#avr Logs
Jan 07 2022
#avr Calendar
01:35 AM specing_ is now known as specing
12:40 PM expon is now known as exp
12:41 PM exp: has been quite quiet in here
12:41 PM exp: i should join generic electronics channel too i guess
12:45 PM qu1j0t3: ola
12:45 PM qu1j0t3: idk i never found that very high valu
12:46 PM * exp idles
12:46 PM exp: i have a problem to solve, but i don't think it's worth bringing it up there
12:46 PM exp: how are you qu1j0t3
12:46 PM exp: good new year?
12:47 PM qu1j0t3: not too bad, thankyou. and you?
12:48 PM exp: well enough, about a week behind on some parts which is irritating
12:48 PM qu1j0t3: i'm back to working on my graphics bs, will post link soon
12:48 PM exp: will be interested to see
12:49 PM exp: my current problem is i wish to terminate a CAN bus
12:49 PM exp: which involves inserting a 120 ohm resistor
12:49 PM exp: but controlled electronically
12:49 PM exp: i have many options and none seem great
12:51 PM qu1j0t3: ic
12:51 PM exp: i was going with common-source N-fets
12:52 PM exp: but my gate driver is esd protected
12:52 PM exp: this is a neat solution: https://www.digikey.co.uk/en/products/detail/ixys-integrated-circuits-division/FDA217S/4573272
12:52 PM exp: fully floating, photovoltaically driven gate drivers
12:52 PM exp: but it feels a bit of a hack, i don't know what's the best option really
01:02 PM exp: lol fuck it, i decided to answer a question
01:02 PM exp: my good deed for the day
01:02 PM exp: now time for food
01:03 PM qu1j0t3: o/
01:03 PM qu1j0t3: almost that moment here too
01:03 PM exp: enjoy
01:06 PM cehteh: exp: there are tiny reed relays too
01:07 PM exp: cehteh: you know i never considered a mechanical solution
01:08 PM cehteh: yes i guessed that, but maybe worth the consideration
01:08 PM exp: my boss might throw a shit fit if i proposed it, but it's a genuinely good idea
01:08 PM cehteh: i have some that are logic compatible (5V, 10mA, internal diode)
01:09 PM exp: i have 12v accessible and i'm not crazy tight on board space for this (as it's on the other side of the termination resistors)
01:09 PM exp: so i think i'll do some looking
01:09 PM cehteh: https://www.reichelt.de/index.html?ACTION=446&LA=0&nbc=1&q=reed%20relais
01:10 PM exp: danke
01:16 PM cehteh: i am not a big fan of mechanical parts either, but sometimes they are just the perfect solution
01:16 PM exp: certainly a lot simpler than a dual floating FET driver and dual FET
01:16 PM exp: just a bit less solid state
01:17 PM exp: i've never seen anything like that FDA217 before and i'm going to buy a bunch spare
01:17 PM cehteh: and rarely fail short, FET's may do so
01:17 PM exp: true but it's for CAN termination so nobody dies
01:17 PM cehteh: who knows?
01:18 PM cehteh: nowadays every shit does can ... imagine emergency switch on can :)
01:18 PM exp: i do, we don't touch anything life safety related cause i set the rules :D
01:18 PM cehteh: haha
01:18 PM cehteh: ok
01:18 PM exp: we do actually do some stuff with safety implications
01:18 PM exp: for that we use isolated CAN drivers in pairs
01:18 PM exp: (with pairs of mcus and trasceivers)
01:19 PM exp: it's not "this fails and someone dies" but "if this fails and so do other systems, danger could be present"
01:19 PM exp: not sure how we can take it to the next level tbqh
01:22 PM cehteh: hah that FDA217 is some weird part
01:22 PM cehteh: t(on) 2ms :D
01:25 PM exp: cehteh: short circuit current also lol
01:25 PM cehteh: PV in a box ...
01:25 PM exp: it's quite a bit beefier than a lot of charge pumps you find though
01:25 PM cehteh: yes surprising
01:26 PM cehteh: what are the aging characteristics of the IR leds?
01:26 PM exp: i think it's quite the elegant solution really
01:26 PM exp: i have no idea how LEDs age frankly
01:26 PM exp: certainly not chip scale ones
01:27 PM cehteh: well they do and at hihg current (aka max norminal rating) sometimes surpisingly fast for leds
01:27 PM cehteh: i would expect an datasheet to tell that
01:27 PM exp: oh no doubt, i can't find any other comparable solution though
01:27 PM exp: (other than a mechanical one)
01:28 PM exp: as the bus could be -50 to 50v
01:28 PM cehteh: what does that thing cost?
01:29 PM exp: about £2, it's quite pricey even in some volume
01:29 PM cehteh: yep
01:29 PM exp: not really a problem for us though as we would be using 1 per unit
01:30 PM exp: my normal solution is a TCK401G (i think, from memory) but -ve becomes an issue
01:30 PM cehteh: depending on reliability requirementis i wols be worried by aging and by safety of a fet failing short .. but both migh be ok
01:32 PM exp: cehteh: i don't see any other particularly attractive options
01:33 PM exp: relays have similar failure modes, and i know of no alternate switch type that would be superior and acceptable
01:34 PM cehteh: relays rather have opposite failure modes, and for this application can be ultra reliable, esp reed relays with sealed contacts
01:35 PM specing_ is now known as specing
01:36 PM exp: cehteh: oh i've got some here i can reliably weld closed, but i take your point
01:36 PM cehteh: welding the contacts together shouldnt happen in such an application unless a lighting strike ... then you prolly have other problems
01:36 PM exp: nah 10A standard relay, couple power supplies on it with decent input xformers
01:36 PM exp: welds that bugger every time
01:36 PM cehteh: and a coil has close to zero aging
01:36 PM cehteh: yes power relays may weld
01:36 PM cehteh: but not signal relays
01:36 PM exp: true, and they're going to be quite resilient to ESD
01:37 PM exp: behind 60Ω resistors too so no concerns at all
01:41 PM twnqx: just use some train-specceed IGBTs
01:43 PM exp: twnqx: oh i was just going with a full on contactor ;)
01:43 PM twnqx: heh
01:45 PM exp: also yep, answered one question in ##electronics, got into argument
01:45 PM exp: and my food has yet to arrive! i must go on the warpath
01:45 PM twnqx: :D
01:46 PM twnqx: i should go there for my amusement, but then it's hard to STFU at times
01:46 PM * twnqx slams 10ns SRAMs on a stupid CGA to VGA converter instead
01:48 PM twnqx: what... component prefix would you use for a complete development board, e.g. an arduino?
01:48 PM exp: DB
01:49 PM exp: i think it's tricky frankly, there's supposedly a standard series of prefixes
01:49 PM exp: but no bugger really sticks by them, and i question their usefulness in general
01:49 PM exp: i've got a few high end boards here that use only numbers for their components
01:50 PM exp: and i've started following that and turning off the label on silkscreens
01:50 PM exp: (if it needs a descriptive label, that is)
01:52 PM cehteh: just use "The" The Board, The Connector, The Label ::)))
01:52 PM exp: "POSITIVE + VOLTAGE 12V NOT GROUND"
01:52 PM exp: for my staff :(
01:53 PM cehteh: haha then they read "POSITIVE + GROUND" and connect both :D
01:53 PM twnqx: well, i am adding an Efinix Xyloni to some board to at the same time get something going i have on my mind for months, and learn there software at the same time
01:53 PM twnqx: their*
01:53 PM exp: that name sounds like a parody of two other names
01:53 PM twnqx: yeah
01:53 PM cehteh: exp: some challenge 12V and GROUND with negation bar over it :)
01:54 PM exp: with the label put inbetwen a bunch of vias, so the bar gets badly truncated and split up
01:54 PM exp: A++
01:55 PM qu1j0t3: Efinix Xyloni!!!! My favourite Star Wars character
01:59 PM cehteh: exp: just ultra safe idea: relay in series with a fuse, in case you must absolutely break the circuit on some (serious) overvoltage event
02:00 PM cehteh: aka whatever would weld the relais would trip the fuse
02:00 PM exp: cehteh: haha, in this case it really is just to make or break the link for CAN termination, so i think i will investigate whether i can fit a relay in there
02:01 PM exp: it really is a genuinely good solution, and i can overrule my boss if i need to
02:01 PM * twnqx uses jumpers for that
02:01 PM cehteh: i am just going crazy ... i think thats not needed here
02:02 PM cehteh: also relays are pretty frequently used for such things, ofc not my idea
02:03 PM exp: cehteh: it's definitely not needed, the resistors will do fine as fuses too, but between you and I, you had the idea, so I thank you for it.
02:05 PM cehteh: i can send you an consulting invoice forward it to your boss :D
02:06 PM exp: i can pay you 100 avrcoins?
02:06 PM cehteh: lol
02:06 PM exp: in 10 years you'll be rich or in jail, either way!
10:00 PM nonlinear is now known as zero-xray