By now we should have a good understanding of how the inputs are used. Next up is the output circuits.

现在我们应该很好地理解了输入是如何使用的，接下来是输出电路。

One of the most common types of outputs available is the relay output. A relay can be used with both AC and DC loads. A load is simply a fancy word for whatever is connected to our outputs. We call it a load because we are "loading the output" with something. If we connected no load to the output (i.e. just connect it directly to a power supply) we would certainly damage the outputs. This would be similar to replacing the light bulb in the lamp you're using to read this with a piece of wire. If you did this, the lamp would draw a tremendous amount of current from the outlet and certainly pop your circuit breaker or blow your fuse or your brains. (Take our word. Please don't try it! Extremely dangerous!)

继电器输出是最常见的输出类型之一。继电器可用于交流和直流负载。负载只是与我们的输出相连接的任何东西的一个花哨的叫法。我们称它为负载，因为我们正在用一些东西“加载输出”。如果我们把空载连接到输出（即直接连接到电源），我们肯定会损坏输出，这就像用一根电线代替你用来阅读这篇文章的灯泡（即直接用电线连接输出点和电源），如果你这样做，电路中将产生大量的电流，肯定会击穿你的断路器、保险丝或使你的大脑短路（相信我们的话！请不要尝试！极其危险！）。

Some common forms of a load are a solenoid, lamp, motor, etc. These "loads" come in all sizes. Electrical sizes, that is. Always check the specifications of your load before connecting it to the plc output. You always want to make sure that the maximum current it will consume is within the specifications of the plc output. If it is not within the specifications (i.e. draws too much current) it will probably damage the output. When in doubt, double check with the manufacturer to see if it can be connected without potential damage.

负载的一些常见形式是线圈、灯、电机等，这些“负载”大小不一，有各种不同的电性能。在将负载连接到PLC输出之前，一定要检查负载的规格。您总是希望确保它所消耗的最大电流在PLC输出的规格范围内。如果它不在规格范围内(即产生太大的电流)，它可能会损坏输出。当有疑问时，一定要与制造商再次检查，看看它是否可以连接且没有潜在的损害风险。

Some types of loads are very deceiving. These deceiving loads are called "inductive loads". These have a tendency to deliver a "back current" when they turn on. This back current is like a voltage spike coming through the system.

有些类型的负载具有很强的欺骗性，这些欺骗性的负载被称为“感应负载”，当它们通电时，会产生一种“反向电流”，这个反向电流就像通过系统的电压峰值（有可能对系统参数危害）。

A good example of an inductive load that most of us see about 6 months per year is an air conditioning unit. Perhaps in your home you have an air conditioner. (unless you live in the arctic you probably do!) Have you ever noticed that when the air conditioner "kicks on" the lights dim for a second or two. Then they return to their normal brightness. This is because when the air conditioner turns on it tries to draw a lot of current through your wiring system. After this initial "kick" it requires less current and the lights go back to normal. This could be dangerous to your PLCs output relays. It can be estimated that this kick is about 30 times the rated current of the load. Typically a diode, varistor, or other "snubber" circuit should be used to help combat any damage to the relay. Enough said. Let's see how we can use these outputs in the "real plc world".

一个很好的感应负载的例子是我们大多数人每年大约要用6个月的空调机组，也许你家里有空调（除非你住在北极，否则你很可能有空调！）。你有没有注意到，当空调“启动”时，灯光会变暗一两秒，然后它们又恢复到正常的亮度，这是因为当空调开启的瞬间，电路里会产生大量的电流，但在空调正常启动之后，它仅需要更少的电流来保证运转，所以灯又回到了正常的亮度。这可能会对你的PLC输出继电器造成危险。据估计，这个冲击大约是负载额定电流的30倍。通常，二极管、压敏电阻或其他“缓冲”电路应有助于防止继电器的任何损坏。无需多言，让我们看看如何在“真实的plc世界”中使用这些来改善输出质量。

Shown above is a typical method of connecting our outputs to the plc relays. Although our diagram shows the output connected to an AC supply, DC can be used as well. A relay is non-polarized and typically it can switch either AC or DC. Here the common is connected to one end of our power supply and the other end of the supply is connected to the load. The other half of our load gets connected to the actual plc output you have designated within your ladder program.

上图显示的是我们将负载连接到继电器输出型的PLC输出端的典型方法。虽然我们的图中显示的输出连接的是交流电源，直流也可以使用。继电器是没有极性的，通常它可以接交流也可以接直流。这里的公共端连接到电源的一端，而电源的另一端连接到负载的一端，负载的另一端连接到您在梯形程序中指定的实际PLC的输出点。

The relay is internal to the plc. Its circuit diagram typically looks like that shown above. When our ladder diagram tells the output to turn on, the plc will internally apply a voltage to the relay coil. This voltage will allow the proper contact to close. When the contact closes, an external current is allowed to flow through our external circuit. When the ladder diagram tells the plc to turn off the output, it will simply remove the voltage from the internal circuit thereby enabling the output contact to release. Our load will than have an open circuit and will therefore be off. Simple, isn't it?

所谓的继电器输出，其继电器位于PLC内部。它的电路图通常与上图所示类似。当我们的梯形图告诉输出打开，PLC将在内部施加电压到继电器线圈，这个电压将使对应的触点闭合，当触点闭合时，外部电流就可以流入我们的外部电路；当梯形图告诉PLC断开输出时，它只需要从内部电路中移除电压，从而使对应的输出触点释放，我们的负载回路就会断开。是不是很简单？