#garfield Logs

Feb 15 2024

02:58 PM Tom_itx is now known as Tom_L
06:51 PM Rue_laptop: I'm alive!
06:51 PM Rue_laptop: 1st day of training
06:52 PM Tom_L: cool
07:11 PM aandrew: hm
07:11 PM aandrew: https://ibb.co/Ht0y8n2 and https://ibb.co/jLKCKmJ
07:11 PM aandrew: why would that LMV992 have *such* poor rail to rail performance with DC signals and in a simple voltage follower config
07:13 PM aandrew: the output is going right into an STM32 ADC pin so it's not high load, LMV982 claims within 30mV of rails with 2k load and 80mV with 600 ohm load but you can see from the graph it starts dropping off like crazy at about 2.5V
07:18 PM aandrew: I wonder if that zener is starting to conduct early
07:19 PM aandrew: it's guaranteed minimum is 3.2V but maybe they stuffed the wrong one or the part is leakier than expected
07:30 PM Rue__laptop: is the adc 3.3v?
07:30 PM Rue__laptop: is the adc 2.5v?
07:32 PM Rue__laptop: whats the zener leakage
07:32 PM Rue__laptop: why are you never here after asking questions?
07:32 PM aandrew: sorry the ADC is 12b, 3300mV reference
07:32 PM Rue__laptop: thats the leakage of the cap?
07:33 PM Rue__laptop: 10uF could be high
07:33 PM aandrew: zener leakage I'm trying to find on the datasheet but it's one of those "thousand parts in one datasheet" kinds
07:33 PM Rue__laptop: how about just unhook it and reameasure?
07:33 PM aandrew: I would *not* expect capacitor leakage to play any meaningful part at DC
07:33 PM aandrew: that's exactly what I'm going to do when I'm back at it tomorrow
07:34 PM Rue__laptop: I'v seen some caps with HORRID leakage, esp if their installed backwards, (stripe on negative)
07:34 PM aandrew: the op-amp was my first suspect but it actually looks resonably good
07:34 PM Rue__laptop: I dont think its the op-amp
07:34 PM aandrew: that's an MLCC and WV is 3x bias voltage at worst case
07:35 PM Rue__laptop: that op-amp is GOOD rail to rail, not just typical, right?
07:35 PM aandrew: it's reasonable. 30mV with 2k load, 80mV with 600 ohm load
07:35 PM aandrew: and again-- at DC so no gain-bandwidth product issues
07:35 PM Rue__laptop: oh I see, ok
07:35 PM aandrew: er sorry unity gain (voltage follower)
07:36 PM Rue__laptop: and is shutdown supposed to have a resistor?
07:36 PM aandrew: my bet is now the zener, I've seen them act funny
07:36 PM Rue__laptop: (probably not)
07:36 PM Rue__laptop: yea, I suspect the zener first
07:36 PM aandrew: shutdown has no resistor
07:36 PM Rue__laptop: they are much less ideal than I used to think
07:36 PM aandrew: yep
07:37 PM aandrew: VERY MUCH not like a voltage controlled switch
07:37 PM Rue__laptop: even the tl431 sucks when you put it under a microscope
07:37 PM aandrew: more like a voltage controlled dimmer where the rating (Vz) is where you say "that's too dark" and call it off
07:38 PM aandrew: rue_laptop eh? that's a new one
07:38 PM aandrew: or at least I haven't seen you IRCing from it before
07:38 PM Rue__laptop: this is my w******* laptop
07:38 PM Rue__laptop: a $1k I got when I took my final year of electrician training
07:38 PM Rue__laptop: "for school"
07:39 PM Rue__laptop: (I was paying anyhow), its meant to be my "good laptop"
07:39 PM Rue__laptop: I'v not put linux on it *yet*
07:39 PM Rue__laptop: but wished I had like 4-6 times now
07:39 PM Rue__laptop: its a Huawei
07:39 PM Rue__laptop: cause thinkpad is c*** now
07:40 PM Rue__laptop: and the other machine I wanted got refunded intead of shipped to me
07:40 PM Rue__laptop: its hard to find a laptop with good vert resolution
07:40 PM Rue__laptop: 1080 lines, forget that!
07:42 PM aandrew: yes it is
07:42 PM aandrew: all the PLC guys had super high res displays as standard
07:43 PM Rue__laptop: @home is 1600x1200
07:43 PM aandrew: I mean now I don't even look at anything not apple for laptops, I've never ever been so happy with the hardware quality as I am with apple. The shitty part now is it's their CPU and they solder the HDD to the motherboard
07:44 PM aandrew: screen DPI was stuck in a holding pattern for years
07:44 PM Rue__laptop: yea, I would pass on apple due to the design lockin
07:44 PM aandrew: well you can run linux on it without any issues
07:45 PM aandrew: and apparently now Asahi Linux OpenGL is better than Apple's on their own hardware
07:45 PM Rue__laptop: huh
07:45 PM aandrew: I *just* read that yesterday, it's pretty new
07:45 PM Rue__laptop: this huawei isn't exactly what I was looking for, but its been good
07:46 PM aandrew: I really liked the older thinkpads, there was a guy local to me who seemed to have an endless supply of them and they worked really well
07:47 PM Rue__laptop: yes
07:47 PM Rue__laptop: then lenovo took over and their garbage
07:47 PM Rue__laptop: I had to send one back for a motherboard replacement 2 times immediatly after I bought it
07:48 PM Rue__laptop: didn't even use it 5 minutes
07:48 PM Rue__laptop: the second time around they tried to make me pay for shipping
07:48 PM Rue__laptop: hah
07:48 PM aandrew: that is shit, sorry
07:48 PM aandrew: that makes me so mad when shit like that happens
07:49 PM Rue__laptop: yup
07:49 PM Rue__laptop: after I got it back the 2nd time I sold it quick
07:49 PM Rue__laptop: so I'll never buy lonovo ever
07:50 PM Rue__laptop: dinner! bbl
11:40 PM Rue_laptop: flakey wifi