Stepper ?
Am I correct to assume that if I have a 3 volt stepper and a 10v power
supply, I can safely PWM the 10v supply to 30% and enjoy additional torque?
Is this what they call a "Chopper Drive?
Can I apply a 30% pwm signal to the drain of a transistor as long as the
freq is much faster than my step sequence?
any help or link would be greatly appreciated.
Jeff
supply, I can safely PWM the 10v supply to 30% and enjoy additional torque?
Is this what they call a "Chopper Drive?
Can I apply a 30% pwm signal to the drain of a transistor as long as the
freq is much faster than my step sequence?
any help or link would be greatly appreciated.
Jeff
Comments
> Am I correct to assume that if I have a 3 volt stepper and a 10v power
>supply, I can safely PWM the 10v supply to 30% and enjoy additional torque?
>Is this what they call a "Chopper Drive?
No, but you can use your 10-volt supply with your 3-volt stepper if you put
a resistor in series with each winding to assure you limit the current to
the specified value for the stepper.
PWM and "chopper drives" are used with standard DC motors, not stepper motors.
>Can I apply a 30% pwm signal to the drain of a transistor as long as the
>freq is much faster than my step sequence?
That isn't how a stepper works. A stepper doesn't work by just pulsing the
current to the windings; it works by applying current to the windings in a
specific sequence.
Go to http://www.google.com and search for "stepper motor" and you'll get a
zillion hits on more info.
Jim H
I do have the stepper operational at this point and I do understand the
stepper sequencing. Instead of providing a second low voltage power supply
for the steppers in this stamp project,I would like to be able to PWM my
main supply voltage down to a voltage specified by the manufacturer. I
bought a stepper/linear actuator from Hayden Switch and Insturment. The
person I talked with on the phone explained that the torque figures in the
specs were obtained with a chopper drive. My question should have read: Can
I PWM the supply voltage for the transisters at each of my stepper windings?
Sorry for the elementary questions that are not directly stamp related.
Original Message
From: Jim Higgins [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=bWMMr3VVncNgc1l6h9oHuahtak94X2Y8iDw5Viu4y7P81vfTqwqxU4JJCVd3sbGLxii4eKZoDgPHk88]HigginsJ@s...[/url
Sent: Friday, November 01, 2002 11:12 PM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Stepper ?
At 22:51 11/01/02, Jeff Mitchell wrote:
> Am I correct to assume that if I have a 3 volt stepper and a 10v power
>supply, I can safely PWM the 10v supply to 30% and enjoy additional torque?
>Is this what they call a "Chopper Drive?
No, but you can use your 10-volt supply with your 3-volt stepper if you put
a resistor in series with each winding to assure you limit the current to
the specified value for the stepper.
PWM and "chopper drives" are used with standard DC motors, not stepper
motors.
>Can I apply a 30% pwm signal to the drain of a transistor as long as the
>freq is much faster than my step sequence?
That isn't how a stepper works. A stepper doesn't work by just pulsing the
current to the windings; it works by applying current to the windings in a
specific sequence.
Go to http://www.google.com and search for "stepper motor" and you'll get a
zillion hits on more info.
Jim H
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little better performance, 48 even better 60volts is a great target
if you have the potential.
Try for between 5 and 25 times the nameplate voltage.
Current is fixed. the listed current is what is needed to energize
the coils. Power output increases proportionally with supply voltage.
Losses in the motor increase with the square of the voltage. At some
point the motor just gets too hot.
There are two places to search
jones on steppers. very good tutorial and will explain why you don't
want to use a unipolar drive with a resistor as the current limit.
My 1.7 volt, 4.5 amp steppers run on 35 volts. figure out how big the
resistor is, how much it would cost, and how much voltage it would
drop. then figure out how to shed the heat
The second place is www.geckodrives.com and read the white paper
about power supplies.
Another thing is that if you build larger units. I have 4 steppers
rated as above, your switching power supply may have a problem. it
is not desigend for that type of load. Much better with a
transformer, rectifier and capacitor. actually a big capacitor.
And remember that DC voltage will be 1.414 time AC when you rectify
and put in the large capacitor. so your 24v transformer will really
offer a 34 volt power supply.
One note is that pac-sci motors may already be rated for 20x. the
nameplate may list 35v. if you do the math on wattage, the voltage
would be much lower.
Steppers are an odd device in that the nameplate rating is the
testing point for induction and capacatance. LC.
Go to the stepper motor manufacturers web site and you'll see the
performance graphs listed way higher than your nameplate voltage.
Dave
--- In basicstamps@y..., "Jeff Mitchell" <EL-JEFE@P...> wrote:
> Am I correct to assume that if I have a 3 volt stepper and a 10v
power
> supply, I can safely PWM the 10v supply to 30% and enjoy additional
torque?
> Is this what they call a "Chopper Drive?
> Can I apply a 30% pwm signal to the drain of a transistor as long
as the
> freq is much faster than my step sequence?
> any help or link would be greatly appreciated.
>
> Jeff
wasting power. why not use a lm317 voltage regulator to regulate the voltage
to 3 volts
neil
Original Message
From: "Jim Higgins" <HigginsJ@s...>
To: <basicstamps@yahoogroups.com>
Sent: Friday, November 01, 2002 11:12 PM
Subject: Re: [noparse][[/noparse]basicstamps] Stepper ?
> At 22:51 11/01/02, Jeff Mitchell wrote:
> > Am I correct to assume that if I have a 3 volt stepper and a 10v power
> >supply, I can safely PWM the 10v supply to 30% and enjoy additional
torque?
> >Is this what they call a "Chopper Drive?
>
> No, but you can use your 10-volt supply with your 3-volt stepper if you
put
> a resistor in series with each winding to assure you limit the current to
> the specified value for the stepper.
>
> PWM and "chopper drives" are used with standard DC motors, not stepper
motors.
>
> >Can I apply a 30% pwm signal to the drain of a transistor as long as the
> >freq is much faster than my step sequence?
>
> That isn't how a stepper works. A stepper doesn't work by just pulsing
the
> current to the windings; it works by applying current to the windings in a
> specific sequence.
>
> Go to http://www.google.com and search for "stepper motor" and you'll get
a
> zillion hits on more info.
>
>
> Jim H
>
>
> To UNSUBSCRIBE, just send mail to:
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Body of the message will be ignored.
>
>
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>
>
>
>
the stepper requires the amps to spin, and amps are the limiting
factor.
the induction load of a non-moving motor is near infinity and will
draw an infinite ammount of amps.
how to they put it ? Pop! goes the Weasle.
the resistor us a cheap way to get a uni-polar motor to spin when you
don't need either power or speed, and you have a small motor. Floppy
disk drive for example.
(yes, a stepper can get high speeds, but that is dependant on size
and number of steps per rev. a floppy or CD motor to spin are
typically around 50 steps per rev, whereas a floppy head posistoning
motor might be 200 or 400 steps per revolution.)
The limiting resistor provides that protection. The chopper drive
allows the needed power to get to the motor without the heat.
Dave
--- In basicstamps@y..., "Neil Excel Representative"
<excelneil@m...> wrote:
> hi jim if you put a resistor in the legs of the stepper motor you
are
> wasting power. why not use a lm317 voltage regulator to regulate
the voltage
> to 3 volts
> neil
>
Original Message
> From: "Jim Higgins" <HigginsJ@s...>
> To: <basicstamps@y...>
> Sent: Friday, November 01, 2002 11:12 PM
> Subject: Re: [noparse][[/noparse]basicstamps] Stepper ?
>
>
> > At 22:51 11/01/02, Jeff Mitchell wrote:
> > > Am I correct to assume that if I have a 3 volt stepper and a
10v power
> > >supply, I can safely PWM the 10v supply to 30% and enjoy
additional
> torque?
> > >Is this what they call a "Chopper Drive?
> >
> > No, but you can use your 10-volt supply with your 3-volt stepper
if you
> put
> > a resistor in series with each winding to assure you limit the
current to
> > the specified value for the stepper.
> >
> > PWM and "chopper drives" are used with standard DC motors, not
stepper
> motors.
> >
> > >Can I apply a 30% pwm signal to the drain of a transistor as
long as the
> > >freq is much faster than my step sequence?
> >
> > That isn't how a stepper works. A stepper doesn't work by just
pulsing
> the
> > current to the windings; it works by applying current to the
windings in a
> > specific sequence.
> >
> > Go to http://www.google.com and search for "stepper motor" and
you'll get
> a
> > zillion hits on more info.
> >
> >
> > Jim H
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@y...
> > from the same email address that you subscribed. Text in the
Subject and
> Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> >
> >
> >
> >