Wearable Electronics
Athletes, runners, joggers - lend me your ears!
A PhD student at the Technical University of Munich has evolved the traditional chest strap heart rate monitor typically worn by athletes, into a sensor to be worn in comfort inside the ear. The tiny heart rate monitor has gone into mass production, and Nordic Semiconductor and Rutronik were both at the birth
I
n response to the trend for keeping fit and an increasing requirement for remote monitoring in medicine, Johannes Kreuzer wanted to develop a monitoring process that could register various vital parameters and mechanical aspects without bothering or hampering users in any way. His research showed that the outer ear was the ideal place to carry out comfortable and precise measurements. The result was the first non-invasive sensor (i.e. outside the body) that measures core body temperature, while also ascertaining heart rate and oxygen saturation in the blood. Eighteen months after successfully completing his doctorate, Kreuzer co-
“I have always had excellent experience
of products from Nordic Semiconductor, which is why I immediately thought of a Nordic wireless solution for the first cosinuss° product,” explained Kreuzer. Since the manufacturer recommends
Rutronik as its preferred distributor in Europe, the distributor was the inventor’s first port of call. Rutronik’s wireless team provided him with technical support in selecting the product he needed. The engineers also put forward components from other manufacturers for consideration. The main requirement was that they needed to be very small and facilitate low energy radio transmission. The choice came back to a Nordic product - the nRF51422 Single Chip SoC. Its 32-bit ARM Cortex M0
processor is designed for maximum computing power yet low power consumption. To optimise performance it is able to quickly switch into sleep mode, waking up again within just 2.5µs. Intelligent software also helps to reduce the power uptake, which can be as low as 1.75V. Cell
founded his company cosinuss° and started to develop a marketable product. Not only does it measure the wearer’s heart rate, but it also sends data wirelessly to any standard smartphone, sports watch or other devices equipped with Bluetooth 4.0 or ANT+. It means that with the cosinuss° sport app, or other apps standardly available on the market such as endomondo, Runtastic Pro or MapMyFitness, amateur and professional athletes can monitor their performance values.
22 July/August 2015
batteries can be used at this minimum voltage, giving the end device a longer service life. The nRF51422 comes inside the tiny 48-pin 6x6mm QFN housing which is easier to process than the same chip inside the even smaller 3.5 x 3.8mm WLCSP housing.
ANT: Small and economical The nRF51422 works on the 2.4GHz band which, compared with the nRF51822, enables the use not only of Bluetooth Low Energy (BLE) but also ANT/ANT+. These proprietary radio network standards are aimed specifically at ultra-low power applications and achieve a lower level of energy consumption than BLE. This is because, at
Components in Electronics
1MHz, their frequency channel is just half as wide as that of BLE, so that the data modulation requires correspondingly less energy.
At just 15kB, the ANT was developed to create wireless connections between sensors and their analysis devices at short distances of up to 50m. This means that the protocol is ideally tailored for sport and fitness applications as well as for health care and telemedicine. It is already installed in many devices, such as in 13 of the widely distributed Samsung
Galaxy and in 26 Sony Xperia smartphone and tablet models. And of course the current top selling S5 and NotePRO 12.2 by Samsung and Z2, as well as the Z2 tablet from Sony, are ANT+ certified. This widespread market acceptance makes the protocol interesting for cosinuss° too, because the sensor needs to be able to communicate with as many devices as possible. Another benefit of ANT is that, as opposed to Bluetooth/BLE, license fees are paid on purchase of the chip or module, so the device manufacturer can use the technology almost without further cost. Unlike with Bluetooth, since February 2014 products using the protocol must have their own ‘declaration of compliance’ which has to be paid for in addition to the actual qualification process (QDID). A further point in favour of the nRF51422 is its 2.4GHz wide range, due to output power of -20 to 4dBm and receiver sensitivity of -96dB. Its software architecture allows strict separation of protocol stack and application software. The two can be stored separately and the user software can be integrated more easily, faster and without error. A whole series of analogue and digital peripherals can interact without the CPU becoming involved. Thanks to 31 integrated GPIOs, which are individually assigned to different pins, as well as PWM, ADC and other features, an additional microcontroller is superfluous. That saves space, money and energy.
Developers require redesigns The first prototype appeared in August 2012. One year later cosinuss° carried out a redesign. They improved the housing, which in turn affected the design of the
circuit board. “It was quite tricky to design the earpiece in such a way that it will not wobble, yet sits well in the ear without bothering the wearer,” said Kreuzer. “Each time we changed something on the housing, we had to make corresponding changes to the PCB. Luckily we were always able to call on the support of Nordic and Rutronik.” The algorithm that calculates the heart rate from the captured data had to be adapted very precisely to the data capture system.
The mobile heart rate monitor of the cosinuss° C-SP 01 enables athletes to monitor their pulse rate without the discomfort of wearing a chest strap. As well as additional models Kreuzer is also already planning further enhancements to make these comfortable sensors suitable for work safety and medical applications. In particular there is a great deal of potential in research into sleep patterns and brain activity, in telemedicine and for hospital use. The device needs some modifications to ensure that the sensor can be easily and safely placed in position by the wearer, as well as by care and medical staff. And it also needs to meet medical requirements such as the ability to resist disinfection procedures as well as the corresponding standards. “This is why we started by concentrating on the sports and fitness sector. We received extremely positive feedback from visitors to this year’s CeBIT,” concluded Kreuzer. “And for our future developments we will be opting once again for the support of Nordic and Rutronik, based on the excellent experiences so far.”
www.rutronik.com |
www.nordicsemi.com
www.cieonline.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45