Adjustable resistor / indicator

• 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: svjatoslav@svjatoslav.eu
• See also:
  • Other physical projects in this repository
  • Other projects hosted at svjatoslav.eu

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:

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:

Here is front panel for switches:

Download:

• FreeCAD project
• 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:

Download:

• FreeCAD project
• STL file

After assembly using prototype PCB:

Following body is used as a case and PCB support:

Download:

• FreeCAD project (body + back cover)
• STL file for body

Result:

Cover on the back:

Download: STL file

Button covers:

Download:

• FreeCAD project
• STL file