Lo-Vo VCO dev. (prev. follow-up)

the ?? std. ?? VCO from LM139 d/s does not perform too good nor stable.fnOf(control voltage)

so needed to retail one for 3.3V ...

... in prior of what picking the Op Amp model capable for this task was essential

. . . & the result ordered by relative change in frequency ::

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In "practice" the controls eat off much like half the power -- e.g. -- the LED-s need to be multiplied by the factor of 10x to get the normal efficiency out of it --or-- the controls need to be replaced by the lower power ones . . . a tricky part . . . also (in case of increasing the number of LED-s) it requires more battery power so the step up conversion is a better approach (and more efficient and easier to control by default)

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[Eop]

about google found VCO-s

Last to First ...

src	mod
as i didn't use the default transistors i was not able to grasp the ® idea behind this mess	finally it best resembled to a phase shift OSC - what it is with a poor fq. ctrl
not a VCO but a Schmitt Trigger

. . . the response speed and frequency range define the possible target app.-s . . . as in fact what i did here was the opposing -- an attempt to find out best range for operation by VCO type (for the ones that didn't work from scratch . . .)

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[Eop]

theoretical wall ~AC line detector

since there is reason to believe the ®´s j-fet input stage rather attenuates than amplifies
the E - field variations i set up a simple band-pass based 1 ::

  

this might still require extra input stage (for deep buried wires)

+ experiment with the layout , sensor , 3-sholds´ sensitivities before we can say if it´s for any good

updated an old Sq.-wave oscillator to a voltage controlled one -
to be mixed with prev. ~50Hz output ::

 

it is good to pre-test and choose + adj. the optos to the same transfer ratio ,

everything else shouldn´t be too much trouble ?

[Eop]