Tom H
LightNews LightNews
tomhodson.tech.lgbt.ap.brid.gy
Tom H
@tomhodson.tech.lgbt.ap.brid.gy
27 followers 5 following 150 posts
Baker, Runner, Programmer, Physics PhD

🌉 bridged from ⁂ https://tech.lgbt/@Tomhodson, follow @ap.brid.gy to interact
Posts Replies Media Videos
tomhodson.tech.lgbt.ap.brid.gy
Why in the world would a TV have a blue only mode?
A photo of a TV showing a computer desktop but only the blue channel is shown. The TVs OSD shows that it’s in “blue only mode”. A photo of the same to with computer desktop showing the normal colours.
January 19, 2026 at 5:12 AM
tomhodson.tech.lgbt.ap.brid.gy
I haven’t seen this pattern in a long time! Reminds me of that opener from Neuromancer https://scifi.stackexchange.com/questions/163304/what-color-was-the-sky-above-the-port-in-neuromancer#163310
A photo of a TV showing black and white static.
January 18, 2026 at 5:16 PM
tomhodson.tech.lgbt.ap.brid.gy
So I’m currently traveling and I made a little blog for my friends and family complete with a little map libre gl globe and icon of me that moves around. I’ve got it behind caddy/authelia so to access it you have to have credentials. However I would quite like it […]

[Original post on tech.lgbt]
A phone screenshot of a webpage. The top two thirds are taken up by a 3d globe zoomed out just enough to see the curvature. The sea and land are rendered in warm colours with a pink line denoting the path of the traveller. The line starts in the south of France, goes north to Paris, Berlin, wiggles about in Germany, then snakes south east through Austria, Hungary and Romania before winding eastward through turkey. Along the line there are small circular photos representing blog posts. At the bottom third there is a photo carousel where each blog post gets a larger square image and a title. Visible are Ephesus, Izmir and Bandirma, locations in turkey. You can see that it’s 16:37 local time, the person had full signal LTE, is in low power mode and their phone is charging. The address bar reads travel.thod.dev
December 8, 2025 at 2:29 PM
tomhodson.tech.lgbt.ap.brid.gy
Wanna know why seal cubs are so cute? 🦭
A picture of a baby seal. This particular one has quite short grey fur, very long whiskers and huge black eyes. Given angle the photo is taken from you can kinda see that the front surface of the left eye is relatively flat, not perfectly but I assert that it is flatter than other land animals’ corneas.
November 29, 2025 at 11:02 AM
tomhodson.tech.lgbt.ap.brid.gy
Here’s a schematic view of the human eye called the Gullstrand schematic human eye. Fun fact: I have intraocular lense implants so my own eyes actually have two extra surfaces compared to this diagram.
A black and white line diagram showing the three refracting surfaces in the human eye, the front of the cornea which is an air-water interface, then the front and back of the lens. The lense has a slightly higher optical density than the surrounding medium. Each of the three interfaces is labelled with a radius and the optical density of each medium is given. This allows to calculate the position where the image is in focus as well as the nodal point which is important because it lets your replace the whole thing with a single surface centred on the nodal point.
November 28, 2025 at 1:49 PM
tomhodson.tech.lgbt.ap.brid.gy
This graph is great, in the text they point out that the range of intensity levels where human eyes work is about 10 orders of magnitude. However photoreceptors themselves only cover about 5 orders of magnitude. To make up the difference we have our iris that […]

[Original post on tech.lgbt]
A graph showing the relative intensities of various light sources in terms of photons per area per unit time. The gist is that bright sunlight is about 10^10 stronger than the darkest levels where human eyes still work. An extraordinary dynamic range. Luminance of a white card under various illumination conditions cd.m? photons.m-2 sr1 ,s-' (555nm) 10^20 Bright sunlight 10^19 Overcast sunlight - 1018 10^17 Room light 10^15 Street light 10^14 Moon light 10^12 Star light 10^10 Absolute threshold of human vision
November 22, 2025 at 11:20 AM
tomhodson.tech.lgbt.ap.brid.gy
TIL: Box jellyfish larvae have eyes but no brain to connect them to so instead the eyes also swim a bit. Source: Animal Eyes, Land & Nilsson, second edition, chapter 1
A cropped photo of an e-reader. The text reads: « The small pigmented ocelli of the planula larvae of box jellyfish (Fig. 1.4a) offer a rare example of a 'visual system' so primitive that it consists of only a single cell type. Apart from making a pigment cup, these cells also have both sensory microvilli and motile cilia, but no neural connections. It is believed that they are self-contained sensory motor units, steering the larva as it swims. »
November 22, 2025 at 10:31 AM
tomhodson.tech.lgbt.ap.brid.gy
I really like how capacitors and inductors are mathematically kinda mirror images of other another. One smooths out voltages and one smooths out currents. One has equation V=LdI/dt and the other I = C dV/dt.

Here's that summed up in a little table where I've also […]

[Original post on tech.lgbt]
A table of equations governing Inductors, Resistors and Capacitors (the column headings from left to right). The 4 rows are: Integral Equation, Differential Eqn, V = ... and Z = .... Here it is formatted in a more linear way with latex, let me know if you'd like a version of the alt text with words instead of latex. ## Integral Equation Inductors: $$ I = \frac{1}{L} \int V \,dt $$ Resistors: $$ V = R I $$ Capacitors: $$ V = \frac{1}{C} \int I \,dt $$ ## Differential Equation Inductors: $$ V = L\dot{I} $$ Resistors: $$ V = R I $$ Capacitors: $$ I = C \dot{V} $$ ## V = ... Inductors: $$ V = L\dot{I} $$ Resistors: $$ V = R I $$ Capacitors: $$ V = \frac{1}{C} \int I \,dt $$ ## Z = ... (Complex Impedance) Inductors: $$ i \omega L $$ Resistors: $$ R $$ Capacitors: $$ (i \omega C)^{-1} $$ For the first two rows, switching between inductors and capacitors requires swapping V and I around and replacing L with C as appropriate. For the third row you basically integrate the right hand side once as you go from Inductor to Resistor to Capacitor. For the fourth row, ignoring constants you divide by omega once, which is related to integrating.
August 30, 2025 at 12:48 PM
tomhodson.tech.lgbt.ap.brid.gy
"A network timeout occurred during relationship request. Please try again."
A screenshot of an orange modal window with a warning icon that says "A network timeout occurred during relationship request. Please try again."
August 2, 2025 at 8:10 AM
tomhodson.tech.lgbt.ap.brid.gy
Cycling in to work today I picked up this completely broken phone holder that had obviously fallen off of a motorcycle. Turns out it has a little wireless charging module in it! Googling the IC numbers it it accepts up to 36v input (only tested it to 24v, just in […]

[Original post on tech.lgbt]
A photo of a small black module, maybe 4cm but 6cm, on the top is a copper coloured flat coil. At the bottom it’s hooked up to a red and black pair of banana plug clip thingies for power and there’s a small blue light visible coming off it in the top right. Picture of the same module but in the background you can see the very broken phone holder it was harvested from.
August 1, 2025 at 4:56 PM
tomhodson.tech.lgbt.ap.brid.gy
Teeheee 😆 pygame is quite fun for just blasting something simple to a frame buffer.
An openflexure microscope (see thread above for descriptions of that) but this one has a small (4cm) circular screen screwed onto the riser piece that holds the illumination. The screen is white and is displaying the text “planes.local” and “wlan: 192.168.1.25” (probably, I can’t actually read the ip address from this interface, but it’s a local ip of some description) An openflexure microscope from a slightly different angle (see thread above for descriptions of that) but this one has a small (4cm) circular screen screwed onto the riser piece that holds the illumination.
August 1, 2025 at 4:40 PM
tomhodson.tech.lgbt.ap.brid.gy
Got a second hand kobo e-reader, it’s my first proper experience with e-paper and it is _really lovely_. I downloaded calibre and loaded some blogs onto it, the html -> epub conversion seems subject the to the vagaries of how each site is formatted but of course […]

[Original post on tech.lgbt]
A photo of a hand sized e-reader showing a page from low tech magazine.com with a black and white image taking up the top half and text in the lower half.
August 1, 2025 at 7:58 AM
tomhodson.tech.lgbt.ap.brid.gy
TIL that you can just connect many displays directly up to an RPI, twiddle some device overlays, and it will show up as a framebuffer in the system.

Might use this to make a slightly ridiculous viewfinder for the microscope, or slightly more useful, to see when […]

[Original post on tech.lgbt]
In the foreground I'm holding a small 4cm-ish circular display which shows, in very small type, a class linux terminal login screen. In the background and slightly blurred is an openflexure microscope which is running the screen.
July 31, 2025 at 3:22 PM
tomhodson.tech.lgbt.ap.brid.gy
New blog post: This site now has an .onion address - Not that it particularly needs one but anyway. (https://thomashodson.com/2025/07/30/this-site-now-has-a-onion-address.html)
July 30, 2025 at 7:28 PM
tomhodson.tech.lgbt.ap.brid.gy
Laid flat
The pieces from the stool cut out in 6mm ply and laid flat on a table. I’ve arranged them so they unfolded like a strange flower or starfish.
July 25, 2025 at 1:50 PM
tomhodson.tech.lgbt.ap.brid.gy
I had fun trying to get the bits to fit into the rectangle I had available.
The flat panels made up the stool laid out to fit into a rectangle that represents my stock.
July 25, 2025 at 12:37 PM
tomhodson.tech.lgbt.ap.brid.gy
Doing some more lasercut stools today!
A cad model of a hexagonal prism stool assembled from sheets of plywood joined with lasercut finger joints.
July 25, 2025 at 12:34 PM
tomhodson.tech.lgbt.ap.brid.gy
Ok I used astropy to convert a bunch of locations on earth into a cartesian version of the Geocentric Celestial Reference System. Locations on earth spin around this system over time but at least the axis of rotation seems to be the Z axis and the north and south […]

[Original post on tech.lgbt]
A 3D plot showing various circular arcs. The legend on the right says "Hackney", "New York", "Syndey" and looking at the arcs you can see they're the path these locations take through space as the earth spins over 12 hours. Also in the legend are the north and south poles and a black line through them labelled "Z axis"
July 19, 2025 at 2:33 PM
tomhodson.tech.lgbt.ap.brid.gy
That's the diagram for geodetic coordinates from Wikipedia. The fact that the point C isn't the centre feels so deeply cursed to me. I really think we should do something about the earth not being spherical, it's just not ok.
A diagram defining geodetic coordinates. The three important coordinates are geodetic latitude (north/south) represented by the symbol ϕ, longitude (east/west) represented by λ, and ellipsoidal height represented by h. Together these define a point P which is a height h above the ellipsoid surface of the earth, so far so good. Naturally h is measured along a line normal to the surface of the ellipsoid, I guess this direction would commonly just be called "up". The horror starts when you follow that normal vector back down, because it's an ellipse not a circle, this line doesn't go to the centre, its goes to some random other point! Awwww the horror!!! P.S: λ is simple and good, it's just the rotation about the Z axis / the axis of rotation of the earth.
July 19, 2025 at 1:06 PM
tomhodson.tech.lgbt.ap.brid.gy
Hackney seems to be approximately on the surface of the WGS84 earth, which is encouraging.
A Jupyter notebook, the first cell is: ``` x, y, z = location.to_geocentric() np.sqrt(x*x + y*y + z*z) ``` which prints 6365066.3 m The second cell is: ``` # WGS84 ellipsoid semi-major (a) and minor (b) radii a = Quantity(6378137, unit = "m") inverse_flattening = 298.257223563 b = a * (1 - 1/inverse_flattening) a, b ``` Which prints (<Quantity 6378137. m>, <Quantity 6356752.31424518 m>) So Hackney is within the range of radii one would expect!
July 19, 2025 at 12:51 PM
tomhodson.tech.lgbt.ap.brid.gy
Ok so I can get a location on earth in astropy and I can convert it to lat,lon,height (presumably this is WGS84 but the neither the docs for to_geodetic nor the object) I can also get it as a (x,y,z) coord using `to_geocentric`. There's no time here so this second […]

[Original post on tech.lgbt]
A screenshot of a jupyter notebook. The first cell is: ``` from astropy.coordinates import EarthLocation location = EarthLocation.of_address("Hackney, London") ``` I evaluate `location.to_geodetic()` and it prints: GeodeticLocation(lon=<Longitude -0.0493621 deg>, lat=<Latitude 51.5432402 deg>, height=<Quantity 2.9766014e-10 m>) Next I evaluate `location.to_geocentric()` and it prints: (<Quantity 3974880.93193404 m>, <Quantity -3424.48466993 m>, <Quantity 4971355.84766419 m>)
July 19, 2025 at 12:38 PM
tomhodson.tech.lgbt.ap.brid.gy
Hey fedi, what is this box?
A photo of a phone box with bunch of wiring inside none of which I can identify. I’ve circled a box in the top left that’s quite chonky with a big alumin heatsink
July 16, 2025 at 5:57 PM
tomhodson.tech.lgbt.ap.brid.gy
On a whim, I strung an led noodle along the top tube of my bike.
July 1, 2025 at 7:56 AM
tomhodson.tech.lgbt.ap.brid.gy
And finally a bed visualiser to see when it's time to fiddle with the screws again instead of just relying on the autoleveling.

https://github.com/jneilliii/OctoPrint-BedLevelVisualizer/
A 3D diagram with x and y axes from 0 - 200mm and z from -2 to 2mm. It shows a colourful, almost flat surface. A colour bar to the right shows that red indicated high spots and purple low spots.
June 28, 2025 at 3:32 PM
tomhodson.tech.lgbt.ap.brid.gy
Next up is slicer thumbnails. If you set your slicer up to embed thumbnails into the gcode then you get nice little thumbnails in your file viewer. Since I never give good names to my gcode files, they're always called something like "part_1_2h13m....gcode" the […]

[Original post on tech.lgbt]
Screen shot of the octoprint files UI box. This displays info like name, size, update time etc for each GCODE file. Because of this plugin there is now a little thumbail too. I chose 128x128 pixels to avoid making the GCODE files too huge.
June 28, 2025 at 3:27 PM