#avr Logs

Mar 18 2022

08:00 AM PublicWifi is now known as PublicWiFi
09:58 AM ColdKeybo[a]rd is now known as ColdKeyboard
10:17 AM mikee is now known as saxicola
02:30 PM WormFood: https://wormfood.net/pictures/electronics/IMG_20220129_185713488.jpg <-- Solder paste grows crystals. This paste hasn't been touched in at least 15 years. (more pictures in that directory, which you're free to browse)
04:08 PM WormFood: have any of your guys ever tried using a supercap like a UPS on an AVR, so that you have enough time to save what needs to be saved to eeprom?
05:00 PM specing_ is now known as specing
08:23 PM rue_bed2: WormFood, not even a supercap just 2200uF
08:23 PM rue_bed2: watched vcc against the internal ref
08:23 PM rue_bed2: I think, was I watching the incomming? hmm
08:24 PM rue_bed2: I didn't use a big enough cap in the final design tho, its been an issue with the eeprom corrupting
08:24 PM rue_bed2: it does a shutdown and halt thing
08:25 PM rue_bed2: I'd probably do better to use NV ram and count cycles
08:25 PM rue_bed2: its an hour counter for the shop lgihts
08:25 PM rue_bed2: I made a comment that it counts in pseudorandom
08:32 PM qu1j0t3: rue_bed2: re switches, i guess there's no discrete solution with the signal ranges rail to rail ?
08:32 PM rue_bed2: no, but a power converter is only like 4 components
08:33 PM rue_bed2: are you making a million of these, or 1?
08:33 PM qu1j0t3: rue_bed2: how paranoid do i need to be about the switch continuous current limits? obv as a reset they're very short transients
08:33 PM rue_bed2: not?
08:33 PM qu1j0t3: rue_bed2: maybe half a dozen, for friends idk
08:34 PM qu1j0t3: rue_bed2: the DG412 has a comfortable 100mA pulsed limit but these other types are as low as 10mA
08:34 PM rue_bed2: can you get them?
08:35 PM qu1j0t3: i can get DG412's, they're just > CAD $4 each (and i already stock the other types)
08:35 PM rue_bed2: so, 2 bipolar transistors, 2 resistors, a cap and 2 diodes...
08:36 PM rue_bed2: and a ferrite inductor, maybe 0.50?
08:36 PM rue_bed2: well, caps are stupid expenisve latley
08:37 PM qu1j0t3: i have PILES of caps :) rather few inductors, though
08:37 PM rue_bed2: well, ferrite toroids work too
08:37 PM rue_bed2: for a little transformer
08:37 PM rue_bed2: get the rails out a bit
08:38 PM rue_bed2: haha, then you dont need those converters too
08:38 PM rue_bed2: how much were they?
08:40 PM rue_bed2: of course I cant be completely sure what I'm thinking of would work fo you, but I think so
08:40 PM qu1j0t3: CAD $5 each
08:40 PM rue_bed2: ouch
08:40 PM rue_bed2: so, I might be able to save you about $8.50
08:40 PM qu1j0t3: i mean.. i'm not QUITE ready to abandon the switch. i might have f*cked something up
08:40 PM rue_bed2: ok
08:40 PM rue_bed2: I'v been here forever so far
08:41 PM qu1j0t3: just need to find patience to get to the bottom of it this weekend
08:41 PM qu1j0t3: rue_bed2: <3
08:41 PM qu1j0t3: slightly annoyed i can't use the -5v rail.
08:42 PM qu1j0t3: since the signal is strictly 0..5v
08:42 PM qu1j0t3: or, i guess cap offset is -2.5v .. +2.5v and the + reference is 2.5v
08:42 PM rue_bed2: hu?
08:42 PM rue_bed2: why not the -5?
08:42 PM qu1j0t3: idk, can i use it?
08:43 PM rue_bed2: you know a max232 generates +-9V eh?
08:43 PM qu1j0t3: i should say, integrator output ranges 0..+5v
08:43 PM qu1j0t3: rue_bed2: hmmm!
08:44 PM rue_bed2: they are a bit pricey tho
08:44 PM rue_bed2: compared to a single tansistor forward converter
08:45 PM rue_bed2: but, you dont have to wind any transformers!
08:59 PM WormFood: rue_bed2, my idea was to feed the cap with a diode, that will isolate the mcu from the rest of the circuit with higher current draw, like an lcd display, or LEDs. The uncapped side, also fed with a diode, can be connected to an interrupt, so when the power is lost, it just triggers and interrupt, and you can do your stuff.
09:01 PM WormFood: of course, I tweak my voltage regulator, to output 5.7 volts, to compensate for the voltage drops across the diodes.
09:01 PM WormFood: I think I can do it, with just 3 diodes, and a cap. But it's good to know that a super cap isn't needed.