Electronics > Projects, Designs, and Technical Stuff
Yet another resistance decade box
Blastcap:
--- Quote from: ez24 on August 05, 2016, 07:38:49 pm ---Can I ask how are you going to cut square holes for the switch.
FYI this message is the first one I have seen with its own scroll bar because of the link
--- End quote ---
Depending on the tools available, CNC milled would be the most elegant overkill solution.
Make a cardboard prototype, to ensure you have the right cutout, and everything fits, then mark the cutout on the faceplate, and drill a hole in each corner. Cut the lines between with a Dremel or other tool.
Then with a square jeweler's file, make the corners... square.
Finish by chamfering the edges slightly with a file or sandpaper so you won't cut yourself.
Mount, and enjoy.
If done right, everything will snap into place and fit snugly, and there will be no need for "hotsnot" or other adhesive.
all_repair:
KM3 still with SMT resistor but no protruding PCB and a provision to tap out 2 resistance end point. Just end-cap and hole on end-cap for connection, and no need for ENCLOSURE. possibile?
Alex Nikitin:
I've measured the relative error (for each value in each decade, the rest set to zero, and the "zero" resistance, 0.5 Ohm, subtracted) of my two 4-decade assemblies (built using MELF 0.1% resistors) on HP3458A. One unit (D0) uses selected resistors, the second (D1) - the rest. As an afterthought - it is possible to get a better relative error by measuring the resistors and arranging them in a certain way (placing the lowest error resistor as the first in the decade, and then go for the resistor giving the lowest error for the sum of the first two and so on, as the weight of the absolute error is diminishing for each next resistor). Next time I'll try that approach.
Cheers
Alex
bitseeker:
Hi Alex,
Thanks for sharing your measurements. I was also planning on arranging my resistors as you described toward the end of your post (lowest error for 1, next-lowest for 2, etc.).
Blastcap:
--- Quote from: Blastcap on August 02, 2016, 01:20:38 pm ---Doing some last minute shopping, could anyone confirm that these will fit?
http://www.mouser.de/ProductDetail/CHERRY/PBC1-E015/
Its a 10 pack from "Cherry", they can't be too bad.
--- End quote ---
Just a heads up, i went to mouser and got one of these, convinced it was a row of 10 pcs.
Nop... 1 segment with 10 positions... for 8,42€.
After a lot of force i got the board out (cherry glued it in), and mounted one of Fortran's (beautiful little boards) with the 100 ohm range.
It fits mechanically, but the displayed number doesn't line up with the value and the numbering is in the reverse order. Also for some reason it had three positions where I suddenly got it fluctuating from 2K to 6M ohm, really strange.
Buttom line... won't work. Don't waste 50€ on a set of these.
So anyone know where i can get some usable switches within the EU so i don't have to wait 6 weeks?
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