Electronics > Projects, Designs, and Technical Stuff

Yet another resistance decade box

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Fortran:
So I've looked in to it.

I would be able to offer a set of Vishay Dale CRCW resistors for an additional ~$0.80.
That's for 6 values from 1R to 100K, 10 of each. Quick specs are 1/4W, ±1%, ±100ppm/°C.
And you don't need to buy in groups of 6. Since I'm getting them V-scored I don't need to spend hours cutting boards, so buy whatever amount and value you like to match the number of switches you have.
I would have loved to be able to offer higher power and precision, but even though the price per set would still be reasonable, it adds up to amounts that would make my wallet cry.

So. ~$0.85 per blank board
or   ~$1.00 per blank board +10 resistors of either value.
I can populate a few for those who really need it.

Sound good?

matseng:
But 1% is really crappy... ;-(
How much more expensive would 0.1% be?

BravoV:
Count me in for 2 groups (12).

Fortran:
If I do a less bulky-ish order I can manage to get 0.1% on all but 1R. (Simply because I can't FIND any 1R 0.1%)
But picking on the poor 1R only being 1% is mean since contact resistance is probably more then that.

The lineup would then be Wishay Dale CRCW 1/4W, ±1%, ±100ppm/°C for 1R,
and Yageo RT 1/4W, ±0.1%, ±25ppm/°C for 10R-100K

I'm only capable of buying these in 100 quantity at a time though. 1000 quantity would mean about $750 upfront for resistors alone and that's just too much for me.
Due to the limited number of sets I'd prefer to sell all 6 values per order to keep an even stock. When all resistors are sold I can order 100 new ones and repeat as long as there is demand.

That would add up to $12.60 for 54 resistors. (No spare to drop under the bench never to see again)
Plus ~$5.10 for the boards and ~$2 for shipping gives a total of ~US$19.7 delivered. (Actual switch not included)

Dave:
I don't think 0.1% resistors would even make sense, because the contact resistance of the contacts would dominate the error in the lower ranges. You wouldn't use this sort of resistance box for any precision application, so 1% is more than good enough for the purpose.

Put me down for 6 boards. :-+

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