#garfield Logs

Dec 26 2020

04:31 AM rue_mohr: morning polprog
04:37 AM polprog: morning rue
04:37 AM rue_mohr: I do seem to enjoy assembling circuits
04:39 AM rue_mohr: how are you with javascript?
04:40 AM rue_mohr: I'm still learning about how core saturation works too
04:40 AM rue_mohr: there is something odd I still dont have right in my head
04:41 AM rue_mohr: hmm
04:41 AM rue_mohr: I suppose, by applying V, your B goes up steady, and at some point it cant take on anymore H
04:42 AM rue_mohr: dH is what enrgizes the secondary, so voltage on that will start to fall
04:43 AM rue_mohr: in that little converter, the transistor gain plays a roll too
04:43 AM rue_mohr: the core going into saturation pushes the transistor into saturation
04:44 AM rue_mohr: the base current cant sustain the collector current
04:44 AM rue_mohr: which is a mode I'm not familiar with
04:44 AM rue_mohr: but I know that at high currents, the gain of a transistor drops
04:44 AM rue_mohr: what I saw was that the base would actually pull more current before it switched
04:45 AM rue_mohr: the combination must be what reversed the core
04:46 AM rue_mohr: once it starts to flip polarity, it will be held off till the core is drained
04:46 AM rue_mohr: but there is a lot going on for a moment while the transistor turns off
04:50 AM polprog: i know a bit of js
04:50 AM polprog: but i dont like it at all :p
04:52 AM darkrose: no one who knows js well enough likes it
05:16 AM polprog: lol, true
06:45 AM polprog: sent off a phys assignment, i hope i got it right
06:47 AM polprog: what's everone up to?
09:30 AM polprog: woohoo
09:37 AM polprog: the spi finally talks to the phy
11:59 AM polprog: set up gitweb on the lab box
12:54 PM rue_bed: trying to sleep in
12:54 PM rue_bed: ugh its only 10:23am
12:56 PM rue_bed: darkrose, did you say you found new search terms to find a place?
12:56 PM rue_bed: artists loft?
12:57 PM rue_bed: ok, its saturday, the world isn't over yet
01:01 PM rue_bed: I should see if I can get that error amp done today
01:01 PM rue_bed: and strip down some printers
01:05 PM polprog: got spi working in hardware, got uart working
01:05 PM polprog: both uarts
01:05 PM polprog: found a routing mistake (another one, tx rx swapped on PCB)
01:06 PM polprog: corrected the io board for that one, ill have to rerun the main PCB anyway (forgot to put some blinky leds)
01:06 PM polprog: ill take a break
01:06 PM polprog: maybe do some physics or chill out
01:07 PM rue_mohr: wifi or wired?
01:27 PM polprog: lora
01:38 PM aandrew: Merry Christmas everyone
01:38 PM rue_mohr: heh
01:38 PM rue_mohr: merry christmas
01:38 PM polprog: thanks aandrew
01:38 PM rue_mohr: (shoudl we tell him?)
01:39 PM polprog: (what?)
01:39 PM aandrew: no don't tell me it was yesterday
01:39 PM polprog: dont worry, i wished merry christmas to people a day too early
01:39 PM aandrew: I was all day in the kitchen and playing with the kids yesterday :-)
03:08 PM rue_mohr: every week I should try to clean somewhere till the garbage is full
03:17 PM rue_mohr: ok,
03:17 PM rue_mohr: - move junkmetal
03:18 PM rue_mohr: - build regulator baord
03:18 PM rue_mohr: - build a hand with ma
03:18 PM rue_mohr: ok
03:28 PM rue_mohr: junk metal moved
03:29 PM Tom_L: room for more!!
03:32 PM rue_shop1: I'm clearing part of the deck so I can get that big cnc up there
03:32 PM rue_shop1: I'm really close
03:32 PM rue_shop1: I was gradually working on it over the year
03:56 PM rue_mohr: I was playing with the design of the error amp last night, I ahve something I like, I hope it works
03:56 PM rue_mohr: the next step is to build the -5V converter
03:56 PM rue_mohr: this board has a LOT going on, in not-that-many-parts
03:57 PM rue_mohr: hmm how did oz time work, add 8 hours and flip the AM/PM?
03:57 PM rue_mohr: 10am
03:57 PM rue_mohr: darkrose, so, technically I think your awake
04:15 PM polprog: who is darkrose btw? do you knoe eachother?
04:15 PM polprog: know*
04:15 PM rue_mohr: twitter, trish, the steam engine builder in oz
04:16 PM rue_mohr: who was taking care of her dad and he passed and the estate had to get divided up and is now trying to find somewhere to live
04:17 PM polprog: oh
04:17 PM polprog: im sorry
04:18 PM polprog: godspeed then. i dont know myself where i will wanna live
04:18 PM rue_shop1: places in oz are NOT affordable
04:19 PM rue_shop1: a literally collapsing house is like $80k
04:23 PM polprog: i remember where we compared rent prices
04:55 PM Tom_L: oz?
05:21 PM rue_mohr: australia
05:22 PM rue_mohr: I was looking at house prices when I was there back in 2005? and it was no different than here
05:22 PM rue_mohr: I dont recall if that was considering exchange rates or not
05:23 PM rue_mohr: its funny
05:23 PM rue_mohr: the dc-dc converter I did for 12V->5V
05:23 PM rue_mohr: outputs a better 5V than a 7805
05:24 PM rue_mohr: it drifts a bit, but even 10k brings it to 5.01V
05:24 PM rue_mohr: it could be smaller, I only need 7mA
05:29 PM aandrew: < rue_mohr> junk metal moved
05:29 PM aandrew: < Tom_L> room for more!!
05:30 PM aandrew: ain't that the truth!
05:31 PM polprog: https://twitter.com/polprogpl/status/1342970491947143168
05:31 PM polprog: ^_^
05:32 PM polprog: i put the counter back on the shelf and it's playing along nice :)
05:41 PM rue_mohr: hey did you have any issues getting the HC14 to oscillate?
05:41 PM rue_mohr: occasionally they give me bias problems,
05:42 PM rue_mohr: did you find any oscillators from network cards?
05:46 PM polprog: no, i just plug in the cap and the resistor
05:46 PM polprog: no, i havent gone thru the cards
05:46 PM polprog: as far as i remember most of the ones id be willing to scrap are too new to have the 4 pin ones
05:46 PM polprog: all are bare crystals
05:47 PM polprog: ive got a token rink one that has a 16M oscillator missing...
05:47 PM polprog: token ring*
06:31 PM rue_shop1: 16 pin machined sockets
06:33 PM polprog: should i go to sleep or try to make a 5 -> -5 converter with the common mode choke
06:33 PM polprog: eh screw that
06:33 PM polprog: ill make teh converter
06:33 PM Tom_L: dude! it's the weekend and besides sleep is way overrated
06:33 PM * polprog is having a timezone identity crisis
06:33 PM polprog: :P
06:34 PM polprog: uln 2003 ftw
06:58 PM polprog: -3.48 @10k load
07:29 PM polprog: ok, i got a nice working concept of a feedback one
07:40 PM polprog: needs more work
07:47 PM polprog: haha, it fell into an interesting oscillation loop
07:48 PM polprog: the output jumps between -2.0 and -2.6, at -2.0 the comparator hct14 flips and it kicks the oscillator on, at -2.6 it kicks it off
07:48 PM polprog: heh
07:48 PM polprog: it's doing it at about 1hz
07:56 PM polprog: needs more thought work
07:56 PM polprog: a regular comparator would work
07:57 PM polprog: i could base this on a hct14 osc + opamp comparator
07:58 PM polprog: basically the idea is that i run a large impedance divider between Vcc and Vout (Vout is negative), and when the divider output drops below the tripping point i ground the uln input with a diode, effectively disabling the coil driver
08:01 PM polprog: goodnight
08:29 PM polprog: aaaaaaa
08:30 PM polprog: hct14 impulse inductor current limiter, put a shunt in series and kill the drive signal when the voltage on the shunt rises above threshold
08:30 PM polprog: now i cant sleep, i keep thinking about circuits which use a hct 14 driving thru a diode
08:31 PM Tom_L: heh
08:46 PM darkrose: rue_mohr: you pinged?
08:49 PM rue_mohr: im not sure now