XPost: sci.electronics.design   
   From: g@crcomp.net   
      
   In sci.electronics.design Robert Roland  wrote:   
   > On Sun, 08 Nov 2020 14:56:12 -0800, Jeff Liebermann    
   > wrote:   
   >   
   >>Or, buy one that does exactly what you're suggesting:   
   >   
   > Sure, but you're taking all the fun out of it.   
      
   There's a few problems with the suggested off-the-shelf solution. [1]   
      
   The most project fun happened last, after piglet (and another at   
   eevblog) suggested 120R for R1 and 24R for R2. (piglet, with my last   
   sentence, it suddenly became obvious to me why you use R to denote ohms.   
   LOL.)   
       Although 120R and 24R certainly work, you may still ask, "Are they   
   optimal?" ROTFL. Let's have some fun and see!   
       First, you set up a system of simultaneous linear equations (details   
   shown at my updated link: https://crcomp.net/pseudocell/index.php ):   
      
   R1   R2   
      
    1   -5     0   
    1    1   150   
      
   Then you "plug and chug" the system through octave:   
      
   octave:1> A = [ 1 -5;   
   >               1  1 ]   
   A =   
      
      1  -5   
      1   1   
      
   octave:2> b = [   0;   
   >               150 ]   
   b =   
      
        0   
      150   
      
   octave:3> r = A\b   
   r =   
      
      125   
       25   
      
   Close enough for government work, no? Now, was that fun or what?   
      
   Note.   
      
   [1] First, there's no nearby electrical outlet to plug it into. Second,   
       it requires a larger, even more unsightly, hole in the wall, to   
       accommodate either a wall wart or pseudocell. The attic's unheated   
       and must be sealed afterward, so the project then creeps into   
       spackle and paint matching.   
      
   Danke,   
      
   --   
   Don, KB7RPU, https://www.qsl.net/kb7rpu   
   There was a young lady named Bright Whose speed was far faster than light;   
   She set out one day In a relative way And returned on the previous night.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)