Voltage Dividers

Working through some example circuit simulations I finally gained an intuitive understanding of the voltage divider equation — it’s just a ratio, but I had never figured this out before.

Given this circuit, where the voltage source is rated at 1V:

The voltage at A is equal to 1V·(R2 / R1 + R2), which is 1·(1/1+1) = 1·(1/2) = 0.5.

Why? Because R1 + R2 represents the total resistance of the path, and as such the total voltage drop. Dividing R2 by the total produces a fraction representing the voltage drop over R2. Multiplying the input voltage by this fraction leaves us with the voltage dropped over just the R2 portion of the circuit, which must be V_A because there are no other branches in the circuit.

Put another way, the equation finds the ratio of resistance (and so voltage drop) R2:R1 and then feeds the input voltage through this. Here’s a more abstract visual representation of what’s going on:

My apologies to the @mozilla staff manning the FF Nightly bug reports today, for the stream of gradually less coherent “FF crashes when I drag leafletjs.com maps around whilst making HTTP requests” reports.

Checked in to C is for Cookie, Reykjavik — working on my #indieweb checkin/note location UI, check it out at waterpigs.co.uk/notes/new!

Received some spam telling me my website needs a responsive layout. I wonder if @beep gets these emails.

“Fail Fast” is the trendy alliterative buzzword version of “have small feedback loops”, just less accurate and more prone to undesirable misinterpretations.

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Emil Björklund: #PHP folks: when fetching from an API, would it be wise to use function_exists to check for cURL, and else fall back to file_get_contents()?

@thatEmil that should work fine — one thing to bear in mind is that by default they both treat redirects differently. IIRC, cURL doesn’t follow redirects by default whereas file_get_contents will.

I helped write a thing which crunches multiple millions of numbers, do I get to call myself a Big Data Scientist now?

SIP/WebRTC call-via-personal-site #tabdump:

When using the display: table trick to move elements around, beware that Opera+FF require the fake-table element to also have table-layout: fixed set in order for descendant img { max-width: 100% } to work. As pointed out by Scott Anderson #css #responsive

Having a go at making Sumendi’s leche frita (fried milk). Just put the mix in the fridge, pretty sure the consistency is perfect, but I’ll find out for sure tomorrow!

Friday’s #wondermark strip perfectly expresses point-scoring as unproductive nonsense cc @brennannovak:

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Sandeep Shetty: @BarnabyWalters Any chance you might share the "~210 lines of code" with me? If not publicly, maybe a private gist?

@sandeepshetty sure! gist.github.com/barnabywalters/7863676 — included the basic functions plus the convenience class I use and a little demo. Very specific to chronological post storage/indexing, and very much in flux. I’d be interested to hear your thoughts about it.

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Sandeep Shetty: @BarnabyWalters Very cool. What's the use-case though? Also is this coming of the doctrine based indexer that you had?

@sandeepshetty thanks! I’ve wanted to plot tag usage over time for a while now to see if there are any interesting patterns. I’m not using doctrine any more, in fact I’m not even using a SQL database for indexing until I really need one — data stored in yaml files, indexed by a csv file in ~210 lines of code — see also waterpigs.co.uk/notes/4TQNY2

When I post a note, #taproot adds one to the week counter for each tag, then I have an endpoint which makes that data into an SVG.

New in #taproot: tag listing page waterpigs.co.uk/tags with sparklines of per-week usage over the last year

What’s the highest-order parody (parody of a parody of a…) ever created?

Lots of good, if a little bizarre, #gurdy playing in this video (fr):

http://www.youtube.com/watch?v=B8W8awew67k

New in #taproot: latest 3 articles and location of last checkin/location post on the homepage — hopefully some useful/interesting context.

Next: mobile-focused homepage design.

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Chloe Weil: Hipster

@chloeweil great article and great work implementing #POSSE! Interested in your choice to use a database for performance reasons, was that prompted by actual experience or just the cited help thread? fwiw I’m having no performance problems storing >2000 notes in flat files with a CSV file index

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Ben Werdmuller: @barnabywalters Getting that sauce right is tough, but totally worth it. Love the idea of @doublebill!

@benwerd any sauce-making tips you’d care to share? And yep, @doublebill is great — met some new friends and seen some interesting/bizarre films at previous ones, hoping to continue the trend!

Second attempt at satay chicken tonight — peanut sauce was too watery (coconut milk was less thick somehow) but the marinade was much better. Need to get it (and maybe chocolate mousse) up to scratch for when I host my #revolution themed @doublebill!