Although the silicon controlled rectifier or SCR has been around since 1957, it doesn’t get nearly the love an ordinary transistor does. That’s a shame because they are quite handy when it comes to controlling AC and DC voltages in things such as lamp dimmers, motor speed controllers, and even soldering iron temperature controllers. [Lewis Loflin] has a short video introduction that will help you get started with these devices.
One of the interesting properties of the device is that once you turn it on it will stay on until you do something specific to turn it back off — sort of, [Lewis] explains it in the video.
The video also has some practical advice for prototyping with cheap devices. He also talks about SCR optocouplers and there are some that are light sensitive, as well. You often hear these devices mentioned along with TRIACs, a TRIAC is very similar but unlike the SCR it can pass current in both directions once it turns on. It’s a surprise to learn that SCR is a specific trade name for the device which is technically a type of thyristor. We always think that the terms are synonymous, but some people think that all SCRs are thyristors but not all thyristors are SCRs.