[sdiy] THAT 2155 on sale

Ullrich Peter Peter.Ullrich at kapsch.net
Fri Apr 10 19:03:06 CEST 2020

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/



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....


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