Compact 24 VDC Main Unit with Integrated Communication
The Mitsubishi FX3G-24MT/DSS is a MELSEC-F series PLC main unit designed for small- to medium-scale machine control where 24 VDC power and transistor sourcing outputs are needed. It carries 14 digital inputs and 10 transistor sourcing outputs on-board, with a program memory of 32K steps stored in EEPROM so no battery backup is required for the program (buffer battery optional for real-time clock and data retention). Cycle time runs 210 ns for the LD instruction and 500 ns for MOV, which keeps the scan overhead low enough for high-speed sorting, indexing, or simple motion sequences using the integrated high-speed counters and two independent pulse-train outputs. The base unit supports 128 local I/O points and can be expanded via the MELSEC-F extension bus to a total of 256 I/O, making it suitable for applications that outgrow the on-board count. For communication, the FX3G-24MT/DSS includes one USB port for programming and one RS-422 port for connection to operator interfaces or higher-level control networks. This eliminates the need for a separate communication module in many standalone or small-cell applications.
How It Differs from the FX3S-30MT/ES
Buyers evaluating the FX3G-24MT/DSS against the FX3S-30MT/ES often need to decide between these two MELSEC-F sub-families. The most immediate difference is the power supply: the FX3G-24MT/DSS runs on 24 VDC, while the FX3S-30MT/ES is rated for AC 100–240 V. This means the FX3G unit requires a dedicated 24 VDC panel supply, which can simplify EMC filtering but adds a power-conversion step if only AC is available. I/O configuration also differs. The FX3G-24MT/DSS has 14 inputs and 10 transistor sourcing outputs; the FX3S-30MT/ES has 16 inputs and 14 transistor sink outputs. The FX3G uses sourcing (positive common) logic, while the FX3S is configured for sink (negative common) wiring. This output logic difference usually forces a rewire or a change in load common if swapping series.
Lifecycle & Sourcing Posture
Lead times remain typical for the MELSEC-F portfolio; a formal quote will provide the current pricing and delivery window. The mature status also implies a deep installed base, so spare units and replacements are consistently accessible through the open market.