Product not available for online order.


Not recommended for new projects.

Some pcs. available for spares only.

EM-121 is bipolar-chopper type stepper motor controller. Bipolar operation suits most stepper motors and provides the best torque. Phase current is set to desired level using chopping type current limit.

The phase current ( current limit ) can be set in seven different levels using jumpers. A wide phase current set range makes it possible to use the device with several different motors. EM-M121 also utilizes steady state current hold, in other words when the motor is stopped the controller decreases phase current, this feature reduces both the motor and controller thermal loss. Two steady state current hold modes are settable.

The controller features an auxiliary oscillator, which has fifteen preprogrammed frequencies. The frequency is set with four control inputs. Auxililary oscillator in EM-121 has also an acceleration ramp feature, which can be used to change frequencies flexibly, so that the motor will start up reliably even at high frequencies. There are three acceleration ramp intervals, that can also be bypassed.

The inputs operate with so called negative logic, in other words the inputs are activated with connecting the input to ground, the inputs also work with TTL-logic level control.

The power state of EM-121 has thermal protection for overload, the device has also self recovery fuse that protects the controller from over current and reversed input voltage polarity.


Technical data


Operating voltage 12-40Vdc
Idle current approx. 40mA 
  (20mA shutdown "0")
Current set 0.25; 0.37; 0.5; 0.63;
  0.75; 0.9; and 1.0A
Steady state I hold 35 or 67% of current set
Voltage loss 3V when Im=1A
Fuse 1A self recovery.
Aux. osc. freq. 20, 50, 100, 200, 300 Hz
  400, 600, 800, 1000 Hz
  1.5; 2; 2.5; 3; 3.5; 4 kHz
Freq. Precision typ. 1%
Digital control OFF, Uin 4 -30V or open
  ON,  Uin 0-1V
Step freq. max. 9kHz
Operating temp. 0-50°C
Dimensions 67x75x25mm
Weight approx. 100g



Product files

Product not available for online order.