How an Optocoupler Works, and How to Use Them -- DC to Daylight 17

In this episode we look at the optocoupler or optoisolator as it's also known. This little device is great at isolating voltage and noise from one circuit to another, and it can even be used to translate voltage levels. We'll dive into how to go about biasing both the input and output of the optocoupler. Then we'll breadboard a demonstration circuit, including use of a schmitt trigger to give our circuit a snappier response time, and also look at the results on an oscilloscope.

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beacon_dave over 2 years ago

I can recall from teardowns of 1950s/60s office dictation equipment, finding LDRs close-coupled with incandescent torch bulbs. They were contained in a light-tight Bakelite housing that was held together with a spring clip allowing you to replace the light bulb.

Presumably a predecessor to the Vactrol device?
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beacon_dave over 2 years ago

I can recall from teardowns of 1950s/60s office dictation equipment, finding LDRs close-coupled with incandescent torch bulbs. They were contained in a light-tight Bakelite housing that was held together with a spring clip allowing you to replace the light bulb.

Presumably a predecessor to the Vactrol device?
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Derek (DCtoDaylight) over 2 years ago in reply to beacon_dave

Interesting. I wonder what their purpose was... maybe in some kind of compressor circuit to prevent overdriving an audio stage, or maybe to limit the current going to the write head of a tape? Bakelite definitely dates it to that era - I had an old bakelite Simpson voltmeter, that I unfortunately had to retire, being dropped too many times. Fragile stuff that bakelite.
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