CQM1-OC222 Wiring Guide: Omron CQM1 Relay Output Unit

Overview

The CQM1-OC222 is a 16-point relay contact output unit for the Omron CQM1 rack family. It runs in machines built from the mid 1990s through the early 2000s: packaging machines, test benches, small assembly cells, and process skids that never got a controller migration. You replace the unit when contacts weld shut, a point stops switching under load, or a rack slot refuses to recognize it.

In the catalog number, CQM1 names the controller family, OC marks a relay contact output unit, and 222 identifies this 16-point configuration within the family. The prefix matters when you order. The same family uses OD numbers for transistor outputs, and a transistor unit will not switch the mains-voltage loads that a contact unit handles. Inside the unit, each output is a dry relay contact that opens and closes an external load circuit, and the PLC backplane supply never touches the load side.

CQM1 production ended years ago, so every unit in service is either original or a replacement pulled from stock. The racks are still common in food packaging, pharmaceutical filling, and material handling equipment. Machines in these industries run for decades, and a functioning 16-point output card is cheaper than a controls retrofit.

Key specifications

The table lists family-level values for the CQM1-OC222. Contact ratings and the exact terminal layout belong to the unit in hand, so confirm them against the Omron datasheet and the label on the module before wiring anything.

Wiring a relay contact output

Relay outputs switch whatever load circuit you wire across the contact, so the wiring starts with the load supply. Bring the load supply positive to the common terminal group, wire each load between a point terminal and the supply negative, and the contact closes the loop when the point turns on. The CQM1 power supply unit powers the logic side and never the loads, so keep the two supplies separate in your drawings and in your head.

Warning: Disconnect all power and follow your lockout and tagout procedure before working on the unit or the load circuit. Relay contact terminals carry the full load voltage when the output is on, and mains-level loads are common on these cards. Wiring work belongs to qualified personnel.

Inductive loads need attention. Contactors, solenoid valves, and motor starters generate voltage spikes that erode relay contacts with every operation. Fit an RC snubber across AC loads or a flyback diode across DC loads at the load itself, as close to the coil as you can get. Fuse each common group at a value that protects the wiring, sized against the datasheet limits for the unit.

After wiring, prove each point before releasing the machine. Command the output on from the programming device and measure the terminal against the common: a live point reads the load supply voltage, a dead point reads zero. Do this once during commissioning and again any time you rewire a group, because swapped commons are a classic cause of loads firing in the wrong order.

Replacing a CQM1-OC222

Pull the same model, because a matching part number keeps the I/O allocation exactly as it was. The CQM1H successor family accepts CQM1 I/O units, which gives you a second sourcing path when a true CQM1 part is hard to find; confirm the combination against the Omron compatibility tables before you order.

The swap itself is short. Power the rack down, note the slot position, release the unit from the rack connectors, and seat the replacement in the same slot. Power up and check that the CPU completes its I/O check without a unit error. Then force the 16 points on and off in pairs while someone watches the loads, or watch the output LEDs against your meter readings if you are on your own.

Old machines drift from their drawings, so do not assume the slot history matches the program. If a point does nothing when you force it, check the field wiring at that terminal before you condemn the new unit. Photograph the terminal strip before you start, because the photos are faster to read than the original schematic on the day.

Common issues and troubleshooting

Work the flow from the top. Each step tells you what to do, what to observe, and where to branch.

1. One point will not switch. Force the point ON from the programming device and watch the output LED on the unit.
2. If the LED lights but the load does nothing, measure at the point terminal against the load supply common. Load voltage present means the contact is working and the fault is downstream: check the field wire, the terminal screw, and the load itself.
3. If the LED lights and the terminal reads zero, check the load supply and its fuse at the common group first. A dead common kills the whole group while the unit looks healthy.
4. If the LED stays dark when forced ON, the unit is not driving the coil. Reseat the unit, power cycle, and force again. A point that stays dark after that indicates an internal fault and a replacement.
5. Check for a welded contact when a load runs with the point commanded OFF. Measure continuity across the point terminal and the common with the output off: continuity on an off point means the contact has welded, and the unit must come out.
6. The whole unit drops out at once. That pattern suggests a shared cause: the rack connection, the backplane supply, or a unit failure on the logic side. Reseat, power cycle, and read the CPU I/O error status before replacing anything.
7. The CPU reports a unit error at power-up. Confirm the unit sits fully home in the rack and that the slot matches the I/O table. A unit moved to a slot the allocation does not expect will register as an error even though the hardware is good.

FAQ

Is the CQM1-OC222 still in production?

No. Omron ended the CQM1 line long ago and current catalogs steer buyers to newer families. Working units remain available from surplus stock, which is the practical option when the machine just needs the same card back in the same slot.

Can I put a transistor output unit in its place?

No. Transistor units carry a different prefix, switch DC loads only, and need both wiring and program changes to work in the same slot. Keep to the OC number unless a migration is planned and engineered.

Does this unit fit a CJ1 rack?

No. The rack connection differs between families. The CJ-family equivalent is the CJ1W-OC211, also a 16-point relay output unit, and it only seats in a CJ rack. Match the unit to the rack family you actually have.