Let’s take a look at sensors, actuators and annunciators separately.
There are a variety of RFID transponders on the market with integrated temperature, moisture, radiation and motion sensors built into them. When a device with, say, an accelerometer is moved, that information is transmitted to the RFID chip in the device via an input/output (I/O) port on the chip. When the transponder next communicates with a reader, it transmits its serial number along with information that the device has moved. Or the transponder can be set up to communicate motion as soon as it is detected. But generally, temperature and moisture readers communicate wirelessly from the device to the reader, and then to a back-end host system, which can be set up to alert someone via e-mail or text message if there is a problem.
An actuator is a mechanical device for triggering or controlling another device. Common actuators often utilize electrical impulses or pneumatic or hydraulic tubes. RFID offers a wireless option that has the added benefit of being able to control many different actuators in a small area. That is, you could send signals to transponders next to one another to trigger one, but not the other.
There are two ways in which RFID systems can work as actuators. First, some microchips used in the transponders, as I mentioned, have I/O ports. That means you could send a signal to a specific transponder and have it transmit a signal via its output port to trigger a device. You could, for instance, have a small diode on a bottle of pharmaceuticals. When those drugs pass their sell-by date, the reader could send a signal to the transponder to turn that diode from green to red, thereby indicating it should not be sold.
The more common way to employ RFID, however, is for the interrogator to act as an actuator. Readers also have I/O ports, so you could connect the output port to a programmable logic controller (PLC) and, for example, have the PLC divert cases on a conveyor down one lane or another, depending on the tag that was read. Or you could read a tag in an ID badge and either open a door or not, depending on whether that individual has permission to enter a facility.
I’m not sure exactly what you mean by annunciators. Annunciator panels are light displays, so perhaps you are wondering if RFID can be used to signal light indicators. Many readers currently have lights to indicate if a tag was read or not. This lets the operator pass the tag in front of the interrogator again if necessary. This is common in many applications. Use of other sensors and actuators has only just begun to gain traction in the RFID arena.
—Mark Roberti, Editor, RFID Journal
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