#+TITLE: Adjustable resistor / indicator
#+AUTHOR: Svjatoslav Agejenko
#+LANGUAGE: en
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* 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]]