Andrew Kohlsmith

A herd of kids and an electronics/sw consulting firm. I occasionally post as @[email protected] as well.

[Andrew Kohlsmith @akohlsmith]

@fuzziphy @blind_via I did the same thing on a FIB/SEM motherboard design I was part of. PCIe sockets are nice because they CAN handle high speed differential signals and are cheap.

[Andrew Kohlsmith @akohlsmith]

@blind_via I try like hell to rip up as little as possible, but sometimes it's a lost cause. I tend to spend a LOT of time on placement; it makes the actual routing go faster and you get really good at forming structures which minimize high current loops and visualizing return paths etc.

[Andrew Kohlsmith @akohlsmith]

@blind_via … and then your client realizes they missed something and all that careful layout goes up in smoke. Now it’s time to crack your knuckles, strap in and do some real layout magic.

[Andrew Kohlsmith @akohlsmith]

@blind_via Get it working, THEN get it good.

I always find it amazing how you look at the ratsnest at the start of a layout and think “how in the hell is all that gonna fit?” and then as you get into it you start to think “oh man I could have made this a lot smaller!”

[Andrew Kohlsmith @akohlsmith]

@natalie_thenerd Now factor in programming and verification time on the line (or preprogramming cost), firmware management even if very stable, MCU vs popcorn component multi-vendor availability, product lifetime from vendor…

What was the latch’s cost? Any particular weird feature?

[Andrew Kohlsmith @akohlsmith]

@fbermingham @bobmackin I agree; high-quality electric footballers are tricky to produce.

[Andrew Kohlsmith @akohlsmith]

@AlgoRhythmEng @i2cjak Not really, we got natural cooling here, except in August.

[Andrew Kohlsmith @akohlsmith]

@davepl1968 @MassSkeptic Do you guys remember the “fractal” compression scam that just marked the sectors of the file as bad, created a “compressed file” which contained a header and the the chain of sectors of the original data? The name of it is failing me but I remember having fun reversing it.

[Andrew Kohlsmith @akohlsmith]

@yacineMTB Yes, yes it is.

[Andrew Kohlsmith @akohlsmith]

@nwsayer I don’t know about you but C is my choice. Most of the population of Canada and you get Northern California and most of the best western states too? Sign me up.

[Claude Lavigne, NASTY CANADIAN 🇨🇦❤️ @ClaudeLavigne12]

THIS “Prime Minister in waiting” is always dependant to shit all over Canada 🇨🇦 and Canadians, each and every day,..
gloating we are in a recession and blaming everything on our PM.
While he lives like a king on taxpayers dime…spending like there’s no tomorrow!
Crypto Imbecile.

[Andrew Kohlsmith @akohlsmith]

@deloisivete I absolutely love this meme template. I envision the director being a mix of Mt. Olympus, Asgard and Inside Out, maybe with a little bit of Bruce Almighty and a dash of Bedazzled thrown in to keep things from getting too serious.

[Andrew Kohlsmith @akohlsmith]

/r/theydidthemath

People assume that since it’s fibre you can just create longer links without considering the link budget implications. Optical fibre purity is amazing but it’s not perfect, and 800km is a lot of accumulated imperfection.

[outside five sigma @jwt0625]

assume 0.2 dB/km, that is 160 dB. If you launch 20 dBm ish into it, you get about 80 photons/s out. 800 km of dispersion limits your bw/time bin to ~ 1 GHz, and you can get ~ 1 kbps with ideal detection

[Andrew Kohlsmith @akohlsmith]

@i2cjak Here's the link to the tale of Excalibur, my high school Magnum Opus (and epic failure), also my electronics teacher's masterfully executed scheme to teach the smartass kid (me) a much-needed lesson: https://t.co/QfGCxGQYPr

[Andrew Kohlsmith @akohlsmith]

@RueNahcMohr Excalibur is what I named the power supply I built in grade 9. Found these huge computer caps in the pile and a 25lb+ transformer and got inspired. Custom PCB, huge heatsunk rectifier… it was awesome.

[Andrew Kohlsmith @akohlsmith]

@i2cjak I learned this the hard way back in grade 10. Found a huge power transformer, a bigass heatsinked rectifier and several hundred thousand uF of blue "computer" capacitors. I posted the long version here before, but TL;DR:

[Andrew Kohlsmith @akohlsmith]

@mlzema "Hey man you've got the real bum's eye for clothes"
https://t.co/0RmTaPNTM3

[Andrew Kohlsmith @akohlsmith]

@RueNahcMohr I think that's where my screwup came from; I mostly use N-channel MOSFETs and the symbol <--> footprint mapping is correct on those.

I was wondering why I couldn't control power to the subcircuit. Damn body diode was smuggling the electrons across the channel. :-)

[Andrew Kohlsmith @akohlsmith]

Pop quiz, pros… which pin is source, and which is drain?

And guess who screwed it up on his prototype?

👍 THIS GUY 👍

An easy fix, but still… 🤦‍♂️

[Andrew Kohlsmith @akohlsmith]

And to save anyone else the trouble… I went through all the 200-some-odd in-stock SOT23-3 P-channel MOSFETs with reasonable 3.3V characteristics on @digikey… none have source on pin 2. Not a single one. Zip. Zilch. Zero. Nada.

[Andrew Kohlsmith @akohlsmith]

That wasn’t so bad. A little isopropyl alcohol and a scrub and nobody’s the wiser. Oh, and updating the schematic symbol <—> footprint pin map so I don’t screw this up again.