XPost: comp.sys.raspberry-pi
From: tnp@invalid.invalid

On 11/12/2025 21:18, Carlos E.R. wrote:
> On 2025-12-09 11:47, The Natural Philosopher wrote:
>> First of all thanks to all those who responded on my first efforts to
>> put a battery power Pi Pico W outside and have it phone home.
>>
>> Having eliminated temperature and supply voltage as issues, I delved
>> into wifi and router logs, and it was clear that it was sometimes
>> getting a DHCP lease and even occasionally opening a TCP/IP
>> connections and sending data. And might be dependent on where I parked
>> the car and the weather.
>>
>> I tried putting a tin tray behind the router and that made it worse.
>>
>> Now the layout was that a ground floor router through the window and
>> the garage was not very good at about 30m range.
>>
>> Then I remembered I had put an Ethernet port in an upstairs bedroom by
>> the window in case I wanted to use it as an office.
>>
>> It was further away - 35m or so - but much less cluttered path. It
>> just had to go through a corner of the garage.
>>
>> Instantly the router reported about 8-10dB more signal and almost
>> reliable comms resulted.
>
> Two ideas.
>
> Some routers can steer the signal horizontally; the technology is called
> "MIMO" (https://en.wikipedia.org/wiki/MIMO). You notice because the
> router has multiple antenas, maybe four.
>
> Then you can replace the antena on the router or the remote with a
> directional WiFi antena. Home made with a box of Pringles. just google
> for "pringles wifi antenna". I made one and it actually works. But maybe
> they are sold, too.
>
I sorta tried that without huge success, In fact I am getting up to 12dB
variation in signal due to who knows what?

The setup is all somewhat experimental. At least  for now the software
is more or less stable - I have a few hanging daemons if the link goes
down mid message - but that is easily fixed .

> ...
>
>> And I knew all that trig would come in handy one day :-)
>
> You can calculate it numerically on a computer, by calculating the
> aproximate integral ;-)
>
Huh? it can be as exact as your measurements are.
No 'approximations' here...		

		diameter= tankDepth - offset;
		radius = diameter * 0.5;
		y = echoDepth - offset -radius;
		theta = asin( y / radius);
		x = radius * cos(theta);
		pie= radius * radius * theta;
		delta = x * y;
		area= (M_PI * radius *radius)/2 - (pie + delta);
		volume=(area/(M_PI * radius *radius ))*tankVolume;

That is about ultimately three days of work. It is redundant but I think
gcc can optimise out the intermediary variables that I used to make sure
even I could understand it.



What has been encouraging is the pinpoint accuracy of the measurements.
Once in a stable environment the ultrasonics are very precise. something
like a mm or two in a couple of metres. Probably more precise than the
speed of sound in air of variable pressures would justify, or indeed the
expansion of the oil in warmer temperatures.

LOL.

Maybe I have built the world's most complicated barometer.

--
“it should be clear by now to everyone that activist environmentalism
(or environmental activism) is becoming a general ideology about humans,
about their freedom, about the relationship between the individual and
the state, and about the manipulation of people under the guise of a
'noble' idea. It is not an honest pursuit of 'sustainable development,'
a matter of elementary environmental protection, or a search for
rational mechanisms designed to achieve a healthy environment. Yet
things do occur that make you shake your head and remind yourself that
you live neither in Joseph Stalin’s Communist era, nor in the Orwellian
utopia of 1984.”

Vaclav Klaus

--- SoupGate-Win32 v1.05
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