Look, No Batteries!
The world of energy harvesting is getting very interesting. The idea of getting something for nothing is appealing and you get to save the environment at the same time. This is what they call a win-win situation. There are lots of fascinating numbers on this subject but my favourite is that 253 billion batteries will not be recycled in Europe over the next 50 years. At the current run rate, that’s about 1000 tossed batteries per person. I wonder how high a mountain 253 billion batteries would make?
It’s all very interesting, you say, but this doesn’t apply to automotive electronics. A car has only one battery and that gets recycled. On the surface this looks like a good argument but I recently attended a conference on Energy Harvesting and Wireless Sensor Networks. Now wireless sensors are something you do put in vehicles, the most common being tyre pressure sensors.
So perhaps energy harvesting is worth looking at a bit further. Everyone is aware that the wiring harness in a vehicle is expensive and heavy, which is why most manufacturers are trying to find a way to reduce its size. Perhaps wireless sensors that harvest energy from the environment are a way to make that happen. Imagine an engine bay with no wiring to any of the sensors!
Let’s start with the easy ones. A sensor that generates energy from rotational movement is relatively easy. There are magnets, coils, piezo sensors and Wiegend sensors that can all generate enough power to conduct useful electronic functions. Energy harvesters that get their energy from vibration are also possible, which can be very effective if the frequency and amplitude of the vibration is well defined. Similarly, collecting energy from an RF field is not so hard if you can tune your antenna to the right frequency. The engine bay of any vehicle is an oasis of opportunity to harvest energy from movement, heat, vibration or RF. So it would seem that harvesting the energy is not technically that difficult.
Ramtron recently released an innovative memory called WM72016. Its a wireless memory that can be read from and written to via an RF port and serial port. You can think of it as a dual-ported memory. The nice thing is that it can be powered either from a local power source or from an RF field. In a wireless sensor application the data could be retrieved even when the sensor is not generating any energy and data could be written by the harvested energy from the sensor without the need for a constant RF field.
Energy harvesting may offer solutions to automotive sensors that could reduce wiring. Ramtron’s Wireless Memory with a serial port gives a simple solution to the problem of transporting data without wires based on the energy harvested from the RF field. Now come on. Be honest. Did you start out thinking that a nonvolatile memory with low-power, high endurance and fast write could actually be a tool for the removal of sensor wiring?
F-RAM Design Hints | Duncan Bennett | 
September 8, 2010 11:28 am
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