12Vdc

35L048B-2U motor

FIG. 1

24 Vdc

Series Resistors

42M048C-1U motor

FIG. 2

DRIVE CIRCUIT

Typical permanent magnet stepper motor performance

Uni-polar drive

Uni-polar drive

Uni-polar drive

Uni-polar drive

Suitable modular drives for above motors: MSE422, PVP134, PM542

Explanation of terminology

The motors may be connected directly to a dc supply of the same value

as the motor rating. For example, the 35L048B-2U motor is a 12 Volt

rated unit and therefore may be connected directly to a 12 Vdc supply

as shown in Fig 1. This is often referred to as L/R Drive

For increased high speed performance however it is quite usual to

connect the motor to a higher supply voltage via series resistors since

the current rise time in the motor’s coils is proportional to the inductance

( L ) divided by the resistance ( R ) in the drive circuit.

For example, the 42M048C-1U motor is a 5 Volt rated unit. When

connected to a 24 Vdc supply via series resistors the ratio of

inductance/ resistance will be greatly improved. In this case the system,

as shown in Fig 2 would approximate an L/5R drive.

Alternatively a more sophisticated drive system can be employed using

chopped constant current techniques when the series resistors are not

required. A suitable drive of this type is PM542

26 series

0

0.1

0.2

0.3

0.4

0.5

0

250

500

750

1000

steps per second

26S024B

26M048B

35L048B series

0

0.5

1

1.5

2

0

500

1000

1500

steps per sec. ( 7.5 degrees )

L/R Drive

L/4R drive

42M048C series

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0

250

500

750

1000

steps per sec. ( 7.5 degrees )

L/R Drive

L/5R Drive

60L048 & MV82 series

0

2

4

6

8

10

0

250

500

750

1000

steps per sec. ( 7.5 degrees )

L/R Drive

L / 5R Drive

DRIVE CIRCUIT

Mclennan Servo Supplies Ltd. Tel: +44 (0)8707 700 700 www.mclennan.co.uk