Sensors Supply Power

A miniature conveyor system that uses wireless sensors with their own power supply could provide a long-awaited solution to assembly snafus.

When a machine breaks down, production often comes to a standstill until the error is pinpointed -- and that can take hours. In many cases, it's all due to a single interrupted contact. Manufacturers have long sought technology that doesn't require vulnerable power and data cables. The idea is feasible using small devices that harvest energy from their surroundings and provide their own power supply, rather like a solar calculator.

Self-sufficient sensor-actuator systems are comprised of a sensor, a processor and a radio module. They measure position, force or temperature and transmit the data instantaneously by radio. Vital machine data -- a machine overheatring, a drive shaft wearing out-- reaches the control center without the need for cables. So far, though, few off-the-shelf solutions have their own energy supply.

A miniature conveyor system, driven by compressed air, uses wireless sensors that provide their own power supply. (Photo: Festo, courtesy FEG)

Research scientists from the Fraunhofer Technology Development Group (TEG) in Stuttgart, Germany, have joined with industrial partners and universities in the EnAS project, sponsored by Germany's Ministry of Economics and Technology, to build a transportable demonstrator -- a miniature conveyer system driven by compressed air that transports small components in an endless cycle. The round workpieces are picked up by a vacuum gripper, transported a short way and set down on a small carrier, which conveys the parts back to the starting point. Every step of the process is monitored by sensors, as usual, but the demonstrator sensing elements need no external power supply.

The machine uses photo diodes to check, for example, whether the carrier has been correctly loaded. If so, the light from the diodes is obscured by the workpieces. Solar cells supply the energy,

In another example, pressure sensors monitor the work of the vacuum gripper, TEG said in a statement. Power is supplied by piezoelectric flexural transducers; the piezoelectric elements contain ceramics that generate electricity on being deformed, when the vacuum pump is switched on and off. The electricity generated is sufficient to send an "okay" signal to the central control unit; the sensor draws its power from existing pressurized air.

TEG said the system components are expected to make their way into everyday industrial use within the next two years.

For more information, visit: teg.fraunhofer.de