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[physical.git] / misc / adjustable resistor / index.org

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+#+TITLE: Adjustable resistor / indicator
+#+AUTHOR: Svjatoslav Agejenko
+#+LANGUAGE: en
+
+* (document settings) :noexport:
+** use dark style for TWBS-HTML exporter
+#+HTML_HEAD: <link href="https://bootswatch.com/3/darkly/bootstrap.min.css" rel="stylesheet">
+#+HTML_HEAD: <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
+#+HTML_HEAD: <script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.5/js/bootstrap.min.js"></script>
+#+HTML_HEAD: <style type="text/css">
+#+HTML_HEAD:   footer {background-color: #111 !important;}
+#+HTML_HEAD:   pre {background-color: #111; color: #ccc;}
+#+HTML_HEAD: </style>
+
+* General
++ DISCLAIMER: I DO ELECTRONICS AND 3D DESIGN SOLELY AS A HOBBY. THERE
+  COULD BE ERRORS THAT CAN RESULT IN ALL KINDS OF DAMAGE. USE THESE
+  DESIGNS AT YOUR OWN RISK.
+
++ This design is released under Creative Commons Zero (CC0) license.
+
++ Author:
+  - Svjatoslav Agejenko
+    - Homepage: https://svjatoslav.eu
+    - Email: [[mailto://svjatoslav@svjatoslav.eu][svjatoslav@svjatoslav.eu]]
+
++ See also:
+  - [[../../index.html][Other physical projects in this repository]]
+  - [[https://www.svjatoslav.eu/projects/][Other projects hosted at svjatoslav.eu]]
+
+* Project description
+I needed a way to experimentally find resistance that works best in
+certain circuits. Usual potentiometers could not handle required power
+dissipation and were not precise enough.
+
+Solution is to build adjustable resistor:
+
+[[file:make.png]]
+
+Logically there is series of resistors that increase in resistance in
+the power of 2: 0.5, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512. Each
+resistor can be enabled or disabled by a switch. This makes entire
+range of 0 -- 1023.5 ohms available with the 0.5 ohms precision.
+
+Schematic:
+[[file:schematic.png]]
+
+Here is front panel for switches:
+[[file:front%20panel.png]]
+
+Download:
++ [[file:front%20panel.FCStd][FreeCAD project]]
++ [[file:front%20panel.stl][STL file]]
+
+Sometimes I would like to use lightbulbs with various parameters as
+test load/indicator. Current device has 4 of them included.
+
+Here is front panel for light bulbs:
+[[file:indicator%20panel.png]]
+
+Download:
++ [[file:indicator%20panel.FCStd][FreeCAD project]]
++ [[file:indicator%20panel.stl][STL file]]
+
+
+After assembly using prototype PCB:
+[[file:make,%202.png]]
+
+
+Following body is used as a case and PCB support:
+[[file:body.png]]
+
+Download:
++ [[file:body%20and%20back%20cover.FCStd][FreeCAD project (body + back cover)]]
++ [[file:body.stl][STL file for body]]
+
+Result:
+[[file:make,%203.png]]
+
+Cover on the back:
+[[file:back%20cover.png]]
+
+Download: [[file:back%20cover.stl][STL file]]
+
+Button covers:
+[[file:button.png]]
+
+Download:
++ [[file:button.FCStd][FreeCAD project]]
++ [[file:button.stl][STL file]]