[sdiy] matching Vactrols

[Crys]

gee seems like a lot of work. i made a jig with clips and 2 meters (one 
for voltage in to the LED and one to measure the resistance of the LDR. 
and a switch for voltage in (which sorta makes the meter redundant). i 
tested and categorized hundreds of unmarked siliconex vactrols.

On 4/10/2020 11:03 AM, Ullrich Peter wrote:
> Hi Pete!
>
> To show curves from an Arduino you don't need a display, you can do it with the serial interface via USB and the Arduino IDE itself by using the serial plotter!
>
> See here: https://www.instructables.com/id/Ultimate-Guide-to-Adruino-Serial-Plotter/
>
> Ciao
> Peter
>
> http://www.ullrich.at.tt
>
> ________________________________________
> Von: Synth-diy <synth-diy-bounces at synth-diy.org> im Auftrag von Pete Hartman <pete.hartman at gmail.com>
> Gesendet: Freitag, 10. April 2020 17:17
> An: synth-diy at synth-diy.org DIY
> Betreff: Re: [sdiy] THAT 2155 on sale
>
>
>
> On Fri, Apr 10, 2020 at 8:43 AM Oren Leavitt <obl64 at ix.netcom.com<mailto:obl64 at ix.netcom.com>> wrote:
>
> I have an idea for "quick matching" photo cells.
>
> Basically one op-amp - a comparator with hysteresis (like that of a basic LFO)
>
> 1) Put the photo cell side in a resistor divider and connect to the comparator input.
>
> 2) Connect comparator output to to LED side thru appropriate current limit resistor.
>
> The circuit should self oscillate at an amplitude/frequency determined by the LDR's light/dark resistance and lag time characteristics. Plug different photocells into same circuit and sort them by matches in amplitude/frequency shown on oscilloscope.
>
> An idea..
>
>
> I rather like it.  I've occasionally started putting on paper ideas for using an Arduino where an analog output drives the LED and steps from 0 to 5V (with appropriate current limiting of course) and an analog input reads from a voltage divider including the resistive side.  The idea being to get a graph.  But then I got stuck on how to display the graph meaningfully without going full blown OLED.  Considered simply sending the output to the serial port and letting a computer read the details.  And that really omits the time factor, although I could do a 0V -> 5V step and observe the time it takes, I guess.  Overall, too complicated, so I never tried to implement it.
>
> I do have a bunch of Silonex Vactrols that would be nice to characterize....
>
> Pete
>
>
>
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