QY50 is a 16-point transistor (NPN sink) output module for Mitsubishi Electric’s MELSEC-Q series programmable logic controller platform, providing 0.1 A per point switching capacity at 12–24 V DC for connection to solenoid valves, indicator lamps, relay coils, and other low-current DC loads. The QY50 occupies a single slot on any Q-series base unit and is the standard NPN transistor output module for Q-series systems requiring moderate output current at economic module cost. Atlantech Drives holds stock of the QY50. Contact us for fast worldwide delivery and competitive pricing.
What Is the QY50?
The QY50 is a 16-point NPN (sink) transistor output module in the MELSEC-Q discrete output range. The «Y» designation identifies it as an output module, and «50» places it in the 12–24 V DC NPN transistor output family. Each output point is an open-collector NPN transistor switch rated at 0.1 A maximum continuous current, with a total common current limit of 0.8 A across all 16 points — meaning the average concurrent load per point must not exceed 50 mA in applications where all outputs are energised simultaneously. The QY50 provides two 8-point commons, each with its own COM terminal, allowing two independent load voltage or polarity groups within a single module. Each output is photocoupler-isolated from the Q-bus backplane at 500 V AC, and a built-in protective Zener diode on each output clamps inductive transient voltages to protect the output transistor against damage from solenoid valve and relay coil deenergisation spikes without requiring external suppression components on every load.
Key Technical Specifications
- Number of Output Points: 16
- Output Type: NPN transistor (sink, open collector)
- Load Voltage: 12–24 V DC (10.2–26.4 V DC operating range)
- Max Output Current: 0.1 A per point
- Max Common Current: 0.8 A per common (8 points per common)
- Residual Voltage (ON state): 1.5 V DC max at 0.1 A
- Leakage Current (OFF state): 0.1 mA max
- Response Time ON→OFF / OFF→ON: 1 ms / 1 ms
- Built-in Output Protection: Zener diode clamp per point
- Isolation: Photocoupler (500 V AC between field and Q-bus)
- External Power Supply: Required (12–24 V DC, user-supplied, connected to COM terminal)
- Current Consumption: 5 V DC, 0.09 A (from Q-bus)
- Operating Temperature: 0 °C to 55 °C
- Dimensions (W × H × D): 27.4 × 98 × 90 mm
- Weight: Approx. 100 g
Compatibility & System Integration
The QY50 is compatible with all MELSEC-Q CPU types and base unit generations, including Universal model (QnUDEH), High Performance (QnPH), Process (QnPRH), and Redundant (QnPRH redundant system) configurations. In Multi-CPU systems where a Q172DCPU or Q173DCPU motion CPU shares the base unit with a sequence CPU, the QY50 modules assigned to the motion CPU’s I/O range are controlled directly by the motion CPU’s servo program output instructions, while those in the sequence CPU’s range are controlled by the ladder program — the assignment is defined in the CPU parameter I/O allocation settings in GX Works2. The QY50’s 0.1 A per point rating is directly compatible with the input current requirements of most intermediate relay modules (such as the Mitsubishi A6RLAY or equivalent third-party relay modules) used to interface the PLC output to higher-current or AC loads. For applications requiring higher output current per point (up to 0.5 A or 2 A), the QY10 (0.5 A NPN) or QY18A (0.5 A source, with external supply) should be specified instead. The QY50 is not suitable for direct switching of 24 V DC motor loads above 0.1 A — for motor starter or contactor coil switching above this threshold, use the QY10 or an interposing relay.
Replacement & Upgrade Notes
The QY50 is the direct functional equivalent of the earlier A1SY50 output module used in MELSEC-A1S systems, and shares identical electrical characteristics, making it a straightforward replacement in A-to-Q series upgrade projects where the field wiring and load characteristics are retained unchanged. When replacing a failed QY50 in an operational system, note that the 40-pin field wiring connector is removable without tools — label the connector and the slot position before extraction to avoid reassigning the connector to an incorrect slot after module replacement. The Q-series hot-swap function (if enabled in CPU parameters) allows the QY50 to be replaced without powering down the base unit on base units that support online module change (check the Q-series CPU User’s Manual for the specific CPU variant’s hot-swap eligibility). After replacement, verify that all 16 output points switch correctly by forcing each output ON and OFF individually via GX Works2’s Device Test function before returning the system to automatic operation — partial connector seating on the replacement module is the most common cause of individual point failures after maintenance replacement.
Frequently Asked Questions
Q: Can the QY50 drive 24 V DC solenoid valves directly without external suppression?
A: Yes, within the 0.1 A per point current limit. The QY50 includes a built-in Zener diode clamp on each output that suppresses the inductive voltage spike generated when a solenoid coil is deenergised, eliminating the need for external flyback diodes or RC snubbers on most standard solenoid valves. However, for solenoid coils with very high inductance (coil resistance below approximately 50 Ω at 24 V DC, drawing close to the 0.1 A limit), verify that the coil inrush current does not exceed the 0.1 A output rating — some solenoid types draw 3–5× rated current during the first few milliseconds of energisation.
Q: What is the correct external power supply wiring for the QY50?
A: The QY50 requires an external 12–24 V DC supply connected to the COM terminals of each 8-point common group. The positive terminal of the external supply connects to the load (one side of each load connects to the output point terminal, the other side connects to the positive supply). The negative terminal of the external supply connects to the QY50 COM terminal. This is standard NPN sink wiring: the output transistor pulls the load terminal to 0 V when ON, completing the circuit through the external supply positive. The external supply is not connected to the Q-series power supply module — it is entirely separate and user-provided.
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