on April 12th, 2009

Dear Colleagues

Don’t forget our Major Disasters in PLC Projects webinar on 21st April – details at the end.

1. Scavenging for Endless Energy – without Batteries

After initially being a doubting Thomas, I’ve become quite enthused with the new wireless networked instruments available (whether flow, temperature, pressure based or …….) which operate for up to ten years (or longer), in some cases, with a single battery. And now, I am astounded to find that the next generation to be released involves wireless instruments that need no batteries at all! Instead they “scavenge energy” from the environment to power the instruments. This is not some sci-fi gimmick, but are real commercial products emerging today. What follows are a few words on this incredible new technology.

As we all know, we are surrounded by energy, and recently (with climate change in the news) we have been harvesting this energy on a more “macro” scale with giant wind turbines and dazzling arrays of solar cells. We are thinking in terms of chunky MWs (rather than mere joules – see later). But what has become increasingly possible today, is to power electronic devices, scattered around your plant and home, by harvesting the ambient energy in the environment – thus eliminating the need for batteries forever (no more periodic battery replacements or other external power supplies!).

This has all resulted with the convergence of four separate technologies. Firstly, microcontrollers are demanding considerably less power than ever before. Secondly, wireless networking has increased data rates for an equivalent lower power (using bursts of transmission). Thirdly, protocols for operation have become far cleverer using less power. And finally, energy harvesting – or gathering energy from the environment – is vastly improved.

Technically there are three free energy types available:
* Radiant – the classical silicon-based photovoltaic (PV) cells – pretty stock standard, but obviously considerably smaller. These are now moving into organic PV cells to operate with ultraviolet and infra red. Some are even gathering energy from RF transmissions (off TV stations).
* Mechanical – the use of electromagnetic or piezo electric conversion to create energy. Vibration, using cyclic movement, is also popular.
* Thermal – which can leverage the Seebeck effect (remember our good old thermocouples from our high school days) by converting thermal into electrical energy.

A key component associated with energy harvesting hardware is a power management block. This is required to manage these disparate and disorganized bursts of energy by delivering the electrical voltage level required by the instrumentation. For example, with movement energy harvesting (eg. from a pushbutton) – the energy delivered ceases when motion is stopped. So it has to be managed to produce a consistent voltage.

Another key device, to address the energy uncertainty, is the incorporation of an energy storage area or reservoir in the system. These reserves result in continued and consistent operation even when there is no energy around. Interestingly, however, the most common uses for energy reservoirs are when the instantaneous power requirements are far more than the converter is able to supply – the device collects energy and then operates for a short burst consuming high levels of power (e.g. for a radio transmission of the instrument’s data).

A few suggestions when applying these technologies in your next system:

* Be energy aware and optimise the microcontroller’s various modes for minimum energy consumption (and naturally eliminate small voltage and energy losses in your circuit design).
* Keep RF transmissions to a minimum. These are very power hungry.
* Don’t think in terms of current draw (amps) in circuits, but in energy consumption (joules).
* Remember that in most applications there is not sufficient energy available to drive the electronics all the time. They can be driven in short bursts, so carefully assess standby requirements, peak current draw and average power needs.

A few years ago, these sorts of applications were impossible. Now we can implement wireless systems anywhere without tiresome cabling, external power and even batteries. With devices now using even less power and energy harvesting still in its infancy, we have incredible opportunities today in our designs. Seize these opportunities now.

Thanks to Richard Quinnell at Electronic Design (use these key words to google the article) for the background research and a very detailed article.

Using batteries with instruments was once considered an enormous problem, but as Lee Iacocca said:” We are continually faced by great opportunities brilliantly disguised as insoluble problems”.

2.Major disasters in PLC projects (and how to avoid them)

IDC Technologies proudly presents another live webinar in our popular series “Avoiding Engineering Failures”.
When: Tuesday April 21
(Registrations close 24 hours before the first session).  There’s a choice of 3 session times on the registration page at http://www.idc-online.com/IDCwebinar.html
Where: At your desk!
What will it cover: This complimentary 45 minute webinar will touch on the many considerations of PLCs, including; installations, planning, purchasing, hardware and software reviews, testing, commissioning, and operational aspects. We’ll also look briefly at good practice for safety PLCs and the documentation requirements. It will not be brand specific.
This is a live, interactive webinar. And it’s free!
Join us from anywhere – and bring our PLC expert to your desk! If you are involved in PLC selection, programming and operation you will benefit from the session. All you need to participate is a computer with adequate internet connection, speakers and (ideally) a microphone.

Yours in engineering learning


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