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Deeply embedded intelligence

17 September 2008

A startup company in North Wales is "taking digital sensor intelligence to the next level."

Photo credit: Johanna Ward, Wardour Publishing
Photo credit: Johanna Ward, Wardour Publishing

It has developed a system to embed deep functionality right into the heart of electromechanical products, such as circuit breakers. The breakthrough promises to move us to the next generation in digital protection.

Look inside any ‘intelligent’ device and somewhere in there you’ll find a printed circuit board. Manufacturers can’t stick microprocessors or memory chips onto just anything available; they have to be mounted carefully on these specially prepared cards for them to work.

The printed circuit board has become the standard way of packaging electronics. Today, sophisticated multilayer boards, manufactured in the millions, handle complex circuits. One hundred years from now someone will figure out how to squeeze all electronic components into a single integrated circuit. Until that happens, printed circuit boards will be used.

Obviously printed circuit boards are not the best way to package electronics for all situations. This thought came to the mind of Mark Crosier in North Wales several years ago. In some foul environments—automotive and industrial come quickly to mind—electronic packages suffer from extremes in temperature and vibration. In those situations, the printed circuit board is the weakest link. It also has dimensional limitations, making it difficult to embed intelligence into awkwardly shaped electromechanical devices.

THE 3D CONCEPT

Mark Crosier
Mark Crosier

Mr. Crosier’s solution was to create a multi-layer 3D electronics packaging technology to replace the 2D topology. The design could assume any three-dimensional shape to fit into the space where it needs to go.

Traditional circuit boards use a thin layer of foil imprinted on the surface of a substrate. Mr. Crosier’s idea was to dispense with the substrate and use just the foil. The foil tracks of the circuit are etched out then ‘sandwiched’ in mouldable plastic. Several circuits can be layered on top of each other, providing a large number of functions in a small area. Traditional circuit boards, to provide the same results, would have to be placed side by side over a much larger footprint. Another advantage of the 3D circuit concept is that by using thicker traces, heat can be dispersed more effectively; the circuit itself becomes a heat sink.

Borrowing some ideas from lead frame technology used in semiconductors, and building specialised equipment to mould and shape the plastic material to accommodate integrated circuits and discrete components such as current sensors, he created a new electronics packaging idea. It allows equipment manufacturers to embed intelligence deeply inside sockets, circuit breakers, and other electromechanical devices.

Part two of this story is the sensor itself. His company, DeepStream, has worked on getting the current sensor as close to the process as possible. It is embedded deeply within the electronics package, moulded into the plastic. To provide flexibility, an 8-bit microcontroller is used to configure the range and provide frequency response filtering so that one sensor can be used for a variety of situations. The company has devoted time to developing efficient signal processing algorithms to make the ‘digital intelligence’ economically viable at low cost points. Networking and peer-to-peer communications can also be a part of the package.

CONTRACT WITH MOELLER

Moeller's Xpole lineup
Moeller's Xpole lineup

In early 2008, DeepStream announced a $16m contract to develop modules for a series of digital Residual Current Devices (RCDs) in Moeller’s Xpole line of products. Invented in the 1940s, the RCD is a safety device that measures the current balance between the line or ‘hot’ conductor and the neutral using a differential current transformer. It opens its contacts when it detects a difference—which may indicate current leakage hazardous to humans. Electric shaver outlets in hotel bathrooms are an example of RCDs.

A comparison of DeepStream’s RCD module with its analogue counterpart shows the power of embedded digital electronics. The analogue RCD is a threshold device; a typical one will trip at a range between 50% and 100% of the nominal residual current specified (according to IEC/EN 61008). In some situations this simplistic method of detection and operation causes numerous nuisance trips. DeepStream’s device samples the current 2,000 times per second and can discriminate between momentary excesses and valid reasons to trip.

In the Xpole product, The digital RCD monitors the current system status. If the system’s current moves to earth within a range of 0 to 30% of the set nominal residual current a green LED will indicate that everything is fine. If the residual current moves to within the 30 to 50% range the LED changes to yellow for caution, and it turns to red when it moves beyond 50%. This indicates a state of alarm but the RCD will not trip until the residual current goes beyond 90%.

Mr. Crosier says that, in total, the digital electronics adds about 20 new features to the RCD. RCDs represent about 10% of the circuit breaker market.

‘This development with Moeller marks a major milestone in our progress as a company and is a strong validation of the potential of our technology,’ said Mr. Crosier. ‘We believe this demonstrates that we are on track to achieve our ambitious growth targets for 2008, and we expect this deal to be the first of many tie-ups with OEMs we will announce throughout this year.’ More information: www.deepstream.com


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