All posts tagged: sensor

Recently an increasing number of networked devices are finding their way into consumer, industrial and medical applications. Such networks often employ distributed nodes which cannot practically be connected to the power grid – through design or through necessity. Therefore powering such devices can possibly be a challenge – due to the costs of either running from battery or solar power, sending technicians for maintenance visits to replace batteries – or having to install one’s own power network for the IoT system.

This is where energy efficiency is key – by using highly energy-efficient design practices in both the hardware and software levels, the power requirements can usually be reduced significantly. In doing so the power supply paradigm can be altered to one of lower cost and higher efficiency. Especially for remote or portable devices that use RF/microcontroller chipsets – the smaller the power requirement the better.

High-power and efficient wireless network nodes can be engineered using modern RF microcontroller system-on-chip devices, activating sensors and peripheral hardware devices only when they are required, and then putting them into low-power sleep modes when not in use. Similarly, the RF transceiver can be switched into a very-low-power sleep state until the microcontroller decides that a transmission of collected sensor data is required. The microcontroller can then wake up the radio, perform the required transmission, and then revert to sleep mode.

In some cases, a burst of data transmission across the wireless network might only occur when a small, intermittent energy-harvesting power supply has accumulated enough energy in a capacitor to power a transmission. Alternatively, a low-power wireless sensor node can “wake-on-radio”, only taking the microcontroller out of its sleep state when a message is received over the wireless network requesting a sensor readout and only powering up the sensors and microcontroller at this time.

With most of the components of the system, such as the microcontroller, radio and sensors – each kept off-line or asleep for the largest practical amount of time – efficiently designed wireless sensor nodes may achieve operating timescales as long as years off a single battery. Today’s typical wireless RF microcontroller system-on-chips targeted at IoT applications typically consume about 1-5 microwatts in their “sleep” state, increasing to about 0.5-1.0 mW when the microcontroller is active, and up to around 50 mW peak for brief periods of active RF transmission.

However when considering the design of energy-efficient, low-power IoT sensor networks, it can sometimes be advantageous to think not just in terms of power consumption, but in terms of the amount of energy required to perform a particular operation. For example, let’s suppose that waking up a MEMS accelerometer from sleep, performing an acceleration measurement and then going back to sleep consumes, say, 50 micro joules of energy; or that waking up an RF transceiver from sleep, transmitting a burst of 100 bytes of data and then going back to sleep consumes 500 micro joules.

If we know the specific energy consumption of each operation, then the average power consumption is simply the energy per operation multiplied by the frequency of that operation, summed over the different kinds of operations. Of course, this assumes that the continuous power consumption of each device when it is asleep is very small and can be ignored. Alternatively, if we have a certain known power budget available and a known energy budget for each sensing, computation or transmission operation – we then know the maximum practical frequency at which a sensor node can perform sensor measurements and transmit its data.

Additionally, efficient wireless sensor nodes can take advantage of some form of energy harvesting power supply – employing energy sources such as solar cells, vibrational energy harvesters or thermoelectric generators to minimise maintenance and extend battery life – with the possibility of completely eliminating external power supplies, but only if the power consumption of the system is small enough and a capacitor is employed for energy storage.

In many applications, solar cells are the most familiar and relatively mature choice for low-power network nodes operating outdoors or under good indoor light conditions. However, other technologies suitable for extracting small amounts of power from the ambient environment exist. For example, a wireless sensor node set up to monitor bearing wear in a generator could employ a piezoelectric crystal as a vibrational energy harvester, converting motor vibration into usable energy, or a thermoelectric generator mounted on a hot exhaust could harvest a small amount of otherwise wasted energy from the thermal gradient.

Typical vibrational energy harvesters usually operate with a cantilever of piezoelectric material that is clamped at one end and tuned to resonate at the frequency of the vibration source for optimal efficiency – although an electromagnetic transducer can be used in some cases. Whilst the electrical power available is dependent on the frequency and intensity of the vibrations, the cantilever tip mass and resonant frequency can generally be adjusted to match the machinery or system that energy is to be harvested from.

Furthermore, energy harvesting management ICs that manage the accumulation of energy in a capacitor over a period of time can enable short bursts of relatively high power consumption, such as when a node wakes up and transmits a burst of data, and are particularly well suited to low-power wireless sensor nodes.

Even with the examples mentioned above, the energy-efficiency possibilities are significant and can be a reality. When designing prototypes or proof-of-concept demonstrations you may put energy use to one side, however when it comes time to generate a real, final product – you can only benefit from taking energy-efficiency into account.

If you are considering creating or modifying existing designs and not sure about the energy-saving and generating options that are available, be efficient and discuss your needs with an organisation that has the knowledge, experience and resources to make your design requirements a reality such as here at the LX Group.

At the LX Group we have a wealth of experience and expertise in the embedded hardware field, and can work with the new and existing standards both in hardware and software to solve your problems. Our goal is to find and implement the best system for our customers, and this is where the LX Group can partner with you for your success.

We can create or tailor just about anything from a wireless temperature sensor to a complete Internet-enabled system for you – within your required time-frame and your budget. For more information or a confidential discussion about your ideas and how we can help bring them to life – click here to contact us, or telephone 1800 810 124.

LX is an award-winning electronics design company based in Sydney, Australia. LX services include full turnkey design, electronics, hardware, software and firmware design. LX specialises in embedded systems and wireless technologies design. https://lx-group.com.au

Published by LX Pty Ltd for itself and the LX Group of companies, including LX Design House, LX Solutions and LX Consulting, LX Innovations.

When considering an Internet-of-Things framework for an existing or new project, one of the greatest challenges is getting the system running within what is most likely a tight deadline. And part of the greater challenge is the choice of interface between you devices and the network – and how will they interact? At this juncture your decision can be to create a bespoke solution, or use an existing product. The latter is ideal for proof-of-concepts, quick jobs or just when you need to get a MVP (minimum viable product) through the door. With this in mind, we’ll check out one example of an existing solution that you may make use of – called “Twine”

Although originally an idea that was brought to fruition using crowdfunding via Kickstarter, Twine has now become one of many viable choices in the IoT marketplace. As usual, it consists of a hardware and software component – so let’s examine those and then see how they can work together to solve your problems.

Hardware – The Twine devices are quite unassuming and compact, measuring approximately 70×71×20mm and can fit in the palm of your hand. With an elastomer coating they’re quite robust, however not water resistant or proof. These devices provide the link between the cloud-based software and a variety of hardware options. Inside each device already exists temperature, vibration and orientation sensors – and a port for external sensors. It connects via an 802.11b wireless network and is powered via a micro USB socket or 2 AAA cells.

You can also acquire a range of external sensors covering moisture, magnetic switches (for doors, etc) and also a breakout board to connect your own hardware. You can connect any device that outputs an analogue or digital signal with a 0~3.3 V range. Furthermore there’s also an Arduino shield for connection to that ubiquitous line of hardware. The last two options then give you the ability to quickly connect your own sensor or interface via an Arduino-compatible board other hardware with which you’d like to interact with over the cloud system. Therefore development costs of this additional hardware will be restrained due to the ease of interfacing with the sensor port or Arduino interface.

Software – There are two primary methods for interacting with the Twine hardware, with their proprietary cloud-based system or via HTTP to your own applications. Using the cloud-based method – you create a series of rules that can monitor incoming sensor data then make decisions based on the results. From simple things like email alerts notifying you of temperature changes to SMS text messages when a device has been physically moved – there are many possibilities that can be constructed in a short period of time. There’s also the option of receiving messages via twitter and text-to-voice call.

The process of creating applications for Twine doesn’t require any coding at all, so demonstrations of the system can be created and modified by general employees and management. Using an online drag-and-drop interface with simple condition parameters is used to generate actions based on the status of the connected sensors. However there is also the opportunity to have Twine directly interact with your own infrastructure using HTTP GET and POST requests. This is also preferable for those looking to keep their data within internal systems.

It can be said that Twine is not the most complex or customisable system on the market at the time of writing, however if your needs meet the capabilities then it can be a valid option. You can get a basic system operating in a few hours, and integrate other hardware in no time at all.

If you’re interested in moving forward with Twine or other platforms, we can guide you through the entire process, from simple installations for demonstration purposes to a complete system with customised external sensors and programming support. Our goal is to find and implement the best system for our customers, and this is where the LX Group can partner with you for your success.

We can discuss and understand your requirements and goals – then help you navigate the various hardware and other options available to help solve your problems. We can create or tailor just about anything from a wireless temperature sensor to a complete Internet-enabled system for you. For more information or a confidential discussion about your ideas and how we can help bring them to life – click here to contact us, or telephone 1800 810 124.

Published by LX Pty Ltd for itself and the LX Group of companies, including LX Design House, LX Solutions and LX Consulting, LX Innovations.

There are many methods of sending data between sensors and devices that require the data, and many newcomers to the industry may be aware of the usual digital data buses such as Serial Peripheral Interconnect (SPI for short) or the Inter-Integrated Circuit bus (known as the IIC or I2C bus). Although they are popular and many devices are available that communicate using these methods, they have several downfalls which can preclude them from some applications. These can include distance – the I2C bus requires repeater ICs fitted along the run after around 20 metres, and care must be taken to ensure the bus capacitance level stays below a certain amount; and interference – any digital signal is susceptible to interference from a variety of sources.

However there is a method of transferring signals and data that is both much simpler to understand and also reliable over long distances – the “4-20mA Current Loop”. This has been used successfully over many years to report analogue values back to a host system from a sensor and also transmit digital data (however not at any great speed).

How the “loop” (as we will now call it for brevity) works is very simple to understand – a DC current loop is formed with a power supply of between 12 to 40 VDC, with the sensor or device in series with system analysing the loop then back to the power supply, for example:

(Image courtesy National Instruments)

The device or sensor (such as the transducer in the image above) is powered by the current in the loop, which is convenient as seperate power runs are not required – saving installation cost and maintenance time.

The data gathered by the sensor is translated to a level of current flow, thus controlling the current flowing through the loop – which will fall between a range of four and twenty milliamps. Finally, the device at the end of the loop can simply measure the current using a simple analogue-to-digital converted and process as normal. This is therefore a method of transmitting either analogue or digital data.

Some systems can also transmit digital data at a slower speed, by simply turning the current on and off in a similar manner as basic logic systems – and although generally used by telegraph and telex systems in the previous century, there may still be applications for this in the future when no other wired alternative is possible. An example of this may be adding new sensors to an existing building with existing wiring that cannot be accessed completely for replacement or heritage reasons.

Almost any type of device that uses a current signal to transmit data can be used on the “loop”, such as position or rotation sensors – ideal for remotely monitoring a machine’s RPM or physical position; environmental sensors such as vibration, humidity and temperature; tank liquid level sensors – and many more. And the system makes troubleshooting quite simple – if current isn’t flowing in the loop, your system can alert to a faulty sensor or line immediately.

It is also possible to run more than one loop from a power supply, as long as each loop is in parallel and the power supply can source the total amount of current required by the individual loops, and that the systems measuring the current are in series with the device in its’ unique part of the loop. Furthermore some engineers have also been able to power other mutually-exclusive devices from the loop – such as ultra-low power TI MSP430 microcontrollers, as long as the current drawn by the new device falls within the tolerance of measurement by the end system. This method has also proved popular by those wishing to upgrade sensor networks without adding or replacing any existing wiring runs.

Thus it can be said that the 4~20 mA current loop system may not be the “latest technology”, but it can effectively solve problems in the right circumstances. However there are many options, and choosing the right one is a fundamental step for the success of your project. So if your design team is set in their ways, or you’re not sure which data communication method is best for your application – it’s time to discuss this with independent, experienced engineers.

At the LX Group we have experience designing a wide range of data gathering and control systems over short and long distances – and using this experience we can determine the most effective method of returning data and control signals no matter the application or geography. Our engineering team have developed a number of systems in this area and have extensive experience with the core technology requirements of such systems.

We understand the importance of high availability, accuracy and integrity of the systems, combined with the need for future proofing infrastructure rollouts. For more information or a confidential discussion about your ideas and how we can help bring them to life – click here to contact us, or telephone 1800 810 124.

Published by LX Pty Ltd for itself and the LX Group of companies, including LX Design House, LX Solutions and LX Consulting, LX Innovations.