{"id":1612,"date":"2026-09-22T11:10:00","date_gmt":"2026-09-22T03:10:00","guid":{"rendered":"https:\/\/lemaele.com\/blog\/5-pin-push-button-led-wiring\/"},"modified":"2026-09-22T09:31:22","modified_gmt":"2026-09-22T01:31:22","slug":"5-pin-push-button-led-wiring","status":"publish","type":"post","link":"https:\/\/lemaele.com\/de\/blog\/5-pin-push-button-led-wiring\/","title":{"rendered":"Verdrahtung eines 5-Pin-Druckknopfschalters mit LED"},"content":{"rendered":"

A typical 5-pin illuminated push button contains two electrically separate parts: a three-terminal changeover switch marked COM, NO and NC, plus two lamp terminals.<\/strong> Wire and test those parts independently. With power isolated, identify COM\u2013NO and COM\u2013NC by continuity; then confirm the lamp\u2019s rated voltage and, for an LED, its polarity. Do not copy a color code or terminal position from another brand. The exact LEMA drawing and markings for the selected PBS variant must control the final connection.<\/p>\n

This guide explains the logic behind a 5-pin push button switch wiring diagram without presenting one terminal layout as universal. It covers momentary control, constant and switched illumination, PLC inputs, commissioning and the information an OEM should place on its drawing.<\/p>\n

Separate the contact circuit from the light circuit<\/h2>\n

The contact section is normally an SPDT changeover contact. COM is the moving common. At rest, COM is connected to NC and isolated from NO. When the mechanism is fully actuated, COM connects to NO and leaves NC. The two remaining terminals supply the lamp. Their voltage is not automatically the same as the load circuit, and an LED normally requires the specified polarity. Some illuminated devices include current limiting for a declared supply; others require an external circuit. Treat the product datasheet as the authority.<\/p>\n\n\n\n\n\n\n\n\n\n
Terminal function<\/th>\nState at rest<\/th>\nState while actuated<\/th>\nVerification<\/th>\n<\/tr>\n<\/thead>\n
COM<\/td>\nCommon path to NC<\/td>\nCommon path to NO<\/td>\nContinuity meter with power isolated<\/td>\n<\/tr>\n
NO<\/td>\nOpen to COM<\/td>\nClosed to COM<\/td>\nRecord resistance in both positions<\/td>\n<\/tr>\n
NC<\/td>\nClosed to COM<\/td>\nOpen to COM<\/td>\nRecord resistance in both positions<\/td>\n<\/tr>\n
Lamp + \/ anode<\/td>\nDepends on the desired illumination behavior<\/td>\nDatasheet marking and controlled low-voltage test<\/td>\n<\/tr>\n
Lamp \u2212 \/ cathode<\/td>\nReturns to the approved lamp supply<\/td>\nDatasheet marking; do not infer from wire color<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The table describes a common arrangement, not a promise that every five-pin product uses it. A lamp may be a bidirectional AC indicator, a polarized LED, or a module with a built-in resistor. A switch may be maintained rather than momentary. Confirm the full ordering code before assigning wire numbers.<\/p>\n

\"LEMA
LEMA PBS product reference: the contact block and illuminated actuator belong to separate electrical functions. Verify the exact variant before wiring.<\/figcaption><\/figure>\n

Identify all five pins safely<\/h2>\n
    \n
  1. Disconnect every source.<\/strong> Isolate the button from the load, PLC and lamp supply. An ohmmeter must not be connected to an energized circuit.<\/li>\n
  2. Read the markings.<\/strong> Look for C or COM, NO, NC, +, \u2212, lamp symbols and a voltage marking. Photograph them for the build record.<\/li>\n
  3. Find the changeover group.<\/strong> With the actuator released, locate the pair showing continuity. One is COM and the other is NC. Press the button fully; COM should transfer to the third contact, NO.<\/li>\n
  4. Confirm the lamp pair.<\/strong> Use the supplier drawing first. If a controlled test is permitted, apply only the specified lamp voltage with current protection. Reverse polarity only when the datasheet permits it.<\/li>\n
  5. Label the harness.<\/strong> Mark each conductor by function, not by a generic color convention. Repeat the continuity test after crimping.<\/li>\n<\/ol>\n

    If the contact readings do not transfer cleanly, stop. A latching button may require a second press to return; a removable contact block may be installed in another orientation; and a damaged actuator may not reach the snap point. Do not \u201csolve\u201d ambiguity by joining lamp and switch terminals.<\/p>\n

    For meter technique, follow Fluke\u2019s resistance-measurement guidance<\/a>, including isolating the circuit and checking the leads. For a PLC circuit, AutomationDirect\u2019s input-current explanation<\/a> helps distinguish sourcing and sinking. Neither source defines the LEMA terminal layout.<\/p>\n

    Three useful illumination behaviors<\/h2>\n

    Lamp always on<\/h3>\n

    Connect the lamp directly across its approved supply so it illuminates whenever that supply exists. The contact circuit remains independent. This can identify a control location in a dark panel, but it does not prove the controlled machine is running. The legend should describe what the light actually means.<\/p>\n

    Lamp on while the button is pressed<\/h3>\n

    Feed the lamp from the switched NO path only if the contact rating, lamp supply and circuit architecture allow it. COM receives the approved source, NO feeds the control input or relay and also provides the intended lamp signal, while the lamp return reaches the correct supply return. A control input and lamp can impose different electrical requirements; use separate contacts or an interface relay when direct sharing would create leakage, loading or voltage conflicts.<\/p>\n

    Lamp follows the machine state<\/h3>\n

    The most informative design drives the lamp from the controller\u2019s confirmed output state rather than directly from the button. The button becomes a request and the PLC, relay or control board illuminates the lamp only after interlocks and feedback agree. This avoids telling the operator that a machine is running merely because the button was pressed. Follow the controller\u2019s output specification and relevant machine-control design.<\/p>\n

    For an introduction to general contact behavior, see the NO versus NC push-button guide<\/a>. For non-illuminated layouts, compare the two-pin<\/a> and four-pin push-button wiring guides<\/a>; they solve different terminal arrangements and should not be substituted for a five-pin diagram.<\/p>\n

    PLC input example without guessing polarity<\/h2>\n

    A dry contact can command a PLC digital input, but the PLC input manual decides which rail reaches the input and where its common is connected. For a typical 24 V DC sinking input whose common returns to 0 V, a protected +24 V source may feed COM and NO may feed the input. Pressing the button completes the current path. A sourcing input requires a different polarity arrangement. The lamp may use the same 24 V supply only if its specified voltage and polarity match and the common architecture permits it.<\/p>\n

    Do not place a high-current motor or solenoid directly on a small signal contact simply because the nominal voltage matches. Inductive loads can create a switching transient, and the utilization category may differ from a resistive rating. Use a properly rated relay, contactor or suppression network selected for the load. The button should command the interface rather than carry power beyond its verified rating.<\/p>\n

    \"LEMA
    PBS variants differ in actuator, illumination and contact arrangement. Select by the full ordering code, not the cap color alone.<\/figcaption><\/figure>\n

    Commission the button and indicator separately<\/h2>\n

    Before energizing, inspect insulation, terminal clearance, crimp retention, strain relief and the panel cutout. Verify COM\u2013NO and COM\u2013NC from the harness end. Energize the lamp supply first where the procedure permits, confirming brightness and polarity without the controlled load. Then observe the controller input or relay coil as the button is pressed and released. Finally test the complete function with interlocks active and record the expected state of the button, lamp and machine.<\/p>\n

    If the button works but the lamp stays dark, measure the lamp supply at the two lamp terminals and check polarity, rated voltage and return continuity. If the lamp works but the control never changes, return to COM\/NO\/NC identification and the input common. If both appear to work only when wired together, check for an unintended backfeed. A lamp circuit must not energize a control input after the contact opens unless that behavior was deliberately designed and validated.<\/p>\n

    Selection and RFQ checklist<\/h2>\n

    Specify momentary or maintained action, contact form, control voltage and current, load type, lamp technology and voltage, desired light behavior, panel cutout, mounting depth, terminal style, cap color, ingress exposure and operating environment. Ask for a terminal diagram tied to the exact model. Compare these requirements with the LEMA PBS series push-button switch<\/a> and the broader push-button range<\/a>. A product photograph confirms appearance; it does not replace the drawing.<\/p>\n

    Common wiring errors<\/h2>\n
      \n
    • Assuming the two closest pins are always the lamp terminals.<\/li>\n
    • Applying the load voltage to an LED marked for a different supply.<\/li>\n
    • Reversing LED polarity and diagnosing the switch as defective.<\/li>\n
    • Using NC when the controller expects an active-on-press NO signal.<\/li>\n
    • Sharing a return that creates a backfeed between the lamp and PLC input.<\/li>\n
    • Testing only the button face and never checking the harness-end connections.<\/li>\n<\/ul>\n

      The underlying distinction between a mechanical contact and an indicator circuit is also shown in practical manufacturer wiring guides, but terminal positions are model-specific. Use independent references only to understand the concept; the LEMA model drawing controls the production harness.<\/p>\n

      FAQ<\/h2>\n

      Are all 5-pin illuminated push buttons wired the same way?<\/h3>\n

      No. COM, NO, NC and two lamp terminals are common, but the physical order, lamp type, voltage and polarity vary. Identify the exact model and meter the isolated contact.<\/p>\n

      Can I leave the NC terminal unused?<\/h3>\n

      Yes, when the design only needs an NO command. Insulate the unused terminal and document it. Do not bridge NO and NC.<\/p>\n

      Can the LED use the same supply as the PLC input?<\/h3>\n

      Only when the LED\u2019s rated voltage and polarity match and the shared supply will not backfeed or overload the input circuit. Otherwise use a separate or interfaced lamp circuit.<\/p>\n

      Why does the LED stay on after I release the button?<\/h3>\n

      It may be wired for constant illumination, driven by a maintained output, or receiving an unintended backfeed. Trace the lamp pair separately from COM\/NO\/NC.<\/p>\n

      Video: switch contact forms<\/h2>\n

      This independent explainer shows SPST, SPDT, DPST and DPDT contact logic. Use it to understand poles and throws, then verify the illuminated button\u2019s own terminal diagram.<\/p>\n