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GSK-187 Stepper Motor
Chopper Driver
The Stepper Motor Chopper Driver is a Bipolar
Stepper Motor Drive with easily adjustable
current control up to 2A, based on the SGS-
Thompson L297 and L298 stepper motor
controller and driver IC’s.
Stepper motors are rated by current and not
by voltage. A chopper driver because it is
switching on and off current allows a set
current to be fed to the coils and not be
dependent on the voltage of the power supply.
The Chopper Driver also allows for the use of
higher voltage power supplies (up to 36V) to
overcome the effects of the inductance of the
coils giving better performance and a higher
top speed.
Features Include:
Easily adjustable motor current
(0.A to 2A)
Full and Half stepping modes
Step and Direction inputs
Synchronise adjust when using
multiple drivers
Enable input can be connected to
ground to disable motor
Connections via screw terminals
Initial Setup:
The Stepper Motor Chopper Driver can be used
with a power supply up to 36V, however, if the
power supply voltage is above 25V a second
power supply less than 26V is required to
produce 5V for the logic.
Connect the motor power supply negative wire
to a COM terminal and positive wire to the Vs
terminal. When using a motor voltage above
26V link LK1 must be removed and a power
supply between 8V and 26V must be connected
to the Vss terminal.
Control signals are connected to the STEP and
DIR terminals. Connect a COM terminal to the
COM terminal of the source of the signals as
well.
The EN terminal is pulled high internally, when
a connection is made to ground through this
terminal current is removed from the motor
Instruction Manual
coils, allowing it to turn freely. This can be
used as a kill switch input. The SYNC terminal
is only required when more than one Chopper
Driver is being used. See the section on using
multiple drivers for details.
Setting the Bipolar Stepper Current:
The current that will be passed through the
motors coils is set using the single turn trimpot
P1 and a Multi-meter. The voltage in volts at
the test point labelled REF will be half the
current in the motors coils in amps. That
means 1V will give 2A, 0.5V will give 1A and so
on.
Full and Half Stepping:
When the DIP switch labelled FULL is in the ON
position the motor will move one step for each
pulse on the STEP input if the switch is set to
OFF the motor will move half a step for each
pulse on the STEP input. This switch should be
set before power is applied to the circuit. Half
step produces a much smoother performance
and less motor resonance.
Multiple Drivers:
When using multiple drivers in the same
system (ex: 3 or 4 axis controller) the drivers
should be synchronized to avoid ground noise
problems. This is done by setting the DIP
switch labelled SYNC on all but one of the
drivers to the ON position and connecting the
SYNC terminals of all the drivers. WARNING:
Unless another Driver is attached via the
SYNC terminal with its SYNC switch in the
OFF position, the Driver should NEVER be
powered with the SYNC switch in the ON
Position. Doing so will cause
CATASTROPHIC FAILURE to the board.
Heat:
The Stepper Motor Chopper Driver is provided
with a heatsink. Care should be taken when
using the driver to ensure that the L298 IC
does not overheat. When the driver is first
used monitor the temperature of the heatsink.
If it begins to get too hot to touch a fan or
larger heatsink will be required. This is quite
important if the motor is turning slowly or is
stopped for long periods.
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Noise:
The switching of currents to the motor can
radiate electromagnetic interference. To
reduce radiated noise the motor leads should
be shielded and as short as possible. The
motor body should be grounded and a
grounded metal housing for the PCB can be
used.
Assembly:
Assembly of the driver PCB is relatively simple.
If the power supply will be over 26V the link
LK1 can be left out. The 1 ohm resistors R1-
R4 need to have the leads bent as close to the
resistor body as possible so that they can fit
into the PCB. Leave the L298 and 7805 IC’s
until last. Attach the two IC’s to the heatsink
using screws first and then mount and solder
the IC’s in the PCB. This will avoid mounting
the IC’s unevenly and preventing the heatsink
from being mounted.
Parts List:
Semiconductors
1 L297 - Stepper motor controller IC
1 L298N - L298Stepper motor driver IC
1 7805 - 7805, 5V Regulator
8 FR302/304, D1-D8 - Fast Recovery Diode
1 1N4004, D9 - Power Diode
Resistors
4 1 ohm, R1-R4 1W - Resistors
4 10 k, R6,R7,R9,R10 - 1/4W or 0.5W Metal
1 18 k, R8 - 1/4W or 0.5W Metal
1 22 k, R5 - 1/4W or 0.5W Metal
1 5 k pot, P1 - Single turn top adjust
Capacitors
6 0.1 uF, C1-C5, C10 - monolithic
1 100 uF, C3 - electrolytic 35V
1 3.3 uF, C6 - greencap
2 220 pF, C8, C9 - ceramic
Miscellaneous
1 PCB – GSK-187 PCB
2 2 way Terminal, X4, X5
3 3 way Terminal, X1-X3
1 2 way DIL Switch, S1-S2
1 Heatsink
2 10mm M3 Bolts (2 sets)
