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

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......

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.

On 6/18/2021 11:25 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.

And the computer knows how to make an "infinite playlist" out of that
music catalog?  Or, do you "contact" it regularly to "change the
programming"?

> 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.

"Snow"?  What's that?!

> 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.

Does this mean the transmitter and controls CAN cycle on and off -- and
you're only worried about the laptop getting into that mode?  Or,
does *everything* have to stay off until the batteries come up?

Why relays?

> 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.....

You can use battery voltage as a crude indication of state of charge.
If you are willing to let the laptop -- and only the laptop -- be
exposed to possible "power cycling", you can let it (attempt to) boot.
EVENTUALLY, it will have enough power available to do so.

When it powers up, it can run a piece of code that looks at the signal
on the audio "line input" (I am assuming it is not being used in your
setup).  This can be driven by an oscillator powered from the "main
battery pack" so that the amplitude of the output signal is directly
related to the power supplied (to the oscillator) by that battery
pack.

When the software detects a signal of sufficient amplitude to suggest
the battery is at "20% charge", the software can power up the rest
of the equipment and switch over to "DJ mode".

[I suggest an oscillator as the line input may be AC coupled so
just putting a DC voltage proportional to the battery voltage on
that input may look like "nothing" to the software.]

If you don't want to subject the laptop to power cycling, then
you would make a comparator that did the same thing -- monitor
battery voltage to exceed some threshold (for some period of time)
and have *it* turn on power to the laptop and everything else.

The advantage of having the laptop do this is you can be more
explicit in defining the conditions under which you allow the
*laptop* to power everything up.

[Regardless, you may want to blank the screen to conserve battery
life]

> 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......

If the laptop was a *tablet* -- or cell phone -- with SMS capability,
it could send text messages to your phone...

On 6/19/2021 6:40 AM, Don Y wrote:
> On 6/18/2021 11:25 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.
> 
> And the computer knows how to make an "infinite playlist" out of that
> music catalog?  Or, do you "contact" it regularly to "change the
> programming"?
> 
>> 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.
> 
> "Snow"?  What's that?!
> 
>> 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.
> 
> Does this mean the transmitter and controls CAN cycle on and off -- and
> you're only worried about the laptop getting into that mode?  Or,
> does *everything* have to stay off until the batteries come up?
> 
> Why relays?
> 
>> 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.....
> 
> You can use battery voltage as a crude indication of state of charge.
> If you are willing to let the laptop -- and only the laptop -- be
> exposed to possible "power cycling", you can let it (attempt to) boot.
> EVENTUALLY, it will have enough power available to do so.
> 
> When it powers up, it can run a piece of code that looks at the signal
> on the audio "line input" (I am assuming it is not being used in your
> setup).  This can be driven by an oscillator powered from the "main
> battery pack" so that the amplitude of the output signal is directly
> related to the power supplied (to the oscillator) by that battery
> pack.
> 
> When the software detects a signal of sufficient amplitude to suggest
> the battery is at "20% charge", the software can power up the rest
> of the equipment and switch over to "DJ mode".
> 
> [I suggest an oscillator as the line input may be AC coupled so
> just putting a DC voltage proportional to the battery voltage on
> that input may look like "nothing" to the software.]
> 
> If you don't want to subject the laptop to power cycling, then
> you would make a comparator that did the same thing -- monitor
> battery voltage to exceed some threshold (for some period of time)
> and have *it* turn on power to the laptop and everything else.
> 
> The advantage of having the laptop do this is you can be more
> explicit in defining the conditions under which you allow the
> *laptop* to power everything up.
> 
> [Regardless, you may want to blank the screen to conserve battery
> life]
> 
>> 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......
> 
> If the laptop was a *tablet* -- or cell phone -- with SMS capability,
> it could send text messages to your phone...
> 


You can get inverters with adjustable low-voltage disconnect/hysteresis 
threshold on the primary side, off the shelf.

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.

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...

On Saturday, June 19, 2021 at 4:26:30 AM UTC-4, 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.

I don't see the original post other than in the replies. 

How are you able to broadcast legally?  Is this a low enough power that it is allowed by the FCC?  Or are you on a different frequency band than commercial FM radio?  

When I was a kid we had low power AM transmitters that were legal, but didn't go very far at all, barely outside the house.  

-- 

Rick C.

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

On 6/19/2021 8:05 AM, bitrex wrote:
> On 6/19/2021 6:40 AM, Don Y wrote:
>> On 6/18/2021 11:25 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.
>>
>> And the computer knows how to make an "infinite playlist" out of that
>> music catalog?  Or, do you "contact" it regularly to "change the
>> programming"?
>>
>>> 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.
>>
>> "Snow"?  What's that?!
>>
>>> 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.
>>
>> Does this mean the transmitter and controls CAN cycle on and off -- and
>> you're only worried about the laptop getting into that mode?  Or,
>> does *everything* have to stay off until the batteries come up?
>>
>> Why relays?
>>
>>> 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.....
>>
>> You can use battery voltage as a crude indication of state of charge.
>> If you are willing to let the laptop -- and only the laptop -- be
>> exposed to possible "power cycling", you can let it (attempt to) boot.
>> EVENTUALLY, it will have enough power available to do so.
>>
>> When it powers up, it can run a piece of code that looks at the signal
>> on the audio "line input" (I am assuming it is not being used in your
>> setup).  This can be driven by an oscillator powered from the "main
>> battery pack" so that the amplitude of the output signal is directly
>> related to the power supplied (to the oscillator) by that battery
>> pack.
>>
>> When the software detects a signal of sufficient amplitude to suggest
>> the battery is at "20% charge", the software can power up the rest
>> of the equipment and switch over to "DJ mode".
>>
>> [I suggest an oscillator as the line input may be AC coupled so
>> just putting a DC voltage proportional to the battery voltage on
>> that input may look like "nothing" to the software.]
>>
>> If you don't want to subject the laptop to power cycling, then
>> you would make a comparator that did the same thing -- monitor
>> battery voltage to exceed some threshold (for some period of time)
>> and have *it* turn on power to the laptop and everything else.
>>
>> The advantage of having the laptop do this is you can be more
>> explicit in defining the conditions under which you allow the
>> *laptop* to power everything up.
>>
>> [Regardless, you may want to blank the screen to conserve battery
>> life]
>>
>>> 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......
>>
>> If the laptop was a *tablet* -- or cell phone -- with SMS capability,
>> it could send text messages to your phone...
>>
> 
> 
> You can get inverters with adjustable low-voltage disconnect/hysteresis 
> threshold on the primary side, off the shelf.
> 
> 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.
> 
> 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...

Actually I believe FM "broadcasting" at any power level in the US 
requires a license if you wanna get technical, the field strength limits 
are for stuff with well-defined receivers in mind like FM transmitters 
for car stereos.

On 6/19/2021 8:09 AM, Rick C wrote:
> On Saturday, June 19, 2021 at 4:26:30 AM UTC-4, 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.
> 
> I don't see the original post other than in the replies.
> 
> How are you able to broadcast legally?  Is this a low enough power that it is allowed by the FCC?  Or are you on a different frequency band than commercial FM radio?

As I understand it FM "broadcasting" at any power level requires a 
license in the US, the field strength limits are for devices with 
intended receivers like car stereo transmitters, wireless mic systems, etc.

> When I was a kid we had low power AM transmitters that were legal, but didn't go very far at all, barely outside the house.
> 

They granted a number of low-power FM broadcasting licenses back circa 
2013 via the Local Community Radio Act, thanks Obama.

In article <gblzI.233931$lyv9.103203@fx35.iad>, user@example.net says...
> 
> > How are you able to broadcast legally?  Is this a low enough power that it is allowed by the FCC?  Or are you on a different frequency band than commercial FM radio?
> 
> As I understand it FM "broadcasting" at any power level requires a 
> license in the US, the field strength limits are for devices with 
> intended receivers like car stereo transmitters, wireless mic systems, etc.
> 
> > When I was a kid we had low power AM transmitters that were legal, but didn't go very far at all, barely outside the house.
> > 
> 
> 

You can find the rules here for the FCC Part 15 low power transmitters.

Mainly for the AM and FM band you are limiated to about 200 feet of 
range for devices with out license.

https://www.fcc.gov/media/radio/low-power-radio-general-information


While I would never advise breaking the law, the FCC has more to do than 
worry about transmitters that go less than a mile or two unless someone 
complaines about them.  Just like the CB radio situation of 40 or so 
years ago.  You needed a license and had lots of rules to follow.  
Almost no one did and finally the government threw in the towel and said 
do what you want , just do not bother any licensed service.

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.

On Saturday, June 19, 2021 at 11:42:51 AM UTC-4, Ed Lee 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.

Any idea what you pay for a 4G connection to an embedded device?  Do they charge a flat monthly fee with a data cap or can it be paid by the MB/GB? 

-- 

Rick C.

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