If you’ve ever used or seen enough electronic RFID door locks at the show, it’s easy to see a pattern – all RFID door locks have plastics on lock shell.
Why is that?
You should know from the RFID features.
RFID can penetrate many common objects
RFID technology originated during the second world war in aircraft radar detection technology.
Radar uses the propagation of electromagnetic energy through space to identify objects.
During world war ii, British forces outfitted allied aircraft with a transceiver, to distinguish them from German aircraft.
1-The seeker on the control tower sends an interrogation signal to the aircraft in the air.
2-When the aircraft’s transceiver receives this signal, it sends a signal back to the seeker.
3-The seeker recognizes whether it is own aircraft based on the return signal it receives.
This technology is still used in commercial and private aviation control systems today. Its q&a mechanism is the prototype of today’s RFID technology.
This is another easy understand drawing.
The water, glass, wood,plastic, paper and textile will not effect the data and power transfering in the air.
Metal is an exception
Metal is an exception material.
The RFID radio can not penetrat it fully. The reason is that the metals are conductors, which will affect electromagnetic fields.
There is attenuation happenes when antenna sent Question and get answer.
Metal can weaken RFID data and power transmission and in more severe cases, the radio signal can be completely blocked.
That means no power can used to read data and the data can not sent out or be received.
To make it working the both side should be keep in a shorter distance.
However the RFID will lose its use value when too much closer.
Metal is major materials of RFID door locks
Unfortunately, metal is the main materials to made a RFID door lock or even most door locks.
For the normal mechanical door locks there is no problem at all. But for the RFID door locks,product designers must consider the interference of metal on RFID.
No body will accept a door lock made by full plastic or wood.
So how to put the electronics into the lock is a major subject for RFID door lock manufacturers.
How design it
Let’s take the picture above apart and divide it into two parts.
You can understand clearly their relations, just as follows
On the RFID door locks,the left side is RFID card.
And the right side is the reader of RFID door lock.
The middle part is the air. RFID can working in the air,without any contacts.-When contactless key (RFID card) locate close to the lock, the chip inside card will be detected by antenna.The Q&A starts.
Put the antenna in front of the lock shell will reduce the interference caused by metal parts.
The plastics have 2 function
- Protect the electronics from outside
The antenna cannot be completely exposed without any protection
- Hold the antenna
The door vibrates when it is closed and the vibration is transmitted to the lock. The plastic housing normally can hold the electronic antenna firmly.This is why you can find all RFID door locks have plastics on the shells.