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13:29
why do we short circuit capacitors when we do an ac analysis?
 
3 hours later…
16:37
@pingOfDoom You don't, as a general rule.
If you're analyzing the circuit at "very high" frequencies, you might.
i mean in the general case
Where "very high" means "high enough that the capacitor has roughly the effect of a short circuit".
why is that the case?
And then, the reason you do it is that the capacitor has roughly the effect of a short circuit.
oh is it that it charges and discharges so quickly
16:38
@pingOfDoom The impedance of a capacitor is 1 / j * omega * C.
So if omega gets large, the impedance trends toward zero.
ohhh ok
At some point it is much lower than other impedances in the circuit, and the capacitor acts like a short circuit.
17:02
would a question about changing the die in a crimp tool (for electrical connectors, that is) belong on here, DIY.se, or Engineering.se?
Stupid gorram memleaks
17:27
Anyone here used the cJSON lib?
And of course I can't replicate the problem on the JTAG debug board.
18:08
@ThreePhaseEel Defnly not here
@Asmyldof OK
It's generally considered installation engineering at best, but the "maintenance" on the equipment is certainly not EE
@Asmyldof ok
I'd wish it were, for then maybe at least one other person in the office would know the downfalls of buying cheapest
@Asmyldof hahaha. I went with a Sargent 6500 series myself -- only problem is that it doesn't come with any instructions whatsoever :P
18:12
No idea what that is
I have AMP/Wurth/Krimpex/Knippex
it's Sargent's low end ratcheting crimper for electrical stuff
And cheapass chinese shit to take to customers, because over coffee break they will suddenly be used to tighten a 13mm nut
you can get dies for solderless terminals of various types, open barrel pins, and coax connectors
Rather throw away a $7 tool and calculate it in the "show up" cost, than have to charge for a $150 one
@Asmyldof yeah
18:14
howdy
@Skyler hey there! how're things going?
@ThreePhaseEel decently less stressful now that finals are out of the way
@Skyler cool. did some design work on the wearable-light thing, although just how small do you want it?
i have a month of break now
MOst important in a universal ratchet is ability to (easily) adjust press force and quality of steel dies
18:16
@ThreePhaseEel I'm trying to go for small
but not tiny
about flashdrive sized
Wearable light?
hrm 37mm by 25mm by oh 10-12mm OK, or too big?
@ThreePhaseEel its certainly a good starting point
@Asmyldof yeah, @Skyler wants a little wearable white LED light
@ThreePhaseEel since the day we talked I've been running a rough battery life test to see how low current I can draw
18:18
@Skyler because that's certainly acheivable with NiMH. would you rather the charge circuit be on-board and just have a micro-USB on the thing for charging, or would you rather have the charge circuit located offboard?
@ThreePhaseEel on board
@Skyler OK
@ThreePhaseEel and I also want to try and use this project to learn how to do basic power electronics
since its an area I'm sorely lacking in
@ThreePhaseEel And no other requirements?
@Asmyldof want to make it rechargable
18:20
@Asmyldof needs to be chargeable from 5V (microUSB)
40hours life on a charge
@ThreePhaseEel on that end, ive had difficulty getting accurate readings on my current draw. I used an ammeter to test out my light directly connected to a CR2032 and it said ~18 mA
BUT, I've had my light connected to a battery since we last talked
still pretty bright
I'm wondering if you're having burden voltage issues?
so its got to be WAY lower
its almost been a week
continually on
yeah, and CR2032s aren't really meant for drains that high!
btw @Skyler -- how handy are you at SMT soldering?
18:25
@ThreePhaseEel ooh, surface mount, haven't tried it before but interested in learning
@Skyler ah. because you'll need SMT to meet the size requirements
@ThreePhaseEel any chance I could peek on what you've been prepping
@Skyler once I find a way to capture it and get it to you m8...
btw
How do you boost the voltage of a DC source
say you have 3V battery and want to supply 4V, I'm pretty sure there was a way but I forgot
@Skyler aye, a boost converter
18:32
so does the switch have to be constantly oscilating
exactly -- the boost converter controller turns the switch on and off at a varying duty cycle to control how much voltage is provided to the load
@ThreePhaseEel so you need to control your switch with an AC source as well...
@Skyler an oscillator, yes
(people build crude ones using a 555 as the oscillator)
which you then need to build a supplemental circuit in parallel
I can see why power electronics gets out of hand really fast
Boost conversion can be done in less than 5mm2
18:41
@Asmyldof yeah
@Asmyldof thats smaller than the 555 form factor
's why I don't use 555's for anything
Although, no it isn't
Bare die a 555 can be microscopic
@Asmyldof good point
@Asmyldof actually now lets say you wanted to have a bare die 555 on a pcb
how does that work in practice?
In theory like any other chip on board. In practise nobody is stupid enough to even think of it
but are you able to order bare die and then add it to the board
18:45
Probably not of the 555
@Asmyldof hmm, maybe im not asking the right way
how would you go about adding in something resembling a bare die when you manufacture a pcb
or if you want to just have a functionality in a really really tiny form factor
Bare die is expensive start up, so it only happens in massively produced. Like birthday cards
@Skyler You glue the chip down on the board. Then pressure-weld little tiny wires onto the pads onto the chip, and the other end onto pads on your board, which you have had the foresight to have gold-plated.
Put the die on the PCB, wirebond it to the PCB
Glooob on top of it
Basically the same thing as when you make a chip, but in stead of a lead-frame that has pins, you attach it to a PCB
@Asmyldof Not really expensive to start up, but labor intensive to do in low volume.
18:54
If you just want small, you probably are more likely to buy WaferScale Bump Packages
@ThePhoton Depends on how you do it, if you have people manual bond it, maybe it'll be linear, but if you want it to potentially beat out WS-packages you'll have automated wire-bonding, which you also want to be set-up for your small batch
Or your process will change and I have seen how many things they can do wrong without properly identifying it unlit weeks later the result comes back
You don't want that to happen to 100k boards
@Asmyldof I am just saying you can do onesy-twosy with practically zero start up cost.
Two boards wirebonded will still be expensive
just finished my circuit for Skyler here in CircuitLab and was going to take a screenshot to show him, and right then the demo expires
But yeah, to do hundreds or thousands you're in a sub-optimal valley, too many to do manually, too few to set up automated bonding.
18:57
so lets say you are making 1000+ of a device, a reasonable batch that you are going to order PCBs, what would you want to do
@ThreePhaseEel wait
did you close the window
@Asmyldof How many pads? I've done it myself, takes maybe 20 seconds per bond.
im pretty sure if a popup came up blocking your view you can right click and inspect element
Maybe 5 s/bond if you get going.
then remove it
18:57
@Skyler 1000+ is puny in these discussions
@Skyler already tried that :P
@ThePhoton Have you ever asked a service for a quote for those 2 minutes of work?
@ThreePhaseEel figured
@Asmyldof Yes, I've done that too.
Because I happen to not personally own a wirebonder
18:58
@Asmyldof well i mean its enough you are ordering a prefabbed board
Over here it starts at $350 minimum
moving to a manufacturer if you will
@Skyler yeah, but still, glob top is mega annoying especially when the thing breaks
@Skyler But not for COB
More expensive than pure pick&place but not prohibitive for what we were doing...boards costing ~$500 fully assembled, built in batches of 10-20.
18:59
@Asmyldof COB?
Chip on Board
@ThePhoton We were talking reasonable domain here
oh ok
@Asmyldof That's because you hire an outside service, there's going to be set-up costs: You tell their engineer what to do, their engineer makes drawings and instructs the tech, mark-up in case they screw up one board, mark-up to make a profit, ...
I have had boards $1000 a piece with all kinds of crap you normally never want, but was needed in the specific case
basically though the smallest form factor thats reasonable for PCBs is just making everything SMT
19:00
Minimum billable time for the tech, maybe 1/4 hour at $200/hr...
I know how it works, believe me, I do
@Skyler yup
@Skyler ^^
Get the volume up in the 10's then you move from tech time to operator time, spread out all the documentation costs a lot thinner, ...
The lab at my work also has tons of idle wirebonding machines because, you know, offshoring.
@Shalvenay D1 is the light right
(R4 is a 1W resistor, the text wound up in the wrong place inadvertently and I didn't notice until after I took the screenshot + the demo had expired)
19:02
@ThePhoton I'll pay shipping plus $1 token
@Skyler and yes D1 is the light
@Asmyldof You could probably even find one for sale surplus in NL for a few euros.
I tried looking once
For lark
Not found for " for lark" prices, even company "for lark" scale
@Shalvenay oh and cuz a light acts like a diode it can be used in the boost converter directly
@Asmyldof Dovebid? but then you might end up buying a lot of 12 machines...
19:04
lol, 24 milliohms
@Skyler an LED, yes -- the ZXSC380's pretty clever like that ;)
@Skyler and yes, welcome to the wonderful world of current sense resistors
Hmmm. The proliferation of everything is a chip, I suppose
@ThePhoton Need to also calculate in the storage for 11 unwanted machines
everything to the left of the battery is for the recharging right
@Skyler righty-o
@ThePhoton Is dovebid an actual thing, or is it giving me a bunch of links right away correct?
19:09
@Asmyldof Apparently it is now go-dove.com...It was the auction site that sold off the fiber optics industry back in 2002-2003 and then again in 2009-2011.
@Shalvenay a little question, in terms of choosing a switch for this, I was thinking since I need to pick something I might as well electrically isolate the light component from charging, so that if the device is on and it fell in water it wouldnt be effected
@Skyler as in an on-off switch?
@Shalvenay yea, lets say that the device will only recharge when the light is off
@ThePhoton And then, because commercial society is so damn good at learning, again in 2020
@Skyler aah. yeah -- an on-off-on SPDT switch would do -- common to the battery positive, one terminal to the charge current output and BAT input, and the other terminal to the boost converter
19:13
@Asmyldof I think the over-under is 2018, but sure...
@Shalvenay so going with an SPDT arranged like this would the device actually be less waterproof when its off than on?
@ThePhoton I'm wishful thinking towards the Stock Appreciation Ramp I signed for
@Skyler dunno. waterproofing AIUI is much more about packaging and such
I'm sure we have some questions here on EE.SE that discuss how to make waterproof electronics :)
I know at least 2 sub-par answers
Or over-par, if you happen to be a golfer too.
@Shalvenay btw, would there be any easy ways to control the timer based on the voltage of the battery
19:15
@Asmyldof We're like 8 years in to a bull market and the US just elected a republican president...expect things to go through the roof in the short term and then crash spectacularly.
@Skyler which timer?
i.e. use it to create a voltage regulator in the booster
@ThePhoton Hmjah. We pretty much have to be on market by end 2017
oh wait
@Asmyldof Cash out and run as fast as you cna
can
19:16
@Skyler the boost chip I picked for driving the LED does the regulation already, but it's constant current as that's what LEDs want
yea, just looked and realized that was a driver chip
@Shalvenay how do you control the current on that btw?
the inductor?
@Skyler yup, changing the inductor value changes the current setpoint
grabbing the spec sheet now
@Shalvenay your name just changed for some reason...
@Asmyldof My company is also in process of going public. Was supposed to happen in November, then in December, now .... ????
19:20
also thanks for all the help
@ThePhoton whats your company do?
@Skyler Mostly connectors.
@ThePhoton sample pic?
@Skyler Think of stuff you'd buy from Molex. We make the same stuff, mostly.
@Skyler huh. must be the chat acting goofy. and no problem man, it was an interesting design exercise (and also gave me a chance to finally start getting my head wrapped around how to apply NTC thermistors)
I believe we're the 3rd-largest connector maker, but you've never heard of us.
19:22
I have so much I could be doing
And pretty much exactly the same amount of stuff I really don't feel like right now
@ThePhoton so are you an engineer or founder or both?
Or a found Engineer
@Skyler engineer.
@Skyler If I were the founder of the 3rd-largest connector company, I'd be busy skiing in Davos, not on the net with you guys.
You love us too much to not take us along on your ski trips
@Asmyldof Only so many seats in my private helicopter
19:25
I'm happy flying it though
@ThePhoton idk, even if I get really rich after I start businesses I really like to make things so I could see myself still perusing here
then again I could just hire personal tutors
I'm pretty much the perfect person to take on a Helicopter
btw guys, do you ever actually delete your emails to your gmail accounts
20:02
He's gotta be sponsored by Hakko, seeing as he doesn't tell you about the flux he's dropping on everything, also, these are vastly personal preferences
And his through hole was jarred during solidification
@Skyler Well, y'know, sometimes you just want to blast Cradle Of Filth while reworking your QFP
@Skyler Or you're testing out your new lead-free solder and it's 40% tin, 60% Nickelback
@Giskard42 haha
@Skyler Or it's like a Tin-Metallica alloy.
@Asmyldof Also it appears he's biased towards hoof tips and doesn't recognize the benefits of our lord and savior of solder bridges, the 45 degree chisel
20:34
An error I've been working on for days has now apparently cleared up on its own. I don't even.
 
1 hour later…
21:57
Now I have to figure out how DoveBid works... Sooo many different T&Cs .... Thanks @ThePhoton with your great ideas....
22:08
@Asmyldof Got your eye on that "late-model high-quality back end semiconductor equipment"?
 
1 hour later…
23:16
@ThePhoton Sh!
But whom will I send to Morocco?
23:50
@Asmyldof It's closer for you than for me.
Some good stuff in Israel too.
@Giskard42 the number of times thats happened to me
@Skyler Turns out it didn't actually go away, just went on a temporary leave of absence just to further my perplexion.
@Skyler I'm not having a good troubleshooting day.
It doesn't help much that we met with the newspaper yesterday (not our decision), so we're taking pre-orders without functional firmware.

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