Great God teaches you to design a simple and low-cost circuit to effectively solve RFID noise
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Radio frequency tags (RFID) is a great technology, but noisy power supplies and other factors may reduce its performance. RFID readers that use low-frequency signals (such as 130kHz), such as the TIRIS RFM-007B commonly used in the industry, are very sensitive to noise in this frequency range. Switching power supplies often produce noise in this frequency range, so in order to get the maximum sensitivity, it is usually necessary to use a heavier and expensive linear power supply.
However, the work cycle of an RFID reader contains multiple stages, and only one stage is sensitive to noise. These stages are: high-power stage (transmit, power 10W, duration 50ms); low-power stage (receive, 18ms); idle stage (up to 33ms, depending on the firmware). Noise is only a problem that occurs during the short reception phase.
This design example turns off the switching power supply during the receiving and idle phases, allowing the module to continue working with the energy stored in C2.
Figure 1: RFID with selective power off.
Buck converters like the LM2576 have a shutdown input pin, making the above operations easy to implement.
The MCU’s RFID module transmission control line (/TXCT) can also control the cut-off line through U3 and Q1. If necessary, an independent MCU output can be used to control the cut-off line.
Figure 2: Typical power supply cycle timing.
Forklifts often use RFID for position detection, so as to realize safety functions such as automatic logistics and speed limit.
The environment of electric forklifts is extremely noisy, and the high-frequency modulation and large current generated in the motor drive make RFID work quite difficult. If the control technology introduced in this article is used to keep the RFID cycle synchronized with the modified motor drive cycle, the problem of reduced sensitivity caused by motor drive interference can be greatly improved.
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