Monitor an older CNC that has no MTConnect

Why the stack light and the spindle

The control already shows what the machine is doing on the stack light. Colours mean different things on different builders' machines, but on any one machine they are consistent, and the lamp wires carry that as a plain voltage.

The spindle current adds what the lamp cannot say: whether the machine is actually cutting. A green lamp with the spindle stopped is a machine in cycle but not making chips. AndonTap reads the spindle as stopped, turning or cutting, and keeps spindle on time and cut time separately.

Neither signal needs the control's cooperation: no software option, no changes to the CNC control or a PLC program.

What this approach does not see is what lives inside the control: the program name, the alarm number or text, overrides, tool data. If you need those and the control can provide them, read MTConnect or a stack-light monitor.

Step 1 · Tap the lamp signals

Find each lamp's switched terminal, in the stack light base or on the machine's terminal strip, and the lamp common. Land them on the 5-pin inputs 1-4 plug:

• COM-A to the lamp common: neutral for a 120 VAC stack light, 0 V or +24 V for a 24 VDC one.
• IN1, IN2, IN3 to red, amber and green (the factory setting). IN4 is free for a fourth tier, a part counter or another signal.

The inputs take 24 VDC or 120 VAC 50/60 Hz, detected automatically, with no jumpers; DC works in either polarity. Each input draws about 2 mA, so the lamps work as before. All four inputs share COM-A, so they must come from one circuit at one voltage. Switch off the stack-light circuit before plugging or unplugging the plug.

Steady and flashing lamps are told apart.

Step 2 · Clamp a CT on the spindle feed

Close the split core around one phase conductor of the spindle feed, for example L1. Around a whole cable the currents cancel. Nothing is disconnected.

• Use a voltage-output CT (333 mV or 1 V AC). Never a 1 A / 5 A current-output CT.
• On a VFD-driven spindle, put the CT on the drive's input or its output, and do the same on every machine.
• For a small motor, loop the conductor through the CT several times and enter the number of passes (1-20) in the setup app.

CT2 can watch a coolant pump, conveyor, hydraulics, main power or a second spindle.

Step 3 · Power it and plug in the network

One PoE cable powers and connects the unit; without PoE, wire 24 VDC to the power plug. A new unit has no IP address and sends nothing on the network, not even DHCP requests, until it is set up.

Step 4 · Set it up from a laptop or phone

Open the setup app in the browser and connect over USB-C, or over Bluetooth (a new unit has Bluetooth on; on a unit with an address, press CFG for 10 minutes of Bluetooth).

1. Machine: enter the machine name and asset ID. They are served in the data, so your software knows which machine this is.
2. Stack light: check each input's role and colour. Each row lights live, so with the machine running you can confirm red, amber and green one at a time.
3. Spindle & CTs: enter the CT rating, output and passes. Then either enter the spindle motor's full-load amps for suggested thresholds, or run the spindle and capture the idle-turning and cutting currents live.
4. Network & security: choose Static and enter the address, mask and gateway from your network administrator.
5. Click Write to unit. The unit checks every change and applies all of it or none of it.

For the next identical machine, save the setup file and clone it; the new unit keeps its own name and address.

Step 5 · Check the state rules

Machine state comes from ordered IF/THEN rules; the first rule that matches wins. The factory rules are:

1. No 24 V on the power plug: Off
2. Red on or flashing: Alarm
3. Green flashing: Setup
4. Green on: Running
5. Amber on or flashing: Warning

Anything else reads Idle. You can have up to 8 rules, each with up to 3 conditions on lamp colours, single inputs, spindle level, CT2 and 24 V power, and the states include Maintenance as well. The app highlights the rule matching right now.

Step 6 · Read the data

The unit is a server on your network: Modbus TCP on port 502 and EtherNet/IP. The layout is the same on every unit. The registers most people start with:

• Input register 8: machine state (0 Unknown, 1 Off, 2 Idle, 3 Running, 4 Alarm, 5 Setup, 6 Warning, 7 Maintenance)
• Input register 9: spindle level (0 stopped, 1 turning, 2 cutting)
• Input registers 56-59: spindle on time and cut time, in seconds
• Input registers 66-81: seconds spent in each machine state

Counters survive power loss and firmware updates. Step-by-step guides cover Kepware and Studio 5000; other Modbus clients read input registers 0-123, or the mirror at holding registers 1000-1123.

Part counts

Any of inputs 1-4 can count parts instead of watching a lamp: set its role to part counter. Inputs 1-4 share COM-A and one voltage with the lamps, so with a 120 VAC stack light a 120 VAC part-count signal can use a spare input 1-4. A 24 VDC part-count signal goes on inputs 5-8, which have their own common (COM-B) and also take other 24 VDC machine signals such as a door switch. Inputs 5-8 are supported from firmware 1.7.

Full wiring details, safety notes and the troubleshooting table are in the user manual. For a side-by-side with a PLC on each machine, see Why not a PLC?