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These days, one machine often performs multiple functions. Humans control the machine, initiating changes based on work assignments or advancing the machine to the next step of the process. This is where pushbuttons come in. Through pushbuttons, workers can interact with the machine’s operation.
Let’s look at examples of what people typically mean when they say “pushbutton.” The part that you can see or adjust on the front of the panel is called the operator
. Here are four common operators:
Figure 2. Four Common Operators
Selector Switch
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Pushbutton
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Key Selector Switch
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Indicating Light
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At the back of the panel, you’ll find contact blocks
and light units
. As the operator is activated, the contact block “makes” the electrical circuit, and the machine starts, stops, or runs in the manner that the worker has selected. If the pushbutton is an indicating light, the lamp lights to signal what stage the machine is in.
Figure 3. Back of Panel
Contact Block
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Light Unit
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When you select a pushbutton from the wide variety available, you make choices that help a customer accomplish specific goals
, such as:
- keeping machines off when power has been restored after a power outage. This allows a worker to manually—and safely—turn the machines back on when the time is right.
- providing the longest lasting indicating lights for important indications and to save labor replacement expenses.
Remember that indicating lights are part of the pushbutton family.
Setting a selector switch, or pushing a button, is what workers do to tell the machine how to operate. Indicating lights tell the worker what the machine is doing (or failing to do).
You can think of pushbuttons and selector switches as being the light switch in your kitchen; they are where you make the decision to turn the light on. Indicating lights are simply the light that turns on. When the light is connected to a machine process, and the light is on, the machine is telling you that it’s working.
Figure 4. Pushbuttons are How Workers Interact with Machines
Workers push or select a button to tell the machine what to do.
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The machine lights an indicating light to tell the worker what it has done.
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What Is a Stacklight?
Stacklights
are a special form of indicating light. They are not lights mounted on the face of a panel for a single operator. Instead, stacklights are a mini-tower of independent lights usually mounted on top of a machine.
Because stacklights are towers, they can be seen from all directions (360°). This way, workers from every angle can see the machine's status.
Workers know what the machine is doing by checking either the position or the color
of the lights that are lit.
Stacklights can also provide an audio alarm and/or a strobe light signal.
Figure 5. Stacklight
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