Ted Dunning

@bsky.tdunning.com

616 Followers 409 Following

That spoon is bigger than it looks. And it isn't a fork (in the road) Member of Apache Software Foundation, committer on many Apache projects, Fellow at HPE.

The crescent moon taken through clouds to get an ambiguous image
A picture of a full moon on a very dark sky with a single branch in front of it
The Methuselah tree with somebody standing next to it for scale. This is a large over 1,000-year-old redwood in the Bay area of San Francisco
The theoretical and measured results for a low pass anti-aliasing filter for the AD9851 direct synthesis signal generator. The blue line shows the simulation with idealized components and has a small bump in response before it reaches 60dB of attenuation at about 120MHz. The green line (four layer implementation) and orange line (two layer implementation) show the measured performance. Each of the real implementations lack the small bump at the cutoff (probably due to finite Q of the inductors) but otherwise track the roll-off of the theoretical response very well. Above 120MHz, the orange line exhibits noticeably (~6dB) less attenuation than the theoretical or four layer implementation. The four layer implementation follows the simulation results very closely, however, all the way out to the limit of measured data at 290MHz.
A rendering of a small electronic component that implements a low pass filter for use with the AD9851. See https://github.com/tdunning/low-pass
The SMA scope probe assembled and connected to cables.
A small circuit board designed to allow a scope probe to be built from SMA- terminated cable. The circuit board has a QR code that links to https://github.com/tdunning/sma-scope-probe
Three wisteria pods are against a dark background. The pods are lit by indirect sunlight and the background shows hints of green, both indicating that a new season is coming. The pods wait with their seeds.
This is the blue police call box at Earl's Court station in London. It is one of the very few police call boxes left in England and is a site of pilgrimage for Doctor who fans
3D rendition of the attenuator to turn an ordinary RG-316 cable into an SMA based oscilloscope probe. This attenuator forms a voltage divider with the 1MΩ input of the oscilloscope with some capacitors included to maintain a flat frequency response.
A large pot full of posole cooking on the stove. The chili has been added and the color has turned very dark red
A large pot of boiling posole colored very red by the red chile powder that has been added. Posole is a soup made largely from expanded kernels of corn sometimes called hominy. It is popular in the southwestern United States at Christmas time.
The back of a t-shirt that says in Spanish "si se puede cultivar conciencia". This can be read in two ways, we can cultivate awareness, or we can cultivate a conscience.
A 2x2mm grid taken through a progressive focus prescription lens. The lens is about 30-40cm from the grid and the camera is about that far behind the lens focussed on the magnified portion of the grid. This image clearly shows the unperturbed portion of the lens above the corrective region and transitional zones left and right of the zone with the highest magnification in the corrective zone itself. The non-linear distortion of the grid shows why it takes time to accommodate this kind of lens. The amazing thing is that once you adjust, your brain compensates nearly transparently.
A picture of a small printed circuit board designed using KiCAD
A leaf which is turning yellow and red. It's suspended on the windshield of a car with a neighborhood and other cars in the background out of focus.
The output from the circuit as a trace. It shows that the signal is low except when the slug is passing by at which time it goes to over 4 volts.
A plot of the voltage that controls the variable inductance. Most of the time, the value is quite low (2mV), but when a slug passes, it rises to a much higher value (10mV) consistent with an increase of permeability by a factor of 500. For a short time, the value is constant as the slug is entirely in the coil and then it declines back to the lower value.
A circuit diagram showing an 80kHz pulse generator driving a 100 ohm resistor and a variable inductor. The voltage across the inductor is amplified and rectified by an op-amp circuit. At the bottom left is a pulse generate that generates a wave-form that drives the value of the inductance in the coil over time. That wave-form represents two slugs being dropped through the coil.
A map showing very high likelihood of Aurora being visible over most of Canada, much of Green and nearly all of Alaska. Only the northern tier of continental US states have a moderate or high likelihood.
Sticker that says I voted in many languages
Demonstrators lining up to get ice cream from an ice cream truck
A picture of three ripe pears. This can be taken as three distinct pairs of pears.
Side view of a small plastic box that is mysteriously full of cables.
Dried grass seed pods
An Olympus camera with a large zoom lens.
A bumblebee landing on a California poppy.
A high contrast picture of a crow descending against a blue sky.
A memorial plaque that reads: "Love Survives" Mary Frances Seaver August 31, 1929 - August 15, 2022 Resting at Loch Vale, RMNP
A picture showing the interior of the train station in Washington DC. There are tables set for dinner in the interior and people wandering around. The ceiling is illuminated in a greenish color. The perspective is distorted because the picture was a panorama stitched from multiple images.
An old cartoon by Dr. Seuss (Theodore Geisler) showing people lining up to get an "Ostrich Bonnet". The person handing out the bonnets has a sign behind them that says "Get your Ostrich Bonnet here. Relieves Hitler headache. Forget the terrible news you've read. Your mind's at ease in an ostrich head! There are many people lined up on the right side of the sign wearing the bonnets with their heads in the sand. The caption says "We always were suckers for ridiculous hats ..."
A picture of a woman on the beach gesturing that she can't hear the speaker
A picture of downtown Salt Lake City shrouded in smog.
A picture of a burned out coastal redwood that was killed during the 2020 fires which burned much of the Big Basin park.
A poster advertising demonstrations to be held in Palo Alto and Sunnyvale on June 14th. The general term for these protests will be "No Kings"