beztlacitkova klavesnice


Posted on Feb 6, 2014

There are several applications in which a buttonless keyboard might be useful. In exteriors, they can capitalize on the fact that without buttons the keyboard can be fully closed and therefore it is weather resistant. Moreover, they seem to be easily made in vandalism resistant forms. Their considerable advantage also lies in the fact that they ca


beztlacitkova klavesnice
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n be made in various design conceptions. Usually, several approaches to the buttonless keyboards are practiced. In this paper a design of a simple optical-based keyboard is described. KlG vesnice bez mechanickG½ch tla G­tek mohou nalG©zt uplatn ›nG­ v nemG lo aplikacG­ch. V exteriG©rech t › G­ z toho, e je lze jednodu e vyrobit ve zcela uzav ™enG©m provedenG­, a tG­m pG dem odolnG© proti vliv m po asG­, p ™G­padn › i vandalismu. VneposlednG­ ™ad › je lze vyrG b ›t vr znG½ch designovG½ch provedenG­ch. Voblasti tG©to konstrukce tla G­tek existuje nemG lo p ™G­stup, p ™i em vtomto lG nku je popsG n nG vrh jednoduchG© a snadno sestrojitelnG© klG vesnice, kterG pracuje na optickG©m principu. The principle of operation of such optical push button is rather obvious. When a reflective object (a finger) moves close to the evanescent field, the light emitted by the LED is reflected into a photo sensor that drives the proper logical circuits. As stated in [1], this technology is rather new with only a few existing prototypes in this research field. The solution is based on a time division multiplex. The keyboard consists of 4 couples of LEDs and a photo sensor. The working period of the keyboard consists of 4 timeslots. In each of them only one LED is driven and when the appropriate button is activated, the logical circuit detects that one the light of which is being reflected to the photo sensor. A block diagram of this solution...




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