Field Engineer’s Notes (From the Trenches)
The “Gotcha” is Common Wiring & Sourcing vs Sinking.
Commons (C1-C3): There are 3 Commons, one per group of 8. They are notinternally tied. You must land a 0V wire from your 24V DC supply to eachCommon terminal (C1, C2, C3) on the IC693TBB003, or jumper them externally if you want a single-point return. Forgetting to land C2 or C3 causes “Inputs 9-16 or 17-24 dead despite LED being Off when open” (actually the LED won’t light if the return is open because no current flows to turn on the opto).
Sourcing (This Card) vs Sinking:
- MDL645 (Sourcing): Module outputs +24V on Input terminal. Field device (contact/NPN) connects to 0V. Use with Dry Contacts or NPN (Sink) Sensors.
- MDL653 (Sinking — IC693MDL653 is the sinking version in 90-30): Module expects +24V from the field (PNP sensor or dry contact with +24V landed to one side).
- Mistake: Wiring a PNP sensor (outputs +24V) to an MDL645 (also sources +24V). Result: No turn-on (voltage fight / open circuit). Match: PNP Sensor → Sinking Input (MDL653 style); Dry Contact or NPN Sensor → Sourcing Input (MDL645).
Wire Gauge & Torque: Uses IC693TBB003 screw terminals. Accept #14-#22 AWG. Torque to 7 lb-in (0.8 Nm). Loose Common connection is the #1 cause of “intermittent inputs” on 90-30 racks. Give the Common terminal an extra tug-test after tightening all wires.
Real-World Applications
- Waste Water Pump Station (MCC Status): A 90-30 rack with reading 24 x dry contacts: Pump Running (52a), Trip (86), High Vibration, Local/Remote, Hand/Off/Auto selector positions. The module sources the 24V sense voltage. The 0V returns from all three groups land to a single DIN-rail mounted 0V bus bar. Easy verification via point LEDs during FAT.
- Automated Bakery (Guard Doors & E-Stops): 24 x Normally Closed guard door contacts and E-Stop segments wired in series per group (8 doors per group). The MDL645 sources +24V through the NC chain; a single door open breaks the circuit, input goes Off, and the safety logic faults the line. The individual LEDs help identify which groupis open during reset attempts.
High-Frequency Troubleshooting FAQ
Q: Point LED is OFF, but the contact is closed (multi-meter shows continuity between +24V at the input terminal and the 0V bus).
A: Common (C) Not Landed or Open Circuit on Return.
- Check the “C” (Common) terminal for that point group on the TBB003. Is a wire landed from your 24V DC Supply 0V/Return? Is it tight (7 lb-in)?
- Measure voltage between the Input terminal (where you see +24V from the module) and the “C” terminal for that group. If it reads 0V (or <5V) there but 24V to the supply 0V, the Common wire is open or floating. The input circuit needs the return at the module’s Common, not just anywhere in the panel.
- If Common is good, check the contact wiring polarity: Ensure you didn’t accidentally land the return wire from the contact to +24V instead of 0V. The sources+24V; the return must go to 0V.
Q: LED is ON, but the CPU Input (%I address) reads “0” or doesn’t change with the switch.
A: Address Mismatch or Rack/Slot Error.
- In Proficy Machine Edition (or LM90), check the Hardware Configuration. Is the assigned to the correct Rack Number and Slot Number? (e.g., Rack 0, Slot 3). If the physical slot is 3 but config says Slot 2, the CPU reads the wrong image.
- Check the Input Address in your logic (e.g.,
%I0001for Slot 3, Point 1 usually maps to%I:slot_base + 0). Verify the base address in the I/O Mapping table. - If addressing is correct, check the Backplane Seating: Loosen the two module screws, press the module firmly into the backplane (ensure ejector levers click), and re-tighten. A partially mated P1 connector can pass power (OK LED on) but not data.
A: Yes. The is fully supported in the RX3i Universal Backplane.
- It uses the IC693TBB003 Terminal Block — notthe RX3i IC694TBB032 (different keying/pinout).
- Configure it in PME as “” under the appropriate slot.
- The RX3i CPU treats it identically to a 90-30 CPU. Ensure the universal backplane firmware is reasonably current to avoid rare detection issues with very old 90-30 module revisions.
Please note: The listed price is not the actual final price. It is for reference only and is subject to appropriate negotiation based on current market conditions, quantity, and availability.
