Pick to Light example device

Pick-to-Light & Put-to-Light

Frequently Asked Questions

Our Pick-to-Light system easily integrates with your existing ERP or WMS or even Microsoft Office.  A simple URL request, sent to our server on the Amazon Cloud, causes the associated Pick-to-Light device to light up with the picker’s name, SKU and quantity to pick!


A Pick-to-Light system optimizes warehouse picking and reduces errors by automating the order picking process. Most pick-to-light systems are costly and difficult to install. Our wireless Pick-to-Light solution brings the Industrial Internet of Things (IIoT) to the warehouse with interactive pick-to-light devices that can display:

  • Picker’s name
  • SKU and quantity of item
  • Custom messages
  • Barcodes
  • QR-Codes
  • Icons
  • Multiple colors

Our Pick-to-Light system is affordable, mobile, easy to implement, and can be integrated with your current ERP or WMS system.

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Put-to-Light is an additional feature of our Pick-to-Light system which assists pickers or re-stockers in putting inventory into the correct location (including picking carts and put walls).  A simple URL call or REST API call can light up a device to show where inventory needs to be placed.


  • Batch picking with separate bins
  • Put-wall
  • Restocking
  • Returning canceled orders to original inventory locations

PTL devices can display:

  • Name of re-stocker
  • Item and/or SKU
  • Number of items
  • Stocking or handling instructions
  • Some other custom data
  • Hazard icons
  • Barcode or QR-Code

Sample pick-list for warehouse order fulfillment

A picklist is a list of lines that need to be picked from inventory to fulfill an order.

Each picklist line typically contains:

  • Product name or SKU number
  • Quantity

Each picklist line can also contain:

  • Picture
  • Area
  • Location
  • Dimensions
  • Weight

It’s far more economical than you might imagine! Unlike other companies offering Pick-to-Light systems, we’re totally upfront about our pricing.  In fact, you can lease a Starter Kit with ten Pick-to-Light devices to see if it boosts your productivity.

Contact us directly for a quote for your system.

Voodoo Robotics offers both solutions!  Most customers purchase devices, but there are some that need the flexibility of a month-to-month lease.  We offer Classic devices on a monthly lease basis.

Order a starter kit!  It comes with 10 devices and a Turbo.  That’s all you need to get a system up and running.  After you’re sure the solution is right for you, you can scale-up from there.

No.  Simply send another ‘completed’ transaction with a one second timeout to turn off a device automatically.

Our Excel spreadsheet demo has an example of this: where a (dynamic) barcode is shown on the device.  The picker scans that barcode (to acknowledge the pick), and that scan causes the device to turn off.

There is a one-time fee for registering your feedback protocol prefix.  Contact us to find out more.


When integrated with a typical WMS or ERP, our Pick-to-Light system requires two things:

It is easy to integrate the Pick-to-Light system into your own ERP or WMS system and not have to change or adopt a new software. It’s as simple as adding URL calls.  A REST API is also available.

Pick-to-Light Cloud Display Device IoT for the Warehouse Pick-to-Light devices are modern IoT devices that you can use as signposts in your business. They can keep track of the SKU’s at a location and/or guide pickers to a destination.  Using a simple URL request, devices can be made to light up with, for example, a pickers name, the SKU and quantity to pick. The devices can even play a custom tune for each picker. The devices are wireless, battery powered (very long battery life) and easy to install.

Pick-to-Light devices can be easily integrated with an existing ERP or WMS.

Turbos connect Pick-to-Light devices to the cloud.

PTL devices cannot connect to the cloud by themselves – they need the help of a Turbo or SKU-Station. The Turbo is the simplest way for the devices to connect to the cloud.

In large warehouses or ones that span multiple rooms, you might need additional Turbos. In busy systems, where multiple requests overlap, adding extra Turbos will decrease response times, making the system faster.

No, but Turbos can get overloaded with 200+ devices around them.  In general, we recommend a Turbo for each 50 devices or so.

No, devices talk to the nearest Turbo.  Handoffs are all automatic, and the customer does not need to deal with these intricacies.

Devices can communicate 75 feet or even more, but we recommend placement of Turbos every 50 feet or so to make sure communications are rock-solid.

Modern devices are approximately 5” wide x 3” height x 0.6” depth (excluding button).

Classic devices are approximately 5.25” wide (closed), 6.5” wide (open) x 1.8” height (excluding button) x 1.125” depth (including display).

Six individual colors.

No.  The display only lights up in green!

We use AWS, Amazon Web Services.  Generally machines running on the Amazon cloud are far more secure than machines running on your LAN behind your firewall!


A single Pick-to-Light device should respond to a URL request in less than a couple of seconds.

A typical picklist with five items will generate five URL requests and light up five Pick-to-Light devices in approximately ten seconds (the first after two seconds, and the last after about ten seconds).  Adding additional Turbo’s can reduce the time.

In the video below, Trevor Blumenau, CEO of Voodoo Robotics shows realist scenarios of latencies customers should expect using Google Sheets (bad) vs. Excel (good).

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No!  Unlike some wired systems, wireless devices, in order to preserve battery life, spend most of their life sleeping.  It takes a couple of seconds for API request to process through the system.  BTW, the latency is largely between the Turbo and the device, so faster routers, higher Internet speeds, etc.  will likely have little or no effect.

You can make marginal improvements in latencies by using extra Turbos.  See Trevor Blumenau, CEO of Voodoo Robotics discuss this:

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One important feature of Cloud Display Devices is that they can display or retain what we call ‘static information’, information that is kept on the device when it is not actively being used.  On Modern devices, this information is always displayed on the device.  On Classic devices, this information is available if you push the button on the device.

In either case, you can set this information using the QueryString or REST APIs, or you can set the information directly using your www.sku-keeper.com account.

If devices are used to identify inventory, you probably will want to store the name, SKU and quantity available of that inventory.

If devices are used to keep track of a customer’s order, you will probably want to store the Order ID, shipping carrier, number of lines of the order, etc.

The Pick-to-Light devices have been designed to maximize battery efficiency.  PTL devices spend most of the time “sleeping”.

With typical use, the two AAA batteries (AA for Classic devices) could last years. It really depends on how frequently you activate the device.

Battery voltage of each device is continuously monitored by the system.

The device itself always displays the current battery voltage or a low-battery warning. And on the SKU-Keeper server, you can easily get a list of Pick-to-Light devices and their locations that have battery levels below a cut-off value that you specify.

Battery changes are quick and easy. Batteries are accessible from the bottom of the device (front for Classic devices), without the need for dismount. Don’t worry, after a battery change, devices come right back to where they were before the battery change.

On Modern devices, we recommend using a dynamic barcode for acknowledgements:  The picker scans a specially constructed barcode (perhaps with Order-ID and line number embedded) on the device to acknowledge the pick.  That scan can also be made to turn off the light, so that the picker doesn’t have to push the button.

On Classic devices, you can rely on the picker pushing the button to acknowlege the pick.  This requires that you receive ack/nacks on your server using our Closed Loop System.

There are two ways to check all your batteries at once:

  • On www.sku-keeper.com you can rank All Devices by battery voltage, or on the Problem Devices page you can list those devices with battery voltages below a certain threshold.
  • Using the REST API, you can first get a list of all devices in your account, and then run a query for the voltage of each.

The prefix is the beginning part of a URL that you provide to Voodoo.  We enter that into our system and when we send an acknowledgement, we simply append the ack/nack to the prefix (along with a transaction ID that you choose).

More Details

Check out our detailed discussion of each part of the QueryString.  We also have a REST API.

The layout is automatic.  The largest test is used for the total number of lines and characters that you choose.  QR-Codes, when specified, are always placed in the top left corner.  Icons, when specified, are placed in the bottom left corner, but are moved to the top left corner if no QR-Code is present.  Barcodes, if specified, are placed along the bottom.

For more information, check out our encoding rules.

Absolutely, that’s the way the system is designed.  For example, after scanning a picklist, send a URL for each line in the list.  If you want a particular item to light up first, you might want to send that one, followed by a 100 ms delay, and then the others.


The easiest way to connect the Pick-to-Light devices to the Internet is to install one or more Turbos. Turbos are typically hung high on a wall or ceiling and can be connected directly over Ethernet (DHCP) to your LAN.  If you already have WiFi in your warehouse, you can connect to the Turbo to your WiFi network.

Pick-to-Light devices work with any ERP or WMS solution, or even Microsoft Office.  A simple URL is all it takes to activate a device.  You can also use our REST API.

Pick-to-Light devices can be mounted to picking carts, boxes, bins, containers, shelving, pallet racking, put-walls, and more. You can mount a device just about anywhere!

The most popular method is outdoor double-sided tape. But you can also use velcro, screws, bolts, zip ties, wire, string, twine or whatever you most feel comfortable using.

Absolutely! Mount Pick-to-Light devices wherever you want to keep track of inventory and products coming in and going out. The PTL devices will help you find and keep an accurate count of what’s on hand 24/7.

The general advice is to mount Turbos above 8 feet on racks or walls with a good (not necessarily perfect) line of site to devices.  The 8 foot guidline gets most customers above the general foot traffic in the warehouse.  Turbos can be mounted to ceilings, but some ceilings in warehouses are very high and so the distance between the Turbo and devices is too large.


Pick-to-Light devices can easily be integrated with any ERP or WMS system.  The simplest way is to intercept the barcode scan at the beginning of a picklist and create a URL for each line of the pick list.

The only limit is your imagination! The devices can light up and display any message you’d like. We challenge you to come up with new ways to use them in your operations.

We do not recommend using Google Sheets because of the inconsist latencies between API calls.  Essentially Google Sheets runs on Google cloud servers that do not have consistent latency performance.

Microsoft Excel, on the other hand, runs directly on the client and shows consistent low latency.

BUT for large operations with existing WMS or ERP systems, we strongly urge you to integrate directly with your WMS or ERP.  Exporting data from your WMS to an Excel spreadsheet for use by pickers, while it may look like a good option, can create data inconsistencies and be difficult to maintain.

The Demonstration Spreadsheet applications that we distribute (in Excel and Google Sheets) are for demonstration only and should not be considered solutions in themselves!

© Copyright 2021 Voodoo Robotics. All Rights Reserved. Patents Pending. Voodoo Robotics, SKU-Keeper, SKU-Turbo, and SKU-Station logos are all trademarks of Voodoo Robotics.