A barcode scanner may read codes correctly during testing but fail to start scanning after it is installed inside a machine. This is often not a decoding problem. The scanner simply does not detect that a barcode has entered the scanning area.

IR sensing and image sensing are two different ways to start automatic scanning.

What Is Image Sensing?

Image sensing uses changes in the camera image to detect that a barcode or object is in front of the scanner. The module then turns on the light and starts reading.

This design uses fewer parts and helps keep the scanner module small. It is suitable for kiosks, vending machines and other equipment with enough light around the scanning window.

The problem appears when the scanner is installed inside a dark enclosure. If there is not enough light for the camera to detect an image change, the scanner may not wake up. Some users find that the scanner works when they shine a flashlight at it, but does not start by itself in normal use.

In this situation, the barcode reading ability may be fine. The problem is the automatic trigger method.

How Does IR Sensing Work?

An IR sensing scanner has infrared transmitting and receiving parts. The infrared light is reflected when a phone, ticket or product moves into the scanning area. The scanner detects this reflection and starts reading the barcode.

It does not need the camera to see a clear image before scanning starts. This makes IR sensing more suitable for:

• Dark areas inside kiosks

• Closed vending machine enclosures

• Access control terminals used at night

• Equipment where the scanner window has very little outside light

IR sensing takes more PCB space because extra transmitting and receiving parts are required. This is one reason many small barcode scanner modules use image sensing instead.

Which XTIOT Module Has IR Sensing?

In the current XTIOT scanner module range, XT203BM is the model with IR transmitting and receiving components. It uses three IR emitters and one IR receiver to detect an object before starting the scan.

XT203BM is suitable when reliable automatic triggering in a dark installation is more important than keeping the scanner module as small as possible.

For equipment with normal light, a compact image-sensing module may still be the better choice. If the host software controls when scanning should start, serial command triggering can also be used instead of relying on automatic sensing.

Test the Trigger After Installation

Testing the barcode scanner on a desk is not enough. The scanner should also be tested after it is installed behind the final panel and window.

Check whether it starts scanning under the actual lighting conditions, especially when the equipment is used in a dark room. If the scanner can read the code after the light turns on but does not wake up by itself, the trigger method should be checked before changing the decoding hardware.