beartato phd

(no subject)

Did some personal archaeology. Helped a little with laundry. Threw some chicken, onions, tomato, stock, peppers in the slow cooker and hopefully shredded chicken and rice and beans dinner will come out of that.
beartato phd

(no subject)

Dinner with akiva and dannel at nuevo portal in carroll gardens. Ate a pile of chicken stew and rice and beans and maduros, good times. I do miss brooklyn a little, still. Hadn't seen dannel in forever, good to catch up.
beartato phd

(no subject)

Achievement unlocked teaching myself things every ece freshman knows, part 938472 and a half: I grok Thevenin's theorem well enough to prove the R-2R ladder works for digital-to-analog conversion.

Reasoning about resistor networks as random walks actually helps quite a bit. Recall that the voltage in a resistor network (with some known voltage sources at the leaf nodes) at point P is equal to the expectation of taking a random walk (with the probability of taking a step across a resistance R being proportional to 1/R) and taking the known voltage of the first voltage source you hit.

So I can reason that
       R1          R0
V1 |---vvvv---O---vvvv ...
              |
V2 |---vvvv---+
       R2

is equivalent to
        R3         R0
V3 |---vvvv---O---vvvv ...

for V3 = (V1R2 + V2R1) / (R1 + R2) and R3 = R1 R2 / (R1 + R2) from considering what happens at point O in the random walk: having a probability of (1/R1)/((1/R1) + (1/R2) + (1/R0)) of ending the walk with value V1 and a probability of (1/R2)/((1/R1) + (1/R2) + (1/R0)) of ending the walk with value V2 is the same in expectation as replacing both those posibilities with a single one whose probability is their sum, and whose terminal value is the weighted average of their values, which comes out to being V3 with probability (1/R3) / ((1/R3) + (1/R0)).

that said, if I ever want to do a project with analog output, I'd probably just buy an Adafruit MCP4725 instead.

Oh, and I can play around with it interactively in this circuit simulator. Nice.
beartato phd

(no subject)

Guy from Seattle team we've been working with showed up today at work; no matter how much I'm generally comfortable working with remote teams (and I think at this point I am quite comfortable with it) it's always fun to hang out with people in person a bit once in a while.