This one came about as I was soldering some other circuit together. As I am a bit ham-handed with a soldering iron, I tend to make solder bridges where there shouldn't be any, so while working I am constantly checking continuity (or lack thereof) between neighbouring contacts. I got a bit tired of having to break out a multimeter, plug in the leads, set it to continuity and then fight with the long leads and probes hanging in my way.
....................................................
So I decided to build something quick and dirty. Design parameters (such as there are for such a small project) were:
- battery powered
- always on - no on/off switches or anything
- light weight
- smallish
This is what I came up with - a dead simple 555 based oscillator driving a small piezo buzzer:
The low side switching transistor is biased so that a resistance between the probes of lower than 150 ohm or so turns it on, sounding the buzzer.
Cobbled together it looks like this:
Simple, maybe too simple, but it has served me well several times already.
....................................................
So I decided to build something quick and dirty. Design parameters (such as there are for such a small project) were:
- battery powered
- always on - no on/off switches or anything
- light weight
- smallish
This is what I came up with - a dead simple 555 based oscillator driving a small piezo buzzer:
The low side switching transistor is biased so that a resistance between the probes of lower than 150 ohm or so turns it on, sounding the buzzer.
Cobbled together it looks like this:
Simple, maybe too simple, but it has served me well several times already.
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