In this project, optimised electrically conductive textile structures were developed that are capable of transmitting high currents and can be produced in a cost-optimised manner. Through a targeted structuring of the interconnection of the conductor paths in connection with an optimised control of the electrical consumers, significant quantities of the expensive electrically conductive thread material are saved and thus the material costs can be significantly reduced.
For reasons of profitability and safety, it is essential to develop conductive textile circuit matrices that are already designed in the circuit layout to optimise the supply lines for high currents and ensure optimal current distribution. To this end, guidelines for the construction of textile circuit carriers that enable the transmission of high currents are to be developed. The aim of the project is the development of current-carrying textile circuit matrices and their cost-effective production. Electrically conductive structures are to be developed that are capable of transmitting currents in the range of 5...10 A.
The circuit structures currently used for textile applications in the field of heating and lighting technology are not optimised for high currents. Likewise, the structure of textile conductors is not designed for such applications. The development of suitable textile circuit matrices with high current-carrying capacity offers great potential for saving expensive electrically conductive thread materials. In order to determine the current-carrying capacity of conductors, their heating under application conditions must be recorded. For this purpose, a measurement setup was developed, which is shown in Figure 1. A defined current is fed into the conductor tracks via a power supply unit with adjustable output voltage, which can be precisely adjusted by means of theelectronic load connected to the other side. A thermal imaging camera is used to record the heating of the conductor tracks and the surrounding tissue. In this way, it is determined whether the conductor paths heat up during a defined current transmission within the temperature range permissible for the application or whether inadmissible heating occurs. Alternatively, temperature sensors or infrared thermometers can be used to determine the temperature of the conductive path.
In general, the following strategies are useful for the success of the optimised circuit design:
Results and Applications
In the project, findings and guidelines from the electronics industry were adapted and further developed for textile applications. It was possible to show how applications with high current requirements can be realised on a textile basis despite the high electrical resistance of the textile-processable conductor materials. In the project, a textile luminaire was developed as a demonstrator in which a high number of LEDs were integrated on textile conductor paths. By applying the strategies developed in the project, it was possible to realise such a luminaire that would result in a current flow of several amperes if the LEDs were simply connected in parallel. Based on the project results, the luminaire can now be operated with a current flow of only 400 mA. The solution here consists of the structured parallel connection of the LEDs in individual segments and the series connection of the segments to each other with an increase in the operating voltage from 3 V to 36 V (see figure 2). This means that commercially available power supply units can be used for the voltage supply. Optionally, the lamp's segments could also be equipped with twice the number of LEDs, which then have to be connected with reversed polarity. If the lamp is operated with alternating voltage, a doubling of the brightness can be achieved, as all LEDs then light up simultaneously. Figure 3 shows the finished LED lamp. The implementation of the R&D results can take place with representatives of the textile industry, embroidery companies, in medical technology as well as in the electronics industry, and with the end users, the manufacturers of smart textiles. Based on the knowledge gained in the project, new products can be developed and new functions can be integrated into textiles.
Dipl.-Ing. Frank Thurner
Phone: +49 (0) 3661 / 611-346