Stepper Drive Guide

Practical notes for pairing and tuning stepper motors with external drivers. Use this when bringing up rovers, telescope mounts, or any axis that values smooth motion and predictable torque without weeks of datasheet spelunking.

🎯Quick Why/When

Use steppers when: you need precise low-speed control, open-loop simplicity, and holding torque.
Watch-outs: torque drops with speed; excessive microstepping can stress step-rate limits.
Good fits: worm-driven telescope axes, pan-tilt rigs, mid-speed tracked rovers, small CNC.

ℹ️

Microstepping improves smoothness and resolution, but not peak torque proportionally. Size torque margins on full/half-step.

🧩Example Motor Spec

A representative card you can duplicate and fill from a datasheet.

Motor: Generic NEMA34

NEMA 34

6 Nm

200 steps/rev

Phase Current

4.2 A/phase

Step Angle

1.8°

Phase Inductance

6.8 mH

Shaft Ø

12 mm

Weight

2.4 kg

Suggested driver: DQ860MA/Leadshine 60V class

Approx. supply: ~60 V

Microstepping improves smoothness/resolution but not peak torque proportionally. Size torque on full/half-step and validate under load and temperature.

🧮Driver DIP Map (Example)

Configure microstepping and phase current via DIP switches. Always verify against your specific driver manual.

Driver DIP Map

Driver: DQ860MA-classExample only — check your datasheet

Legend:ONONOFFOFFX- (don't care)

Microstepping

Example mapping — confirm with your driver manual

Setting	SW1	SW2	SW3	SW4	SW5	SW6	SW7	SW8	Note
Full step (1)	OFF	OFF	OFF	X	OFF	OFF	OFF	OFF	x = don't care
1/2	OFF	OFF	OFF	X	OFF	OFF	OFF	ON
1/4	OFF	OFF	OFF	X	OFF	OFF	ON	OFF
1/8	OFF	OFF	OFF	X	OFF	OFF	ON	ON
1/16	OFF	OFF	OFF	X	OFF	ON	OFF	OFF
1/32	OFF	OFF	OFF	X	OFF	ON	OFF	ON

Current (A/phase)

Start at ~70–80% of motor rated current, then tune thermals

Setting	SW1	SW2	SW3	SW4	SW5	SW6	SW7	SW8
2.4 A	OFF	OFF	ON	X	X	X	X	X
3.0 A	OFF	ON	OFF	X	X	X	X	X
3.5 A	OFF	ON	ON	X	X	X	X	X
4.2 A	ON	OFF	OFF	X	X	X	X	X

⚠️

If you hear harsh buzzing with no rotation, power down immediately — coils may be miswired or current set far too high.

📐Plan Torque & Step Rate

Estimate the required motor torque and step rate for linear and rotary systems. Use this to sanity-check gearing, microstepping, and efficiency assumptions before fab.

Torque Planner

Estimate motor torque & step rate from basic mechanical parameters.

Mode

Gear Ratio (motor:load)

Efficiency

70%

Mass (kg)

Wheel Radius (mm)

Acceleration (m/s²)

Target Speed (m/s)

Rolling μ

Steps / Rev (base)

Microsteps

Motor Torque (Nm)

0.014

Motor Speed (RPM)

8594.4

Load Torque (Nm)

0.572

Step Rate (steps/s)

229183

Warnings

Step rate >100k steps/s — reduce microsteps or increase gear ratio.

Heuristic

Use step-rate as your early red flag. If you exceed ~100k steps/s, reduce microstepping or increase gear ratio; otherwise you may run into missed steps or MCU ISR limits.

stepRate > ~100k steps/s is a smell — reduce microsteps or increase ratio.
Keep efficiency realistic (0.6–0.85 typical with belts/worms).
Validate thermals with a 20–30 minute loaded run; derate current if too hot to touch.

✅Best Practices

Wiring: Twist A/B phase pairs; keep STEP/DIR short and isolated from motor power.
Power: Start at 24–36V for NEMA23, 36–48V for NEMA34 (within driver limits).
Bring-up: Verify coil pairs → set current → microsteps → no-load test → loaded test → thermal soak.
Docs: Record DIP settings, current, microsteps, PSU voltage, pulley/gear ratios in the repo.

Filed under: Hardware, Stepper Motors, NEMA34, DQ860MA, Microstepping, Torque Planning