Welcome to the training module on Handheld Laser Barcode Scanners. This training module will introduce a solution for handheld laser barcode scanner and recommended some related components.
Barcodes allow you to easily and accurately track items and reference data associated with those items. From Wikipedia, a barcode is an optical machine-readable representation of data, which shows certain data on certain products. The barcode doesn't contain descriptive data, but just a reference number. A barcode is a series of varying width vertical lines (called bars) and spaces. This Symbology defines the technical details of a particular type of barcode: the width of the bars, character set, method of encoding, checksum specifications, etc. There are lots of different bar codes. Some bar codes are numeric only whiles other have both letters and numbers. Some bar codes are fixed length whils others are not. 2D barcode, also called matrix code, is a two-dimensional way of representing information. This barcode has more data representation capability.
A barcode scanner is designed specially to read barcodes printed on various surfaces. As we said before, a barcode is an optical machine readable data, so it is read by an optical scanner that measures the relative widths of the bars and spaces, translates the different patterns back into regular characters. The black lines of a barcode reflect less light, and more light is reflected by the white spaces. Many different types of bar code scanning machines exist, but they all work on the same fundamental principles. A optical sensor receives reflections to obtain analog waveforms. Then the analog signal is converted into a digital signal via an ADC. Finally, the digital signal is sent to microcontroller for further process.
There are three basic types of bar code scanners: wand, charge couple device, and laser. The wand scanner is the simplest and least expensive scanner available. It is durable and contains no moving parts. It must, however, come into contact with the bar code, which can present a challenge. So it must be held at the proper angle and moved at the proper speed. The CCD, or &quot;Charge Couple Device,&quot; is another common scanner. Similarly, the CCD scanner does not have any moving parts thus it is reliable and less prone to failure. It is able to read bar codes quickly and easily, but it has a short read range, and must be held no more than 1 to 3 inches from the bar code. The laser scanner is perhaps the most popular bar code input device. A laser scanner need not be close to the bar code to do its job. A standard range laser scanner can read a bar code from about 6 to 24 inches away. But compared to other two scanners, it is more expensive.
Handheld laser barcode scanners are portable barcode scanning devices featured with advantages such as long scanning distance, fast scanning speed, high motion tolerance and wide scanning range because of its laser light source. It is widely used in commodity circulation, library management, mail management, warehouses, factories, supermarkets and other business. Now let us look at how a laser barcode scanner works. The laser scanner works by sending a low energy light beam or laser beam to read the spacing between a pattern on the image one space at a time. The beam is moving back and forth by using a mobile mirror which causes a blinking effect. You can usually see the red line moving over the barcode. The reflection comes back and is then read by the fixed mirror in the scanner. The scanner then generates analog and digital signals that match the pattern. A barcode reader decoder then processes the information and sends it through the data communications interface.
A handheld laser barcode scanner has a switch button. When the switch is triggered by a user, it sends out a trigger signal to MCU. Then the MCU instruct the driver circuit to drive a laser diode. Meanwhile, the motor driver is also activated to drive the motor to rotate the polygon mirror. Laser beams emitted from the laser diode hit the polygon mirror and scan a barcode. The light-receiving element (photodiode) receives the light of diffuse reflection from the barcode. The diffuse reflection looks like an analog waveform. The barcode scanner amplifies the analog signal using an amplifier and converts the waveform from analog to digital (A/D conversion). The barcode scanner identifies the narrow/wide bars and narrow/wide spaces using digital signals. The barcode scanner converts the signal combination of the bars and spaces into data according to the barcode rules (decoding). It outputs the decoded data to the external unit through RS-232C or a wireless interface.
A hand held barcode scanner employs a laser diode as its light source for an efficient and compact construction. The advantage of laser light is that it can be focused and collimated to a very small beam. Because the light is coherent, the beam will not spread much over a given distance. Therefore, the diameter of the beam will remain small enough to resolve the wide and narrow bars of the bar code even if the reading distance varies. The visible laser diodes are selected with the wavelength from 630nm to 670nm, so the color of the light beam is red. Because we design a handheld device, the power consumption of the laser diodes is one of requirements.
For driving a laser diode, a suitable circuit is required. A laser diodes behaves like usual PN-diode which is biased in the forward direction, so the driver must provide proper biased current. The excessive reverse voltage or forward current can easily destroy it. In our design, the laser diode is driven by a microcontroller through an integrated driver. The laser diode driver should be able to protect the laser diode against transients and keeps the output power stable over a wide supply voltage range.
The ONET4211LD is a laser driver for multiple fiber optic applications up to 4.25 Gbps. The device accepts CML input data and provides bias and modulation currents for driving a laser diode. Also provided are automatic power control (APC), temperature compensation of modulation current, fault detection, and current monitor features. This laser driver circuit consists of a high-speed data path and a bias-and-control block. The function of the data path is to buffer the input data and then modulate the laser diode current according to the input data stream. The bias-and-control block generates the laser diode bias current, maintains constant optical output power, generates a modulation current that can be temperature compensated, and controls power on during start-up and shutdown after failure detection.
In our solution, a small DC motor controls to rotate the polygon mirror. Then a motor drive is used to drive the small DC motor.
The photo detector can be a silicon photovoltaic cell, a photodiode or an optical transistor, used to convert the light reflected by the barcode into electric signals. In our design, we select a photodiode. The photodiode generates voltage waveform to represents the bar and space pattern in the barcode. We select the parts based on three parameters, wavelength, maximum sensitivity, and dark current.
Here is overview of BPW34S photodiode from OSRAM.
A handheld laser scanner can use an 8/16-bit low-power microcontroller to analyze barcode information. The MCU analyzes the datastream from the photo detector, isolates any section that appears to be valid data, decodes the barcode symbols, and sends the result to the host computer via a RS232 interface or wireless interface.I 2 C
The wireless transmitter is an optional module. It is used to transmit barcode information to a computer through wireless connection.
The tale lists out some additional components which are used in laser barcode scanner solution. The power management part can be a DC/DC converter or LDO regulator that provides a wide range of input voltage, stable output voltage, and low standby current. EEPROM or flash memory is used to store barcode information. As it is a handheld device, battery is used as power source which may be a a rechargeable battery with small size, low weight, large capacity and long service life. The amplifier is used to amplify the small signals coming from the photo detector. The interface and driver component is used to communicate the barcode scanner with the host computer.
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Handheld Laser Barcode Scanners
Handheld Laser Barcode Scanners
Introduction <ul><li>Purpose </li></ul><ul><ul><li>To introduce a solution for handheld laser barcode scanner and recommended some related components suitable for the application. </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>Barcode overview </li></ul></ul><ul><ul><li>Barcode scanner basics </li></ul></ul><ul><ul><li>Laser barcode scanner </li></ul></ul><ul><ul><li>Our solution </li></ul></ul><ul><ul><li>Core chip solution </li></ul></ul><ul><ul><li>Peripheral solution </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>17 pages </li></ul></ul>
What is Barcode? <ul><li>From Wikipedia, a barcode is an optical machine-readable representation of data, which shows certain data on certain products. </li></ul><ul><li>The data in a barcode is just a reference number. </li></ul><ul><li>A barcode is a series of varying width vertical lines (called bars) and spaces </li></ul><ul><li>A Barcode Symbology defines the technical details of a particular type of barcode: </li></ul><ul><ul><li>The width of the bar </li></ul></ul><ul><ul><li>Character set </li></ul></ul><ul><ul><li>Method of encoding </li></ul></ul><ul><ul><li>Check sum specifications </li></ul></ul><ul><li>There are lots of different barcodes. </li></ul><ul><ul><li>Numeric-only barcodes </li></ul></ul><ul><ul><li>Alpha-numeric barcodes </li></ul></ul>Numeric only barcode Alpha-numeric barcode
Barcode Scanning Overview <ul><li>An optical scanning device simply emits a bright light and reads what is reflected back to it. </li></ul><ul><ul><li>White stripes reflect light very well, while black stripes reflect hardly any light at all. </li></ul></ul><ul><ul><li>The bar code scanner shines light sequentially across a bar code. </li></ul></ul><ul><ul><li>It then detects and records the pattern of reflected and non-reflected light. </li></ul></ul><ul><ul><li>The scanner then translates this pattern into an electrical signal that the computer can understand. </li></ul></ul>Source from DENSO WAVE
Types of Barcode Scanners <ul><li>Wand Scanner </li></ul><ul><ul><li>Simplest and least cheap device available </li></ul></ul><ul><ul><li>Durable and no moving parts </li></ul></ul><ul><ul><li>Need to be held at proper angle an moved at the proper speed. </li></ul></ul><ul><li>Charge Couple Device (CCD) Scanner </li></ul><ul><ul><li>Able to read bar codes quickly and easily </li></ul></ul><ul><ul><li>Durable and no moving parts </li></ul></ul><ul><ul><li>Short read range </li></ul></ul><ul><ul><li>Limited barcode width </li></ul></ul><ul><li>Laser Scanner </li></ul><ul><ul><li>Most popular barcode scanner </li></ul></ul><ul><ul><li>Long read range </li></ul></ul><ul><ul><li>Using moving mirrors </li></ul></ul><ul><ul><li>More expensive </li></ul></ul>
Handheld Laser Barcode Scanners <ul><li>A handheld laser barcode scanner is an active contactless type. </li></ul><ul><li>The laser beam is used as the light source. </li></ul><ul><li>The rotating optical components, like lens, polygon mirror, and transparent mirror, scan the laser beam back and forth across the bar code. </li></ul><ul><li>The captured data is converted into electrical signals and are then processed by a MCU. </li></ul><ul><li>The handheld device usually has wireless communication capability. </li></ul><ul><li>Common Applications </li></ul><ul><ul><li>Point of sales </li></ul></ul><ul><ul><li>Warehouse </li></ul></ul><ul><ul><li>Industrial </li></ul></ul><ul><ul><li>Retailer </li></ul></ul><ul><ul><li>Libraries </li></ul></ul><ul><ul><li>Medical facilities </li></ul></ul><ul><ul><li>Legal office </li></ul></ul>
Laser Diode Driver Selection Guide 100mA 3.3V 155 Mbps to 4.25 Gbps Laser Driver ONET4211LD TI 100mA 3.3V 11.3 Gbps Laser Diode Driver ONET1101L TI 100mA 5V Laser Diode Driver ADN2870 ADI 100mA 5V Laser Diode Driver ADN2841 ADI 100mA 3 to 3.6V Differential Laser Diode Driver ADN2531 ADI 300mA 2.4 to 15V 15V CW Laser Diode Driver IC-WKN Laser Components 70mA 3.6 to 15V M-TYPE CW Laser Diode Driver IC-WKM Laser Components 70mA 2.4 to 6V 2.4V CW Laser Diode Driver IC-WKL Laser Components Laser Drive Current Supply Voltage Description Part Number Manufacturer
TI’s ONET4211LD Laser Driver <ul><li>Multirate Operation From 155 Mbps up to 4.25 Gbps </li></ul><ul><li>Bias Current Programmable From 1 mA to 100 mA </li></ul><ul><li>Modulation Current Programmable From 5 mA to 85 mA </li></ul><ul><li>APC and Fault Detection </li></ul><ul><li>Fault Mode Selection </li></ul><ul><li>Bias and Photodiode Current Monitors </li></ul><ul><li>CML Data Inputs </li></ul><ul><li>Temperature Compensation of Modulation Current </li></ul><ul><li>Single 3.3-V Supply </li></ul><ul><li>Surface-Mount, Small-Footprint, 4 mm × 4 mm 24-Lead QFN Package </li></ul>
Motor Driver Selection Guide 2A 4to 14V Inverting High Speed MOSFET Driver TPS2816 TI 2A 4to 14V Inverting Dual High-Speed MOSFET Drivers TPS2814 TI 2A 4to 40V Inverting Dual High-Speed MOSFET Drivers TPS2811D TI 1A 8 to 14V High Voltage 1A Peak Half Bridge Gate Driver LM5109 NS -- 8 to 48V Quad Protected High-Side MOSFET Driver LT1161 Linear -- 4.5 to 18V High-Side Micropower MOSFET Driver LTC1154 Linear -- 4.5 to 18V Quad High Side Micropower MOSFET Driver LTC1156 Linear -- 8 to 48V Protected High Side MOSFET Driver LT1910 Linear -- 3.3/5V 3.3V Dual Micropower High-Side/Low-Side MOSFET Driver LTC1157 Linear 0.5A 3 to 12V Full Bridge Driver with Integrated 0.5A Power FETs for Small 3V, 5V and 12V DC Motors HIP4020IBZ Intersil Output Current Supply Voltage Description Part Number Manufacturer
OSRAM BPW34S Photodiode <ul><li>Especially suitable for applications from 400 nm to 1100 nm </li></ul><ul><li>Short switching time (typ. 20 ns) </li></ul><ul><li>DIL plastic package with high packing density </li></ul><ul><li>Suitable for reflow soldering </li></ul>photosensitive area
MCU Selection Guide I2C/UART/SPI No 10-bit 8 0.364 N/A 8 ST7FLITE29F2M6 ST I2C/UART/SPI No 10-bit 8 0.364 N/A 8 ST7FLITE20F2B6 ST I2C/UART/SPI Up to 9 bit 14-bit 4 0.256 N/A 24 CY8C24x23A Cypress I2C/UART/SPI Up to 9 bit 14-bit 16 0.256 N/A 24 CY8C27x43 Cypress I2C/UART/SPI Up to 9 bit 14-bit 32 2 N/A 24 CY8C29x66 Cypress UART/SPI 54 10-bit 16 1 4*25 16 ATMEGA169P Atmel UART/SPI 69 10-bit 32 2 4*40 20 ATMEGA3290P Atmel I2C/UART/SPI 24 10-bit 16 1.536 N/A 16MIPS PIC24F16KA102 Microchip I2C/UART/SPI 18 10-bit 4 0.512 N/A 12MIPS PIC24F04KA201 Microchip I2C/UART/SPI 34 10-bit 64 3.8 N/A 12MIPS PIC18F46J50 Microchip I2C/UART/SPI 34 10-bit 64 3.8 N/A 12MIPS PIC18F46J11 Microchip USB/I2C/UART/SPI 36 10-bit 64 3.936 N/A 16MIPS PIC18F46K20 Microchip USB/I2C/UART/SPI 14 10-bit 16 0.768 N/A 12MIPS PIC18LF14K50 Microchip I2C/UART/SPI 36 8-bit 14 0.368 N/A 5MIPS PIC16F727 Microchip SPI/I2C/SCI No 12-bit up to 32 2 4*41/8*37 40 S08LG series Freescale SPI/I2C/SCI No 12-bit Up to 64 2 4*28/8*36 20 S08LL series Freescale I2C/UART/SPI 2 Ch 12 Bit 12-bit SAR 92~120 4~8 160 8 MSP430FG461x TI I2C/UART/SPI 1 Ch 12 Bit 16-bit ΣΔ 32~60 2 128 8 MSP430F47x TI I2C/UART/SPI 2 Ch 12 Bit 16-bit ΣΔ 32~60 2 128 8 MSP430FG47x TI Interface DAC ADC Flash (KB) RAM (KB) LCD Segments Frequency (MHz) Part Number Manufacturer
Wireless IC Selection Guide SPI 2.405 to 2.48GHZ 2.4GHz RF transceiver for ZigBee applications MC13203 Freescale SPI 2.405 to 2.48GHZ 2.4GHz RF transceiver for 802.15.4 applications MC13202 Freescale SPI 2.405 to 2.48GHZ 2.4 GHz, Low Power Transceiver for 802.15.4 MC13192FC Freescale SPI 2.4 to 2.483GHz 2.4 GHz CyFi™ Transceiver CYRF7936 Cypress SPI 402-470/804-940 Low Power RF Transceiver for Narrowband Systems CC1020RSS TI SPI 2400-2483.5 Low power RF Transceiver CC2400-RTB1 TI SPI 863-870/902-928/950-960MHZ Ultra-Low Power Transceiver Chip SX1211I084TRT Semtech SPI 433/868/915MHZ Multiband Transceiver Embeded microcontroller and ADC NRF9E5 NORDIC SPI 2.4GHZ nRF24E2 - System on Chip with 8051 MCU NRF24E2G NORDIC SPI 2.4GHZ nRF24E1 - System on Chip with 8051 MCU NRF24E1G NORDIC SPI 2.4GHZ nRF2402 ultralow power 2.4GHz transmitter nRF2402 NORDIC SPI 2.4GHZ nRF2401A ultralow power 2.4GHz transceiver NRF2401 NORDIC Serial 300-450 Crystal-based, Fractional-N Transceiver Chip MAX7032 Maxim Serial 80-650/862-950 High Performance Narrow-Band Transceiver Chip ADF7021 ADI Serial 135 to 650 MHz High Performance, ISM Band, FSK/ASK Transceiver IC ADF7020 ADI Digital ADI/Q™ 2.3 to 2.7GHZ / 4.9 to 6GHZ WiMAX/WiBro RF MxFE Transceiver AD9352 ADI SPI 2.4 to 2.4835GHZ SoC for ZigBee/IEEE 802.15.4 Wireless Sensor Network CC2430 TI SPI 2.4 to 2.4835GHZ Z-Accel 2.4 GHz ZigBee Processor CC2480 TI SPI 2.4 to 2.4835GHZ SoC for ZigBee/IEEE 802.15.4 Wireless Sensor Network CC2431 TI SPI 2.394 to 2.507GHZ SoC for 2.4-GHz IEEE 802.15.4 and ZigBee Applications CC2530 TI SPI 2.394 to 2.507GHZ 2.4 GHZ IEEE 802.15.4/ZigBee® RF Transceiver CC2520 TI Interface Freq. bands Description Part Number Manufacturer
Peripheral Solution Click Click Interface & Driver Click Click Laser Driver Click Click Laser Diode Click Click DC Motor Driver Click Click DC Motor Click Click Amplifier Click Click Battery Click Click Flash Memory Click Click EEPROM Click Click Power Management ICS Newark Farnell Block
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