<div dir="ltr"><div>I bought some of the THAT2155's, and not only is the picture of them quite literally what they look like, they also didn't picture that back side that clearly says "CHINA" on it. I have low hopes, and I don't recommend anyone else buy them. Most likely they just purchased a lot from some Ebay seller.</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Apr 10, 2020 at 11:57 PM Kylee Kennedy <<a href="mailto:kmkennedy@gmail.com">kmkennedy@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">I'm with Adam who said use your ears in the diode testing thread. <div>I have an LPG pcb with sockets for the vactrols and while using the same trigger and noise source for all tests just go in and swap vactrols. <div>I go with the vactrols that sound the best. Some I like the ping/bongo sound while others I like for their slower filter sweep long tail response. <div><br></div><div>So I usually end up with two LPG's per panel with different responses.</div><div><br></div><div>Trial and error,</div><div>Kylee</div><div><br></div><div>PS I did go through a period where I would capture the tail response on my Rigol scope single shot capture. Also use my Fluke multimeter to compare their on resistance and off resistance. This did help me remove wildly low resistance variable vactrols.</div><div><br></div><div><br></div><div><br>On Friday, April 10, 2020, Laughing Man <<a href="mailto:laughingman647@gmail.com" target="_blank">laughingman647@gmail.com</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>I'll give the comparator circuit a shot, though I'm still curious what the datasheet is referring to in regards to some specific amount of current being pushed through the LDR. The Excelitas datasheet also mentions that currents lower than 1mA would result in excessively high resistances. <br></div><div><br></div><div>That's the main thing that's stopping me from being sure I've tested them right: I'm not sure how I know I've got the right amount of current flowing through the LDR. If I don't, then the specs won't line up by a long shot. It seems as if I just have to get a 'golden vactrol' that I know will work in the situation I want, and just line them up, which is bugging my scientific side.</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Apr 10, 2020 at 10:08 AM Ullrich Peter <<a href="mailto:Peter.Ullrich@kapsch.net" target="_blank">Peter.Ullrich@kapsch.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Pete!<br>
<br>
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!<br>
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See here: <a href="https://www.instructables.com/id/Ultimate-Guide-to-Adruino-Serial-Plotter/" rel="noreferrer" target="_blank">https://www.instructables.com/id/Ultimate-Guide-to-Adruino-Serial-Plotter/</a><br>
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Ciao<br>
Peter<br>
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<a href="http://www.ullrich.at.tt" rel="noreferrer" target="_blank">http://www.ullrich.at.tt</a><br>
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Von: Synth-diy <<a href="mailto:synth-diy-bounces@synth-diy.org" target="_blank">synth-diy-bounces@synth-diy.org</a>> im Auftrag von Pete Hartman <<a href="mailto:pete.hartman@gmail.com" target="_blank">pete.hartman@gmail.com</a>><br>
Gesendet: Freitag, 10. April 2020 17:17<br>
An: <a href="mailto:synth-diy@synth-diy.org" target="_blank">synth-diy@synth-diy.org</a> DIY<br>
Betreff: Re: [sdiy] THAT 2155 on sale<br>
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On Fri, Apr 10, 2020 at 8:43 AM Oren Leavitt <<a href="mailto:obl64@ix.netcom.com" target="_blank">obl64@ix.netcom.com</a><mailto:<a href="mailto:obl64@ix.netcom.com" target="_blank">obl64@ix.netcom.com</a>>> wrote:<br>
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I have an idea for "quick matching" photo cells.<br>
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Basically one op-amp - a comparator with hysteresis (like that of a basic LFO)<br>
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1) Put the photo cell side in a resistor divider and connect to the comparator input.<br>
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2) Connect comparator output to to LED side thru appropriate current limit resistor.<br>
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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.<br>
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An idea..<br>
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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.<br>
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I do have a bunch of Silonex Vactrols that would be nice to characterize....<br>
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Pete<br>
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