A high frequency Unipolar Stepper Motor Current Limiter Circuit.
(Their is Picture included of the Circuit.)
After looking all over the Internet trying to find a circuit for a
Stepper Motor, Chopper current Limiter Circuit. I found only ideas
but not real circuits. So I went about designing my own. It has
been a difficult task with my original design being modified quite
a few times, still using the same basic components and configuration.
Finally I have a working circuit driving 3 motors all from one
board. As far as my hearing goes, I have no high frequency noise.
I do not have an oscilloscope to look at the waveform, but
adjusting the value of "R" I can hear a whining noise and a voltage
drop on my power supply, outputs getting hot. (Examples)
After home experimentation and at work issues, I have found 8 Volts the
minimum voltage to drive MOSFET's into full saturation, anything
less will cause over heating.
This design is set for about 2.0+ amps per motor. I am only running
16 volts but that is to keep cost down, and still provide 12.4 volts
over the coil max voltage.
Below are the Motors Specs I am running.
Motor Frame size: NEMA 23
Holding Torque: 20 kg.cm / 277 oz.in
Step Angle: 1.8 Deg ± 5°
3.6 Volts
3.0 Amps Per Phase
1.2 ohms 10% Per Phase
I've seen pulse width modulation and constant frequency
modualated circuits. This circuit is entirely based on current
feedback to control the switching. This circuit is as simple as I
could get it and still operate properly.
As a constant current circuit it requires that the driver be completely
shut off, as just reducing the drive would only exacerbate overheating.
Their-forth the CMOS with an output enable does just that.
3 Channel Stepper Motor Driver Board, With Chopper type Current Limiting,
Must Use a CMOS PreDriver. The CMOS must have an Enable Pin Active Low.
Otherwise an inverter will be required with no voltage gain.
(If you are using discrete drivers ie: transistors they will have to have
their voltage source shut off, are their outputs driven LOW)
Shown in the JPEG is the LM324 with 3 outputs, Only showing one CMOS driver
and MOSFET as Example. 2 more output sets, are required to complete circuit.
I am not showing my pre-driver design as I plans for it at later date.
My circuit is unique, at first I did not find anything like it, but looking for
a long time I finally found something similar, but not well used as I really had
to look for it. This is a wave drive circuit meaning only one coil per motor
is energized at any one time. This is what I wanted. I even tried some commercial
drivers but they did not do what I wanted properly. Of course I did not try them
all. What I wanted was something very inexpensive for my future plans.
Circuit Descript When current reaches desired level across the, MOSFET Source Load
Resistor, the LM324 output will go HIGH this is tied to the CMOS Enable Pin
Shutting off the output of the CMOS.
As soon as the current goes below the set amperage The Enable Pin will then go
LOW. Starting the CYCLE again. Repeating above.
Resistor "R" and Diode D1 control the current setting and "R" will need to be set
in accordance with the Drivers and Load Resistor that you may use. Possibly having to
use a resistor instead of a diode.
Optional Capacitors are for possible noise suppression. On E1,E2,E3 outputs to ground.
If you have any problem reading R Values they are, 100 , 4.7k , 2.2k and 0.33 ohm 3 Watt.
and a 10uf capcitor across Diode D1. where the "+" sign is shown.
The JPEG is a modified board layout from my board, Modified for clarity. Is is entirely
surfaced mount, using conventional components.(DIP,s * 1/4 watt resistor with leads etc...)
What is truely amazing is. For 2 weeks I have been testing the board trying
to get the X and Y axis working. When I finally got to the Z axis, trying everything
else I went straight to the motor and found that all 4 leads were shorted together, and
One of the leads of the motor was soldered from Drain to Source on my board.
and nothing had blown out. The entire 2 weeks it was hooked up. The current limiter had
done its job.
Bob Brandt
Hartsburg Missouri.
(Their is Picture included of the Circuit.)
After looking all over the Internet trying to find a circuit for a
Stepper Motor, Chopper current Limiter Circuit. I found only ideas
but not real circuits. So I went about designing my own. It has
been a difficult task with my original design being modified quite
a few times, still using the same basic components and configuration.
Finally I have a working circuit driving 3 motors all from one
board. As far as my hearing goes, I have no high frequency noise.
I do not have an oscilloscope to look at the waveform, but
adjusting the value of "R" I can hear a whining noise and a voltage
drop on my power supply, outputs getting hot. (Examples)
After home experimentation and at work issues, I have found 8 Volts the
minimum voltage to drive MOSFET's into full saturation, anything
less will cause over heating.
This design is set for about 2.0+ amps per motor. I am only running
16 volts but that is to keep cost down, and still provide 12.4 volts
over the coil max voltage.
Below are the Motors Specs I am running.
Motor Frame size: NEMA 23
Holding Torque: 20 kg.cm / 277 oz.in
Step Angle: 1.8 Deg ± 5°
3.6 Volts
3.0 Amps Per Phase
1.2 ohms 10% Per Phase
I've seen pulse width modulation and constant frequency
modualated circuits. This circuit is entirely based on current
feedback to control the switching. This circuit is as simple as I
could get it and still operate properly.
As a constant current circuit it requires that the driver be completely
shut off, as just reducing the drive would only exacerbate overheating.
Their-forth the CMOS with an output enable does just that.
3 Channel Stepper Motor Driver Board, With Chopper type Current Limiting,
Must Use a CMOS PreDriver. The CMOS must have an Enable Pin Active Low.
Otherwise an inverter will be required with no voltage gain.
(If you are using discrete drivers ie: transistors they will have to have
their voltage source shut off, are their outputs driven LOW)
Shown in the JPEG is the LM324 with 3 outputs, Only showing one CMOS driver
and MOSFET as Example. 2 more output sets, are required to complete circuit.
I am not showing my pre-driver design as I plans for it at later date.
My circuit is unique, at first I did not find anything like it, but looking for
a long time I finally found something similar, but not well used as I really had
to look for it. This is a wave drive circuit meaning only one coil per motor
is energized at any one time. This is what I wanted. I even tried some commercial
drivers but they did not do what I wanted properly. Of course I did not try them
all. What I wanted was something very inexpensive for my future plans.
Circuit Descript When current reaches desired level across the, MOSFET Source Load
Resistor, the LM324 output will go HIGH this is tied to the CMOS Enable Pin
Shutting off the output of the CMOS.
As soon as the current goes below the set amperage The Enable Pin will then go
LOW. Starting the CYCLE again. Repeating above.
Resistor "R" and Diode D1 control the current setting and "R" will need to be set
in accordance with the Drivers and Load Resistor that you may use. Possibly having to
use a resistor instead of a diode.
Optional Capacitors are for possible noise suppression. On E1,E2,E3 outputs to ground.
If you have any problem reading R Values they are, 100 , 4.7k , 2.2k and 0.33 ohm 3 Watt.
and a 10uf capcitor across Diode D1. where the "+" sign is shown.
The JPEG is a modified board layout from my board, Modified for clarity. Is is entirely
surfaced mount, using conventional components.(DIP,s * 1/4 watt resistor with leads etc...)
What is truely amazing is. For 2 weeks I have been testing the board trying
to get the X and Y axis working. When I finally got to the Z axis, trying everything
else I went straight to the motor and found that all 4 leads were shorted together, and
One of the leads of the motor was soldered from Drain to Source on my board.
and nothing had blown out. The entire 2 weeks it was hooked up. The current limiter had
done its job.
Bob Brandt
Hartsburg Missouri.