CNC Electronics Reference
Mesa Electronics Cards
| Card | Type | Interface | I/O | Features |
|---|
| Mesa 5i25 | FPGA interface | PCI | 2× DB25 (34 I/O) | Parallel-port replacement; pairs with 7i76/7i77 breakouts |
| Mesa 6i25 | FPGA interface | PCIe | 2× DB25 (34 I/O) | PCIe version of 5i25 |
| Mesa 7i76 | Breakout — step/dir | DB25 (from 5i25/6i25) | 5 axis + 32 I/O | Step/dir output, analog spindle (0–10 V), isolated field I/O |
| Mesa 7i76E | Breakout — step/dir | Ethernet | 5 axis + 32 I/O | Standalone Ethernet version of 7i76; no PCI card needed |
| Mesa 7i77 | Breakout — servo | DB25 (from 5i25/6i25) | 5 axis + 32 I/O | Analog ±10 V servo output, encoder inputs, isolated I/O |
| Mesa 7i92 | FPGA interface | Ethernet | 2× DB25 (34 I/O) | Ethernet replacement for 5i25; pairs with any DB25 breakout |
| Mesa 7i96 | All-in-one — step/dir | Ethernet | 5 axis + built-in I/O | Integrated breakout; step/dir, analog spindle, isolated I/O |
| Mesa 7i96S | All-in-one — step/dir | Ethernet | 5 axis + built-in I/O | Updated 7i96 with improved I/O and features |
| Mesa 7i97 | All-in-one — servo | Ethernet | 5 axis + built-in I/O | Analog ±10 V servo, encoder inputs, standalone Ethernet |
Parallel Port Breakout Boards
| Type | Features | Axes | Typical Use |
|---|
| Simple BOB | DB25 passthrough, opto-isolated I/O | 3–4 | Basic Mach3/LinuxCNC setups on low-cost machines |
| C10-style BOB | Charge pump support, relay output, opto-isolated I/O | 3–5 | Hobby CNC routers and mills with safety relay |
| Smooth Stepper | USB or Ethernet to step/dir; high pulse rate | 4–6 | Mach3/Mach4 compatible; replaces parallel port on modern PCs |
Stepper Motors
| NEMA Size | Frame (mm) | Holding Torque Range | Typical Current | Common Use |
|---|
| NEMA 17 | 42 | 30–90 oz·in | 1.5–2.5 A | 3D printers, small CNC |
| NEMA 23 | 57 | 100–400 oz·in | 2.0–4.0 A | Desktop / benchtop CNC mills & routers |
| NEMA 34 | 86 | 400–1200+ oz·in | 4.0–8.0 A | Full-size mills, plasma tables |
| NEMA 42 | 110 | 1200–3000+ oz·in | 6.0–10 A | Large industrial machines |
Stepper Drivers
| Driver | Type | Max Current | Microstepping | Voltage Range | Interface |
|---|
| DM542 | Digital | 4.2 A | 256 | 20–50 V | Step/Dir |
| DM556 | Digital | 5.6 A | 256 | 20–50 V | Step/Dir |
| DM860 | Digital | 7.2 A | 256 | 24–80 V | Step/Dir |
| DQ542MA | DSP | 4.2 A | 256 | 20–50 V | Step/Dir |
| Gecko G203V | Analog | 7 A | 10 | 24–80 V | Step/Dir |
| Gecko G540 | 4-axis combo | 3.5 A | 10 | 18–50 V | Step/Dir (DB25) |
Servo Motors
| Type | Voltage | Feedback | Advantages | Disadvantages |
|---|
| AC Servo | 100–400 V | Encoder (absolute or incremental) | High torque density, high speed, excellent dynamics | Expensive drives and motors |
| DC Servo | 24–90 V | Encoder | Simple drive electronics, smooth at low speed | Brush wear, maintenance |
| Closed-loop Stepper | 24–48 V | Encoder | Stepper simplicity with no lost steps, lower cost | Lower top speed than true servos |
NEMA frame sizes (23, 34, 42) apply to servos as well — choose based on torque and mounting requirements.
Servo Drives
| Drive | Type | Max Current (cont) | Voltage | Feedback | Interface |
|---|
| LCDA357H | AC Servo kit | 3.5 A | 220 V | 2500 ppr encoder | Pulse/Dir, ±10 V analog |
| AMC (Advanced Motion Controls) | DC/AC Servo | Varies (1–30+ A) | 20–340 V | Encoder, resolver | ±10 V analog, PWM, CANopen |
| Mesa 7i77 + amplifier | Generic servo interface | Per amplifier | Per amplifier | Encoder via 7i77 | ±10 V analog from 7i77 |
| DMM DYN4 | AC Servo | 4 A | 100–240 V | Encoder (serial) | Pulse/Dir, EtherCAT option |
Spindle Motors
| Type | Power Range | Speed Range | Drive | Use Case |
|---|
| Router (trim router) | 1–2.25 HP | 10 000–30 000 RPM | Manual / VFD | Wood, aluminum, small CNC routers |
| ER11/ER16 spindle | 0.8–1.5 kW | 0–24 000 RPM | VFD | Small CNC mills & engravers |
| ER20 spindle | 2.2–3.0 kW | 0–24 000 RPM | VFD | Mid-size CNC mill / router |
| BT30 spindle | 3–7.5 kW | 0–8 000 RPM | VFD | Full-size CNC milling machine |
| CAT40 spindle | 5–15 kW | 0–8 000 RPM | VFD / direct drive | Production machining centers |
| Servo spindle | 1–15 kW | 0–6 000 RPM | Servo drive | CNC lathe, rigid tapping capable |
NEMA Frame Reference
| NEMA Frame | Width (mm) | Width (in) | Bolt Pattern (mm) | Shaft Dia (mm) |
|---|
| NEMA 17 | 42 | 1.654 | 31 | 5 |
| NEMA 23 | 57 | 2.244 | 47.14 | 6.35 |
| NEMA 34 | 86 | 3.386 | 69.6 | 14 |
| NEMA 42 | 110 | 4.331 | 89 | 19 |
VFD (Variable Frequency Drive)
A VFD converts single-phase household power (110 V or 220 V) to three-phase output to drive an AC spindle motor. By varying the output frequency (typically 0–400 Hz), it provides smooth, stepless speed control from zero to maximum RPM.
Common VFD Brands
- Huanyang — popular low-cost option for hobby CNC; widely available on eBay/AliExpress
- Hitachi WJ200 — compact industrial VFD with sensorless vector control
- Yaskawa — high-quality industrial drives; excellent V/f and vector modes
- ABB — industrial-grade with advanced diagnostics and communication options
Key VFD Parameters
| Parameter | Description |
|---|
| HP / kW rating | Must match or exceed spindle motor rating |
| Input voltage | 110 V single-phase or 220 V single/three-phase |
| Output voltage | Typically 220 V three-phase (for 220 V spindles) |
| Max frequency | Determines max spindle RPM (e.g., 400 Hz → 24 000 RPM on a 2-pole motor) |
| Control mode | V/f (simple), sensorless vector (better low-speed torque), closed-loop vector |