Pick by Light: How does it work?
SPS FulfillmentIndex
The architecture and principles of Pick by Light
At the heart of the most advanced logistics operations lies a seemingly simple yet revolutionary technology: the Pick by Light system. Its essence consists in using directional lights to guide the operator to the exact position of the items to be picked, without having to use paper documents or manually consult lists. Imagine a corridor of shelves where, at the right time, small light bulbs light up to clearly indicate where the goods are located. This is not a simple light signal, but a complex architecture that connects management software, a central control unit and a series of light modules arranged on the shelves.
The management software, often a dedicated ERP ( Enterprise Resource Planning ) system or WMS ( Warehouse Management System ), sends the list of items to be picked to the control unit. The control unit acts as a silent conductor: it organizes the execution of orders, divides the picking into logical sequences and orders the intelligent modules to light up at the exact positions. These modules, mounted directly on the shelves or inside specific containers, integrate both LED light emitting diodes and sensors or buttons that allow the operator to confirm the completion of the action. Beyond simple flashing, the choice of color, frequency and intensity of the light can be programmed to distinguish different priorities or to signal particular events, such as the exhaustion of the batch or the need for quality control.
In some modern systems, the connection between the light modules and the control unit occurs via wired networks, usually industrial Ethernet or serial bus, ensuring speed and reliability in data transmission. In environments where there are numerous picking stations or frequent reconfiguration of the shelves, wireless solutions based on proprietary protocols or industrial Wi-Fi networks are used instead, in order to reduce the complexity of the wiring and allow for faster maintenance or reorganization of the space. At first glance, the simplicity of the lit LED seems disconnected from the larger IT systems, but in reality each light depends on a series of two-way communications: the operator presses the button to confirm the picking, the sensor records the quantity actually removed and the order status is updated in real time in the WMS, with immediate effects on the stock levels and the planning of subsequent activities.
When considering the adoption of Pick by Light, it is crucial to understand how its roots lie in the desire to minimize errors and waiting times. Before this technology, the operator had to focus on barcodes, labels, optical readers, printing documents and manually marking the picked pieces. All this implied not only a slowdown of operations, but also a greater margin of error: a mistaken code, a number written incorrectly, a product moved from place. With Pick by Light, attention is focused exclusively on the light: the width of the warehouse ideally narrows into a single point of light, and the operator can dedicate himself to picking with a simplified mental order, knowing that, as long as the LED remains lit, that exact position and that exact quantity are part of the same order.
From offtake to operational efficiency and beyond
Once installed, the Pick by Light system becomes an integral part of daily procedures within the warehouse. The start of a picking wave (often called “wave picking”) is triggered as soon as the WMS sends the final list of items to be moved. Let's imagine an operator who, around 8 in the morning, receives on the control unit display the task of picking items for various orders grouped by route efficiency. At that point, the first LEDs light up: a linear warehouse, with shelves on multiple levels, becomes a luminous path, where each green light indicates the exact point to go.
There is no more immediate solution than a light that flashes at the shelf containing the product. The operator reaches that point, picks the indicated quantity, touches the button integrated into the module and, in the blink of an eye, the light signal goes off, while another LED lights up a few meters away. The transition from one module to another occurs seamlessly, creating an uninterrupted flow that avoids prolonged stops or manual checks of documents. At this stage, any discrepancies detected (for example, the lack of one or more pieces, or an item not found) become immediately visible to the system, which may require a recheck or stock integration intervention at the very moment they appear.
The real advantage, however, is not just the speed of picking. Traceability is taken to a higher level: each confirmation of the button instantly reports the information to the WMS, updating the warehouse availability with precision. Any operator, at any counter, can check the real status of the stock, reducing the need for frequent physical inventories and optimizing the management of reorders. Pick by Light also allows you to segment more complex scenarios : in large industrial companies, different warehouse areas can be divided into independent sectors, each with its own light control. Thus, while one area concentrates urgent orders for priority customers, another can dedicate itself to orders with a lower rotation without interfering with cross-flows.
In addition to picking, the system can be adapted for the packing or sorting phase : this is the so-called Put to Light . Here, the lights do not indicate the point from which to pick, but rather the destination of the products already collected. After completing the picking, the operator places the items in the distance and, during the order consolidation phase, follows the lights that light up on the destination containers, ensuring that each piece ends up in exactly the right package. In this way, errors in associating product and order are further reduced, and the operator's route is organized according to shipping priorities.
A further development concerns the integration of Pick by Light with automated transport systems : moving walkways or AGV (Automated Guided Vehicles) trolleys can receive input from the WMS as soon as a batch of items is completed, automatically transporting the boxes to the packing area or shipping dock. The light modules, no longer limited to traditional shelves, also extend to trolleys and workstations, offering the same visual clarity. In this scenario, the operator becomes part of a highly synchronized system, where his only concern is to follow the lights and spot any anomalies: in the event of missing pieces, wrong items or stock outs, the system will immediately generate a light alert of a different color, allowing for a quick correction without having to interrupt the entire operational chain.
The adoption of Pick by Light, therefore, is reflected on multiple levels: on a human level, it improves operator productivity and reduces mental fatigue, since interaction occurs intuitively. On a management level, it increases the transparency of flows and makes resource planning, both human and technical, more timely. Finally, from a competitive point of view, a warehouse that uses Pick by Light is able to guarantee faster order fulfillment times, lower error costs and greater flexibility in quickly reorienting logistics in the event of sudden changes in demand.
Ultimately, Pick by Light is not just a set of lights and buttons, but a real operational paradigm that redraws the concept of efficiency and precision in the contemporary warehouse. The lights that turn on and off are not a simple aid, but the visual manifestation of an integrated information flow, where technology and operator converge to create optimized, reliable and scalable processes over time.