1 #+TITLE: Adjustable resistor / indicator
2 #+AUTHOR: Svjatoslav Agejenko
5 * (document settings) :noexport:
6 ** use dark style for TWBS-HTML exporter
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16 + DISCLAIMER: I DO ELECTRONICS AND 3D DESIGN SOLELY AS A HOBBY. THERE
17 COULD BE ERRORS THAT CAN RESULT IN ALL KINDS OF DAMAGE. USE THESE
18 DESIGNS AT YOUR OWN RISK.
20 + This design is released under Creative Commons Zero (CC0) license.
24 - Homepage: https://svjatoslav.eu
25 - Email: [[mailto://svjatoslav@svjatoslav.eu][svjatoslav@svjatoslav.eu]]
28 - [[../../index.html][Other physical projects in this repository]]
29 - [[https://www.svjatoslav.eu/projects/][Other projects hosted at svjatoslav.eu]]
32 I needed a way to experimentally find resistance that works best in
33 certain circuits. Usual potentiometers could not handle required power
34 dissipation and were not precise enough.
36 Solution is to build adjustable resistor:
40 Logically there is series of resistors that increase in resistance in
41 the power of 2: 0.5, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512. Each
42 resistor can be enabled or disabled by a switch. This makes entire
43 range of 0 -- 1023.5 ohms available with the 0.5 ohms precision.
46 [[file:schematic.png]]
48 Here is front panel for switches:
49 [[file:front%20panel.png]]
52 + [[file:front%20panel.FCStd][FreeCAD project]]
53 + [[file:front%20panel.stl][STL file]]
55 Sometimes I would like to use lightbulbs with various parameters as
56 test load/indicator. Current device has 4 of them included.
58 Here is front panel for light bulbs:
59 [[file:indicator%20panel.png]]
62 + [[file:indicator%20panel.FCStd][FreeCAD project]]
63 + [[file:indicator%20panel.stl][STL file]]
66 After assembly using prototype PCB:
67 [[file:make,%202.png]]
70 Following body is used as a case and PCB support:
74 + [[file:body%20and%20back%20cover.FCStd][FreeCAD project (body + back cover)]]
75 + [[file:body.stl][STL file for body]]
78 [[file:make,%203.png]]
81 [[file:back%20cover.png]]
83 Download: [[file:back%20cover.stl][STL file]]
89 + [[file:button.FCStd][FreeCAD project]]
90 + [[file:button.stl][STL file]]