| Electronics > Projects, Designs, and Technical Stuff |
| Yet another resistance decade box |
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| julian1:
Thanks Fortran, boards arrived well, and look really nice! |
| Blastcap:
Thanks a lot Fortran! As everyone else is saying, the packaging was perfect and professional, shipping lightning fast. The boards are really nice, with a sexy blue stop mask. I had to file a little of edges of the board to make them fit, and the make the chamfering on the corners a little bigger, but that was probably because my thumbwheels had some molding errors. you can make a decent little decade resistance with those boards, and for our German viewers, here are the parts used to make it, and what it costs. 0,1% Kit from Frotran, 20€ https://www.eevblog.com/forum/projects/yet-another-resistance-decade-box/msg978465/#msg978465 Housing 1,76€ https://www.conrad.de/de/1423193-534346.html Bannana plug/Binding post 2x 1,72€ (= 3,44€) https://www.conrad.de/de/sicherungs-steckverbinder-schwarz-10-a-sci-1-st-732314.html Thumbwheels 4,29€ http://www.aliexpress.com/item/10pcs-Black-16mm-x-6mm-0-9-Digits-BCD-Code-Pushwheel-Thumbwheel-Switches-KM2/32698134731.html Total material cost for a 6-digit 0,1% Decade resistace: 29,49€ :wtf: At that price everyone should have one... or three. I know i'm going to build a bunch more. edit: Sorry for the messy workspace, i know, i know. A 1% box would end up costing only 15,49€! |
| Fortran:
Glad you like it :) A decent decade it is indeed. Not really professional, but for the price it's a lot of bang per buck. My first decade was made of similar switches but with the original boards, and 5% resistors. I'd be better off with a potentiometer and a multimeter :) I have been toying with the idea of bodging a trimmer across the first resistor on the first boards to improve performance a tad more. By reducing the contact resistance (of ONE board) (times TWO) on the 1R 10R and 100R setting, you would get an optimal performance at 111ohm. Simulations show that about 50xR trimmers put you somewhat right in the 50% zone they are delivered in. Over 1K, half an ohm of contact resistance doesn't matter (to me at least). Any opinions on that? Also.. since I still have a lot (lots and lots) of boards left and the 0.1% kits seems to be all the rage these days, I'm making another run on those. I need 10 kits booked to justify an order, so be sure to notify me if you want one. 1% kits are still available. |
| Blastcap:
How bout just having the 1st resistor on the 1 ohm range be a 0,5ohm? That would offset the contact resistance i've measured in mine to a reasonable precision. But i like your idea of a trimmer across the first. Stay tuned i might just order a buttload (that would be 20pcs) boards, and 1%'ers to play with, and do just that. |
| Fortran:
Well.. if you want 47 ohm then? or 150? 111 seems to be the best compromise between all ranges but I'm open to suggestions :) |
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