  I'm too
lazy to look up the specifics in the Rules-n-regs (part 73.801) but
I'm quite sure that the limit for LPFM is 100 watts EIRP (Effective
Isotropic Radiated Powah).  If you fail to believe me, dig through the
list of LPFM stations at:
<https://en.wikipedia.org/wiki/Category:Low-power_FM_radio_stations>
and see if you can find any licensed for more than 100 watts EIRP.
Notice that many stations are licensed for less than 100 watts because
of height limitations:
<https://www.fcc.gov/media/radio/lpfm>
  "LPFM stations are authorized for noncommercial
  educational broadcasting only (no commercial operation)
  and operate with an effective radiated power (ERP) of 
  100 watts (0.1 kilowatts) or less, with maximum 
  facilities of 100 watts ERP at 30 meters (100 feet) 
  antenna height above average terrain (HAAT)."

For details see section 73.801.  It should be in there somewhere but I
couldn't find it.  Maybe when I'm not half asleep:
<http://mai.hallikainen.org/org/FCC/FccRules/2020/73/801/>

Also, note that the 100 watt limit MIGHT be increased to 250 watts and
additional LPFM stations added:
"Low Power FM Back In Front of FCC - Another Proposal to Raise Power
and Word of a New Filing Window"
<https://www.broadcastlawblog.com/2021/06/articles/low-power-fm-back-in-front-of-fcc-another-proposal-to-raise-power-and-word-of-a-new-filing-window/>


-- 
Jeff Liebermann                 jeffl@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann      AE6KS    831-336-2558

On Sat, 19 Jun 2021 19:57:55 -0400, bitrex <user@example.net> wrote:

>I got my technician license late last year cuz I figured at age 40 it 
>was probably something I should do and might be useful to have at some 
>point, my "rig" so far is an N-75 transceiver:
>
><http://www.4sqrp.com/n-75.php>

RetroTech AM modulation on 75 meters?  I can see some value in raising
the dead, but not for anything that is expected to be "useful".  If
you want to irritate the "old timers", design a radiation hardened
transceiver that will survive a nuclear apocalypse.  The politics on
75 meters is worse than in S.E.D.

>and MFJ tuner:
>
><https://mfjenterprises.com/collections/tuners/products/mfj-971>

I have an MFJ-941C, which similar.  
<https://www.google.com/search?q=mfj-941c&tbm=isch>
I've had to rebuild it several times to fix cold solder connections,
loose hardware, and burnt switch contacts.  (My fault for switching
while in transmit).  

Your MFJ-971 was designed specifically for QRP and probably won't
survive if you upgrade to a higher power transceiver.
<https://www.google.com/search?q=mfj-971&tbm=isch>

>Unfortunately haven't had a lot of time to get deep into it due to work 
>and family commitments and the general excitement of the past year but 
>should have more time this summer

Same problem.  I've effectively been in hibernation mode.  I even
tried to retire.  However, my customers won't let me retire and I'm
not doing well trying to work out of my house.  All my former hobbies
were paused so I could devote myself to untrashing the house, car,
website, and neighborhood.

Good luck with the ham radio.  However, I suggest you look into the
newer digital modes such as WSJT-X:
<https://physics.princeton.edu/pulsar/k1jt/wsjtx.html>
<https://en.wikipedia.org/wiki/WSJT_(amateur_radio_software)>
or DStar on VHF/UHF.  Lots of other modes to try, all of which are
more "useful" than AM on 75 meters.


-- 
Jeff Liebermann                 jeffl@cruzio.com
PO Box 272      http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann      AE6KS    831-336-2558

On Saturday, June 19, 2021 at 5:30:54 PM UTC-7, Jasen Betts wrote:
> On 2021-06-19, Ed Lee <edward....@gmail.com> wrote: 
> > On Saturday, June 19, 2021 at 1:26:30 AM UTC-7, Rheilly Phoull wrote: 
> >> On 19/06/2021 2:25 pm, Unlisted wrote: 
> >> > Im setting up a low powered FM radio station transmitter to play 
> >> > continuous music 24/7 from a remote off grid location. The entire setup 
> >> > will run from solar panels and batteries. The station will consist of 
> >> > the transmitter, a small mixer board, audio compressor, and a laptop 
> >> > computer filled with MP3 music. 
> >> > 
> >> > The station should run 98% of the time without human intervention. But 
> >> > many cloudy days in a row, or snow on the solar panels may cause a 
> >> > battery drain and shutdown of the station. 
> >> > 
> >> > When the sun comes back the station transmitter and controls should 
> >> > restart on their own. However I am working on a system using relays, to 
> >> > reboot the computer. 
> >> >
> >> > However, one problem. When the sun comes back and the batteries begin 
> >> > recharging, I dont want the equipment to turn on until the batteries are 
> >> > up to at least 20% charge, or the equipment will begin cycling on and 
> >> > off. (Bad for the equipment). 
> >> > 
> >> > What can I use to sense percent of charge and delay turning on the 
> >> > equipment until that (pre set) % of charge is achieved? Im sure it can 
> >> > be done, but I have no clue how..... 
> >> >
> >> > Most of the time no persons will be there to manually flip switches. But 
> >> > I have thought of sending charge data to my smartphone, where I can 
> >> > manually turn things on via my phone. But I have no knowledge of 
> >> > smartphone controls. I just know its possible...... 
> >> > 
> >> > 
> >> Perhaps a micro like Arduino would suit the task. It could for instance 
> >> measure the battery voltage and charging current and deduce battery 
> >> state from that data. Amongst the many other things you may want to 
> >> monitor or control. 
> > 
> > And a usb host micro (STM32F411 black pill, for example) can send 
> > data via 4G with a stick (T-mobile web-connect, for example). That's 
> > what i am working on. Unfortunately, there is no example driver for 
> > it, exact hidden deep inside Linux.
> At low data rates something like swarm (swarm.space) might be worth 
> considering, the hardware is more expensive but the subscription is 
> less. 

OK, $5 per month for couple hundred bytes per hour.

The $10 per month 2G can transmit 100Kbps all the time.  My clients sometimes want to send pictures from security camera.

I pay $10 per line, but they might be paying less.  T-mobile doesn't talk about 2G plan in public, but i am sure they will talk to bigger users.

2G might not be in T-mobile's future, but it's in many users' future and past.  If they want to exit 2G, they should let someone else take over.

On 6/19/2021 9:40 PM, Jeff Liebermann wrote:
> On Sat, 19 Jun 2021 19:57:55 -0400, bitrex <user@example.net> wrote:
> 
>> I got my technician license late last year cuz I figured at age 40 it
>> was probably something I should do and might be useful to have at some
>> point, my "rig" so far is an N-75 transceiver:
>>
>> <http://www.4sqrp.com/n-75.php>
> 
> RetroTech AM modulation on 75 meters?  I can see some value in raising
> the dead, but not for anything that is expected to be "useful".  If
> you want to irritate the "old timers", design a radiation hardened
> transceiver that will survive a nuclear apocalypse.  The politics on
> 75 meters is worse than in S.E.D.

Oh, I've basically been using it just as a receiver which it works 
pretty well at over 3 - 6.2 MHz to experiment with different antenna 
configs.

Full-power transmit is limited to 3.6-4 MHz and for the moment 
technician privs are very limited on HF, the only non-CW allocation is 
some USB in the 10 meter band for that class. Trouble is phone on the 
higher freqs in my area is kinda dead...but looks like the new band plan 
for 2021 is going to add some more phone allocation in HF including 
3.6-4 MHz for that class to use which I'm sure the old timers will hate 
but whatevs.

Or I could just upgrade to general, the test doesn't seem hard.