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   teddy (tedyapo@fosstodon.org)'s status on Thursday, 24-Jul-2025 07:49:56 JST teddy

   i have to take a break to clear my head, so i bought an analog scope -- haven't owned one in a few years -- and am going to make some things to display on there. eventually, i'll simplify the number of transistors on this circuit -- i think you can do it with two and a bunch of pot tweaking -- but this is a start

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     botvolution (botvolution@mastodon.sdf.org)'s status on Thursday, 24-Jul-2025 07:49:55 JST botvolution

     in reply to

     @tedyapo yeah build this then ya big nerd

     https://chaos.social/@janbeta/114903534241194668

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     botvolution (botvolution@mastodon.sdf.org)'s status on Saturday, 16-Aug-2025 06:16:58 JST botvolution

     in reply to

     @tedyapo
     This is a fairly accurate representation of a retinal migraine.

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     teddy (tedyapo@fosstodon.org)'s status on Saturday, 16-Aug-2025 06:17:00 JST teddy

     in reply to

     i did manage to get one more video before the scope died. it shows how bad the soundacrd in my laptop is. it should say "FPS" in the bottom right, with the fps number to the left. on other soundcards, this looks fine.

     this soundcard is AC-coupled, so the display has to add a dc-restoration dot so that the average signal value is zero to keep the display from drifting around. you can always do this with one dot

     i've thought about distributing this dot around the border of the display

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     teddy (tedyapo@fosstodon.org)'s status on Saturday, 16-Aug-2025 06:17:00 JST teddy

     in reply to

     i've had to turn to other things for amusement. i measured the impulse response of the laptop soundcard: output a single nonzero sample, and the soundcard yields its impulse response. the time between the two minima shown is 60 us. if i did the math right, this corresponds to a low-pass filter with a cutoff at 23.8 kHz

     i am revising my opinion of this soundcard. it's good as an audio device, but i want a first-order-hold instead of a reconstruction filter for these time-domain shenanigans

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     teddy (tedyapo@fosstodon.org)'s status on Saturday, 16-Aug-2025 06:17:00 JST teddy

     in reply to

     the inexpensive galvos work at slow speeds. next to test frequency response

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     teddy (tedyapo@fosstodon.org)'s status on Saturday, 16-Aug-2025 06:17:01 JST teddy

     in reply to

     i caught the analog display bug and ordered a $50 analog laser galvo from ebay. a couple of op-amps to shift the voltage levels will be all i need to drive this from the chaos circuit

     i'm thinking of using a 405nm blue laser and a phosphorescent screen to get the fun persistence effects

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     teddy (tedyapo@fosstodon.org)'s status on Saturday, 16-Aug-2025 06:17:01 JST teddy

     in reply to

     well, that was fun while it lasted! the tektronix 2246 doesn't power on anymore. capacitors from 1987 probably, lol.

     i've only had it on for maybe two hours total. do i ask for a different one from the ebay seller, or just fix this one?

     different one would have the same or different issue sooner or later. maybe i'll fix it

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     teddy (tedyapo@fosstodon.org)'s status on Saturday, 16-Aug-2025 06:17:02 JST teddy

     in reply to

     the construction my look chaotic, but the waveform even more so. of course, i need to find some probes for the analog scope to hook it up, but it looks pretty good on the digital one

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     teddy (tedyapo@fosstodon.org)'s status on Saturday, 16-Aug-2025 06:17:02 JST teddy

     in reply to

     yep, it works!

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     teddy (tedyapo@fosstodon.org)'s status on Saturday, 16-Aug-2025 06:17:03 JST teddy

     in reply to

     i wound an inductor for chua's circuit. 18mH. I was pretty surprised by the Q, actually; i didn't expect it to be so high.

     i twisted and paralleled two 28ga wires because i didn't have any heavier ones available.

     the core is some "random" green one from amazon. A_L seems to be around 3900 nH/N^2

     will it work?

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     teddy (tedyapo@fosstodon.org)'s status on Saturday, 16-Aug-2025 06:17:04 JST teddy

     in reply to

     3-bit grey code transitions each edge of the unit cube exactly once. with the right slew rate, this could draw a cube in x-y mode. add some stuff in between to rotate the data in xyz and project onto x'y', and it makes an interesting display, maybe

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     teddy (tedyapo@fosstodon.org)'s status on Saturday, 16-Aug-2025 06:17:05 JST teddy

     in reply to

     it powers up!