#garfield Logs

Jul 23 2020

06:00 AM polprog: so Moon is at rues
06:06 AM polprog: and already has two irc terminals :p
06:06 AM polprog: terminal illness :D
08:33 AM rue_bed2: no, he lives a ways down the street
09:38 AM rue_mohr: ok
09:38 AM rue_mohr: thrusday...
09:38 AM rue_mohr: the 4th monday of the week
12:21 PM Tom_L: ?
12:21 PM Tom_L: how do ou get 4 a week when i only get one???
02:42 PM polprog: https://polprog.net/blog/thyrosc2/ ^_^
02:42 PM polprog: moved that from the irc junk
02:43 PM polprog: these thyristor oscillators were a lot of fun
02:43 PM polprog: rue_mohr, Tom_L ^
08:20 PM rue_mohr: :)
08:21 PM rue_mohr: Tom_L, there are 4 mondays and a friday, then saturday and sunday
08:21 PM rue_mohr: monday1 monday2 monday3 monday4 friday saturday sunday
08:21 PM MoonyMoon: sheesh
08:22 PM rue_mohr: MoonyMoon, you gonna come over help sort junk?
08:22 PM MoonyMoon: tired / need sex
08:23 PM rue_mohr: sex? how about finding a 2x20 smart lcd module!
08:24 PM MoonyMoon: Sat. possibly. I'm a tired family man now :/
08:25 PM MoonyMoon: though I'm turned onto this lately
08:25 PM MoonyMoon: https://www.youtube.com/watch?v=gYRrGTC7GtA
08:26 PM rue_mohr: what if we take an 8088, stick 16k of static ram on it, and load/run it with switches and leds!
08:27 PM MoonyMoon: sweet talk me all you want ;)
08:29 PM MoonyMoon: that radio cas I dropped off is for a computer project like that.
08:29 PM MoonyMoon: case*
08:30 PM MoonyMoon: ____________
08:30 PM MoonyMoon: < wow 16k ?! >
08:30 PM MoonyMoon: ------------
08:30 PM MoonyMoon: \ ^__^
08:30 PM MoonyMoon: \ (oo)\_______
08:30 PM MoonyMoon: (__)\ )\/\
08:30 PM MoonyMoon: ||----w |
08:30 PM MoonyMoon: || ||
08:32 PM rue_mohr: well I kept the case, threw the rest out
08:37 PM Tom_L: sure it's not Moonday?
08:45 PM aandrew: hm, this "replace the LM334 with a stupid current mirror" might just work
08:45 PM aandrew: I lose the source voltage immunity because it's not a constant current source
08:46 PM aandrew: but it's *tiny*
08:46 PM aandrew: three transistors and a resistor
08:57 PM aandrew: rue_mohr: any reason why I *wouldn't* want to replace an LM334 used as a constant current source for measuring thermistors with a matched pair of transistors to set a current?
08:58 PM rue_mohr: you can do a crude current source with 2 parts
08:58 PM rue_mohr: a PNP and a REALLY large resistor (ok, only about 500k)
08:58 PM aandrew: yeah. three actually. two matched transistors and a current setting resistor
08:59 PM rue_mohr: k
08:59 PM rue_mohr: which one is the 334?
09:00 PM aandrew: https://imgur.com/a/QXS4nzz
09:00 PM aandrew: delete the 7.89k and make the 47R 7.5k and you don't get the inverse relationship
09:00 PM aandrew: 334 is a 3-terminal constant current source
09:00 PM rue_mohr: hmm
09:01 PM rue_mohr: the other 3 terminal things like that never work out well for me
09:01 PM rue_mohr: how much current do you need?
09:02 PM aandrew: not more than 1mA
09:02 PM aandrew: http://mixdown.ca/dump/tempsensor2.pdf is the crude schematic
09:02 PM rue_mohr: what is the draw from a 555 locked in reset?
09:02 PM rue_mohr: (all its internal current sources will be active)
09:02 PM aandrew: heh, I don't know
09:02 PM rue_mohr: oh but its got that voltage divider... hmm
09:03 PM aandrew: I honestly wasn't expecting you to use a 555 ofr this, that is impressive
09:03 PM rue_mohr: but your on a regulated supply
09:03 PM rue_mohr: ;)
09:03 PM aandrew: rue_mohr: I'm hoping not to be
09:03 PM rue_mohr: ah
09:03 PM rue_mohr: I couldn't use an op-amp on my temp sensor for the tap
09:03 PM aandrew: ideally I want to drive nothing but the RS485 trx and MCU from the 3.3V LDO, and eliminate the RS485 if I can
09:03 PM rue_mohr: the battery supply wasn't enough for the standby draw on any of the op-amp chips
09:07 PM aandrew: hm?
11:05 PM rue_mohr: the chipshave internal current sources
11:05 PM rue_mohr: when the chip is not doing anything,t he current sources are still running
11:06 PM rue_mohr: so, when not operating,the chip is a parallel set of current sources, with fixed currents
11:06 PM rue_mohr: its an apocolypse thing, I suppose
11:11 PM aandrew: an apocalypse thing where transistors don't exist anymore
11:18 PM rue_mohr: ... maybe