27938 Datasheet 27938 | P1-P3

Little Step-U

Unipolar Stepper motor controller

TLA Microsystems Ltd http://www.tla.co.nz 1

Features

• Unipolar motors to 35V, 3.0A

• Full step, half step and wave drive modes

• 1-5,000 steps per second

• Inbuilt speed ramp (0.1-20.0 seconds)

• Simple serial commands (TTL interface)

• Separate power input for motor and logic

• Suitable for direct and L/R operation in all

modes

• On board clamping diodes

• Current position register (+/-100,000,000)

• Zero position and user marker registers

• Absolute & Relative movement commands

• Busy output

• Two inputs suitable for optical stops

• Slave mode using inputs for STEP & DIR

• Stop with motor coils on or off

Description

The Little Step-U is a complete, serially

controlled, drive system for unipolar stepper

motors. Using an intelligent module allows the

host system to concentrate on the task at hand

while the Little Step-U performs all calculations

and operation of the motor.

The desired operating speed, ramp time and

drive mode can be configured once and then a

single command used as required, to move to

fixed or relative positions. While the motor is in

motion, a BUSY output is active and the

movement can be optionally interrupted by one

of the two external inputs. The position of the

motor is maintained in a readable register which

can be set to zero (Home) by a command or

when an input is activated. A similar register is

available to save a second position (Mark) either

by command or from an input. These points

can then be referenced directly with a 'Move to

home' or 'Move to mark' command.

A built-in ramping function accelerates the

motor from a standstill to the desired speed over

a specified time period, allowing faster final

speeds to be achieved, and also to decelerate

the motor to give maximum load braking. When

the motor is stopped, a command specifies

whether the windings are left energized (for

maximum holding torque) or turned off (for lower

power consumption / dissipation).

A remote function is included for use in more

complex systems. Once activated, the two

external inputs become STEP and DIR, with the

motor stepping in the indicated direction with

every pulse applied to the step input.

/IP1

/IP2

BUSY

SERIAL OUT

SERIAL IN

Vcc (+)

GND (-)

COIL A

COIL B

COIL C

COIL D

CT - AC

CT - BD

Vom (-)

Vm (+)

CON 2

CON 1

CON 3

1.0 in

2.0 in

Vom

CT-AC

CT-BD

Vcc

GND

Logic Signals

Microcontroller

2 Little Step-U

DC Characteristics

Characteristic Symbol Min Typ Max Unit Notes

Logic Supply Voltage V

4.5 5.0 5.5 V

Vcc risetime t

VCC

0.05 V/ms 1

Logic supply current I

1.5 3.0 mA

Input Low Voltage V

0.0 1.0 V

Input High Voltage V

4.3 Vcc V

Output Low Voltage V

0.6 V

Output High Voltage V

4.3 V

IP1/2 Source Current I

1.0 mA

Motor Voltage V

50 V

Motor current I

3.0 A

Motor resistance R

2.8 Ω

Clamp diode current I

250 mA

Step rate F

STEP

1 5000 steps/sec

Speed Error F

ERR

+/- 0.5 % 2

Comms bit rate F

BIT

2400 bps

BUSY rise/fall time T

10 25 ns

Response time to IP1/2 T

INP

1 ms 3

DIR hold time T

DIR

8 us

Max Slave step rate F

EXT

10000 steps/sec 4

Operating temp t

0 70 °C 5

Storage temp t

-40 100 °C

[1] Required to ensure reliable startup.

[2] As a percentage of requested speed

[3] Response to IP is lesser of 1ms or 1 step

[4] If no comms while stepping. Max = 6000 steps/sec with comms

[5] Refer loading derating graph

Pin functions

Connector 1 Pin Function

/IP1 Optional input 1. Set home. Emergency stop.

/IP2 Optional input 2. Set mark. Emergency stop.

BUSY Output - High when motor moving

SERIAL OUT Data from Little step-U to controller. TTL

SERIAL IN Data from controller to Little Step-U. TTL

Vcc Supply to logic circuits

GND Supply ground. Common with motor circuits.

Connector 2 Pin Function

A Winding A output

B Winding B output

C Winding C output

D Winding D output

CT-AC Common for windings A & C

CT-BD Common for windings B & D

Connector 3 Pin Function

Motor supply ground. Common with logic circuits

Motor Supply +

TLA Microsystems Ltd http://www.tla.co.nz 3

Hardware Connection

Power Supply

The Little Step-U divides the circuitry into two distinct sections with separate power supplies

required for the motor drive and the logic. The logic/control section must be powered by a

regulated 5V supply applied to the VCC and GND pins. The motor power supply voltage is

dictated by the motor characteristics and is connected to the VM(+) and VOM(-) pins. The

GND and VOM pins are connected on the circuit board as a common reference. The motor

power supply must have sufficient capacity for the motor and if the power supply is not

physically close to the motor/controller, a capacitor (eg. 4700uF) may be required at the

controller to ensure smooth operation of the motor.

Motor Connection

The motor connector has 4 connections (A, B, C & D) that are switched to ground in the

sequence required to cause the motor to step. Note that stepper motor manufacturers have

several methods of labelling the connections to the motor. The Little Step-U labels the pins in

the sequence they are switched when operating the motor with one coil on at a time and driving

in a clockwise direction. ie. A, then B, then C, then D and back to A. The centre taps of the

two coils are connected to CT-AC and CT-BD, corresponding to the common connection of coils

A & C and coils B & D respectively. These two connections provide the freewheel diodes for

each of the motor coils and are connected on the circuit board.

IMPORTANT: A poor or intermittent connection to any of the stepper motor terminals can result

in destructive voltages being generated and causing permanent damage to the Little Step-U.

Similarly, do not connect or disconnect any stepper motor connections while power is applied.

The connection point between CT-AC and CT-BD is indicated on the circuit board by the

designator "LK". This track can be cut and rejoined by soldering a wire between two pads if

needed. In most cases this isn't required but is provided for applications using and L/xR

configuration in half step mode.

Interface connections

The Little Step-U acts on commands received serially from a host controller via the SERIAL IN

pin. This is an asynchronous interface operating at 2400 bits per second, 8 data bits (LSB

first), 1 stop bit and no parity. The signal levels are TTL. Some commands illicit a response

and these are sent via the SERIAL OUT pin using the same protocol and signal levels as the

SERIAL IN pin.

When a command has been sent to the Little Step-U that causes the motor to move, the BUSY

pin will be high while the motor is in motion.

Two input pins are provided for use with stepper operation in the form of limit or home switches

or can be used as general inputs which can be read by software. These pins accept logic level

inputs and will source 1mA when pulled low, making them suitable for direct connection to the

output of opto-couplers.

P1-P3 P4-P6 P7-P9 P10-P12

27938

Mfr. #:

Buy 27938

Manufacturer:

Parallax

Description:

Daughter Cards & OEM Boards LITTLE-STEP CTRL

Lifecycle:

New from this manufacturer.

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27938