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Hi, and welcome.

 

This attempts to be a free-form, (sometimes) co-hosted podcast about tech-oriented hobby-projects. Do not proceed if you're looking for a high-quality production. However, if you enjoy friendly chatter, read on.

 

On a semi-weekly basis, Michai talks about software, electronics and mechanical engineering from a hands-on point of view. Most of the time, that means giving excuses for not having done any work at all.

 

Apr 8, 2018

(First of all, apologies for the many "uhhh"s and "ummm"s you can hear - no idea what was going on there. Edited out a lot, and next time it should be better.)

Topics this time are my effort so far for the RetroChallenge 2018/04 (25% in), a short and biased discussion of some available handheld oscilloscopes, disassembling consumer-scales to see what was going on inside, hacking together a small digital probe to distinguish high/low/floating pins, and blowing a fuse while poking at electronics. 

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Links/show-notes, in that order:

W.r.t the blown fuse: I made the rookie mistake of connecting probe-ground to something main-referenced (but not earth)... #makeagoodfirstimpression

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Some pics of scales-disassembly:

load-sensor mounted in one of the scales' 4 feet

(load-sensor mounted in one of the scales' 4 feet)

strain-gauge element (?) embedded in metal spring-thing

(strain-gauge element (?) embedded in metal spring-thing)

Note that when the metal thing is flexed, both "halves" of the element would decrease in resistance - a few hundred Ohms when flexing them by hand. That's why I don't understand why there were 3 wires bonded to this thing. Why not use 2? (From what I read and discussed with a friend, one "half" would ideally have to have a constant or at least less-decreasing-when-flexed resistance, to be used in a Wheatstone bridge.)

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Schematic and pics of the digital probe:

schematic

probe

 probe in a blob of hot-glue

(probe in a blob of hot-glue)