math’s notes: “Tricks” with Relays

Irwin Math, WA2NDM

Most of us are familiar with the electromagnetic relay and I am sure many of us have used one or more at some time. There are several “tricks” that can be used to make these a bit more applicable to many tasks and I would like to describe a few this month. A relay consists of a coil and a set of contacts that can range from a single normally-open or normally-closed to a combination of many different configurations. The coil can be activated by DC or AC, depending on the particular model. Regardless of which type, you apply power to the coil and the contacts pull in. So much for basics. Relay coils all have operating voltages and, while these are nominal “normal” values, most relays will pull in…

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CQ Amateur Radio (Digital) - 1 Issue, November 2015

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