Electronic – Are there “inverted relays”

relay

I'm a total beginner with circuitry, but for thinking through a project for I want to build as a hobby some day, I'd need an "inverted relay."

A relay is, from my understanding this:

I have a main powerline that I either want on or off, and I want to control whether this is on or off by sending little bit of power through another powerline (i.e a control wire, e.g. controlled from a yes-no-switch). It's on when there is electricity in the control wire and off when not.

Now, I'd need something that breaks the current in the main line if it's set.

I can imagine that this very well exists, but through my lack of knowledge in this field I'm missing the correct terminology to google this properly.

So what's this name if such a component exists?

Best Answer

schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. A typical relay circuit.

How it works:

  • A control signal, 12 V in Figure 1a, and a small switch is used to power the relay coil.
  • The relay coil pulls the contact across from the NC (normally closed) contact to the NO (normally open) contact. Mains power can then flow to the lamp.

Alternatively the lamp could be fed from the NC contact as shown in Figure 1b. In this configuration SW1 turning on will turn off the lamp.

When specifying the relay you choose the coil voltage, the contact rating (both voltage rating, current rating and DC or AC) and the contact type - a changeover contact is shown in Figure 1.

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