LED there be Light Photos by Aymar. 1 - 7 of 7 Total. 464 Visits.
1 The two strips from a flat light panel fixture Opening a defective LED panel showed that there is not too much difference between a backlit LCD and a such a panel. Basic architecture, a glass panel which is framed by two rows of LEDs (Light Emitting Diodes). Panel case, everything is covered by opaque 'milk glass' (or 'diffusion foil', actually plastic something, the optical equivalent of a muffler), LCD case, the cover consists out of an array of easily polarized crystals. Adjustable louvres for all occasions.
Timeline: polarized crystals first showed up in wrist watches (unchecked, 70ties?). Selective reflectivity permitted a 'block' display of numbers (in my own words, numbers made up out of wedged shaped tangram pieces). No actual connection but these block numbers did resemble railroad signals for switches. Semaphoric part, a big 'X', trains will go straight on, semi brackets '<' and '>', the train will switch tracks. The railway implementation was mechanical. Model train case, a ...
2 Power pack The usual culprit, the rectifier cum voltage converter, was for once blameless. Voltmeter reading: 60V - reasonable close to the promised output 56-86V. The step down was supposed to work over a wide range of currents. Input range according to the sticker: AC 85-265V.
More likely cause for the demise, three LEDs in the middle of one strip were dead. (There were also two 'zombies', in distal position, which only lit up after a delay.) The LED strips were were attached an alum rod to help with heat dissipation.
Promised power output by the Zochlon power pack: 300mA. That tallies reasonably well with the actual device. Number of LEDs, in both parallel strips, about 132. Rule of hand, each LED will draw about 2mA.
[The shown power pack is from a replacement panel. Selfsame manufacturer.]
3 the LED wiring: in parallel The live LEDs still gave off light, although at a much diminished rate (2 to 3% or the normal output). Flashback (Ohm and Kirchhoff): Xmas light chains (made up of incandescent light bulbs) can be wired either in series or parallel. The latter is somewhat more expensive. Drawback of an in series wiring, a single burnt out light bulb will act like a blown fuse. All lights will go out. Parallel case, the remaining bulbs will just draw fractionally more current. Something did clearly not fit. Peeling off some of the strip light coating showed that the wiring was parallel. Two meandering 'friezes' of copper foil were bridged in regular intervals by the LED elements. So why the dimness. Conjectural: subliminal-shorts. Elastic formula, circuit integrity will be breached if there is leakage in any shape or form. Surgically removing the overbaked LEDs would remedy the situation if the erstwhile assumption was correct. That was done, but only in a roundabout way. The bad rod was r...
4 Corn-cob LED The remains of a 'corncob' LED with a busted rectifier (actual life span, less than a fortnight, banshee flickering towards the end).
5 Corn-cob LED What to do with a drunken sailor. The parallel strips, secured to a slab of wood with builder's glue, make for a good HHPCIL (hand held pc inspection light). Hooked to a power pack. Esthetic considerations were not paramount.
6 Corn-cob LED in rank and file
7 Illustration from 'Uncommon-Sense' (ASF) Beyond LEDs (Ray Tracing Stories)
The worse ray tracing story I ever read (title unknown) did feature an accidental tourist on the run from a golem (actually a rogue robot, some Yul Brynner attributes). Showdown: the golem crashes the apartment door and the tricky mortal is forced to hide in a fridge. The unleashed golem, limited to infrared vision, is duped. Highlight, he opens the fridge but cannot detect the stowaway. Selfsame rules as for military encounters. You want to be invisible to the enemy: stand right before a gigantic spotlight. Do a spotlight angel even. Nobody will detect your silhouette, skylight promise. Unvoiced, hidden by a draft of cold air.
Hal Clement's short story 'Uncommon Sense' deals with the selfsame subject matter but has much more to offer. Defining light as everything that moves in a straight line, reasonably unperturbed by a traversed media, he arrives at the astonishing conclusion that even ordinary evaporation can act in lightl...
