#qi-hardware IRC log for Friday, 2015-06-05

wpwrakhmm. another one goes up on smoke. seems that some current-limiting may be beneficial :)00:08
wpwrakwell, another FET could detect if Vout < ~0.7 V and trigger an interrupt. or directly cut power00:25
wpwrakand a 1 Ohm series could further limit inrush current. just in case00:27
wpwrakwhitequark: also tried a load step from ~100 Ohm to ~18 Ohm (at 1.8 V). i can't see any voltage change. not sure if this is good or bad ;-)03:01
wpwrakat least the FET, 3rd in this role, didn't go up in smoke :)03:02
DocScrutinizer05huhß life in here?06:33
DocScrutinizer05(<wpwrak> i wonder if this simple adjustable regulator could actually work)  it would, but pretty poor efficiency06:35
DocScrutinizer05so it's OK for very low loads (except you'd still want a dedicated series resistor in line with D-S of FET), but for real supply it burns exactly same amount of energy like a linear regulator06:40
DocScrutinizer05while introducing nasty noise06:41
DocScrutinizer05actually it doesn't introduce any noise when that's an opamp and not a comparator (with hysteresis), since then your FET does work in linear range and not switched like you implied06:43
DocScrutinizer05you should add some small buffer capacitor on output of opamp, to avoid it starting oscillation06:44
DocScrutinizer05the problem with your design though seems that you want to use a *comparator* in a MCU06:47
DocScrutinizer05this won't fly06:47
DocScrutinizer05unless you intentionally design in some RC elements that determine the oscilation frequency06:48
DocScrutinizer05your design best case is using the output buffer C and the assumed Ron of FET as such determining values, and that means you _will_ get wild oscillation at least in the magnitude of comparator's hysteresis06:49
DocScrutinizer05oooh, and of cours Rload for discharge of the buffer C06:50
DocScrutinizer05in theory the circuit works. In practice it's a nasty critter hard to tame and get stable06:51
DocScrutinizer05wpwrak: you probbaly should add a R-C lowpass/integrator after the comparator output and drive the FET gate from that integrated analog voltage06:53
DocScrutinizer05that might actually work and result in a semi-usable and semi-stable output voltage06:54
eintopfhi DocScrutinizer05 :-)06:59
wpwrak(RC) naw, that would defeat the idea of operating in switched mode. what i want is to minimize the power burnt in the FET, so i want it either all on or all off11:21
wpwrakso far, the critter seems to work suspiciously well, but with a slight tendency of regulating too high with fast settings11:23
wpwrakwhat is a little odd is that it drives the FET with bursts of pulses. so yes, there's more noise than strictly necessary11:24
eintopfin germany it's hotter than in buenos aires15:13
larsconly 27degree C in the office...16:14
wpwrakeintopf: winter here ...16:14
wpwrakso much about the $9 PC: https://olimex.wordpress.com/2015/06/05/how-to-get-in-the-news-tell-people-that-you-will-make-and-sell-something-which-cost-you-20-for-9/16:41
DocScrutinizer05roh: CCC?18:12
DocScrutinizer05by: http://www.raumfahrtagentur.org/18:19
DocScrutinizer05Just wondered if you'll be there18:21
rohDocScrutinizer05: sure19:04
rohno clue about details yet19:04
DocScrutinizer05me neither19:06
DocScrutinizer05but I might want a "village" with a tad of advertising for Neo90019:06
DocScrutinizer05if anybody gets the point about that project, then the CCC visitors19:07
rohhehe... so the project is still on track?19:15
eintopfmhh, the camp19:27
DocScrutinizer05roh: well, sort of, yes19:35
DocScrutinizer05more and more organizational crap getting in the way though, time sinks everywhere. Webshop, PayPal, markiting and PR and whatnot19:36
eintopfDocScrutinizer05: you are from russia moscow?19:37
eintopfand wants to tracel to the camp?19:37
DocScrutinizer05hmm, why?19:37
eintopfI had something like that in my mind :/19:37
DocScrutinizer05nah, never seen Russia19:37
DocScrutinizer05~weather eddn19:38
infobotNuernberg, Germany; (EDDN) 49-30N 011-03E 318M; last updated: 2015.06.05 1920 UTC; Dew Point: 50 F (10 C); Pressure (altimeter): 30.09 in. Hg (1019 hPa); Relative Humidity: 38%; Temperature: 77 F (25 C); Visibility: greater than 7 mile(s); Wind: from the E (090 degrees) at 5 MPH (4 KT)19:38
eintopfoh yes19:43
unclouded~weather chc22:59
unclouded:~( not working for me22:59
--- Sat Jun 6 201500:00

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