Truthfully, the GFCI may only shut off when there is a current leak across a connection to ground - and not an over-current condition. When the outlet detects an abnormal amount of current, it assumes that a large amount of potentially fatal current is flowing through your body, and therefore switches off - saving you and your project. It's the type of outlet you'll find near anything that outputs water (kitchen sinks, batchroom tubs, etc). A normal outlet costs $0.59 - but I went for the $10 GFCI. Please notice that we are using a Ground Fault Circuit Interrupter (GFCI) Outlet and not a normal outlet. Thick 3-wire type extension cord, 8 feet (2-wire cords will not work) ($7).The goal is the get a GFCI outlet into some sort of a housing, with a power cord, the relay, and control circuitry. If you need don't use a relay rated for instead use a bigger one (such as Remember, power = current * voltage so a relay can handle up to a 6,000W device (two hair dryers). Like we do with capacitors, we under-rate the relay so that we mitigate the risk of relay failure. Obviously this would be very bad on many levels. If these sparks get large enough, you can actually spot weld the movable paddle to stationary paddle causing the relay to fail, potentially in the 'on' position. When the voltage/current becomes large enough, there will be sparks inside the relay as you switch the paddles.
I have heard reports that the relay will begin to heat up. What happens if you violate this limit? I have thankfully never been in that situation. It can handle a lot of power - 30A at 220VAC. The relay that we will be working with, in this tutorial, is a beefcake in my opinion. A relay can be used to control a DC motor, or an AC lamp. The paddles are capable of carrying very large currents. If you have 120VAC running through the paddles, you don't have to worry about that 120VAC sneaking back into and vaporizing your microcontroller (connected to the coil). It is important to note the coil is physically isolated from the paddles. So you see, controlling the low-power coil allows us to actually control quite a lot of power! The coil requires a small amount of power (5VDC 80mA). If you send current through the coil, a magnetic force is created, which pulls on the steel paddle causing it to move (flip) and touch the copper paddle - as if you flipped a light switch. This is basically a small electro-magnet. The other half the relay is called the coil. When these paddles touch (the closed switch state), they are capable of allowing a large amount of power to flow - like (huge!). The other paddle is made of copper and stationary.
#Arduino relay power strip free
One paddle is made of a ferrous material like steel and is free to move. Inside the relay are two paddles made of metal.
In this example we are going to talk about the simplest version of a relay.
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