When I first wrapped my hand around this hand-held pistol-style barcode scanner, I thought, "what a nice feel!" The unit is lightweight (weighs only 300g / 0.66 pounds), gives the impression that it's robustly built, and the plastic enclose has a nice design for users (ergonomically correct and made out of smooth plastic).
I'm looking forward to tearing open this 1D cordless barcode scanner from Besteker because I've always wondered how these devices work.
The Besteker cordless 1D barcode scanner.
Below are the advertised specifications:
- Size: 165mm x 70mm x 98mm
- Weight: 300g
- Charging interface: RJ45 plug
- Housing material: ABS+PC
- Light source: visible laser diode, wavelength 650nm.
- Trigger mode: manual
- Scanning mode: single line scanning
- Scanning speed: 150±2 scans/sec
- Resolution: >4 mil
- Error rate: 1/50 million
- Transmitting frequency: 2.4G Bluetooth
- Transmitting distance: 10m (visible distance)
- Prompt mode: beeper and LED
- Laser safety level: EN60825-1, Class 1, National Class 1 Laser Safety Standard EMC
- EMC: EN55022, EN55024
- Electrical safety: EN60950-1
- Light intensity: 3000-12000 lux
- Temperature: 0°C - 50°C (operational) / -40°C - 60°C (storage)
- Package level: IP52
- Charging time: 2 hours
- Charging voltage: 5VDC (±5%)
- Power: 100mW
- Current: 20mA (operational) / <20mA (standby)
Only two small screws hold the top plastic piece to the main housing. After removing these screws, I quickly noticed three PCBs: one for the Bluetooth transmitter, one for the laser diode, and the last one—buried in the hand grip portion—is dedicated to the trigger and battery (see below).
Discovering three PCBs
Taking a Closer Look at the Laser Diode PCB
Before disassembling the unit any further, I wanted to see it energized. However, let's first identify some of the major components on the laser diode PCB.
Laser diode PCB (primary components)
As called out in the above figure, we can see two mirrors (one stationary and one moveable), the laser diode, and a laser detector/sensor. Let's take a closer look at those two mirrors.
Laser diode PCB—two mirrors
Both mirrors have some sort of metal coating on them and look to be made of either gold or copper material. According to photonics.com, "...a mirror’s ability to conduct heat is important. In these cases, metal substrates are often used because metal is much more conductive than glass." Furthermore, "Copper and gold are useful only in the red and IR spectral regions."
You may have noticed (take a closer look at the image above) that the stationary mirror has a mirror within the mirror. More on this later...
Give It Some Power!
After ensuring my eyes were clear from where the laser would shine, I turned on the device by depressing the trigger. A loud beep informed me that the unit was indeed energized, and then the PCB came alive: LEDs turned on, the "moveable" mirror started oscillating, and the laser diode illuminated. Cool stuff!!
The barcode scanner is energized
Let's revisit the "mirror within a mirror" discovery. As can be seen in the figure below, the small mirror within the stationary mirror is what the laser diode is aimed at. This small mirror directs the laser onto the oscillating mirror which, in turn, "creates" the scanning laser.
The laser is aimed at the small mirror within the stationary mirror
Investigating the Oscillating Mirror
Now, you might be asking, as I did, what causes the mirror to oscillate?
The answer lies in a permanent magnet that is attached to the end of the plastic piece holding the mirror—and in that big black and white circular component, which is an inductor. As current passes through the inductor, a magnetic field is generated which, in turn, influences/moves the permanent magnet. The "oscillating" trick is to quickly cycle (on - off - on) the magnetic field by quickly cycling the current through the inductor.
I was curious to know the rate of oscillation of the moving magnet. So I connected my trusty Saleae logic analyzer between one of the inductor's leads and ground and, as shown in the figure below, we can see that the inductor is charged every ~25 Hz. Therefore, the mirror oscillates at the same frequency, 25 cycles per second.
Saleae logic analyzer measuring inductor charge rate
Inspecting Other Components/PCBs
All the components, once removed from the housing, can be inspected below.
All the components removed from the housing
Laser Diode PCB
Laser diode PCB components/findings
The major components and findings on the laser diode PCB, include:
- LM324DG is an operational amplifier.
- The epoxy is used to secure the components/nuts in place.
- The manually trimmed edges of the PCB suggest that a 3D analysis wasn't completed prior to the final design.
- Due to the fashion in which the inductor (no part number listed) was installed, perhaps this particular inductor was a last-minute change. Nonetheless, the inductor looks to be installed in a sloppy manner since its leads have not been trimmed.
- Neither of the two mirrors has a part number.
- Neither the laser diode nor the laser detector has a part number.
Battery PCB components
The "brains" of this cordless barcode scanner are located on the battery PCB.
Most, but not all, of the parts have no markings:
- The castellated PCB is noticeably installed crooked. I would guess that there's little to no quality control during the assembly process.
- The NPN transistors (part marking 1AM) are just general purpose-type transistors.
- Processor: This part serves as the brains of the systems and has no markings at all. My guess is that this IC was custom manufactured to omit any IC markings.
- It appears that the "unknown IC" has had its IC markings mechanically/manually removed. It looks like someone took a grinder to it!
- Neither the switch nor the audio alarm has any part markings.
- The memory IC has a marking of ATMLH536.
The 3.7V 700mAh rechargeable battery (see figure below) has its own PCB.
Rechargeable battery with integrated PCB
The Bluetooth PCB uses what appears to be an OTS (off the shelf) Bluetooth castellated PCB.
This PCB has only two ICs:
- BCM20730 from Cypress is the Bluetooth IC. It's advertised as a single-chip transceiver for wireless input devices.
- Although the STMicroelectronics device is marked with 4HDR8 and K645, I was not able to locate any datasheets for this part. I'm assuming this IC is a memory (Flash) device, but I'm not certain.
- The crystal utilized is a 24.000MHz device.
I really enjoyed tearing down this 1D cordless barcode scanner! And although some quality-control measures have been demonstrated to be missing during the assembly process, all in all this handheld barcode scanner appears to be a well-built and creative design, especially the oscillating mirror scheme!
Featured image used courtesy of Amazon.
Next Teardown: Bluetooth Car FM Radio Transmitter