The QX42 is a 64-point DC input module from Mitsubishi Electric, designed for the MELSEC-Q series programmable logic controller platform. It accepts 5 V DC or 12 V DC sink/source input signals and provides high-density discrete input capability within a single slot of a MELSEC-Q base unit. Atlantech Drives holds stock of the QX42. Contact us for fast worldwide delivery and competitive pricing.
What Is the Mitsubishi QX42?
The QX42 is a high-density digital input module occupying a single slot in a MELSEC-Q main or extension base unit, providing 64 input points addressable by the Q series CPU. Its 5/12 V DC input voltage range makes it specifically suited for interfacing with TTL-level logic signals, low-voltage proximity sensors, and encoder output signals in semiconductor manufacturing equipment, electronic assembly machines, and test and measurement systems where standard 24 V DC input modules are incompatible with the field device signal levels. The QX42 uses a 40-pin connector interface rather than screw terminals, requiring a dedicated connector block (A6CON1 or equivalent) for field wiring.
Key Technical Specifications
- Number of input points: 64
- Rated input voltage: 5 V DC or 12 V DC (selectable by wiring)
- Input current at 5V: Approx. 4 mA per point
- Input current at 12V: Approx. 7 mA per point
- Input type: Sink/source compatible
- ON voltage/current: 3.5 V DC min / 2 mA min (5V range)
- OFF voltage/current: 1 V DC max / 0.5 mA max (5V range)
- Input response time: 1 ms (default, adjustable via parameters)
- Isolation: Optical isolation between input circuits and internal bus
- Connector type: 40-pin connector (A6CON1, A6CON2, A6CON4)
- Number of occupied I/O points: 64
- Power consumption: 5 V DC, 0.50 A (internal bus)
- Operating temperature: 0 to 55°C
Typical Industrial Applications
The QX42’s 5/12 V DC input range addresses a specific gap in standard MELSEC-Q I/O — most Q series input modules operate at 24 V DC, which is incompatible with low-voltage logic signals common in high-technology manufacturing environments. Typical applications include: semiconductor wafer handling equipment where robot position sensors and alignment detectors output 5 V TTL signals; PCB assembly and inspection machines interfacing with vision system digital outputs and barcode reader data lines at logic voltage levels; high-speed packaging machines using 12 V DC proximity switches for product detection on high-speed conveyor lanes; and laboratory automation systems integrating analytical instrument digital I/O at sub-24V signal levels. The 64-point density per slot also makes the QX42 the preferred choice for applications requiring maximum I/O count within a constrained base unit footprint, minimising rack space and power supply loading compared to using multiple lower-density 24V input modules.
Installation Advice
The QX42 uses a 40-pin MIL connector rather than the screw terminal blocks found on standard Q series I/O modules. Use Mitsubishi A6CON1 (soldered wire), A6CON2 (IDC crimp), or A6CON4 (spring clamp) connector assemblies — generic 40-pin MIL connectors may fit mechanically but do not meet the vibration retention specifications required for industrial panel environments. When wiring at 5 V DC, keep signal cable lengths as short as practically possible and use shielded cable for runs exceeding 2 m, as the low signal voltage makes the QX42 inputs more susceptible to capacitive noise coupling than 24 V DC modules. Connect cable shields to the panel earth at one end only. Verify that the external power supply regulation is within ±5% of the nominal 5 V or 12 V — the QX42’s ON voltage threshold leaves minimal margin for supply droop, and an under-voltage supply is the most common cause of intermittent input recognition failures on this module type.
Frequently Asked Questions
Q: Can the QX42 be used with 24 V DC field devices?
A: No. The QX42 is rated for 5 V DC and 12 V DC input signals only. Applying 24 V DC to its input terminals will exceed the maximum input voltage rating and will permanently damage the input circuitry. For 24 V DC sink/source inputs at 64-point density, use the QX42-S2 module instead.
Q: What connector accessory is required to wire the QX42?
A: The QX42 requires a 40-pin connector assembly. Mitsubishi offers three options: A6CON1 (individual wire solder type), A6CON2 (IDC mass-termination crimp type for flat ribbon cable), and A6CON4 (spring clamp type for individual wires). The A6CON2 with flat ribbon cable is the fastest wiring method for high point-count installations.
Q: Is the input response time of the QX42 adjustable?
A: Yes. The default input response time is 1 ms, but it can be adjusted in GX Works2 intelligent function module parameters between 0.1 ms and 70 ms per group of inputs. Reducing response time below 1 ms increases susceptibility to noise-induced false triggering — only reduce below the default when the application genuinely requires sub-millisecond input detection.
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