#garfield Logs

Apr 12 2023

12:30 PM rue_mohr: what was the name of that charting program
04:00 PM polprog: aandrew: dont ask. I might learn pi pico just to unfuck this project
04:00 PM polprog: I mean, They made a fork of sigrok to add support for that
04:00 PM polprog: i dont want to shit on them. It's a damn good analyzer, it works and gives you 22 channels + 3 analog for the price of pi pico
04:00 PM polprog: while the cheapest 16 channel china premium analyzer is 200 euros
04:01 PM polprog: but ugh. Why did they reinvent the wheel instead of using OpenWorkbench Logic Sniffer/SUMP protocol
04:01 PM polprog: sigrok supports that
04:01 PM polprog: it's as easy as 123 to implement
04:01 PM polprog: I was thinking about implementing it on an FPGA even
04:01 PM polprog: imagine that, 128 channels!
04:02 PM polprog: the colorlight boards are good for this, they have DRAM (16M iirc!) and you can resolder the buffers to other pin compatible to get input capability with *some* 5V tolerance
04:02 PM polprog: it's the ideal board
04:02 PM polprog: in other news - i unfucked my laptop
04:03 PM polprog: Windows decided to kill itself throwing CRITICAL_PROCESS_DIED bsod on boot
04:03 PM polprog: so i went ahead and tried to fix it, no dice, cant reinstall from install medium without nuking files, gotta boot windows and run setup.exe from *within* windows
04:03 PM polprog: ... which does not boot ...
04:03 PM polprog: I just bought a new 1TB SSD and did a fresh install
04:04 PM polprog: just copied over PuTTY registry hive to transfer my saved SSH sessions
04:04 PM polprog: and here I am back on IRC
04:19 PM rue_mohr: hi
04:20 PM rue_mohr: yay
04:20 PM rue_mohr: always put your data on a sperate partition for exactly that reason
04:21 PM rue_mohr: doesn't help much if your data is in a windows registry tho
04:21 PM rue_mohr: dont know how to tell polen from a cold, but I'm home sick today
04:49 PM rue_mohr: Tom_L, you ok?
04:52 PM Tom_L: other than the crud... yes
05:01 PM rue_mohr: ?
05:07 PM polprog: User data on separate partition never works with windows
05:07 PM polprog: you end up with half of important stuff on C: drive anyways because apps are stupid
05:07 PM polprog: I could probably remount C:\Users
05:07 PM polprog: as a different partition (Volume in NT lingo)
05:07 PM polprog: and that would work seamplessly, NTFS supports that
05:11 PM polprog: $ wget [some-url]
05:11 PM polprog: [403 forbidden]
05:11 PM polprog: $ wget -U "Fuck you (Mozilla/4.0 compatible)" [some-url]
05:11 PM polprog: [ =======> ] 100%
05:11 PM polprog: some-url saved
05:11 PM polprog: :P
05:12 PM polprog: i swear some people
06:06 PM rue_mohr: heh
06:06 PM rue_mohr: I need to learn how to deeply hack the ID of my browser
06:06 PM rue_mohr: but
06:07 PM rue_mohr: I want to hack the processor in a lcd screen
07:46 PM aandrew: hm these 1300:8 audio transformers are more like 80:3 at least purely resistively
07:47 PM rue_mohr: yep
07:47 PM rue_mohr: 1.3k, an old radio transfomer?
07:48 PM aandrew: not sure. I bought 'em to try to solve my amplifier problem and hooked up "backwards" they seemed to do the trick
07:48 PM rue_mohr: I'v never managed to pin down exactly what they use for 70V:8ohm transformers
07:48 PM rue_mohr: amplifier problem?
07:48 PM aandrew: DAC that wants 8R output gets the 1300 side, amp that wants several tens of k gets the 8R end
07:49 PM aandrew: I have some 600:600 here but I have to dig around
07:49 PM rue_mohr: erm
07:49 PM rue_mohr: 1.6k isn't usually at a lot of power, is it?
07:50 PM aandrew: I think I was blowing up amps for three main reasons. 1) I was feeding them 3vrms 2) I am feeding them the output of a class D amp so its actually seeing 5V and noise like crazy and 3) each "leg" is 0-5V, not -1 to +1.
07:51 PM rue_mohr: ... what the heck are you doing?
07:51 PM aandrew: I adjusted the output of the DAC so it's emitting about 1Vrms but I was still getting wild positive side clipping on the amp, then I noticed the huge DC offset so I added the transformer to get rid of that and readjusted the DAC output again since the transformer was adjusting the voltage too
07:52 PM aandrew: three I2S power DACs feeding three amplifiers which feed three single phase, 12:120V transformers
07:52 PM aandrew: I send three 60Hz sinewaves in and get wye or delta three phase out plus the ability to screw with the waveforms
07:54 PM aandrew: the DACs could drive the 12:120 transformers directly but I wanted some more oomph which is why I got these cheap TPA3110D2 amplifier boards but they're all stereo and single-ended input. The chip can be reconfigured for bridge and takes balanced audio natively, but now since I need the transformers in there anyway to get rid of that nasty DC offset I may as well just leave them single-ended and ground
07:54 PM aandrew: one leg of the transformer secondary
07:55 PM aandrew: I also got some 150W mono amps but haven' really done much with 'em
07:55 PM aandrew: basically I wanted a low frequency, three phase signal generator that had some balls
08:33 PM Tom_L: what determines the amperage and voltage in a transformer? windings=v wire size=amps?
08:34 PM Tom_L: and how do you know just how many windings you need for a given voltage? not ratio but primary windings
09:40 PM rue_mohr: the wire size and core saturation engineering
09:41 PM rue_mohr: there is an old rule of thumb for iron cores that was like 0.5 or 0.25V/turn
09:41 PM rue_mohr: cant remember which anymore, I think 0.5 (for iron at 60Hz)
09:42 PM rue_mohr: if working with 120V transformers, its easiest to just find a transformer thats already got a 120 primary and leave it
09:52 PM aandrew: there we go. 128V line-to-line, about 80V line to neutral on the secondary
09:52 PM aandrew: about 70mA short circuit current
09:54 PM aandrew: the next version will use the 150W amps and 20VA transformers, this one has 15W amps and 2.5VA transformers
09:54 PM aandrew: I can probably bump it up more, I'm only at 15V and it should be able to do 28V but I'm not keen on popping any more of these
10:23 PM Tom_L: more a curiosity for me..
10:35 PM rue_mohr: got it
10:39 PM aandrew: https://ibb.co/NmZy2R3
10:39 PM aandrew: https://ibb.co/K0mxXBR
10:40 PM aandrew: not the cleanest waveform (that's the scope averaging it), I think I should likely add a good steep 1kHz LC filter after the DACs, but this should be good enough for now
10:41 PM aandrew: incredibly, this draws almost 4W just running unloaded
10:42 PM aandrew: the transformers are humming and you can feel it if you put your hand on them
10:48 PM rue_mohr: ksklfskldfjkljsdfkl;j
10:48 PM rue_mohr: !!!!!!!!!!!!!!!$@#$!!!!
10:48 PM rue_mohr: serial uploading is working on the 1 bit computer
10:48 PM rue_mohr: but only at 9600 baud
10:50 PM aandrew: it's a 1-bit computer. how much data do you really have to send it? :-)
10:51 PM rue_mohr: heh
10:51 PM rue_mohr: with 32 bit instructions