{"id":360,"date":"2011-11-21T01:34:30","date_gmt":"2011-11-21T01:34:30","guid":{"rendered":"http:\/\/toyservice.ro\/stories\/?p=360"},"modified":"2013-10-09T00:28:01","modified_gmt":"2013-10-08T22:28:01","slug":"led-dynamo-flashlight-tuning-and-repairs-july-2011","status":"publish","type":"post","link":"https:\/\/toyservice.ro\/stories\/2011\/11\/21\/led-dynamo-flashlight-tuning-and-repairs-july-2011\/","title":{"rendered":"LED Dynamo Flashlight: tuning and repairs – July 2011"},"content":{"rendered":"

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\n\t\t\t \t\n \"lanterna-led-dinam-demontata-dupa-cazatura-focus-bun\"\n\n \t<\/a>\n\t\t <\/div>\n Long before the idea of this website ever occurred to us, as a result of our mutual interest for ecological illumination (along with many other interests), we changed a LED flashlight with dynamo, a very cheap model, but whose performances we improved. Now, because of an accident, this flashlight had to be fixed \u2013 and it also got to be the subject of this article.<\/p>\n

The history of the defect\/ accident<\/h2>\n

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\n\t\t\t \t\n \"lanterna-led-dinam-demontata-detaliu-generator\"\n\n \t<\/a>\n\t\t <\/div>\n The LED flashlight fell apart as a result of its smashing against concrete(*)<\/a> \u2013 falling from about 1.2 m high \u2013 and all its guts<\/em> spread all over the place, but, lucky us, they were all recovered. Hence, with a little bit of luck, we had a chance to make it work again, as we had started liking to use it \u2013 as much of a cheap Chinese piece of crap as it was.<\/p>\n

Action plan<\/h2>\n

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\n\t\t\t \t\n \"lanterna-led-dinam-demontata-detaliu-circuit-focus-bun\"\n\n \t<\/a>\n\t\t <\/div>\n After a first brief examination of the recovered pieces and being familiar with the type of plastic of its case (hard and breakable: celluloid?) we only had one option: gluing it with solvent, followed by the trussing<\/strong> of its frame. Later on, we were going to find a way to make it more durable.
\nOn the other hand, I need to mention the initial story too, that of me buying the flashlight. It is indeed a cheap<\/strong> model but not misleading(**)<\/a>, so it did contain an 8 pole single phase generator, below 1000 rpm, that could charge an 3 cell Ni-Mh rechargeable battery at 3.6V and 40mAh. As it had a small battery, we were not at all satisfied with a single-wave rectification, and from here to the idea of completely changing the rectifier there was just a small step.<\/p>\n

Necessary tools and parts<\/h2>\n

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\n\t\t\t \t\n \"lanterna-led-dinam-carcasa-superioara-profunzime-maxima\"\n\n \t<\/a>\n\t\t <\/div>\n For the first operation \u2013 the tuning<\/em> \u2013 we needed electronic parts (diodes, electrolytic capacitors), Weller, wires, a gauge and some more room inside for some extra wires.
\nFor the actual repairing, we used solvent (dichloroethane), a grip vice and some plastic for fillings (also celluloid).<\/p>\n

The repairing process<\/h2>\n

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\n\t\t\t \t\n \"lanterna-led-dinam-carcasa-superioara-reparata\"\n\n \t<\/a>\n\t\t <\/div>\n W can\u2019t get over the modifying (the tuning) of the original LED flashlight without having this conversation about rectifiers. I will try to keep it short, but it is a \u201cgood\u201d topic(***)<\/a>, and for a complete understanding of the phenomena, please go to wikipedia<\/a> or, better than that, professional courses.<\/p>\n

Single-wave rectifier:<\/h3>\n

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\n\t\t\t \t\n \"redresor-mono-alternanta\"\n\n \t<\/a>\n\t\t <\/div>\n This is the initial rectifier, which uses only half of the energy available in the generator (dynamo), not to mention asymmetries, bias and other \u201cbenefits\u201d.<\/p>\n

Double-wave rectifier:<\/h3>\n

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\n\t\t\t \t\n \"redresor-punte\"\n\n \t<\/a>\n\t\t <\/div>\n This seems to be the ideal choice as it uses both waves and 100% of the available energy (minus the collateral losses \u2013 wires, diodes…) Unfortunately for us, the bridge rectifier, under practical circumstances, causes a loss of 2×0.7V = 1.4V, which is bit too much.
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\n\t\t\t \t\n \"redresor-dubla-alternanta-cu-priza-mediana\"\n\n \t<\/a>\n\t\t <\/div>\n For the center-tapped design, we didn\u2019t plan for such a major intervention (riveted coil, unwinding, rewinding with center-tap, …) We probably had room for the necessary extra amount of copper and YES<\/strong>, we will give it a try sometime later…<\/p>\n

Voltage Doubler rectifier:<\/h3>\n

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\n\t\t\t \t\n \"dublor-de-tensiune\"\n\n \t<\/a>\n\t\t <\/div>\n We chose this option (it uses both waves, with one diode on branch and doubles the tension) for several reasons:<\/p>\n