Bluetooth and batteryless meat thermometer

Cooking meat properly requires a steady and precise internal temperature to guarantee optimal taste and texture. Meat thermometers play a crucial role in achieving accurate cooking temperatures for each type of meat. You can regularly monitor and prevent temperature fluctuations by sticking them into your chops or steaks.

The market offers a variety of meat thermometers, all of which may appear reliable at first glance. However, closer examination reveals numerous disadvantages. Ubiquitous cables, inaccurate temperature values, temperature changes that impact the final result, or a lack of versatility are only some downsides. Moreover, they share a common design flaw that makes them even potentially dangerous: the use of batteries. Clearly, no one desires chemicals as condiments.

A meat thermometer that requires no batteries, functions without interfering with the cooking process, and adapts equally to ovens, flat grills, and rotating rotisseries would be the perfect solution for users.

Inventive solutions, such as the one described above, often stem from a fundamental change in approach. In this case, devising this thermometer involved incorporating short-range technology and modifying the internal structure, which brings an additional advantage.

But let’s hear from Markus Wejrot, engineer at u-blox, who can tell us all about how he came up with the idea for the Thermomeatcaster, a new Bluetooth and batteryless meat thermometer.

What was the motivation behind your idea, Markus?

I am a passionate griller. My wife comes from Uruguay, where the ‘asado’ is the most traditional way to spend time with family and friends. From those gatherings, I have learned that the best way to cook your meat efficiently is by using a thermometer that you stick into the meat. However, every time I used one, apart from facing some practical challenges, what disturbed me the most was thinking that my food was cooking right next to a battery. So, I decided to come up with my own design. 

How does it work?

The simplicity of the device is what makes it highly efficient. It comes equipped with a temperature sensor connected to a u-blox module which, powered by a series of small capacitors, broadcasts a Bluetooth message within a 5-10 m range.

Why is internal temperature so relevant?

The internal temperature of the meat while cooking should be different depending on the type of meat being prepared. For instance, beef requires the lowest internal temperature, usually between 55 and 70 °C, while chicken demands the highest, typically between 75 and 80 °C.

The problem is that only a few thermometers provide an accurate value. Because whenever you want to measure the temperature, you need to open the grill or pull out the meat from the oven and check the temperature displayed on the device. This may not sound incredibly relevant initially, but it can become a significant issue when you need to do it several times. Every time you open the grill or the oven, you lose thermal energy. In the long run, these temperature variations affect the cooking.

A significant advantage of this thermometer is that you don’t need to alter the environment surrounding your food. You simply turn on the device every time you want to check the temperature, perhaps every five or ten minutes, and get a reliable value. Even for grilling fans like me, over time, I have learned that this makes an enormous difference.

Please, tell us more about how you can read the data

The thermometer requires a compact Bluetooth module. For the initial version, I used the smallest Bluetooth module in our offering (42,25 mm²), ANNA-B1. Although it functions well with this module, I quickly realized that it could benefit from more power and a higher temperature range.

Therefore, I upgraded the device with the u-blox ANNA-B4 instead, which is way more powerful and withstands higher temperatures than ANNA-B1. In practice, you would never need to cook anything beyond 90 °C. But if need be, and since the u-blox ANNA-B4 withstands up to 105 °C, you could extend its applications.

To read the Bluetooth messages and know the temperature in a snap, you need either an application on your phone or a server/cloud-based solution with a base station connected to the network. The latter solution is the most straightforward. It requires a network server and a user interface, for instance, a Raspberry Pi with a Node-RED implemented dashboard.

And you say it does not require batteries?   

Every single thermometer that you can find on the market nowadays requires batteries. If anything goes wrong, even though you don’t notice it at first sight, chemicals could contaminate your food. Alkaline batteries, the ones these thermometers need, are made of highly toxic and harmful compounds, which entail potential health risks.

To do without batteries, the energy is sourced from a series of 30 connected capacitors of low-power consumption. Since 99.995% of the time, the thermometer is ‘sleeping,’ the capacitors' power consumption is extremely low, extending its functional time for many hours. This thermometer ensures a five-hour use without any external power source. And if the barbecue extends for longer, you need not worry as you can recharge it in no time and again enjoy another five hours of usage.

What about its design?

The structure is covered by a thin brass pipe that takes the shape of an arrow. With 8 mm in diameter, it looks almost like a pen. You insert the arrowhead into the meat, where the thermometer is located, and leave the shaft uncovered, which functions as an antenna. The meat protects the electronics from 200 °C or higher temperatures on a grill or inside an oven.

This shape enables to use the thermometer in various scenarios. Since you stick it to the meat without cables, a grill's inner structure could rotate, and your thermometer would keep registering without interference. Using it inside an oven or on a grill makes no difference since you will always get a reading, irrespective of the method used to cook the meat.

Anything else you want to add?

Grilling is one of my main hobbies, and my invention, the Thermomeatcaster, is simple, efficient, and reliable—no more dry, raw, or overcooked meat.

I found a creative way to use our u-blox modules. But remember, this is only an example of what you can do with them. The versatility of ANNA-B1 and ANNA-B4 enables you to give shape to your ideas. So, don’t lose any time. Put your hands to work and discover how our modules can be at the core of your inventions.