42J1840-408 Low Current NEMA17 Stepper Motor - 0.8 A

The 42J1840-408 is a Low Current NEMA17 Stepper Motor, a 40 mm 2-phase unit that draws just 0.8 A per phase while delivering 0.40 N·m of holding torque through a 5 mm shaft. The reduced current draw makes it a natural fit for optical, laboratory, and inspection equipment where heat budgets, driver size, and wiring gauge are all limited.

Why Low Current Matters in Precision Instruments

Every ampere that flows through a winding becomes heat in the motor and load on the driver. At 0.8 A the 42J1840-408 keeps both in check: it can be driven by compact, low-cost driver boards, fed from small power supplies, and operated inside enclosed instrument housings without disturbing temperature-sensitive optics.

The 0.40 N·m torque covers focus stages, light positioning axes, filter changers, and similar light-load mechanisms that need smooth, repeatable stepping rather than raw force.

Specification Summary

• Frame: NEMA17 (42 mm)
• Body length: 40 mm
• Phase current: 0.8 A
• Holding torque: 0.40 N·m
• Shaft: 5 mm
• Type: 2-phase, open-loop

Typical Application Scenarios

In 3D printers the motor handles extruder feed and Z-axis lead screws, where keeping carriage electronics cool during long prints is a real advantage. Laboratory stages and medical instrumentation use it to move probes, slides, and dispensing heads with repeatable step counts, while optical filter changers rely on its low-vibration motion to keep measurement paths stable.

Inspection equipment advances sample conveyors one index at a time, and small peristaltic pumps use the steady low-speed torque for dosing. Because the motor draws only 0.8 A, it pairs naturally with portable and battery-powered devices where every milliamp counts.

Selection and Operating Advice

Confirm the driver delivers the rated 0.8 A per phase and check the torque available at your working speed, since microstepping increases smoothness but reduces peak torque. The low winding current inherently reduces heating, which supports reliable operation in enclosed, thermally sensitive housings. The standard NEMA17 mount and 5 mm shaft work with common small couplings and compact driver boards, easing integration into a wide range of instrument designs.