Bluetooth LE liquid heater provides sustainable kettle alternative

Nordic Semiconductor today announces that Berlin, Germany-based start-up, BrandBrandNew (BBN) has selected both Nordic’s nRF52832 and nRF52805 Bluetooth® 5.2/Bluetooth Low Energy (Bluetooth LE) Systems-on-Chip (SoCs) to provide the processing power and wireless connectivity for its ‘Heatle’ smart liquid heater. 

Designed as an alternative to the often wasteful and expensive electricity requirements of a traditional kettle, Heatle is said to be the world’s first induction/immersion heater that can heat any fluid directly in its intended vessel or container, to a specified temperature. The product consists of a base unit powered by the nRF52832 SoC, and a rod with an integrated temperature sensor and a heating disc employing the nRF52805 SoC wafer level chip scale package (WLCSP).  

In operation, the user sets the desired temperature via the ‘Heatle’ app on an iOS or Android Bluetooth 4.0 (and later) smartphone. The temperature information is communicated to the base unit using Bluetooth LE wireless connectivity provided by the nRF52832 SoC, and in turn relayed to the nRF52805 WLCSP in the heating rod. When the vessel and liquid to be heated is placed on the base unit, and the rod and heating disc is immersed in the liquid, the induction heating process begins. When the liquid reaches the desired heat as determined by the in-built temperature sensor, this information is relayed back to the base unit, and user’s smartphone, instructing that the liquid is at the requested temperature and is ready to serve. In the absence of a smartphone the temperature can also be set using the base unit in ‘offline’ mode.  

Energy harvesting circuit 

While the base unit is mains-powered, the rod employs a customized energy-harvesting circuit that draws power from the base unit’s magnetic field and charges two 300mF capacitors small enough to fit inside the rod’s 5.4mm diameter hollow tube. The energy harvesting system’s efficiency is boosted by the ultra low power consumption of the nRF52805 WLCSP. The nRF52805 radio’s peak power draw is only 4.6mA (TX 0 dBM, RX 1 Mbps) and the SoC’s current draw is as low as 0.3µA in System OFF and and 1.1µA in System ON with 24 KB RAM retained and RTC running).

Nordic’s nRF52832 multiprotocol SoC combines a 64MHz, 32-bit Arm® Cortex® M4 processor with floating point unit (FPU), with a 2.4GHz multiprotocol radio (supporting Bluetooth 5.2, ANT™, and proprietary 2.4GHz RF protocol software) featuring -96dB RX sensitivity, with 512kB Flash memory and 64kB RAM. The SoC is supplied with Nordic’s S132 SoftDevice, a Bluetooth 5-certifed RF software protocol stack for building advanced Bluetooth LE applications. The SoC enables the Heatle base unit to perform both Central and Peripheral roles when either receiving temperature data from the rod, connecting to the smartphone app during setup, or relaying the device’s telemetry data such as power and internal temperature logs to the user’s smartphone. 

The nRF52805 WLCSP combines a 64MHz, 32-bit Arm Cortex M4 processor, with a 2.4GHz multiprotocol radio (supporting Bluetooth 5.2 and proprietary 2.4GHz RF protocol software) featuring -97dB RX sensitivity, with 192kB Flash memory and 24kB RAM. The nRF52805 is supported by the S112 and S113 SoftDevices, Bluetooth 5-qualified RF software protocol stacks, and the nRF Connect SDK. The number of connections and bandwidth per connection is configurable, enabling memory and performance optimization. Because the nRF52805 WLCSP measures just 2.48 by 2.46mm and is optimized for two-layer PCBs, it enables a range of space-constrained designs such as the Heatle heating rod. 

Nordic’s nRF Connect SDK can be used for nRF52 Series software development. The SDK brings developers a wealth of varied examples, including Bluetooth LE profiles and driver support for all peripherals. The product also incorporates the Zephyr RTOS. The nRF Connect SDK supports applications using Bluetooth LE, Bluetooth mesh, Thread and Zigbee. The SDK also includes a migration of Nordic’s Bluetooth SoftDevice Controller from the company’s proven SoftDevices used with the nRF52 Series. 

Powerful Zephyr RTOS

“The nRF52805 WLCSP ticked all the boxes when we looked at the requirements for the heating rod, while the nRF52832 in the base unit was selected for its memory and cost advantages,” says Heatle engineer and co-founder, David Riding. 

“The powerful Zephyr RTOS allowed us to speed up development without having to worry about the finer details of the Bluetooth LE stack. We were able to quickly implement the supplied SoftDevice to get up and running quickly.  

“I have worked with Nordic for many years on a range of applications and Nordic has always come out on top when it comes to pricing, product range, technical support and knowledgeable technical staff.” 

• About Heatle
• About nRF52832
• About nRF52805
• About Nordic Semiconductor