Instructables

What is this mystery electronic component?

I bought an assortment of components: resistors, diodes, capacitors, all mixed together on about a meter of cut tape from a reel for an automatic PCB populating machine. The original reel was marked as surplus from DEC and looks to be about 20 years old. One of the components is this black cylinder, like a very fat resistor, about 5 mm long and 3mm diameter. No resistance or diode action. Brittle and crack off with a pliers like ferrite. They do not melt or burn with a candle flame. The wire lead goes straight through and out the other side. Can be picked up by a magnet, but are not themselves magnets. They have no markings of any kind, but have shiny flecks. Are they some kind of magnetic tape position marker to tell the insertion machine what component is next? Say like a binary code?

Picture of What is this mystery electronic component?
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wware4 years ago
I think they're just ferrites, as you surmised. The metal around the wire is of high permeability so you get a lot of B field for the H field you create by running a current through the wire, making it a good inductor that blocks high frequencies.
http://en.wikipedia.org/wiki/Ferrite_bead
http://en.wikipedia.org/wiki/Permeability_(electromagnetism)
NachoMahma4 years ago
.  Wow! Fantastic question.
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Seconded! I was gonna feature it, someone beat me to it!