The QD70P8 is Mitsubishi Electric’s 8-axis high-speed counter and simple positioning module for the MELSEC-Q programmable controller series — doubling the channel count of the QD70P4 to provide eight independent channels of pulse train input counting and pulse train output positioning in a single base unit slot, making it the highest channel density pulse I/O module in the MELSEC-Q range for applications requiring simultaneous multi-axis position measurement and control across a large number of independent axes within a compact system footprint. Atlantech Drives holds stock of the QD70P8. Contact us for fast worldwide delivery and competitive pricing.
What Is the QD70P8?
The QD70P8 is a MELSEC-Q series intelligent function module providing eight channels of high-speed pulse counter input and pulse train output — identical in function to the QD70P4 but with twice the channel count in the same module housing. Each of the eight channels is independently configurable as either a high-speed counter input (AB quadrature, CW/CCW, or single-phase) or a pulse train positioning output (open-collector step/direction or CW/CCW), with the channel direction set via GX Works2 buffer memory parameters. The QD70P8’s 8-channel architecture provides the highest pulse I/O density in a single MELSEC-Q slot, enabling systems such as 8-axis rotary indexers, 8-zone conveyor position tracking systems, and 8-spindle machine tool position monitors to be implemented with a single module rather than two separate 4-channel modules. Like the QD70P4, the QD70P8 provides simplified positioning functionality (preset position, home return, JOG, speed control) rather than the advanced multi-step pattern and interpolation features of the QD75 series, making it the cost-efficient choice for applications where basic position control is required across many axes simultaneously.
Key Technical Specifications
- Model: QD70P8
- Channels: 8 (each independently configurable as counter input or pulse output)
- Counter Input Types: AB quadrature (×1, ×2, ×4 multiplication), CW/CCW, single-phase
- Maximum Counter Input Frequency: 200 kpps per channel
- Counter Range: -2,147,483,648 to +2,147,483,647 (32-bit signed)
- Pulse Output Type: Open-collector, step/direction or CW/CCW
- Maximum Pulse Output Frequency: 200 kpps per channel
- Positioning Functions: Preset position, home return, JOG, speed control
- External Signals: Near-point DOG, limit switches (per channel)
- Current Consumption (5 VDC internal bus): 0.90 A
- External Power Supply: 24 VDC ±10%, 0.25 A (required)
- Operating Temperature: 0°C to 55°C
- Compatible CPUs: All MELSEC-Q series CPU modules
- Weight: Approx. 0.35 kg
Typical Industrial Applications
The QD70P8 is deployed in applications where the simultaneous measurement and control of eight independent motion axes must be consolidated into a single module to minimise base unit slot usage and system cost. In multi-spindle CNC drilling machines, the QD70P8 simultaneously tracks the Z-axis position of eight drilling spindles via encoder feedback on eight counter input channels, with the CPU program coordinating depth control for each spindle independently based on the real-time position data. In eight-zone pallet conveyor systems for engine assembly, the QD70P8 monitors the position of eight conveyor drives via encoder feedback, detecting zone occupancy and pallet positioning accuracy for workpiece handoff between assembly stations. Eight-axis rotary indexing tables used in pharmaceutical blister packaging, where eight filling stations must be indexed precisely to align with product pockets, commonly specify the QD70P8 to manage both the indexing position feedback and the station drive pulse commands within a single module. In automated warehousing and ASRS (Automated Storage and Retrieval System) applications, the QD70P8 tracks the position of eight independently moving shuttle axes on a rack storage system, with the CPU program managing collision avoidance and routing logic based on the real-time position data from all eight axes simultaneously.
Replacement & Upgrade Notes
The QD70P8 is a direct capacity upgrade from the QD70P4 for systems where the initial 4-channel specification has proven insufficient as the machine has been expanded. When upgrading from two QD70P4 modules to a single QD70P8, the GX Works2 buffer memory address mapping changes — the QD70P4’s buffer memory addresses are referenced relative to the module’s slot position, and replacing two QD70P4 modules in two different slots with a single QD70P8 in one slot requires updating all FROM/TO instructions and auto-refresh settings that previously referenced the second QD70P4 module’s slot address. For systems currently using QD75P4N positioning modules but only requiring the basic positioning functions (no multi-step patterns, no S-curve acceleration, no interpolation), migrating to the QD70P8 can provide 8-axis coverage in a single slot versus two QD75P4N modules occupying two slots — the trade-off is the loss of QD75’s advanced positioning features, which must be evaluated against the slot and cost savings. In retrofit projects replacing legacy MELSEC-A series AD70 pulse I/O modules with MELSEC-Q QD70P8, the buffer memory address structure changes between platforms — update the ladder program’s FROM/TO instruction references to the QD70P8 address map documented in Mitsubishi’s MELSEC-Q QD70P8 user manual after the hardware substitution.
Frequently Asked Questions
Q: Can all 8 channels of the QD70P8 operate as pulse outputs simultaneously?
A: Yes. All eight channels can be configured as pulse outputs simultaneously in GX Works2’s buffer memory parameter settings, enabling the QD70P8 to control eight independent stepper or servo axes at the same time. The maximum output frequency per channel (200 kpps) applies independently to each of the eight channels — configuring all eight as outputs does not reduce the per-channel frequency limit.
Q: Does the QD70P8 support absolute position detection using a home sensor after power-up?
A: Yes. The QD70P8 supports a home return function on each pulse output channel, using a near-point DOG sensor input to detect the home position and establish an absolute reference point for the counter. After power-up, initiating the home return operation on each axis drives the axis to its home position at the configured home return speed, touching the DOG sensor and setting the counter to the preset home position value. Once home return is complete, all subsequent positioning is executed in absolute coordinates referenced to the established home position.
Q: What is the internal power consumption of the QD70P8 compared to using two QD70P4 modules?
A: The QD70P8 consumes 0.90 A at 5 VDC from the internal bus, while two QD70P4 modules consume 2 × 0.60 A = 1.20 A total. The QD70P8 therefore reduces internal bus current consumption by 0.30 A compared to two QD70P4 modules, which can be significant in systems where the power supply module’s current capacity is approaching its rated limit.
Do you need more references from this brand? Explore our full catalog of Mitsubishi here: https://atlantechdrives.com/manufacturers/mitsubishi/
