the required control output type and any load or polarity restrictions.<\/li>\n<\/ol>\nThen compare those details with the PLC output or relay contact in the machine. A controller output that can energize one channel is not automatically suitable for a multi-color assembly. The selection must include the output\u2019s voltage, current, sourcing or sinking arrangement, off-state behavior, and any suppression or diagnostic circuit. If the output type is uncertain, resolve that with the controller manufacturer or a qualified controls engineer before wiring.<\/p>\n
Use standards as a framework for indication design<\/h2>\n IEC 60073 describes coding principles for indicators and actuators, and IEC 61310-1 addresses visual, acoustic, and tactile methods for safety-related information at the human-machine interface. These standards are a reason to treat indication as part of machine design, not as a decorative color choice. Their scope does not mean that a generic online color chart can replace the full standard, a risk assessment, or applicable machine requirements.<\/p>\n
Document the meaning of the selected colors in the machine\u2019s operating instructions and electrical drawings. Where a signal is safety-related, verify the full design against the machinery requirements that apply to the equipment and installation location. This article does not assign a universal meaning to red, green, blue, or any other color.<\/p>\n
A single tricolor indicator can save panel area, but it concentrates multiple meanings in one point. Separate lights may be easier to read when conditions can occur at the same time. For example, if \u201cmachine running\u201d and \u201cservice due\u201d may both be true, a one-color-at-a-time device may hide one of the conditions unless the control logic provides another display.<\/p>\n
Ask whether the states are mutually exclusive. If they are not, decide how priority is shown. A higher-priority alarm may need its own indicator or audible signal instead of replacing the normal status light. If operators must read the panel from a distance, separate position and a short label can be easier to interpret than a small light cycling through colors.<\/p>\n
The physical layout also matters. Keep the indicator within the normal operator sightline, avoid placing it behind a door or handle, and check it at realistic viewing distances. Review the intended panel cutout, mounting depth, nut access, and neighboring components. A compact round illuminated push button can integrate indication with an operator control, but do not assume that the button\u2019s electrical contacts and the lamp are the same circuit.<\/p>\nDefine the operating states and operator response before choosing a two- or three-color indicator.<\/figcaption><\/figure>\nCommission every state and transition<\/h2>\n Commissioning should confirm not only that each color can turn on, but that the machine reaches the intended color for each defined condition. Create a short test matrix with the process state, controller command, observed light, and expected operator response. Include startup, stop, fault, recovery, and power restoration.<\/p>\n
Test one command at a time first. Then test invalid combinations, such as two color commands asserted together, if the hardware or control logic could permit them. Confirm whether the indicator goes dark, displays one priority color, or behaves in another documented way. Do not assume the result from the product family name.<\/p>\n
Finally, ask an operator unfamiliar with the panel to interpret each indication using the label and instructions. If the operator has to guess, revise the state name, label, placement, or method of indication. A color-count decision is complete only when the meaning is clear in the real machine, not just in the drawing.<\/p>\n
Frequently asked questions<\/h2>\nIs a tricolor indicator always better than a bicolor light?<\/h3>\n No. Use a third color only when it communicates a distinct condition that operators need. If there are only two useful states, the added color may complicate drawings, control logic, and operator instructions without improving the interface.<\/p>\n
Not necessarily. Internal design and terminal arrangement vary by product. Confirm the wiring diagram and exact model; never derive terminal count from a front-view image.<\/p>\n
Can the three colors be used to mean the same thing on every machine?<\/h3>\n Do not assume a universal mapping. Color coding should follow the applicable standards and the machine\u2019s documented operating design. Check the full requirements for the equipment and market.<\/p>\n
Can two colors be on at the same time?<\/h3>\n Only the exact product documentation and the designed circuit can answer that. If simultaneous commands are possible, test the result and define an intentional priority or invalid-state response.<\/p>\n
Should the indicator replace a text or alarm message?<\/h3>\n Not by default. A light is useful for quick status recognition, but a safety-related or complex condition may need additional text, position, sound, or machine-specific instructions.<\/p>\n
Educational video<\/h2>\n The following PLC lesson shows how indicator outputs can represent defined machine states and why state logic should remain understandable. It is an educational example, not a universal color code or a wiring diagram for a particular ONPOW model.<\/p>\n