XPost: comp.os.linux.misc   
   From: robin_listas@es.invalid   
      
   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 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.   
      
   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🇪🇺;   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)