2/26/2023 0 Comments 24 volt photo sense relay switchThe energized electromagnet pulls the metal bar in the output circuit toward it, closing the switch and allowing a much bigger current to flow through the output circuit.When a small current flows in the input circuit, it activates the electromagnet (shown here as a dark blue coil), which produces a magnetic field all around it.The output circuit (red loop) is also switched off. The input circuit (blue loop) is switched off and no current flows through it until something (either a sensor or a switch closing) turns it on.The relatively smallĬurrent in the input circuit thus activates the larger current in the When this circuit is activated, it feedsĬurrent to an electromagnet that pulls a metal switch closed andĪctivates the second, output circuit (on the right side). On the left side, there's an input circuit powered by a switch It's essentially the same thing drawn in a slightly different way. Here's another animation showing how a relay links two circuits Normally open relays are the most common. Other relays are "normally closed" (NC the contacts are connected so a current flows through them by default) and switch off only when the magnet is activated, pulling or pushing the contacts apart. This is an example of a "normally open" (NO) relay: the contacts in the second circuit are not connected by default, and switch on only when a current flows through the magnet. When the power is switched off, a spring pulls the contact back up to its original position, switching the second circuit off again. When power flows through the first circuit (1), it activates the electromagnet (brown), generating a magnetic field (blue) that attracts a contact (red) and activates the second circuit (2). Here are two simple animations illustrating how relays use one circuit to switch on a second circuit. This is how relays work: they use a small electric current to trigger a much bigger one. It wouldn't be much use as a guard dog! But what if you bought a small, very alert dog as well? If the small dog heard a noise, it would start barking and wake the big dog, which could then attack an intruder. (turning things on and off) or as amplifiers (converting smallĪrtwork: If relays were dogs: Suppose you had a huge, ferocious dog that slept so soundly it never woke up when it heard a noise. That means relays can work either as switches Relays bridge the gap, making it possible for smallĬurrents to activate larger ones. Often we need them to drive bigger pieces of apparatus that useīigger currents. Suggests, many sensors are incredibly sensitive pieces ofĮlectronic equipment and produce only small electric currents. Switch it on with a tiny current and it switches on ("leverages") another appliance Temporary magnet when electricity flows through it). The heart of a relay is an electromagnet (a coil of wire that becomes a Small electric current that can turn on or off a much larger electric That allows a very much bigger current to flow through the spring contacts to power the element that heats the hot water.Ī relay is an electromagnetic switch operated by a relatively The electronic circuit in the programmer switches the magnet on or off at preprogrammed times of day using a relatively small current. This is a relay from an electronic, hot-water immersion heater programmer. The magnet pushes a switch to the left, forcing the spring contacts together, and completing the circuit they're attached to. In this relay, when a current flows through the coil, it turns it into an electromagnet. You can see the two spring contacts on the left and the electromagnet coil (the red-brown copper-colored cylinder) on the right. Photo: A typical relay with its plastic outer case removed. Let's take a closer look at how they work! Off in a fraction of a second using clever magnetic switches called Same trick at work in all kinds of machines and electricalĪppliances, where sensors are ready to switch things on or Is provoking a much bigger and more useful response. What's happening here is that a tiny stimulus Your eyelashes will send a signal to your brain that make yourĮyelids clamp shut in a flash-fast enough to Tool, for example, and a tiny wood chip flies toward your eye, one of Slightest danger threatens your existence. Of evolution have primed your brain to save your skin when the You might not realize it, but you're constantly on-guard, watching out for threats, ready to act at a moment's notice.
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