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On 2025-12-12 11:41, The Natural Philosopher wrote:
> 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 leastÿ 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...
> 
>  ÿÿÿÿÿÿÿ diameter= tankDepth - offset;
>  ÿÿÿÿÿÿÿ radius = diameter * 0.5;
>  ÿÿÿÿÿÿÿ y = echoDepth - offset -radius;
>  ÿÿÿÿÿÿÿ theta = asin( y / radius);
>  ÿÿÿÿÿÿÿ x = radius * cos(theta);
>  ÿÿÿÿÿÿÿ pie= radius * radius * theta;
>  ÿÿÿÿÿÿÿ delta = x * y;
>  ÿÿÿÿÿÿÿ area= (M_PI * radius *radius)/2 - (pie + delta);
>  ÿÿÿÿÿÿÿ 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.

You can aproximate the chord with a rectangle. If you divide the chord 
in two, it is two rectangles. Up to a thousand rectangles, or a million. 
The numerical result is close to the real result with a math formula. 
Kind of  Runge-Kutta.

:-D

Or ask ChatGPT for the formula. I sure don't remember it, I doubt I ever 
saw 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.
> 


-- 
Cheers, Carlos.
ES??, EU??;

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