Hacker News Reader

jmwilsonon ReMarkable 2.0 – A digital notebook that feels like paper

What are your expectations and applications for color in an e-ink writable tablet? The best available color e-ink displays support a spot color palette of 3-7 colors. They're nowhere near being able to show a full-color image. If you want something for illustration, a Cintiq is the best option and you get to use software (like Illustrator) that's up to the task. Even the Cintiq Pro displays are only able to hit about 15 ms response time.

jmwilsonon What’s Flying Above Us?

Technical details are described here: https://gitlab.com/jjwiseman/advisory-circular/

Things flying near an airport are excluded ("The centroid of the last 3 minutes worth of positions must be more than 2.5 km away from all known airports."). I've never seen it tweet about planes doing obvious pattern practice.

jmwilsonon Uber CEO says its service will probably shut down temporarily in California

Of course they could do that, but any corporation or LLC that does business in California [1] (surely a Uber driver operating in California would be considered as such) has to pay the fee. Incorporating out of state would just mean a second set of fees and more forms to file.

[1] https://www.ftb.ca.gov/file/business/doing-business-in-calif...

jmwilsonon Uber CEO says its service will probably shut down temporarily in California

There's the $800 California LLC annual fee, which is the highest in the country, and applies before you make a dollar in revenue.

jmwilsonon Y Combinator has lost its soul: A YC founder's perspective

The author didn't say anything about "interesting" vs. "boring" companies or ideas. He said YC should curtail funding of dev tools/SaaS startups, because the traction they appear to have is misleading. They're selling to each other, revenue moving in a circle, without demonstrating value creation outside of the sphere of similarly-situated startups. Not explicitly stated, but he's also implying it's a portfolio risk for YC.

jmwilsonon As Qualified Immunity Takes Center Stage, More Delay from SCOTUS

The Federal criminal law analogue of 42 USC 1983 is 18 USC 242 ("deprivation of rights under color of law"). It probably doesn't surprise anyone to hear that referrals to prosecute under 242 have steadily declined over the years, regardless of the party of the administration.

jmwilsonon Show HN: Raspberry Pi garage door opener

It's a Fritzing diagram, which is to say it's a schematic, not a layout. So the thickness of lines should not be taken as indicative of any physical properties like connector style, wire gauge, or insulation. Clearance and creepage are concerns for PCB designers, but there doesn't seem to be any custom PCB layout and design work here - why mention it?

jmwilsonon Trading Is Hazardous to Your Wealth [pdf] (2000)

That's not a helpful way of looking at things since individuals do not trade the average strategy. They trade whatever theory they are seeking to validate, which is too often "their gut" or the latest technical analysis woo. These people are cannon fodder for algorithmic traders and market makers. The average of all retail trader strategies is definitely not the market.

jmwilsonon Redditor finds unsecured surveillance cameras seemingly placed by US government

There are twitter bot accounts that post live when they detect aircraft flying in circles:

@SkyCirclesSF @SkyCirclesLA @SkyCirclesDC

jmwilsonon Show HN: Make Your PDF Look Scanned

From the github repo, the site is a wrapper around exactly two shell commands. Instead of uploading your data to an untrusted site, you can run from the comfort and safety of your local computer:

  convert -density 150 input.pdf -colorspace gray -linear-stretch 3.5%x10% -blur 0x0.5 -attenuate 0.25 +noise Gaussian -rotate 0.5 temp.pdf
  gs -dSAFER -dBATCH -dNOPAUSE -dNOCACHE -sDEVICE=pdfwrite -sColorConversionStrategy=LeaveColorUnchanged dAutoFilterColorImages=true -dAutoFilterGrayImages=true -dDownsampleMonoImages=true -dDownsampleGrayImages=true -dDownsampleColorImages=true -sOutputFile=output.pdf temp.pdf

jmwilsonon I designed and built my own function generator

Sure, the voltage divider works ... if the load impedance is high. Not a good idea for a 50 Ω load.

Op amp needs a dual-rail power supply, so it needs some auxiliary power, then power electronics to get both rails. Stuff starts to get complicated, and now that $1500 Keysight box starts to looks worth its price...

jmwilsonon Pitch Detection with Convolutional Networks

Resolution in the frequency domain can be significantly improved over the natural resolution of the DFT (19 Hz in your case). If the fundamental frequency exactly matches one of the DFT bin frequencies, it would mean the frame size is an exact multiple of the period, so the DFT of successive frames would look the same, and there would be no phase shift at the fundamental component. (Or if overlapping frames were analyzed, there would be an expected phase shift in proportion to amount of overlap.) In the more likely case that the fundamental doesn't match a bin frequency, there's a phase shift between successive frames that's proportional to difference between the fundamental and the associated bin frequency. This can be extracted to get a more accurate estimate of the actual fundamental. I wrote a STFT-based chromatic tuner as a hobby project using this technique and it would easily resolve better than .1 Hz changes using 10(ish) ms frame sizes.

jmwilsonon Using floating-point numbers for money

> I would argue that financial math by definition needs to be accurate to the penny. Where is "pretty close" financial calculations considered acceptable?

There is a difference between analysis and accounting. There are many financial models (e.g. Black-Scholes-Merton option pricing) that are analytic in nature and use transcendental functions, so the idea of getting an exact, arbitrary-precision answer is hopeless. Using a decimal type for this kind of computation would be an exercise in slowing down processing by a few orders of magnitude.

jmwilsonon The Essential Guide to Electronics in Shenzhen (2016) [pdf]

There's certainly no place else like it.

What some of the previous reportage ("What $50 buys you in Huaqiangbei") misses about what makes the place unique, is it's less about what you can buy there, and more about what you can make there. There are oddball consumer electronics for sale, but you can find them, or substitutes, almost anywhere. What isn't everywhere is access to components and their manufacturers. There are almost countless booths that will sell you whole reels or cut tape of components, trays of chips, display technologies in various sizes in quantities big or small ... the list goes on. Walking around, you'll see people are leaving the markets with armfuls of component reels headed off toward labs and factories elsewhere. Unless you live across town from Digikey or Mouser, there is no way you can get things that quickly for prototyping. The upper floors of the buildings are more occupied by reps from manufacturers or factories, so if there's something custom you want, there's someone you can talk to in person about it.

On one hand, it's inspiring to see and take in. But for any complicated project, being able to manage ordering online and see exact part specs probably beats same-day access, when you have to schlep through the chaos to get it yourself. I have heard that things are moving in that direction in Shenzhen, and the concept of a central market is perhaps past its prime.

jmwilsonon Ex-FDA Advisor Says of Lasik Eye Surgery: ‘It Should Have Never Been Approved’

The FDA's mandate is to ensure safe and effective therapies, not high customer satisfaction.

jmwilsonon Building a Reflow Oven

High temperature turns the fibers from irritants into carcinogens like asbestos.

Well, high temperature in this case being above 1800 F/1000 C, over 4 times the operating temperature of these ovens.

jmwilsonon The Backbone of VHF Amateur Radio May Be Under Threat

> Encryption isn't actually necessary for any of the stated purposes of amateur radio (experimentation, recreation, training, contesting, emergency comms, etc)

It is, or will be, needed for experimentation. Wireless security cannot be an afterthought anymore; communication modes and protocols need to be built with security in mind from day 1.

There is one area where encryption is expressly permitted in amateur radio: satellite control, for obvious reasons. The future of amateur radio is not people talking to people over narrowband voice channels; it's going to be machines talking to other machines, and being able to control them. This is going to require encryption, or innovation will shift off the ham bands. And if the ARS is just ragchews, contesting, and doing things that have already been done instead of advancing communication, then there's not much defense when someone like Thales comes in and suggests reallocating bandwidth to something new and enterprising.

jmwilsonon SymPy makes math fun again

The times I have used CAS to help with algebraic simplification, I've found the same problem, regardless of using SymPy or the more feature-filled Mathematica: the package's rules for simplification often obscure useful forms that lead to insight. The CAS gives you the correct result, of course, but I end up having to apply significant post-processing to the result by forcing substitutions that can take almost as much time as doing the algebra by hand.

As a simple example, consider the transfer function of a RLC circuit from basic electronics. It might contain a expression of the form: s^2 + (R/L) * s + 1/(LC). What's often helpful is to express this in terms of the unitless form 1 + s/(Q * w0) + (s/w0)^2, where w0 is the resonance frequency and Q is the quality factor. In a complicated example with more components, the value of w0 might be related to the simple form of 1/sqrt(LC) by some unitless factor, or there's some other helpful way to write things that neatly relate it to the basic case, but SymPy/Mathematica will drag its feet showing you that. I wish there was more done on improving the insight and meaningfulness of results from CAS to the experimenter.

jmwilsonon On Ocracoke Island, the only American dialect that is not identified as American

In the case of Louisiana, I'm guessing the Cajun and Creole areas were never wealthy compared to the cities. Young people from the country seeking jobs and money in urban centers has been a theme throughout the 20th century, and geographic mobility was actually higher in the past [1], so what's causing these cultures to evaporate so quickly now?

It seems like wherever you look in the US, regional cultures are vanishing at an accelerated pace. From Portland, Oregon to Portland, Maine, and everywhere in between, shops and restaurants that not outright bland national chains have converged around a common contemporary hipster aesthetic optimized for Instagram. Is the Internet and social media that powerful that they are the real cause of this cultural compression, or are there other factors?

[1] https://www.citylab.com/equity/2017/02/american-mobility-has...

jmwilsonon KiCad 5.1.0

As someone who bought a license to Circuit Studio (the $500 version), I can't recommend it. Missing some of the higher-end features is being polite; while there is no agreement on what is high-end, I found that many general-use features from Designer were carelessly stripped out or left in a broken state. Then, of course, are the bugs and Altium's refusal to share a product roadmap for CS. Despite not communicating what they want to improve about the product, and when they plan to deliver it, they still want a subscription fee.

jmwilsonon Drone Control via Alexa

Second the recommendation for Snips. I recently built a Snips-based voice assistant for hands-free oscilloscope control (https://github.com/jmwilson/ollie), and snips is a much better fit for this kind of domain-specific, field-deployable (offline) voice assistant.

Consider the whole of infrastructure required for this application. The Pi sends a request to Alexa, which sends a request to a lambda server, which sends a request to SQS, which is polled by the Pi. Each of those AWS servers has possible subsystems and some load balancer in front of it. Single device, offline processing is so much cleaner when there's no need for general connectivity.

jmwilsonon Show HN: DIY Oscilloscope Voice Control

Pretty easy, I had no background in voice assistants before. You set up the intents on their console site, rack your brain for every way you could phrase a command, and then press a button and Snips will let you download the trained assistant in a .zip file.

They have examples in JS and python for simple client apps to build from; the platform sends processed intent messages over local MQTT, so it's just a loop to listen and process those intents into commands to send via USBTMC.

jmwilsonon Launch HN: DevFlight (YC W19) – Helping open-source maintainers make money

Can you share publicly any of the projects & maintainers you're currently working with?

jmwilsonon B612 is a highly legible open source font to be used on aircraft cockpit screens

Their own legibility study shows it's about around the same as Verdana: https://i.imgur.com/M0C3TkY.png (excerpt from the PDF in the download .zip, vertical axis is misidentifications). Their design goal was beating their current font (CDS), which seems a bit of a sandbagged goal if you look at the sample in the report. I wonder if we've reached a plateau of legibility for technical fonts after identifying the easy wins in typeface design for screens.

jmwilsonon Button offers instant gratification for those plagued by airplane noise

The amount of data it collects and files hopefully makes it harder to dismiss. It is using the same ADS-B data as flightradar and similar sites, so it's able to report detailed information- exact time, what aircraft passed overhead, how far away, what altitude and ground speed. At a lot of airports, there are requirements for climb-out paths (in terms of position and altitude) for noise abatement, and if operators aren't observing existing rules, these detailed reports can have a lot of force.

jmwilsonon Fog Waves Are the Most Beautiful Thing I Captured After 8 Years of Experimenting

At midday on a sunny day, by the sunny-16 rule you can expect to set the camera exposure to f/16 1/100 s at ISO 100. To get to even 1/50 s, you're now at f/22, the limit of most commercial lenses. So yes, ND filters are still useful to those of us who understand manual exposure.