Path: csiph.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: "Carlos E.R." Newsgroups: comp.sys.raspberry-pi,comp.os.linux.misc Subject: Re: More on wifi range - Pi PICO W Oil level sensor Date: Sat, 13 Dec 2025 13:57:10 +0100 Lines: 97 Message-ID: <6e401mxo86.ln2@Telcontar.valinor> References: <10h8unl$oq21$1@dont-email.me> <10hgrgu$2r3rh$2@dont-email.me> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Trace: individual.net loA2p2WdRw/tPwn0/Mp0SA3RV05iVLzvq7xky6PXL9PmF9i6ul X-Orig-Path: Telcontar.valinor!not-for-mail Cancel-Lock: sha1:gDMiTkfNl/ANAKTdhlnHVSeaAhs= sha256:4z3UMl+DLuEPu+o7E0xePAOP0EcbOiKrDgXMw/4KN9A= User-Agent: Mozilla Thunderbird Content-Language: es-ES, en-CA In-Reply-To: <10hgrgu$2r3rh$2@dont-email.me> Xref: csiph.com comp.sys.raspberry-pi:37448 comp.os.linux.misc:78995 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🇪🇺;