04:19 <esden> Can someone remind me again why we are using the polymer cap instead of a "normal" electrolytic one?

04:23 <esden> Ohh to clarify, I am talking about the bulk capacitance capacitor.

05:25 <d1b2> <emeb> polymers have lower ESR and longer lifetimes. Are these important in this application?

05:32 <esden> That is what I am not sure about. It is "just" a bulk capacitor as far as I can tell... so besides trying to be "super cautious" I don't really know why we would need to go the extra length.

05:32 <esden> That is why I am asking. :)

05:48 <electronic_eel> esden: marcan and I experimented with the ldo in short-circuit condition. we found that a low esr and a high series resistor after the ldo was best to stabilize it

05:49 <electronic_eel> it oscillated when these values were wrong

05:50 <electronic_eel> we did not test all variants of course and the datasheet of the ldo does not say anything about these special conditions, so if we change it, we'd have to do these tests again to ensure that it still works reliably

05:56 <electronic_eel> you can see the issue here https://github.com/GlasgowEmbedded/glasgow/issues/135

05:57 <electronic_eel> some nice screenshots of ldos behaving weird if treated wrong

06:07 <esden> electronic_eel: perfect, this is exactly the type of answer I was hoping for. :D

06:08 <esden> I wish we could get away with a normal electrolytic... but if you have a good reason to use something else I am fine with that. :)

06:09 <electronic_eel> why would you prefer a normal electrolytic? in 6.3mm diameter there are a few polymer ones available and when you look at lcsc, they aren't that expensive either

06:09 <esden> And I agree. We definitely should test this with the new prototypes.

06:09 <esden> polymer is not as common as electrolytic. At the end I again found just two candidates.

06:10 <esden> even with the better footprint

06:10 <esden> two is better than one that is difficult to buy, but still

06:10 <esden> also they cost $0.25 a piece... I bet an electrolytic would be cheaper

06:10 <esden> LCSC has no fitting candidate as polymer at all

06:10 <esden> I mean it does have one but it is too tall

06:11 <electronic_eel> hmm, strange, I remember getting like 20 candidates on mouser and still a few on lcsc

06:11 <esden> ohh but did you filter for height?

06:11 <electronic_eel> yes, height wasn't the problem

06:12 <esden> well, I guess we searched differently then

06:12 <electronic_eel> maybe I added 10V and 180µF and 220µF as additional options

06:12 <esden> yes definitely over 10V

06:12 <esden> minimum 10V

06:12 <esden> that was part of my parameters

06:12 <electronic_eel> the one we currently use is 6.3v

06:13 <esden> yeah that is pretty bad

06:13 <esden> 2x rating should be the minimum for these I think

06:13 <electronic_eel> the usb output, with the limiter and the cabling in between, won't go above 5.2v, there is still quite some margin to 6.3v

06:14 <electronic_eel> you don't need this kind of high overrating for polymer ones

06:15 <esden> the problem is that these ratings have tolerances too...

06:15 <esden> all things added together can result in trouble

06:16 <esden> I will not fight you on this, but I know a bunch of people that feel much stronger than me about this. :D I mean maybe polymer caps are less of an issue, but if they are any where near to elko ratings, 6.3 is definitely too low.

06:17 <esden> Anyways, I did find the right part for this that will do the job.

06:18 <electronic_eel> ok, then I can have some breakfast ;)

06:18 <esden> Enjoy! :D

06:18 <esden> I will head to bed.

06:18 <esden> Stream day tomorrow. :D

06:19 <esden> Will probably only do the communit updates, and then head down to the glasgow batcave and continue working on the board. :D

06:29 <marcan> esden: I tested with a normal electrolytic and it worked, but for the short circuit cases we already are in "works but not guaranteed" territory (there is a big 5V bus drop, just not enough to brownout the 3V3 rail), and we had an issue where it still wouldn't survive shorting both rails at once

06:29 <marcan> so I feel more comfortable with the extra margin of a low ESR cap

06:30 <marcan> and yeah, 6V3 is tight on a 5V bus, but I think we went over this and concluded it wasn't likely to be a problem? not sure tbh

23:34 <d1b2> <disasm> Re: today's stream and the idea of Glasgow shields. It's just my guess, but looks like the distance between connector A and B pins is not a multiple of 2.54mm, and it would be great to have it multiple 2.54mm to use regular prototyping boards as shields.

23:36 <d1b2> <Attie> correct - it's 35.46mm

23:36 <d1b2> <Attie> i have a feeling that the LVDS connector's mating height is also going to be problematic...

23:37 <d1b2> <disasm> Not a big problem I think, since in general you don't need a full-length contact

23:38 <d1b2> <Attie> true, if there's enough... seems like quite a large gap

23:38 <d1b2> <Attie> https://cdn.discordapp.com/attachments/613461005392936961/745426515713327114/unknown.png

23:39 <d1b2> <Attie> maybe longer pins might be worth looking into?