What's Best - A Solid State Relay Or An Electromechanical Relay? If not for relays, numerous electronic devices that are used today wouldn't be possible. In their simplest form, relays are electronically controlled switches. They're most often used in cases where large voltages need to be turned on or off through a smaller, lower-powered control signal. For instance, a lot of the electric functions in a car are controlled by relays. This permits the sensors to operate with less current than the full power of the car’s 12-volt battery, making them far better to operate. Solid state and electromechanical will be the two most popular kinds of relays. Each kind has its advantages and disadvantages, and it is important to know about each kind before choosing which to use. Utilizing a solid state relay in times calling for an electromechanical relay, or the other way around, can lead to failure of the system, but most importantly, could cause an unsafe situation. A solid state relay, or SSR, operates by utilizing a low power sensor to manage a larger load circuit. It has no moving parts, which may be an advantage over an electromechanical relay (EMR). For this reason, SSRs are incredibly quiet to operate, and will likely outlive any comparable EMR under normal operating circumstances. SSRs are around to work over a very large range of voltages and currents, and usually feature a “zero-voltage crossover." This means that when the circuit switches on or off, there's no voltage surge, which is useful for sensitive equipment. Instead of using semiconductors, electromagnetic relays use a coil of wire with a movable switching device inserted in it. When the coil is energized, the magnetic field created within it causes the switching element to make or break connection with the circuit it is controlling. As a result of the moving parts in an EMR, it carries a limited lifespan. This could be something you need to think about when choosing whether or not to use one, based on the relative lifespan of the equipment being controlled. An EMR can certainly make some noise when turning on and off unlike a solid state relay - both electrically and physically. It will arc once an EMR breaks contact with a circuit and produce electrical interference with all devices in the area sensitive to RF interference. Solid state relays will have some disadvantages. One of the disadvantages is that they are never completely on or off - even when it's off, there'll be a small voltage present that may affect sensitive equipment. Electromagnetic relays are totally open when off, so there is no voltage leakage across the poles. Plus, they have a very big resistance when the SSRs are on. This necessitates the use of a massive heat sink to dissolve the resulting heat. On the other hand, EMRs have a very low resistance, so no heat sink is needed. The SSRs can be very unpredictable if they fail. They generally fail by shorting out, which can cause serious problems down the road. EMRs will normally fail in the coil that may simply cause a break in the circuitry, safeguarding the equipment. The most critical aspect to bear in mind about the two types of relays is never attempt to adapt one to a use that'll be better suited for the other. Actually, neither kind will be better suited to use all the time - every one just has their own pros and cons. Choosing the right kind will guarantee
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