How does Keycard Entry work?
Hey friends, Happy Wednesday!
Answer to the question I posed last week
Last week, we discussed electric cars. The reason why lithium-ion batteries out of all the other ones are used here is because it has a high charge density, which means they can store a large amount of electrical energy in a smaller volume.
Let’s look at how access cards work this week. I aim to write my newsletter issues in a way one can follow them while traveling on a bus, having a coffee, waiting for your food, etc. Let's jump in!
Tweet of the week
I’m sharing a cool fact about gadgets and sharing behind the scenes of this newsletter every day on Twitter. And here is one of them for you. Follow me on Twitter to join the community :)
How do Access badges work?
Introduction: We use access badges every day when we go to work, enter a secured apartment using a tag, unlock hotel rooms, electronic toll payments like Fastrak in many countries, etc. Most of the RFIDs in the market use PVC or PET material for the base as they are durable and have high heat resistance. These employ a technology called RFID (Radio Frequency Identification). This uses radio frequency to authenticate and let you in. Let’s see how this works.
Figure 1: RFID reader (Left) and Tag (Right)
How RFID works: RFID system consists of a reader and a tag as shown in Figure 1.
The RFID reader is constantly emitting radio waves trying to give access to the right tags when they come in close contact.
The RFID tags have a small memory module and an antenna for sending the stored information to the reader. This data can be a unique tag serial number, for example. So the memory stored is very small, in kilobytes.
As the tag approaches the reader, it receives the energy from the emitted radio waves, storing it in its capacitor. Most commonly used tags do not require a battery; instead, they rely on the energy from the reader’s radio waves.
The RFID tag responds with its information from the memory by sending radio waves back to the reader. The reader picks them up using its receiver and interprets the frequencies to decode the unique information using its microcontroller.
Due to unique serial numbers on the tags, the RFID system can differentiate among multiple tags within the reader’s range and read them concurrently. Once it finds matching information in its records, access is granted to the corresponding person or item.
What are the types of RFID tags: RFID tags come in three types: passive, active, or battery-assisted passive. Active tags have a built-in battery and periodically send their ID signal. Battery-assisted passive tags have a small onboard battery and become active when in the vicinity of an RFID reader. On the other hand, passive tags are more affordable and compact since they don’t have a battery; instead, they utilize the radio energy transmitted by the reader. The majority of the existing RFID tags fall into the passive category, and that’s why we focused on this type for our study.
Bonus: Geek Info
How is unique information encoded in the RF signal sent by the tag to the reader:
The data sent by the tag to the reader is encoded in the signal using the following techniques. Let’s say you have a badge ID. The number needs to be sent over to the reader. It is first converted into binary and modulates the signal as follows.
Amplitude Shift Keying (ASK): This method involves modulating the amplitude of the reflected signal to represent 0s and 1s. For example, a high amplitude could represent a 1, while a low amplitude could represent a 0.
Frequency Shift Keying (FSK): In FSK, the tag modulates the frequency of the reflected signal to convey binary data. For instance, a higher frequency might represent a 1, and a lower frequency might represent a 0.
Phase Shift Keying (PSK): PSK involves altering the phase of the reflected signal to encode binary data. A specific phase shift could represent a 1, while another phase shift could represent a 0.
Thank you for reading!
Have a nice rest of the week, and take care!
Until next Wednesday,
Chendur
