Electromagnetic interference in the automotive industry – part 2


Electromagnetic interference in the automotive industry – part 2

The noise around us

Today, devices are increasingly operating online, which means they need to exchange information. For reasons of convenience, by far the most common is communications using radio waves. Examples are indeed plentiful. Starting with simple wireless doorbells, all kinds of control systems whether for gates or lighting through contactless parking lot entrance identification systems. For parents, a good example would be a device called an electronic nanny. Many security agencies use their own monitoring equipment operating on leased frequencies so that the area is better covered and the system is reliable. The city’s water supply and sewage disposal are other areas that are monitored on an ongoing basis. All of these areas of communications can be affected by electromagnetic interference in automobiles.

Home amenities known in the form of smart homes also use radio waves whether WiFi, Zigbee or other bands generally available. A few months ago, there was a buzz about unauthorized detentions of trains using a security system known as the “security system. radio-stop. Aircraft communication with airports also takes place via radio waves. These devices can cause interference. Thanks to strict standards, however, they are definitely more likely to be the recipients.

The matter is somewhat complicated by the use of frequency spectrum bands that can be used virtually voluntarily – the so-called. ISM bands (from Industrial, Scientific, Medical). The problem is that they are relatively narrow, unlicensed and a good portion of their scope has been taken over by wireless transmission systems like WiFi and Bluetooth. Moreover, depending on the continent, there are these bands located in different frequency ranges.

Better because foreign.

And here we come to the first problem, which is the use of devices intended for a market other than the EU. The aforementioned electronic nannies imported from the US or Canada work in the frequency range that mobile telephony uses in Poland. Thus, they can locally disable the ability to make a phone call. A device that was intended to help take care of a child may unknowingly become the cause of an inability to call for help by calling 112.

The same is true of imported cordless phones (in the DECT standard) which also use bands in the EU intended for mobile telephony.

Lack of knowledge and universality.

Electronics designed for sale in many countries are often made in a specific variant for a particular market. However, often in order to optimize the device is one but has the ability to be configured. This is the case, for example, with WiFi devices that may use different channels depending on location. There are other devices that also need to be set up. E.g., longer-range RFID systems that allow you to open a parking lot barrier on the basis of carrying the appropriate key fob. Such a universal device mounted without the relevant knowledge can operate by default in the 902-928MHz range. That is, again in the telephony band. To make matters worse, this versatility of configuration can cause the system to switch to the forbidden band as a result of a malfunction, despite consciously switching to the EU band.


The significant spread of LED lighting has resulted in the import of many light sources that do not meet emission standards. Often such sources generate interference in the much lower spectrum (but not always). And that means they interfere with those bandwidths that are used by long-range devices. And so, for example, a poor light bulb can jam the operation of a clock that uses a radio signal broadcast from Germany (DCF77). Or reception of the national radio program that is Radio One will not be possible. Shockingly, however, the LED bulb can also prevent LTE Internet use in the 2600MHz band.


Sometimes it feels like Far Eastern products are optimized one element too much. The question is simple: is an element or two less enough to make the circuit work? If so, why install them… A good example of this is the battery charger system, very popular if only for its ability to charge a battery that is so discharged that it has almost water instead of electrolyte. Well, this charger connected in the tin garage, to the same phase as the illuminator with a sensor on the house nearby causes the inability to turn off the lamp. Why? Because it does not have a line filter to isolate the interference produced by the power supply towards the mains.

Chinese battery charger devoid of any input filter.
Chinese battery charger devoid of any input filter.
Another type of charger with a robuded mains filter.
Another type of charger with an extended mains filter.

Custom ideas.

There are unfortunately many cases like the above. Some are mistaken for the failure of some device. But popularly so-called “peeing” also makes others miserable. A case was described where, in a certain housing development in Poland, drivers could not use the remote-controlled central locking system in their vehicles. The problem concerned a section of the parking lot, one might say closely adjacent to one of the spaces rented in the area.

As it turned out, the source of the disturbance was a dental office. And the problem was not at all related to professional equipment, at least not directly. Well, after a fresh renovation, it was realized that the control system for the pump that generates the vacuum had not been laid. It is needed for the operation of the saliva-sucking mammal. How was the problem solved? With the help of a wireless bell that controlled the pump. When the patient was in the chair, the bell emitted a continuous signal in a band that prevented remote controls from operating in a certain area. Perhaps the “American” style subtitles should no longer be surprising: this bell is not suitable for controlling a medical mammal?


Nowadays, there will be more and more cases of this type as described. The causes are to be found in many places. They are highlighted most strongly in the issue of unit cost optimization. Removal of filters is a profit for the manufacturer. Unfortunately, this has implications for users of various devices. Lack of information about other standardizations prevailing in different continents is another cause of problems. Many of the examples described here were detected thanks to the activities of the institution that upholds the protection of radio band resources – the Office of Electronic Communications. How many sources of interference went undetected because, for example, they did not affect air traffic safety? One thing is certain. If more than a hundred and thirty years ago Napoleon Cybulski and his research on EEG recording had taken place in such a littered electromagnetic environment as today it would have happened much more slowly. Development is producing more and more electromagnetic smog problems. Fortunately, it also gives effective methods for its elimination. May we only be able and willing to take advantage of these options.


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