{"id":375,"date":"2014-07-13T22:24:31","date_gmt":"2014-07-14T02:24:31","guid":{"rendered":"http:\/\/www.compdigitec.com\/labs\/?p=375"},"modified":"2024-03-15T08:55:05","modified_gmt":"2024-03-15T12:55:05","slug":"reverse-engineering-the-fischertechnik-blinker","status":"publish","type":"post","link":"http:\/\/www.compdigitec.com\/labs\/2014\/07\/13\/reverse-engineering-the-fischertechnik-blinker\/","title":{"rendered":"Reverse engineering the Fischertechnik blinker"},"content":{"rendered":"

The Fischertechnik blinker comes in a enclosed case with no other sensory\u00a0inputs with two wires, a yellow wire and a blue wire.<\/p>\n

\"The<\/a>

The Fischertechnik blinker<\/p><\/div>\n

As such, I reverse engineered the Fischertechnik blinker to understand how it\u00a0works through desoldering, a camera, and a lot of drawing on the GIMP.<\/p>\n

It turns out that the blinker is intended to be used like a switch in a\u00a0series circuit before a load, with the yellow lead being the positive end and\u00a0the blue lead being the negative end.<\/p>\n

\"Series<\/a>

Series circuit with FT blinker on mySTEM board<\/p><\/div>\n

The main idea here is that the board uses a 555 timer (555C EZ606 with\u00a0STMicroelectronics logo, surface-mounted) with fixed frequency (fixed R1, R2 and\u00a0C) in astable<\/b> mode to control a BSP 75N<\/b> MOSFET transistor.<\/p>\n

The power supply for the ICs is controlled in parallel with a diode and a\u00a0470\u03a9 resistor to protect the ICs, while the MOSFET controls the connection to\u00a0the other lead.<\/p>\n

It features an unknown-model fuse (VW UG4 GP613) on the emitter of the\u00a0transistor, presumably to protect the circuit from excess.<\/p>\n

A diode and 100 \u00b5F capacitor cap are present, possibly to smooth out the\u00a0power input for the ICs during temporary dislocations. Considering that it is a\u00a0Fischertechnik component, its purpose is probably to ensure continued\u00a0reliability when it is handled roughly, shaken, and dropped by students.<\/p>\n

After complete disassembly:<\/b><\/p>\n

\"Fischertechnik<\/a>

Fischertechnik blinker, disassembled<\/p><\/div>\n

With traces and PCB features:<\/b><\/p>\n

\"Front<\/a>

Front view, with traces and PCB features<\/p><\/div>\n

\"Back<\/a>

Back view, with traces and PCB features<\/p><\/div>\n

Schematic:<\/b><\/p>\n

\"Fischertechnik<\/a>

Fischertechnik blinker schematic<\/p><\/div>\n

Since C is a generic-looking ceramic capacitor with no markings, its\u00a0capacitance was estimated by using the period.<\/p>\n

The light was measured to blink 100 times in 41.21 seconds, giving:
\n$$
\nT = 0.4121 \\text{s} \\\\
\nf = 2.426 \\text{s}^{-1}
\n$$<\/p>\n

Given R1 = 1 M\u03a9 and R2 = 1.2 M\u03a9 from above and f = 2.426, we can calculate C using the following equation:
\n$$
\nf = \\dfrac{1}{\\ln 2 * C * (R_1 + 2*R_2)}
\n$$<\/p>\n

C then works out to about 0.175 \u00b5F.<\/p>","protected":false},"excerpt":{"rendered":"

The Fischertechnik blinker comes in a enclosed case with no other sensory\u00a0inputs with two wires, a yellow wire and a blue wire. As such, I reverse engineered the Fischertechnik blinker to understand how it\u00a0works through desoldering, a camera, and a lot of drawing on the GIMP. It turns out that the blinker is intended to […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[948],"tags":[851,852,853,854,850,849,846,848,847],"_links":{"self":[{"href":"http:\/\/www.compdigitec.com\/labs\/wp-json\/wp\/v2\/posts\/375"}],"collection":[{"href":"http:\/\/www.compdigitec.com\/labs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.compdigitec.com\/labs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.compdigitec.com\/labs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.compdigitec.com\/labs\/wp-json\/wp\/v2\/comments?post=375"}],"version-history":[{"count":0,"href":"http:\/\/www.compdigitec.com\/labs\/wp-json\/wp\/v2\/posts\/375\/revisions"}],"wp:attachment":[{"href":"http:\/\/www.compdigitec.com\/labs\/wp-json\/wp\/v2\/media?parent=375"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.compdigitec.com\/labs\/wp-json\/wp\/v2\/categories?post=375"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.compdigitec.com\/labs\/wp-json\/wp\/v2\/tags?post=375"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}