Conductive yams

The electrical resistance of a material is determined by the material itself and the geometric shape of the conductor. In general. Ohm s law is applied to calculate the electrical resistance. This principle can be applied to measure pressure by applying conductive yams in textiles that are bent and deformed when a mechanical load is applied on them. Measuring elongation using electrical resistance is a well-known concept in the world of smart textiles. 

For each material conductive yam combination, 20 experiments were performed and the potential difference (in V) was displayed against the temperature difference (in °C), as shown in Figure 9.5. In general, there was no linear correlation between the two measured parameters for thermocouples, except in narrow temperature ranges. The measured temperatures between 20 °C and 40 °C show, for the yam-based thermocouple pairings, a nearly linear relation to the measured voltage. 

The second step is to prepare the conductive paths. For manual production each conductive path is applied on the foam and knitted fabric. For large-scale production the whole conductive path layer can be produced via flat knitting with a specified distance between the conductive paths. The contact between the cross-wise conductive paths and the control unit is made by sewing with conductive yam as shown in Figure 9.8. An overview of the steps needed for production of the movement sensors is given in Figure 9.9. 

Figure 9.8 Conductive paths contacted with conductive yam.

The interconnection between the conductive textiles and the electronic unit safeguards the reliability of the whole system. Hence, the textile arts needed to be prepared for contacting to the electrical units. For this purpose end sleeves for strands and lustre terminals were attached to the conductive yams. After having prepared the circuit board layout and the control system console, the lustre terminals were connected to the console. Figure 9.10 shows an overview of the budding of the control system. 

Textile-based strain sensors have been demonstrated using stretch fabrics modified with inherently conductive polymers (Rovira et al., 2011) or carbon-loaded mbbers (Tognetti et al., 2005). Knitting with conductive yams is another approach to creating... 

From a manufacturing perspective, it has been demonstrated that it is possible to seamlessly fully integrate conductive yam electrodes into mass produced knitted garments (NuMetrex, 2014 SmartLife, 2014). In the case of the NuMetrex garments, the data from the electrodes are collected and transmitted to an external device by a small electronic device to be inserted manually in a pocket on the garment prior to use. 

Fig. 12.11 (a) Schematic of the fabric structure with the position of various yams in the structure (h) cross-sectional SEM image of the actual fabric clearly showing the position of piezoelectric and conductive yams. 

The authors of this paper have conducted some exploratory experiments with several techniques intending to achieve measurement of heart beat and respiratory rate, using both inexpensive off-the shelf sensors and piezoelectric polymer sheets, as well as fabrics knitted with conducting yams, acting as sensors. A review of the state-of-the-art, an overview of general principles and the results obtained in the expmments will be discussed. 

Several efforts to create prototypes of wearable functional devices have been made in the last years. Most of them consider the approach of joining conventional off-the-shelf electronic devices to fabrics, such as microcontrollers, LED s, optical fibres and all kinds of sensors, especially electrodes for ECG measurement. The consolidated textile technology for integrating conductive yams into knitted or woven fabrics and the implementation of sensors through embroidery has encouraged their use as suitable means for connection, data communication and power transfer. 

Figure 8. Electrical resistance versus extensicm for conductive yam. Sample length SO cms. 

Conducting polymer fibers were prepared by melt mixing and chemical coating on fibers. Different conductive materials were used in order to obtain conductive PP-based fibers with specific electrical and mechanical properties. The electrical conductivity and morphological characteristics of these fibers were investigated (Kim et al. 2004). The conductive fibers are intended for use in creating conductive yams, conductive fabrics (which can be used as electromagnetic shields), and multifunctional textile stractures for novel applications. 

The conductive fibers pUed and or twisted with a nonconductive fiber can also form conductive yams. E-textile yams (Slade, 2014) can be made by using insulated copper wires wrapped around a cotton/nylrai/polyester core yam that demonstrates electrical and mechanical properties. The cmiductive yams and fibers are replacing traditional heavy solid or twisted wires that are too fragile and break down after repeated bends. The conductive yams and fibers are rapidly becoming the smart choice for engineers... 

There are many conductive fibers and yams available (Tables 9.1 and 9.2). The Conductive Fiber Manufacturing Council (CFMC) has published a list of manufacturer and product directory. The Conductive Fiber Manufacturers Council (CFMC ) is the international trade and business development resource for companies that manufacture conductive yams, threads, and fibers. The mission of CFMC is to increase understanding and utilization of conductive fibers and fabrics through information dissemination, advocacy, research, and administration of programs to the members benefit and the advancement of their industries. 

Conductive fibers or yams can be woven, knit, embroidered, braided, sewn, and so on, thus becoming conductive textiles. When woven into or sewn onto a tape, stranded or braided, or connected between two points, conductive yams act like wires. When knit or woven in a mesh, the yams act as an EMI shield or a ground plate. 

MINATEC Entreprises— Prance. Makes a conductive yam, PRIMOID, with... 

Schwarz, A., 2011. Electro-Conductive Yams Their Development, Characterization and Applications (Ph.D. thesis). Ghent University, Ghent. 

To integrate the ultrasonic sensor to textile structures as well as to form electric circuits in the stmcmres, silver-plated nylon yarn with a linear resistance of <50 n/m and with a yam count of 312/34f x 4 dtex is used. To prevent formation of short circuits in the textile-based electric circuit, conductive yams are hidden in the stmcture. A fabric stmcmre is considered as a double-woven fabric, and conductive yarns are placed in the middle layer of the stmcmre. The set of warp yams of the upper layer are linked to the set of weft yarns from the bottom layer, and thus the two layers are held together. A four-harness satin weave is chosen for both layers. Fig. 3.2 shows the diagram representing the drawdown, threading, and lift plan of the double-woven cloth together with the 3D-graphical representation of the woven fabric stmcture. 

Figure 3.2 (a) The draft for double-woven cloth with weft stuffers and conductive yam position (b) 3D representation of the double-woven cloth. 

Figure 3.4 Fabric overview conductive yams corresponding to sensor ground, Vcc, TX, RX, analog voltage, and BW output points.

The removable fabric for microcontroller connection is produced by sewing. Similarly, snap fasteners provided connections the among main circuit and microcontroller. The fabric used for producing the base stracture of interactive garment is also used to produce both microcontroller connection and pockets for batteries (see Fig. 3.12). The conductive yams are again inserted as well as hidden in the middle part of knitted fabric. 

Other hand, during the movement along 1.25 m and 15 cm, in addition to the first vibration motor, the second vibration motor on the right arm also shows vibration in order to present the proximity of the obstacle (see Table 3.3). Signals over the conductive yams measured by the oscilloscope at the point of connection with first, second, and third vibration motors on the left and right arms during the movement toward an obstacle located at the left side are shown in Fig. 3.33. 

Based on these results, the recommended voltage range to be applied on a smart shirt should not exceed 6—7 V in case of utilization of silver-plated conductive yams (<50 0/m) in order to guarantee comfort and safety. 

S. K. Bahadir, Wearable Obstacle Avoidance System Integrated With Conductive Yams for Visually Impaired People (Ph.D. thesis), Universite LiUe, Sciences et Technologies, Computer Engineering/Automation, France, 11/2011. 

Xue, P., et al., 2007. Electrically conductive yams based on PVA/carbon nanotubes. Composite Stmctures (78), 271—277. 

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