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Binary (additive) resistor or capacitor box
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eti:
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?
Ed.Kloonk:
Use a 8 position dip switch.

https://www.ato.com/8-position-dip-switch

The sub 10 ohm setting precision might drive you bonkers.
eti:

--- Quote from: Ed.Kloonk on December 11, 2022, 06:56:02 am ---Use a 8 position dip switch.

https://www.ato.com/8-position-dip-switch

The sub 10 ohm setting precision might drive you bonkers.

--- End quote ---

Hence me saying thumb wheels would be used. Yeah it would be a silly design to use DIP switches.
ledtester:
Teardown of a IET Decade Resistance Box at 3:00:

EEVblog #211 - IET Decade Resistance Substitution Box -- EEVblog
https://youtu.be/37gYHdY0DAM?t=3m

It 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.

Ed.Kloonk:

--- Quote from: ledtester on December 11, 2022, 07:52:38 am ---Teardown of a IET Decade Resistance Box at 3:00:



--- End quote ---

I had forgotten about that. Gee, you're resourceful.
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