Circuit with Relay

Relays are used for a few things, controlling large voltage with small voltage, isolation, and in old school electronics they were used as for logic devices. Some examples of controlling large voltages with small ones might be 5vdc passing through the coil, to energize the relay so it can say pass 12 vdc through it. Another instance would be having a 28 vdc signal to energize the relay so 440 vac could pass through (this is known as a contactor). For isolation there are a few examples to use them for, say you want a low voltage to turn on a high voltage motor, or you want a 5 vdc signal to control a different 5 vdc signal that runs a motor or anything that would create noise. This set up would require two different power supplies but it would keep the control voltage power supply from having noise induced into it. The final use for them is in old logic circuits. This is before transistors were common and relays were used. It was very slow, but there was never any leak by current like you get in a transistor. A relay is either on or off, but they use more energy in order to turn on. Relays are still used a lot today, just not in the logic sense. If you have a plasma tv and you turn it on, it takes a second, then you hear a click and your display turns on, that's the relay energizing to power the display. Also used in your washing machine and in ac systems. Hope this helps and it's not just information overload.

Justin - Yes, you made sense, thank and that is what I thought like tv remote to turn on in seconds like Relay as you stated. Thank for information!