Stack Light: Steady, Flashing or Strobe for the Machine

A packing line stops at 2 am and nobody on the floor can tell from across the room whether it is a jam, an empty hopper or a tripped guard. A stack light answers that at a glance, but the order form still wants a supply voltage, steady or flashing, LED or incandescent, and a colour count. The sections below take those choices one at a time so the tower you order matches the machine it goes on.

What a Stack Light Tells the Operator

A stack light is a column of coloured signal modules fitted on or near a machine, so an operator can read its state from a distance. Each colour is wired to one condition, usually running, warning, fault, or waiting for the operator.

Colour conventions for machinery indicators are generally covered in AS 60204.1, but many sites run their own colour code. Match what the operators already know, because a tower that follows a standard nobody on site uses ends up ignored.

Steady, Flashing or Strobe

Steady means a state: running, idle, ready. Flashing means something needs attention soon, and strobe is the hardest signal to miss on a busy floor. Most towers keep steady for normal states and use flashing or strobe for faults, so the eye goes to whatever changed.

For a fault that has to be noticed across a large shed, a strobe module such as the 50mm 24V AC/DC clear strobe is usually a better fit than a flashing one. For a state that should stay calm, a steady module does the job without adding visual noise.

LED or Incandescent

LED modules are described in the listings as energy-efficient and long-lasting, which cuts the number of lamp changes on a machine nobody wants to stop. Incandescent modules are still listed for sites that want a like-for-like replacement in an existing tower.

For a new install on 240V, a steady LED module such as the IP65 amber 240V steady LED stack light is a straightforward starting point, and the listing shows a socket-mount 50mm lens. When replacing an old incandescent tower, check the voltage and lamp type before ordering instead of assuming an LED module will drop straight in.

24V AC/DC or 240V Supply

This is the choice to settle first. 24V AC/DC modules suit towers fed from the machine's control supply, which keeps the signalling on extra-low voltage. 240V modules suit towers fed from a mains circuit, but the wiring then needs the same protection and isolation as any other mains circuit.

Read the listing for what is included, too. The 24V AC/DC steady LED control light shows a NEMA 4/4X/13 rating and lists the lamp as sold separately, so confirm what is in the box before you order.

How Many Segments and Which Colours

Start from the states the machine actually reports, then count. Three segments, usually green, amber and red, cover running, warning and fault on most machines. Blue is commonly added when the operator has to act, such as reloading or clearing a jam, and clear or white for a process-specific state. Past four or five segments, operators tend to stop reading the tower.

If building the tower module by module is more work than the job needs, a 70mm preassembled stack light comes as a ready-made unit, and a multi-colour option such as the 24V AC/DC LED control tower stack light puts several colours in one stack.

Mounting and Wiring a Stack Light

Mounting changes the product, not only the bracket. A 30mm surface mount LED stack light fits a tight spot on a frame or panel, while a wall-mount signal light, also in the range, suits a wall or column.

Where machines are moved or swapped often, a tower with a 5-pin M12 connection, such as the 24V AC/DC 5-pin M12 stack light, can be cabled with a mating M12 lead instead of being hard-wired. Check the pin layout in the listing before buying the lead.

When a Stack Light Is Not the Right Tool

If only one state matters, such as power on, a pilot light on the panel door does the job, and the options are covered in pilot lights for control panels.

If operators only need one warning point rather than a status display, a single lamp from the strobe beacons range is simpler than a tower, and choosing a flashing beacon LED is covered separately.

For a warning at a gate, roller door or open floor area, choosing a rotating beacon usually makes more sense than fitting a tower.

Common Mistakes When Ordering a Stack Light

• Ordering a module without checking what is in the box. Some listings show parts such as the lamp as sold separately, and the tower may arrive and not light. Read the technical specifications on each module before it goes in the cart.
• Matching colour and shape but not supply. A 24V module and a 240V module can look the same on the shelf, and the wrong one on the wrong supply is damaged or stays dark. Write the supply voltage on the order before choosing the colour.
• Using strobe for everything. When every state flashes, nothing stands out and operators learn to ignore the tower. Keep steady for normal states and save strobe for faults.
• Adding more colours than the machine reports. Each unused segment is a light that means nothing, which dilutes the ones that do. Count the real states first.

Frequently Asked Questions

Choosing a Stack Light

What do the colours on a stack light mean?

There is no single fixed code. Red is widely used for faults or stops, amber for warnings, green for running and blue for operator action, but many sites set their own. AS 60204.1 is generally the reference for machinery indicator colours, so check it and the site standard before wiring.

Do I need a buzzer on my stack light?

Only if nobody is watching the tower, such as a machine that runs unattended or sits out of line of sight. If you add sound, sounder beacon selection covers the sound, light, voltage and IP rating choices.

Wiring and Supply

Can I run a stack light from a 24V PLC output?

Check the module's listed current draw against the output rating. If the load is close to the limit, switch it through a relay or feed the tower from a supply sized for it, instead of loading the PLC output directly.

Which stack light works on a 240V supply?

Pick a module listed for 240V, such as the 50mm 240V red strobe stack light, or one of the steady and flashing 240V modules in the list below. Wiring to a 240V supply should be done by a licensed electrician.

Compliance and Outdoor Use

Does a stack light need a licensed electrician?

Connecting a stack light to a 240V supply is generally licensed electrical work in Australia, and the product listings recommend installation by a qualified electrician. Rules for extra-low voltage work can differ by state, so check with your regulator.

Can a stack light be mounted outdoors?

Check the ingress rating on the listing. The 24V AC/DC IP65 steady stack light is listed as IP65, which generally means dust-tight and protected against water jets, but the base and cable entry still need to be sealed properly for outdoor use.

Shop Stack Light at Schnap

Trade discounts are available on the range below, and orders go out with same-day dispatch from Kingsgrove NSW.

50mm modules, 24V AC/DC

• Steady LED control light, 24V AC/DC (855E24TL7)
• Flashing LED stack light, amber, 24V AC/DC (855E24GL5)
• Steady stack light, red, IP65, 24V AC/DC (855E24DN4)
• Strobe stack light, clear, 24V AC/DC (855E24BR7)

50mm modules, 240V

• Steady LED stack light, amber, IP65, 240V (855E20TL5)
• Flashing LED stack light, green, IP65, 240V (855E20GL3)
• Steady incandescent stack light, green, 240V (855E20DN3)
• Flashing incandescent stack light, red, 240V (855E20FN4)
• Strobe tower stack light, red, 240V (855E20BR4)

Multi-colour and preassembled towers

• LED control tower stack light, 24V AC/DC (855ECG24Y3Y5Y4P1)
• Preassembled 70mm stack light (855FSBSC20B24Y3L4)
• Modular tower light, 60 multi-LED, IP65 (SCHXVUC29)

Compact, wall mount and M12 options

• 30mm surface mount LED stack light, green, 24V AC/DC (855DP00SC20B24Y3)
• Wall mount signal light, 24V AC/DC (855WC24Y7Y6Y3Y5L4P1)
• 5-pin M12 stack light, 24V AC/DC (856TB24QD5C)

Browse the full stack light range at Schnap.