Pick-by-Light : Order picking with displays

Shelf with red containers and Pick-by-Light displays in a warehouse

What is itPick-by-Light?

Pick-by-Light plan and set up?

What hardware and software do you need?

Interface to Pick-by-Light?

Pick-by-Light build it yourself?

...and much more.

We provide answers to all these questions here. We supply systems for professional order picking, such as Pick-by-Light and others. Use our know-how. All our systems are controlled by the central LUCA-Server. In this article you will find the most important information, technical details, application examples and prices for our Pick-by-Light process. This guide is addressed to planners, technicians and buyers. Take your time and read this article carefully.

In this and many other blog posts we explain how you can correctly plan, buy and introduce our Pick by Light yourself. We don't just give you a few tips, but explain in detail how you can increase the performance of your picking and at the same time minimise error rates.

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But why is it Pick-by-Light so special? What makes the system different from other picking systems? How is a modern Pick by Light structured? Where is the system best used and what costs do you have to expect? Do not buy the Pick-by-Light system until you are absolutely sure that you will benefit from it. We will give you an answer to all these questions. Let us start ...

What is a Pick-by-Light system?

For newcomers a short definition before we start with the details. Pick-by-Light is a fast and error-free method for picking, sequencing and production. After data acquisition and activation of the order, the picking process begins. The appropriate compartment displays light up directly at the storage compartments. This enables the order picker to find his storage compartments on the shelf very quickly and confirm the activity directly on site. Read more about: What isPick-by-Light?

What is paperless picking?

In paperless picking, a computer system directly supports the picker. There are no more paper lists! Many different technologies support paperless picking. This Pick-by-Light is one of the most effective and successful paperless, manual picking systems worldwide.

In a conventional warehouse, employees pick with paper lists and mark each order item on the list with a ballpoint pen. Not only the speed but also the quality depends very much on the picker. Sei job is not easy and monotonous. The employees search the storage compartments and can quickly make a mistake.

Institut Fraunhofer in Dortmund is very specialized in this topic with its own publications.

Performance and quality of the process

Performance and quality are opposing parameters. As a result, the more performance is expected, the less quality can be guaranteed. So it is not very easy to increase performance and quality at the same time.

As the leading process in order picking, this is Pick-by-Light just one excellent example of how performance and quality can clearly increase. The performance increases up to 40%. The targeted support of access to the storage compartments also increases quality by more than 15%. If sensors are used on the displays, this figure is increased by about 10%.

When planning a paperless picking system it is essential to consider the economic efficiency. The system requires a relatively large amount of hardware, which does not exactly make the procurement of the equipment cheap. An ROI calculation must show whether the investment is profitable. Get in contact with us. We will help you to make the calculations.

If the demand for performance is not particularly high and the storage areas are large, we can alternatively supply other technologies for picking such as Pick by Scan, Pick by Watch, Pick by Voice, etc.

Where is the system used?

The system is very versatile. The hardware itself (displays) serve only as output and input devices. The whole logic of the control, as well as the process, takes place in oursLUCA-Server. Therefore our solutions are very flexible and cover a very wide range of tasks. Customer-specific adaptations are possible at any time.

The following industries have been successfully using our systems for many years:

  • eCommerce: picking and replenishment in the dispatch warehouse
  • AutomotiveSequencing of shopping baskets and JIT racks for the assembly lines
  • Production: assembly stations, set formation and machine assembly

Read more here: Where is Pick by Light used?

Pick-by-LightPick-to-light or put-to-light - which is right?

Our answer is: all terms are correct!

Whereby Pick-by-Light and Pick-to-Light are often used as synonyms, which is actually wrong. Even the term Pick-to-Light already points to an action that has something to do with a levy. Pick-to-Light is therefore often used as the name of a multi-order picking method in a Pick by Cart system. Finally, the term Put-to-Light clearly refers to a sorting or replenishment.

We mainly use the term: Pick by Light, although the other terms have their justification, depending on the function.

How is a Pick-by-Light system structured?

Our system is highly modular and very flexible. All available displays can be used together. The main role of the control system is played by our LUCA-Server. In the server, we not only implement the communication to the displays, but also control the entire process logic, as well as the connection to the superordinate system and the additional components (e.g. scanner, RFID reader, machines, conveyor technology, etc.).

Here are the components:

  • LUCA-Server (often as a virtual Windows server)
  • Controller (several BUS systems)
  • Mounting rails with integrated BUS system
  • Displays with Quick-Click-System

More information about the extensions can be found in a separate article in our blog.

The controllers

The individual displays must be supplied with power and data. This is ensured by the Pick-by-Lightcontrollers connected to the Ethernet and power. Each controller is assigned to an IP address and is LUCA-Server controlled by it.

The controller can supply up to 400 displays
This controller can supply and control up to 400 displays.

A single controller has several BUS systems and controls (depending on the model) about 100 - 400 displays. The intelligent power supply of the controllers is designed in such a way that all displays can light up simultaneously. In such a cascaded system with several controllers, even more than 50,000 displays can function simultaneously.

The reaction times to the individual events are very short and are only a few milliseconds. In summary, the entire system is designed to be highly multitasking. This is exactly the reason why we can guarantee the fast response times.

Mounting rails with integrated BUS

First, the BUS system is integrated into an aluminium mounting rail (marked yellow here). Second, a double clamp is installed at the mounting rail. The mounting rail is then connected to the controller with a 4-wire cable (plus, data signal, minus and ground) via the double terminal. The cable can then be led from the double terminal to another mounting rail. No cables are required between the individual Pick-by-Light displays! This makes our system so very flexible. The displays can be installed at any position of the mounting rail. The cabling can be over 300 meters long in total and is designed as "star" or "serial".

Mounting rail

The BUS system is supplied with 24V and may also be operated without cover. The advantage of the open solution is that it is very easy to convert the system. The displays only have to be moved.

Pick-by-Light Displays with Quick-Click

Our displays are connected without cables (via spring contacts) to the BUS system of the mounting rails. Each display has a unique MAC address. The controller can use this address to differentiate between the displays and control them in a targeted manner. The installation is done without tools by simply clicking on the mounting rail (Quick-Click-System).

If necessary, the storekeeper can remove the Pick-by-Light display from the mounting rail with a simple tool and then click it back in again. With this system, every conversion is made very easy.

Option: Sensor for monitoring access

Pick-by-Light Sensor
The sensor (upwards) monitors access to the storage compartment and can also automatically acknowledge the removal or release the button for acknowledgement.

The absolute innovation of the Pick-by-Light displays is the optional integration of sensors. First, the sensors monitor the correct access to the storage compartment. Secondly, they ensure acknowledgement on removal. Third, they can fully automate the acknowledgement process. Depending on where the displays are mounted, the sensors are aligned either upwards or downwards. Almost every display can be equipped with a sensor.

Pick-by-Light sensor activates the acknowledgement key.

Only if the employee has correctly accessed the storage compartment, the button is released for acknowledgement.

A manual acknowledgement of the removal at the button is therefore not absolutely necessary. However, we recommend a complete automatic acknowledgement only for quantity = 1. Such picks often take place during sequencing in theAutomotive

Counting the number of pieces with a sensor is possible, but only recommended in rare cases. Here the construction of the storage compartments and the articles is decisive. It is imperative that each withdrawal generates only one sensor signal. And this is exactly what is rarely possible in practice.

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Pick-by-Light plan

From a technical point of view, one Pick-by-Light consists of individual BUS systems with a maximum length of up to 500 meters and up to 100 displays. For this reason, certain electrical rules must be observed on each BUS and on each controller. Correct data acquisition is very important here. Only then can the entire system function stably and quickly.

When planning larger plants, we calculate the following parameters in particular:

  • Controller performance
  • Resistance of all BUS lines
  • Electrical capacity of the BUS system

The decisive factor is that the entire communication between the individual displays runs without interference. Each display, each cable and each mounting rail has its own electrical capacity, which in total must not exceed a certain value.

When planning our systems, we assume that each display can be controlled simultaneously. Some other suppliers impose a limit on the number of displays that can be switched on at the same time. We do not do that! We have implemented an intelligent control of the power supply units and therefore always have enough power reserves available.

Each planning is different for the other systems. With Pick-by-Scan or Pick-by-Vision the planning is done completely differently. We are happy to help you with this!

What happens if the calculated parameters are not correct?

Even an electrical overload of the controllers will then automatically switch off the system. The automatic fuses then blow.

If the capacity of the overall system is too high, the electrical edges of the signals are so flat that the receivers no longer work. As a result, the entire communication is partially or completely disturbed.

The answer to the question is: Then we redesign the cabling and the distribution of the controllers until everything fits. In principle, all this is not difficult, but it is essential to take it into account for every installation. This is precisely why we use a special cable with low electrical resistance and capacity in our systems.

What reserves do you need to plan for?

Basically, the question cannot be answered very easily. During the Pick-by-Light planning phase we consider the necessary requirements together with the customer. We always consider the conversion and expansion plan. For some plants the need for reserves is 2-3%, but for some plants it is 10-12%. Therefore, we always clarify this question in the course of the discussions during the preparation of the specification sheet.

Important: Consider reserves for expansion and conversion!

For the planning, a layout of the planned plant is normally sufficient for us. The positions of the controllers and the cable routes are then derived precisely from our planning. Based on this, the customer can then prepare his power supply and network connections.

Assembly made easy

At that time, in the 90′ years, the Pick-by-Light installation was very complex. Each display had its own cable to a small mini-controller in the mounting rail. All mini-controllers were in turn connected via a BUS system to a large controller. The large controllers were then connected to a PC via many serial interfaces. Very, very many cables ...

Today, the installation is quick and easy, so that the costs are also low. Aluminium rails are mounted on shelves or beams. A single 4-wire cable connects the rails to the LAN controller. Thanks to the Quick-Click system, the displays can be mounted on the rails very easily and without any further cabling. Optimum spring contacts ensure a perfect connection between the display and the BUS system.

Build it yourself?

This question can definitely be answered with a "yes". How exactly this works and what you need and have to prepare for it is explained in a separate article. Of course, we are also happy to support you in the planning phase. Please read a separate article on building yourPick-by-Light own.

... and if drilling is not allowed?

No worries. In such cases we deliver the mounting rails with magnets. On the heavy load shelves (SLR) the magnets hold very well. Depending on the length and number of displays, we mount one magnet at a distance of approx. one meter. In this case, the final assembly takes only a few minutes! After the "clack" only the BUS cable with 4 wires has to be connected. It is as simple as that.

How flexibly can the system be converted?

Due to the special Quick-Click-System the conversion is very easy and flexible. A BUS system is integrated in the aluminium profiles. The displays are connected via three spring contacts so that the power and data supply is guaranteed. To remove the displays, you only need a simple tool. No cables and no screws. Then you can easily change the position of the displays. The controller automatically recognizes the displays. For a simple transfer within a picking zone, not even an IT conversion is required. The display can simply be moved with the goods.

Add new or exchange displays (modules)

Also very simple... A new display is simply clicked into the aluminium profile with a quick click. With a small tool (spatula) the mounted displays can be removed from the profiles very easily. The displays can then be very easily configured via a web interface. In the event of a system expansion, the new displays log on to the system fully automatically. At the beginning each display has the name of its physical address. Via configuration, the preset name is flexibly adapted to the desired name (e.g. storage location). Replacing the displays is also very easy. Only the physical addresses of the replaced displays are exchanged. The rest happens automatically. The assignment to the zones is also configured via the software. Who can carry out the exchange or configuration of the displays? Actually anyone who is authorized to operate the web-based configuration program. No technicians need to be employed for the conversion or expansion.

Picking areas

Almost every Pick-by-Lightsystem is divided into picking zones. There several pickers can process several orders at the same time. Can several employees work in one picking zone? This question is answered in the article: Pick Pick-by-Light Zones.

How do I connect Pick-by-Light with SAP and LVS?

The LUCA system is very flexible and can be easily connected to SAP or other warehouse management systems. This LUCA-Server forms the interface. The interface supplies the electronic pick list and reports back the picked items. As a rule, the data fields are adapted to customer-specific requirements. However, there are also standards. Please contact us.

RFC or IDOC's are available for the SAP connection Database tables or TCP sockets can also be used for other connections. The system is very flexible.

Procedure and the work steps in order picking

We offer standard packages in which the process already meets 80% of your picking requirements. Very often, however, the requirements for the system are very specific. We integrate different solutions and build up the process steps also customer-specific. The entire logical data processing is handled by our LUCA-Server.

We will now explain the simple picking process:

Start of picking

There are already several options when starting the picking process. But how can this Pick-by-Light start the correct orders? Can the completeness of the last order also be checked? Here you will be given the answers to the questions. Basically there are two different start methods:

  • Start via a document with bar code
  • Paperless picking (FIFO or external trigger)

If the cartons or containers are marked with a barcode (1D or 2D), stationary or mobile scanners can be used for Pick-by-Light activation. In this case, the displays can also be activated via the delivery note or invoice. RFID technology is also supported.

With paperless systems, the orders usually start automatically, either from a data buffer or by automatic ejection of the containers via a conveyor system. In both cases, it LUCA-Servermonitors the individual processes and ensures the appropriate quality. With some solutions, the start of the next order will only be possible after the previous order has been completely completed. If an error occurs here, the system generates an error message.

Simultaneous, sequential or pagewise?

If you have already started picking, the displays on the shelves must actually be lit now. But how should they best light up? All together, one after the other, first one and then the other side of a shelf aisle? With different methods we achieve different goals. As a planner, you need to understand the exact procedure at the shelf and choose the correct method, taking cognitive ergonomics into account. This point is very important when creating the systems. Take your time to find an optimal solution.

Although a Pick-by-Light display is very simple in principle, the process can be very differently structured. A software module on the LUCA-Server. If necessary, we also use different techniques simultaneously. With the simple systems, all displays in a picking zone light up simultaneously. This is also the standard. In other cases we form a picking route and control the withdrawals sequentially.

Confirmation of withdrawal and end of order

When all articles have been picked, the employee confirms the picking at the compartment with the button. The confirmation of the pick triggers a feedback to the higher-level warehouse management system.

Pick-by-Light Costs

We will be happy to provide you with a free offer. In another article we have described different versions of Pick-by-Light and pick-to-light and defined the required information. We would also be pleased to support you in your planning. Please contact us.

The history of 1988

In 1988 Udo M. was a young logistician for a pharmaceutical company and absolutely had to improve his dispatch warehouse. There were many problems with performance and quality, and the computer technology of the time was already very modern. Paper lists and ballpoint pens were the only aids to picking.

Udo described the problem to his good school friend Rainer. Also some weeks later Rainer K. (young electronic technician from Iserlohn) decided to develop the first "Paperless Order Picking". Udo was very enthusiastic about the idea. A large system with many displays. The displays should signal the picking quantity directly at the storage compartment. No more paper lists and ballpoint pens! "Simple and ingenious!" said Udo.

So the first Pick-by-Light one with over 2,200 advertisements was created, although the task was not as easy as first thought for Rainer and his team. But it worked. The performance of the system has increased significantly, and the error rate has also dropped almost to zero. Do you want that too? ... then you've come to the right place!


In logistics and production is Pick-by-Light one of the best and very common picking methods. The simple assembly and flexible conversion possibilities make the system very attractive. However, with many storage compartments in large warehouses the price is also high. Therefore it makes sense to use the system for picking A-items and to support B- and C-items with other technologies.