How to increase the RF range of a switch?
The RF range means the maximum distance from a switch to a reciever. How do we increase this distance ?
You thought of other ways to communicate with your electric gate? Your garden lighting? Command your pool pump from your home? Make a general switch?
There are wireless devices, of course, but also devices running with powerline communication (PLC)
Wireless devices use a technology called radiofrequency or RF. Increasing the communication range raises certain problems.
The communication range reached by the radiofrequency or RF switches rarely exceed fifty meters. Why ? Because the level of the signal is proportional to the "square of the distance". So if the distance increases by 2m, the signal will be attenuated by 4. (Friis equation)
If a solution is integrated into the walls, the range will be reduced.
The distance will depend on several factors:
The antenna: the antenna design ie how the antenna is constructed, what its geometry is and especially if it is well adapted to the frequency it can transmit. (See impedance matching )
- The power of the transmitter: radio transmitters can not emit more than a certain limit especially in domestic use. For comparison, we will transmit to 2W on a mobile phone and to 100mW for a Wifi antenna and 700W for a microwave.
- The frequency of the transmitter: The frequency of a radio transmitter defines the speed at which the signal to be transmitted will be varied. This frequency is expressed in Hz (Hertz). Long wave radios generally operate at a frequency of 700Khz, that is 700,000 times per second. Mobile phones operate between 900MHz and 2.4GHz, or between 900 million and more than 2 billion changes per second. For information the frequency of a microwave is around 2.5Ghz.
The higher the frequency, the smaller the range and the smaller the antenna. If the antenna is not "suitable" (too large or too small) in relation to the frequency, the transmitter and the receiver can not communicate.
- Environment: Obstacles can stop electromagnetic waves, thick walls made of stone or concrete can drastically reduce radio signals. Metallic structures also have a catastrophic effect. Try calling in a large supermarket or in the subway! Another factor that is well taken into account in mobile telephony is the speed at which the user moves. The signal is degraded when the user moves. This phenomenon is called " fading ".
Another ill-known phenomenon comes from the reflection of the waves on the different objects of a room. The reflection of the waves will lead to a significant attenuation on these same waves. Moving a few cm can sometimes radically change the power of the signal received.
Influence on health
Numerous studies have tried to highlight the effect of electromagnetic waves on health. The only concern is that none of these studies can really be independent of a manufacturer, if not how to finance it? What is certain is that our nerve cells communicate with each other by electric currents. The effect of an electromagnetic field on a conductor traveled by an electric current is not negligible, we see it every day in the devices we set at the points and the rules of electromagnetic compatibility to which we must comply. Being ourselves conductors, the influence of electromagnetic fields obviously has an effect.
The larger the field, the greater the effect. In the absence of irrefutable evidence of the safety of these effects, a precautionary principle must be followed.
This is why European standards define threshold limits that should not be exceeded. The threshold is calculated according to the energy received by our brain. The maximum threshold is set at 2W / kg brain. ( SAR or SAD ) This limit set by the European Union is based on technological limits that can be reached in the years 2000 and is in no way related to clinical studies.
This limit applies only to mobile telephones. For domestic appliances, there is no rule to test the products according to this test.
In conclusion, the higher the power level, the greater the potential impact on health.
The battery problem:
In order to increase the range, we can increase the power, so we must increase the available energy. In order to supply radio equipment (switch, presence detector, etc.), manufacturers often use batteries or batteries. It is very good when there is no power supply available near a switch for example, but it is a short-term economic solution. But what happens when the whole house is equipped with these systems? We are constantly changing the piles especially if the habitat has been equipped gradually.
This problem is particularly annoying on wall-mounted systems. Each switch must then be removed to change the battery.
- Put a radio repeater that will repeat the signal (as can be found in Z-Wave or Zigbee networks)
- Pull cables in a conventional manner, at least when possible
A current carrier system uses existing cables To communicate and makes it possible to control an apparatus very far from a switch for example. The range can reach several km *
This technology perfectly responds to the need to be able to communicate far and without emitting an electromagnetic wave. The only signals conveyed remain in the electric cables with a level lower than 2V. (Domestic Standard EN50065).
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