Everything You Need to Know About Stack Lights

What are they?

LED stack lights are widely used on machines in automotive manufacturing and process management settings to provide system owners, mechanics, project managers and plant workers with visible and auditory indications of the condition of a system. It is a manufacturing type of andon-systems which detect errors as they occur. Also known as signal tower lights, stack lights are used as warning lights or strobes in related systems, but the details they usually display contain more machine or process conditions. They usually utilize strobes of the incandescent, lead, or xenon type as their source of illumination.

Stack lights are typically columnar structures in a number of forms, putting color coded indicator parts in a “stacked” configuration on top of one another. Typically up to five separate colored segments would have a stack light to show various conditions on the system or operation. Stack lights are sensitive instruments that can be managed directly to computer controls, such as clocks, sensors and latching relays, by programmable logic controllers, distributed control systems, desktop control systems or hardwired.

What are their functions?

Stack lights are found in a number of equipment and operation environments; the device builder determines unique color-coding. Commonly used color codes for status of system state include:

  • Red: Malfunctions such as an emergency stop or machine fault
  • Yellow: Warnings such as overheated or too-pressured situations
  • Green: Normal operation
  • Blue: Request for external assistance in which an operator might require raw materials, scheduling or assistance from maintenance staff
  • White: Conditions identified by the consumer for a particular system, sometimes connected to productivity monitoring

Aside from colors, an audible warning buzzer may optionally be attached to warn system operators of high priority conditions.


Typical usage of stack lights involve, but are not limited to:

  • Efficiency monitoring (machine production control of parts-per-hour displays mostly dependent on the rate). Uptime & downtime control, which is the total equipment effectiveness, is a very popular use for such tools.
  • Warning signals and management of faults in machinery
  • Maintenance call stations
  • Equipment of CNC machining and progress checking and feedback
  • Broadcast studios, particularly radio stations, Display status of issues such as an air stage, live microphones, phone calls and even a doorbell in a sensitive atmosphere where silent signal is required

Reasons to Use Them

Stack tower lights are one of the first means of communication of machine state and events to plant personnel. The primary purpose of a stack light is to project an instant message regarding high visibility system output. Efficient visual contact with stack tower lights has a significant effect on the uptime of output and the efficiency of the goods. When contemplating a technique for visual contact, exposure to a few specifics can help allow efficient use of stack towers in manufacturing.

Stack lights should be utilized because:

  • They are in many ways an effective way of having a first line of protection to realize what the condition of a system is. Pilot lights and HMI / touch-screens do a fine job of offering information, but their weakness is place — operators aren’t always at the control panel.
  • What stack tower lights inform them about the unit, operators get easily used to. Typical use is linked to computer state — red is down or wrong; yellow is an alert condition; green is regular activity, etc. With a brief look at the stack tower display, operators will say a ton about the system condition.
  • In situations where operators may leave a system unattended or minimally treated, a very clear stack tower light & buzzer may take advantage of up time. Nothing is worse than an unattended computer that is idle from an alert or malfunction where the condition is only reflected at an HMI or when the user is not supposed to be with the system. Stack lights with buzzers, sometimes though workers are some distance away from the unit, draw attention to this situation.
  • For stack lights, lean manufacturing strategies are well tailored to signify processes and procedures that are specified for the equipment. That could be an essay in its own right, putting it outside the reach of this brief description.
  • Another reason for visual communications is indicator of the safety situation. Posting the red light on a stack tower when an E-stop is breached is normal. In manual reset circuits, red segment flashing means that the safety circuit is now fulfilled and ready for reset activation by the operator.
  • Applications for health protection warn staff about the presence of dangerous situations. Examples involve plant areas where lasers are present and/or working, manual machine tools that work with pinch points such as plate rollers, and hot exposed surfaces. 2D protection area scanners will trigger an alert light & buzzer when the coded notification area has been breached. As they see the alert sign, they hopefully avoid before reaching the configured dangerous area and triggering a trip to safety.

In conclusion, stack lights are very useful and should be implemented in factories or places that involve a lot of machinery.