Programmable Decade Resistor: Components

After being asked about some aspects of the mechanical design and components used a few times, I’d like to address those questions. I have to admit that I’m neither very good at the mechanical design, nor do I have a 3d printer (yet) or a shop where I can do metal work myself. That being said, I was still able to design a reasonably professional looking device and bring it to life with the help of modern prototyping services.

CaseELMA, Stylebox 15 Standard;
2 RU, 42HP (half 19″)
Probably fairly expensive when bought new
Front/Rear panels1.6mm Aluminium PCB with white solder mask and black silk screenDidn’t want to have a conductor left floating (potentially), so I removed the copper
New Rotary knob3d printed (MJF)Most pictures were taken with the old temporary knob
Push buttonsC&K/littlefuse PVA series switches with matching capsDifferent force ratings available
Line switchC&K NE18 series switchCan be a pain in the *** to design and print a connecting rod if the switch is located far back in the unit. I just used a thin wood rod and some tiny shaft coupling to connect the rod with the switch. Seems to work just fine. A 3d printed part would be more professional, no doubt about it
Red filter for displayColor filter, Red foil, 0.3mm; random amazon product; glued to the back of the front panelWorks surprisingly well, however it’s obviously not as strong as acrylic glas. Reminds me of the HP/Agilent 66xx series power supplies (and other products) with the thin foil covering their LCD displays. Wouldn’t like that for commercial use 😉
Components used in the programmable decade resistor

There will be a separate post where I explain the fairly straight forward process of designing the front and rear panels.




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