A MULTI-CHANNEL SYSTEM FOR DETECTING METAL CONNECTORS IN WASTE WOOD-BASED MATERIALS

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1 th December 0. Vol. No JATIT & LLS. All rights reserve. ISSN: -8 E-ISSN: 8- A MULTI-CHANNEL SSTEM FOR DETECTING METAL CONNECTORS IN WASTE WOOD-BASED MATERIALS JIANGMING KANU, MINGKUO CHEN, XINTONG CUI, WENBIN LI School of Technology, Beijing Forestry University, Beijing 0008, China *Corresponing author: WENBIN LI, leewb@bjfu.eu.cn ABSTRACT Metal connectors in waste woo-base materials shoul be remove before reuse. A multi-channel metal connector etecting system is presente, etecting the metal connectors in waste woo-base materials. It inclue three parts: a high precision sensor for etecting metal connectors in waste woo-base materials, a multi-channel ata logging an processing system base on microcontroller unit, an a moel for positioning the metal connectors in waste woo-base materials. The high precision sensor has a magnet an, Holzer element an a ifferential amplifier an peak etector circuit. The multi-channel ata logging an processing system has a micro-controller unit, an 8-channel AD converter an some auxiliary circuits. The moel shows the relationship between the positions of metal connectors with the signals from 8 sensors. The experimental results show that the maximal etecting height is.0cm for the 0.8хmm nail, as well as.8cm for the. 0mm nail an the position error between the real positions of the nails an those get from the moel is less than cm. The system can meet the practical nees of the reusing waste woo-base materials. Keywors: Waste Woo-base Materials; Metal Connector Detection; Positioning Moel. INTRODUCTION Waste woo-base material inclues waste woo, woo-base boar an its proucts. Processing an utilizing waste woo-base material has an important significance for the conservation of woo resources an achieving the sustainable evelopment of woo-base panels inustry. It is estimate that China's annual waste woo an woo-base resources is about 8 million cubic meters, as three cubic meters of woo waste to prouce one cubic meter of woo-base panel, which can prouce 8. million cubic meters woo-base panels, equivalent to annual savings of 8 million cubic meters of timber, less eforestation of. million hectares. Recycling of waste woo-base materials, not only has playe an important role in alleviating the shortage of raw materials of woo base panel inustry, but also can change the traitional one-way timber consumption patterns an take the recycling economy evelopment moel to buil a resourcesaving an environment-frienly society [-]. The first for waste woo-base materials re-processing is to remove the impurities in it, incluing the connectors. Waste woo-base materials inclue a lot of metal connectors, especially the ferromagnetic metal parts, an these connectors not only exist on the surface of the woo material, but also in its internal, ifficult to etect by the nake eye, thus it increases the ifficulty for repartition an processing waste woo-base materials. The metal connectors may amage the processing equipment, such as cutting tools. So how to quickly etect an locate these connectors becomes the first solve problem for comprehensive utilization of waste woo-base material [].The methos for etection of metal connectors in waste woo-base material are that base on X-rays an the principle of electromagnetic inuction. The metho base on the X-ray can etect metal connectors in waste woo-base material very accurately an etermine its position, but it has a high cost an nees professional security []. A single coil metal etectors can etect metal connectors, but because the etection coil is only one [,8], can not position the metal connectors, so you nee a lot of human to position the metal connectors, which increases a heavy cost for reusing the waste woo materials. The effect of the metho base on the principle of electromagnetic inuction epens on the performance of the etection coil, more parameters affecting the etection coil [, 8]. [] escribe a metho base on the principle of electromagnetic inuction to etect the connectors, but the stability of the etection sensor is poor, an it can only fin out that whether there is a metal connector in waste woo-base materials. 0

2 th December 0. Vol. No JATIT & LLS. All rights reserve. ISSN: -8 E-ISSN: 8- In orer to accurately etect an locate the metal connectors in waste woo-base materials, this paper inclues four parts, incluing the esign of high-precision etection sensor, multi-channel ata logging an processing system base on MCU (microcontroller unit), the positioning moel for the metal connectors in waste woo-base materials an experimental results & analysis.. SENSOR FOR DETECTING METAL CONNECTOR. Principle Of Detecting Metal Connector If there are no ferromagnetic objects near the magnet, its surrouning magnetic fiel strength oes not change. While there are ferromagnetic objects near the magnet, the magnetic inuction lines aroun the magnet will change, an then the magnetic inuction B of a fixe point aroun the magnet will also change []. We can etermine whether a metal connector exists in waste woobase material by sensing the changes in the magnetic fiel aroun the magnets. Accoring to this principle, the metal connector etecting sensor contains the etection probe, the Holzer element, ifferential amplifier an peak etecting circuit, as shown in Figure. Magnet can prouce a fixe magnetic fiel, an a Holzer element is use to etect the changes of a fixe point in the magnetic fiel of the magnet, the ifferential amplifier an the peak etecting circuit can amplify the weak output signal of the Holzer element an etect the peak value of magnetic fiel changes. The output voltage range of the sensor for etecting the metal connector is 0-V. magnet Holzer elements Differential amplifier An Peak Detecting circuit Figure: The Block Diagram Of The Sensor For Detecting Metal Connector. Differential Amplifier An Peak Detector In this stuy, a roun magnet (iameter of.cm, thickness 0.cm) was use as etecting probe an the Holzer element (UGN0) fixe in the center of the magnet as a probe to etecting the changes of the magnetic fiel. The UGN0 has the sensitivity of.mv / G, the static output voltage of.v an operating voltage of.-v. When ferromagnetic objects are close to the etecting probe, the magnetic fiel aroun the etecting probe will be larger. The Hall element can accurately etect tiny changes of the magnetic inuction. The Hall element output voltage of the Holzer element, which is in millivolt level, is very small. Taking the effect of noise into account, the ifferential amplifier was use to suppress noise an zero rift an provie a large enough amplification factor. The peak etector was use to etect the changes of the ensity of the magnetic fiel. The thir amplifier was use to ensure that voltage output of the metal connection etection sensor is 0-V. The schematic iagram of the ifferential amplifier an peak etector is shown in Figure. UGN0 R 00K R K R 00K R 00K R 00K LM N8 0.uF R8.K R 00K R K R 0K R0 K R K LM R 0K LM Figure : The Schematic Diagram Of The Differential Amplifier An Peak Detector. MULTI-CHANNEL DATA LOGGING AND PROCESSING SSTEM BASED ON MCU. Harware Of Multi-Channel Data Logging An Processing System In orer to accurately position the metal connectors in waste woo-base materials, this system shoul have the function of logging multichannel sensors simultaneously an communicating with personal computer (PC). The STC8C microcontroller unit (MCU) is use as the main chip in this system, which is a low-power, low-cost, high-spee, highly reliable 8-bit microcontroller, an compatible with the MCS- instruction set, with internal Flash that can be rewritten 00,000 times or more. The analogy signals from sensors are igitize by an Analog-to-Digital converter (TLC, an 8-channel A/D converter with 0-Bit resolution) an processe in the microcontroller. A ual river/receiver (MAX) was use between microcontroller an PC [0]. The structure of the multi-channel system is shown in Figure. The stability of the power subsystem is an important factor that affects the accuracy of the whole system, because the sensors an Analog-to- Digital converter all nee a high- stability electrical power as reference voltage. The input of the power subsystem is irect current power with about +V. A linear regulator (AMS-.0, a low ropout three- terminal regulator with A output current capability) was use to keep electrical power in +V with maxim tolerance of.0%. Some capacitors are use as filters with resistances. The schematic iagram of the power subsystem is shown in Figure. 0

3 Journal of Theoretical an Applie Information Technology th December 0. Vol. No JATIT & LLS. All rights reserve. ISSN: -8 E-ISSN: 8- J POWER sensor 0 sensor sensor sensor sensor sensor sensor sensor A0 A A A A A A A TLC Serial port circuit CPU STC8C Power subsystem Figure: The Block Diagram Of The Structure Of The Detecting System A B C SP KE-POWER C 0uF/0V C 0.uF U VIN ASM GND OUT C 0.uF C 0uF/V R K POWER LED system initialization, system calibration, ata acquisition, the meian filter, RS communication an so on. The program flow chart is shown in Figure.. System initialization mainly refers to the configuration of the microcontroller serial communication an other operating parameters. System calibration is collecting the reference value that is the output voltage values of each metal connection etection sensor when no metal connectors aroun the sensors. Meian filter moule is to eliminate the ranom noise in the ata from all sensors. RS communication moule cooperates with the serial communication software in PC to transmit the ata between PC an microcontroller. Start system initialization Fig. The Schematic Diagram Of The Power Subsystem Some auxiliary circuits are inispensable for the smooth running the whole system, for example reset circuit an crystal oscillator circuit. The complete schematic of the multi-channel ata logging an processing system is shown in Figure. GND system calibration Set Channel Number A=0 Set sampling number M Rea M ata from Channel A meian filtering A=A+ S RESET C 8 0 0uF C 0p C 0p R K R 0K.0M C 0 U P0/T P/T P P P P 8 P P INT INT0 T T0 EA/VP 8 X X RESET RD WR STC8C 0 GND 0 P00 P0 P0 P0 P0 P0 P0 P0 P0 P P P P P P P 8 8 RXD TXD 0 ALE/P PSEN 0 P.0 C 0 P.0 D LED C 0 U A0 0 A EOC A I/OCLOCK A ADDRESS 8 A DATOUT A CS A REF+ A REF- C A8 A0 GND A 0 TLC MAX C+ VS+ C- VS- C+ C- GND TIN TOUT 0 TOUT TIN ROUT RIN ROUTRIN 8 U Figure : The Complete Schematic Diagram Of The Entire System. Software Of Multi-Channel Data Logging An Processing System The software of multi-channel ata logging an processing system inclues the low-level software an up-level software. The low-level software running in the lower computer such as MCU or Programmable Logic Controller (PLC) is responsible for controlling the harware an lowlevel ata processing an transmitting. The up-level software running in the human-interface computer such as personal computer is responsible for uplevel ata processing an isplaying its results... low-level software The low-level software running in the STC8C microcontroller inclues programming moules, R K C 0 C 0 C 0 COM 8 J Is ata to sen? Serial Port Communication Is the channel #? Figure : The Flow Chart Of Low-Level Software.. up-level software in pc The up-level software in PC can transmit ata an commans between PC an microcontroller, also can further process the ata from sensors an locate the metal connectors when there are some metal connectors in waste woo materials. It inclues serial port initialization, locating metal connectors an isplaying the results. Serial port initialization moule sets the parameters of the RS communication (such as bau rate, communication moe, the size of sener/receiver buffer an so on) []. The moule of locating metal connectors calculates the position of the metal connectors from the receive ata using the metal connector positioning moel that will be etaile introuce in the next part of this paper. The program flow chart of the up-level software in PC is shown in Figure. N N 0

4 th December 0. Vol. No JATIT & LLS. All rights reserve. ISSN: -8 E-ISSN: 8- Start Set serial communication moe an bau rate Empty the receive/sen buffer a U = a U a n+ n () Un+ = + U n U n+ N Sen Comman g Data Arrive? z s= n a + + () Met al Connect or a - a h Rea an Store Data o 0 / Sensor Number x Position the Metal Connector Display Position Results y S Figure 8: The Schematic Diagram Of The Installation Of Sensors. EXPERIMENTS AND RESULTS ANALSIS Figure : The Flow Chart Of Up-Level Software. POSITIONING MODEL OF METAL CONNECTOR In this stuy, 8 etecting sensors are arrange in line, as shown in Fig.8. The sensor number of these 8 sensors is form 0 to. The iameter of the sensor (marke as ) is.cm. The coorinate origin is at the left margin of the sensor 0. The s references to the istance from coorinate origin to the position of the metal connector. The former experimental results show that only one output of 8 sensors is change when the metal connector is above the sensor an there are two change outputs of 8 sensors when the metal connector is above two sensors. When there is only one change output of 8 sensors, the positioning moel is shown in formula. The sensor number is labele as n. s= + n () When there are two change outputs of 8 sensors, the istance from the position of the metal connector to the center of the left sensor that have the change output is labele as a, as shown in Figure 8. The relationship between the two change output U an the istance a is shown as formula. The sensor number is labele as n. Un is the change of the output from sensor n (n is from 0 to ), an U n + is the change of the output from sensor n+. In this case the metal connector positioning moel is shown in formula. In this stuy, there are two types of experiments. One is test the ability of the sensors to acquire the changes of the magnetic fiel aroun them, the other is test the performance of the positioning metal connectors in waste woo-base materials. In the first type experiments, kins of metal nails with ifferent specifications were selecte to be hung above a sensor separately. The maximal height (labele as h) was recor where the output of the sensor change, as shown in Figure 8. The name, specification an the maximal height o of kins of nail were liste in Table. Table. Experimental Data Of The Maximal Heights Of Different Types Of Nails Nail Name Specification Maximal Height(cm ) Roun nail Roun nail Hinge (nickel) High strength ouble ry wall nail High strength ouble ry wall nail Galvanize Galvanize Flat cross rill tail screw Sala hea cross galvanize Sala hea cross galvanize Sala hea cross galvanize Cross recesse high strength flat countersunk hea tapping Cross recesse high strength flat countersunk hea tapping 0.8 mm. mm. mm. mm. 0mm. mm..mm. mm.8хmm.8 mm.8 mm. mm. mm.0 0mm.0 mm

5 th December 0. Vol. No JATIT & LLS. All rights reserve. ISSN: -8 E-ISSN: 8- Cross recesse high strength flat countersunk hea tapping Roun cross rill tail screw.0 mm. mm From table, 0.8xmm roun nail is alreay a kin of smallest metal connectors use to fasten woo-base materials. From table, the maximal height for the sensor evelope in this research is.0cm for the 0.8xmm roun nail. The bigger nails are the maximal height for the sensor evelope in this research is larger. The first type experimental results show that the sensors evelope in this stuy can etect the metal connector in waste woo materials up the epth of.0cm. In the secon type experiments, 0 pieces of waste woo-base materials, from ol furniture an for frame of winows an oors, an kins of metal nails with ifferent specifications that are same with those in the first type experiments, were use to test the performance of the positioning metal connectors in waste woo-base materials. Nails were implante into the waste woo-base material at the epth less than the maximal heights that the sensor can etect them. The waste woobase materials move uner the sensors, as shown in Figure. The etecte istances of the metal connectors to the coorinate origin got by this system an the actual istances of the metal connectors to the coorinate origin got by straight scale were recor. The metal connector positioning experimental ata was liste in Table. y o z 0 Met al Connect or i r ect i on of movement Wast e woo- base mat er i al s.. Sensor Number x Figure. The Schematic Diagram Of The Positioning Experiments Table. Experimental Data Of Metal Connector Positioning Nail Name Specifications S 0 S S (cm) (cm) (cm) Roun nail Roun nail Hinge (nickel) High strength ouble ry wall nail High strength ouble ry wall nail Galvanize 0.8 mm. mm. mm. mm. 0mm..mm Galvanize Flat cross rill tail screw Sala hea cross galvanize Sala hea cross galvanize Sala hea cross galvanize Cross recesse high strength flat countersunk hea tapping Cross recesse high strength flat countersunk hea tapping Cross recesse high strength flat countersunk hea tapping Roun cross rill tail screw * S= S S0. mm. mm.8 mm.8 mm.8 mm. mm. mm.0 0mm.0 mm.0 mm. mm From Table, it is known that the etecte istance measure by the system evelope in this stuy, from the position of the nail etecte from the coorinate origin to the position of the metal connector in waste woo-base materials is basically same with the actual one that measure by the straight scale. The absolute value of the ifference between the etecte istance an the actual one is mostly less than cm that is accurate enough for reutilize the waste woo materials, because the position error of the metal connect is less than cm for the most Woo processing equipments in China.. CONCLUSIONS From the esign of the sensor for etecting the metal connector, the harware an software of the multi-channel ata logging an processing system, the metal connector positioning moel an experimental ata analysis, some conclusions are summarize as follows: () The esigne sensor can etect the metal connector which size is larger than 0.8mm even uner the surface of the waste woo materials with the epth of.0cm. The bigger nails are the maximal etecting height of the sensor is larger. The performance of the sensor is better than that esigne before. () The Multi-channel ata logging an processing system can simultaneously recor, 0

6 th December 0. Vol. No JATIT & LLS. All rights reserve. ISSN: -8 E-ISSN: 8- process an transmit the ata for 8 sensors. The system can communicate with PC via the serial port. () The metal connector positioning moel shows the accurate relationship between the changes of the output from the sensor an the position of the metal connector in waste woobase materials. The position error is less than cm in this stuy, which can meet the nee of the utilization of waste woo-base materials in China. () The sensor an the system base on MCU are cheaper than that base on X-ray, because the price of the electrical component an MCU is very low. The multi-channel etecting system for metal connectors in waste woo-base materials has higher cost performance Ratio. () The sensor base on the principal of electromagnetic inuction can not etect the plastic an non-ferromagnetic metal connectors in waster woo materials that shoul be etecte an remove, which is the further research in future. ACKNOWLEDGMENTS This stuy is financially supporte by the Beijing Key Acaemic Subject Research Project of Forest Engineering (00). (Natural Science Eition), Vol., No.,00, pp. -. [] J. Wang, A. Wang,. Liao, Stuy on the Effects of Coil Parameter of Electric Ey Transucer on the Performance of Transucer, Process Automation Instrumentation, Vol., No., 00, pp. -. [8]. u, P. Du,. Liao, Stuy on effect of coil shape an geometric parameters on performance of ey current sensor. Chinese Journal of Scientific Instrument, Vol. 8, No., 00, pp [] M. Chen, J. Kan, Z. Hao, Design of etection system for metal connectors in waste woo materials. Science Technology an Engineering, Vol. 0, No. 8, 00,pp.- 0. [0] X. Ma, Z. Tong, L. Zhou, COM port communication an program esign between SCM an PC base on VB. Ornance Inustry Automation, Vol., No. 0, 00, pp. -. [] Z. Ma, Z. Wu,. Wang, Research an realization of the serial communication system base on VB between PCs an microchips. Journal of Tangshan College, Vol., No., pp. -. REFERENCES: [] K. e, G. Chen, W. u, Utilization of waste woo-base materials, China Woo Iustry, Vol. 0, No.,, pp.-. [] S. Wang, F. Sun, X. Duan, J. Zhao, Utilization an prospect of recycle woo materials, Journal of Northwest Forestry University, Vol. 0, No., 00, pp [] L. Ma, W. Shi, S. Zhang, The situation an problem of proucing woo-base panels with recycle woo materials, Woo Processing Machinery, No., 00, pp.-. []. Wang, W. u, F. Ji. Present situation on recycle utilization of waste woo materials. Woo Processing Machinery, No., 00, pp. -0. []. Wang, W. u, F. Ji, Situation an prospect analysis on recycling an utilization of the woo materials, China Woo-Base Panels, No., 00, pp. -. [] J. Liu,. Zhu, J. Kan, The application of image processing for the segmentation of measure image of waste woo-base materials connector, Journal of Guangxi University 0