Binary (additive) resistor or capacitor box - Page 1
Forum section: electronics / general

author: eti
author_rank: Super Contributor
timestamp: December 11, 2022, 05:09:43 am
content: Has anyone ever made a resistor or capacitor box (thumb wheel selectable increments) which works like this:[jumper 0 ohms] [1 ohm] [2 ohm ] [4 ohm] [8 ohm] [16 ohm] [32 ohm] [64 ohm] [128 ohm]You'd have all those resistance values and switch them in and out of series with the other resistors to additively create any ohmic value from 0 ohms to 255 ohms. To do the same for capacitors, you'd just switch the values in and out of parallel connection with the others.This is binary of course.I hardly think this could be a new thing I'd thought of. Ideas?

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: December 11, 2022, 06:56:02 am
content: Use a 8 position dip switch.https://www.ato.com/8-position-dip-switchThe sub 10 ohm setting precision might drive you bonkers.

author: eti
author_rank: Super Contributor
timestamp: December 11, 2022, 07:14:27 am
content: Quote from: Ed.Kloonk on December 11, 2022, 06:56:02 amHence me saying thumb wheels would be used. Yeah it would be a silly design to use DIP switches.

author: ledtester
author_rank: Super Contributor
timestamp: December 11, 2022, 07:52:38 am
content: Teardown of a IET Decade Resistance Box at 3:00:EEVblog #211 - IET Decade Resistance Substitution Box -- EEVbloghttps://youtu.be/37gYHdY0DAM?t=3mIt uses only 5 resistors per decade in a 1-2-2-2-2 pattern. It uses a custom wiper pattern to accomplish this.I recall there being a project discussed on the forum where a custom pcb was developed for an existing thumbwheel switch and then you could get that pcb manufactured at pcbway/jlc pcb/etc. to create some sort of substitution box -- can't seem to find it at the moment.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: December 11, 2022, 08:14:00 am
content: Quote from: ledtester on December 11, 2022, 07:52:38 amI had forgotten about that. Gee, you're resourceful.

author: Tigerwoods
author_rank: Contributor
timestamp: May 07, 2023, 04:57:09 am
content: For binary box better use relays to handle the switching, since there are 2^n combinations that beyond the capability of mechanical switch. Google "programmable resistance box" you may find such products.

author: Benta
author_rank: Super Contributor
timestamp: May 07, 2023, 07:40:57 pm
content: Quote from: eti on December 11, 2022, 05:09:43 amIt's an attractive idea, but the problem is that you'd need a thumbwheel switch that places the resistors in series. Never seen that.Your idea would place them in parallel.On the other hand, it would work for your capacitor box.

author: Zero999
author_rank: Super Contributor
timestamp: May 07, 2023, 09:00:56 pm
content: Just use a rotary switch for each decade.9 x 1R9 x 10R9 x 100Retc.By the way, the original poster has been banned. Is it worth keeping the thread alive?

author: Benta
author_rank: Super Contributor
timestamp: May 07, 2023, 09:13:56 pm
content: Quote from: Zero999 on May 07, 2023, 09:00:56 pmReally? Is that what the blue non-smiley indicates?

author: tooki
author_rank: Super Contributor
timestamp: May 08, 2023, 07:26:38 am
content: Quote from: Zero999 on May 07, 2023, 09:00:56 pmBased on the moderator’s comment added under the name, I guess the ban was for having multiple usernames, which is the only TOS violation they seem to enforce very diligently here. So maybe OP is still around under one of those other names.