Stamps and motor control
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Posts: 46,084
Hello,
I have an old Hero 2000 robot arm, which was sold by Heathkit. The same arm
was sold separately from the robot as an "arm trainer". Not counting the
gripper, the arm is moved by four identical, 12V gearmotors. One for
shoulder, one for elbow, and two for wrist (the wrist is a differential
mechanism).
I have been trying to create an interface so that I can control the arm with
my PC. I am using the Basic Stamp II for PC interfacing. To drive the
motors, I am using SN754410NE motor driver chips. For PWM speed control, I'm
using the PAK Va from AWC.
Here's the problem: I'm a bit new at motors, and I'm having some troubles.
At low PWM duty cycles, the motor makes a high pitched sound and won't move.
At slightly higher speeds, the tone is still there but the motor starts to
move. What is this tone?
Also, I was under the impression that the SN754410NE had built-in diodes for
backEMF protection. One of the chips exploded (sparks, little divot out of
the top of the IC) today, leading me to believe that something was wrong.
Does anyone have experience working with the Hero 2000 arm? What I'd really
love is a circuit to build that lets the PC or Stamp (or other
microcontroller) drive the arm's motors. I can handle control algorithms,
etc. I'm just having trouble with the hardware interfacing. I'd like to see
someone's
circuit to see where I'm going wrong.
Thanks,
Joe Driscoll
I have an old Hero 2000 robot arm, which was sold by Heathkit. The same arm
was sold separately from the robot as an "arm trainer". Not counting the
gripper, the arm is moved by four identical, 12V gearmotors. One for
shoulder, one for elbow, and two for wrist (the wrist is a differential
mechanism).
I have been trying to create an interface so that I can control the arm with
my PC. I am using the Basic Stamp II for PC interfacing. To drive the
motors, I am using SN754410NE motor driver chips. For PWM speed control, I'm
using the PAK Va from AWC.
Here's the problem: I'm a bit new at motors, and I'm having some troubles.
At low PWM duty cycles, the motor makes a high pitched sound and won't move.
At slightly higher speeds, the tone is still there but the motor starts to
move. What is this tone?
Also, I was under the impression that the SN754410NE had built-in diodes for
backEMF protection. One of the chips exploded (sparks, little divot out of
the top of the IC) today, leading me to believe that something was wrong.
Does anyone have experience working with the Hero 2000 arm? What I'd really
love is a circuit to build that lets the PC or Stamp (or other
microcontroller) drive the arm's motors. I can handle control algorithms,
etc. I'm just having trouble with the hardware interfacing. I'd like to see
someone's
circuit to see where I'm going wrong.
Thanks,
Joe Driscoll
Comments
Don't know about the SN754410NE chip but the MC33030 chip is very easy to use
with a STAMP2 . I am using them with an x-Y control system and it is fairly
simple.
I found that the STAMP needs expansion for both analog signal and digital data
handling.
If you want I can email my prgm ( not yet fully debugged ) and it will give you
some idea of the complexity.
The noises are the PWM causing the windings to vibrate. If you are using a PWM
to control speed
you must be sure that the inductance of the motor is high enough so that the
current continues to flow during the off
time. Try the chip in a simple config before using it in a STAMP control system
to make sure you have that part working smoothly.
Also you need diodes to make sure that the stored energy in the inductance has
somewhere to go.. In the case of full H bridge that means 4 diodes
for each motor. Usually they are built in to the control chip.
( PLEASE NO MORE DIODE RELAY STUFF!!! [noparse]:)[/noparse])
To: <basicstamps@egroups.com>
Date sent: Thu, 6 Apr 2000 17:51:40 -0500
From: "Joseph Driscoll" <driscoll85@h...>
Send reply to: basicstamps@egroups.com
Subject: [noparse][[/noparse]basicstamps] Stamps and motor control
> Hello,
>
> I have an old Hero 2000 robot arm, which was sold by Heathkit. The same arm
> was sold separately from the robot as an "arm trainer". Not counting the
> gripper, the arm is moved by four identical, 12V gearmotors. One for
> shoulder, one for elbow, and two for wrist (the wrist is a differential
> mechanism).
>
> I have been trying to create an interface so that I can control the arm with
> my PC. I am using the Basic Stamp II for PC interfacing. To drive the
> motors, I am using SN754410NE motor driver chips. For PWM speed control, I'm
> using the PAK Va from AWC.
>
> Here's the problem: I'm a bit new at motors, and I'm having some troubles.
> At low PWM duty cycles, the motor makes a high pitched sound and won't move.
> At slightly higher speeds, the tone is still there but the motor starts to
> move. What is this tone?
>
> Also, I was under the impression that the SN754410NE had built-in diodes for
> backEMF protection. One of the chips exploded (sparks, little divot out of
> the top of the IC) today, leading me to believe that something was wrong.
>
> Does anyone have experience working with the Hero 2000 arm? What I'd really
> love is a circuit to build that lets the PC or Stamp (or other
> microcontroller) drive the arm's motors. I can handle control algorithms,
> etc. I'm just having trouble with the hardware interfacing. I'd like to see
> someone's
> circuit to see where I'm going wrong.
>
> Thanks,
> Joe Driscoll
>
>
>
>
ron... the motor man...
Ronald Doctors
http://www.members.home.net/rdoctors
Thanks for the reply. Yes, please send me your program -- that would help a
lot. When you say "you must be sure that the inductance of the motor is high
enough so that the current continues to flow during the off time", I'm not
sure I understand that part. With the SN754410NE and the L293D, when the
enable pin is low, the outputs are at a high impedance state. Is that a
problem? It seems like the back emf produced during that "off" time needs to
go somewhere. Maybe this is the problem?
Thanks,
Joe Driscoll
Original Message
From: Ronald Doctors <rdoctors@h...>
To: <basicstamps@egroups.com>
Sent: Thursday, April 06, 2000 6:32 PM
Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> HI,
>
> Don't know about the SN754410NE chip but the MC33030 chip is very easy to
use
> with a STAMP2 . I am using them with an x-Y control system and it is
fairly simple.
> I found that the STAMP needs expansion for both analog signal and digital
data handling.
> If you want I can email my prgm ( not yet fully debugged ) and it will
give you some idea of the complexity.
> The noises are the PWM causing the windings to vibrate. If you are using
a PWM to control speed
> you must be sure that the inductance of the motor is high enough so that
the current continues to flow during the off
> time. Try the chip in a simple config before using it in a STAMP control
system to make sure you have that part working smoothly.
>
> Also you need diodes to make sure that the stored energy in the inductance
has somewhere to go.. In the case of full H bridge that means 4 diodes
> for each motor. Usually they are built in to the control chip.
>
> ( PLEASE NO MORE DIODE RELAY STUFF!!! [noparse]:)[/noparse])
> To: <basicstamps@egroups.com>
> Date sent: Thu, 6 Apr 2000 17:51:40 -0500
> From: "Joseph Driscoll" <driscoll85@h...>
> Send reply to: basicstamps@egroups.com
> Subject: [noparse][[/noparse]basicstamps] Stamps and motor control
>
> > Hello,
> >
> > I have an old Hero 2000 robot arm, which was sold by Heathkit. The same
arm
> > was sold separately from the robot as an "arm trainer". Not counting the
> > gripper, the arm is moved by four identical, 12V gearmotors. One for
> > shoulder, one for elbow, and two for wrist (the wrist is a differential
> > mechanism).
> >
> > I have been trying to create an interface so that I can control the arm
with
> > my PC. I am using the Basic Stamp II for PC interfacing. To drive the
> > motors, I am using SN754410NE motor driver chips. For PWM speed control,
I'm
> > using the PAK Va from AWC.
> >
> > Here's the problem: I'm a bit new at motors, and I'm having some
troubles.
> > At low PWM duty cycles, the motor makes a high pitched sound and won't
move.
> > At slightly higher speeds, the tone is still there but the motor starts
to
> > move. What is this tone?
> >
> > Also, I was under the impression that the SN754410NE had built-in diodes
for
> > backEMF protection. One of the chips exploded (sparks, little divot out
of
> > the top of the IC) today, leading me to believe that something was
wrong.
> >
> > Does anyone have experience working with the Hero 2000 arm? What I'd
really
> > love is a circuit to build that lets the PC or Stamp (or other
> > microcontroller) drive the arm's motors. I can handle control
algorithms,
> > etc. I'm just having trouble with the hardware interfacing. I'd like to
see
> > someone's
> > circuit to see where I'm going wrong.
> >
> > Thanks,
> > Joe Driscoll
> >
> >
> >
> >
>
>
> ron... the motor man...
> Ronald Doctors
> http://www.members.home.net/rdoctors
>
>
>
>
Original Message
From: Dave Paton <suprdave@p...>
To: <basicstamps@egroups.com>
Sent: Thursday, April 06, 2000 8:48 PM
Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> On 4/6/00 at 5:51 PM, Joseph Driscoll <driscoll85@h...> wrote:
>
> > Does anyone have experience working with the Hero 2000 arm?
>
> Way back when I assembled one and installed it into a hero 2K for my
junior high science class. The only things I recall vividly are that:
>
> 1. the motors were driven by large heatsinked H-bridges. I suggest getting
a much more robust controller. 5A @ 12V would not be unreasonable.
I've measured the current draw, and it's usually around 0.5 amp.
> 2. failure to monitor the limit switches caused biiiiiiiig problems. The
cable drive is more fragile than it looks.
My plan is to monitor the limit switches from the stamp, by running them to
input lines. Or, I could just have a hardware shutoff, using an OR gate or
something.
> I have a vague recollection of encoders on the arm as well, but this might
be a figment of my imagination. I do remembr clearly the ordeal that getting
to e arm to 'home' was. It seems the hero 2K SW was very picky.
Right, there are optical encoders on all of the motors. They output pulses,
which are squared up via a LM393. I plan to use a PAK VII pulse coprocessor
(from AWCE) to keep track of pulses. The stamp can then ask the PAK
periodically for pulse counts, and that way the position of the arm is known
(assuming it started from a known location).
I plan to use the stamp as an arm "server": it polls sensors (and the PAK
VII) and sends that data to a PC. The PC then sends speed and direction
commands. The control algorithms can then be carried out on the PC.
> Does anyone have experience working with the Hero 2000 arm?
Way back when I assembled one and installed it into a hero 2K for my junior high
science class. The only things I recall vividly are that:
1. the motors were driven by large heatsinked H-bridges. I suggest getting a
much more robust controller. 5A @ 12V would not be unreasonable.
2. failure to monitor the limit switches caused biiiiiiiig problems. The cable
drive is more fragile than it looks.
I have a vague recollection of encoders on the arm as well, but this might be a
figment of my imagination. I do remembr clearly the ordeal that getting to e arm
to 'home' was. It seems the hero 2K SW was very picky.
-dave
Passion must be present. Everything else can be learned.
WCCR chief engineer, Professional student, geek at large, and I'm 6'4
dave paton http://homepage.mac.com/dpaton dave at ieee dot org
The TI datasheet states that external clamp diodes should be used with
inductive loads. The equivalent circuit they show does not have clamp
diodes. This is probably what caused your smoke. You need 4 diodes. At
each motor terminal, connect two diodes: one to the bridge positive supply,
the other to bridge gnd or negative. All diodes should "point" up toward
plus supply.
Ray McArthur
Original Message
From: Joseph Driscoll <driscoll85@h...>
To: <basicstamps@egroups.com>
Sent: Thursday, April 06, 2000 8:50 PM
Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> Hi,
>
> Thanks for the reply. Yes, please send me your program -- that would help
a
> lot. When you say "you must be sure that the inductance of the motor is
high
> enough so that the current continues to flow during the off time", I'm not
> sure I understand that part. With the SN754410NE and the L293D, when the
> enable pin is low, the outputs are at a high impedance state. Is that a
> problem? It seems like the back emf produced during that "off" time needs
to
> go somewhere. Maybe this is the problem?
>
> Thanks,
> Joe Driscoll
> > 1. the motors were driven by large heatsinked H-bridges. I suggest getting
> > a much more robust controller. 5A @ 12V would not be unreasonable.
>
> I've measured the current draw, and it's usually around 0.5 amp.
Er..that's what I meant. Missed the '.'. Still, half an amp at 12V is 6W. I
doubt most IC drivers could handle that. Besides, an h-bridge isn't very hard to
build. Also don't forget the starting current will be a little higher. The
motors are geared way down, but there is still a largish kick needed to start
them, especially when they are loaded heavily. And then there's the inductive
kick when you turn it off, or reverse it...
Of course, I'm fond of overdesigning my controllers by a fcator of 2, so take
this with a grain or two of salt.
> My plan is to monitor the limit switches from the stamp, by running them to
> input lines. Or, I could just have a hardware shutoff, using an OR gate or
> something.
Mmm...I'd go for the switches as inputs to the stamp. MUX them if required.
Using the limit switches as hardware cutoffs will complicate things
unnecesarially, IMHO, as you'll have to bypass them to restart the motor, and
with reversing factored in....ugh.
> > I have a vague recollection of encoders on the arm as well, but this might
> > be a figment of my imagination. I do remembr clearly the ordeal that
> > getting the arm to 'home' was. It seems the hero 2K SW was very picky.
> Right, there are optical encoders on all of the motors. They output pulses,
> which are squared up via a LM393. I plan to use a PAK VII pulse coprocessor
> (from AWCE) to keep track of pulses. The stamp can then ask the PAK
> periodically for pulse counts, and that way the position of the arm is known
> (assuming it started from a known location).
Cool. Sounds like a nice imple way to get it to go. It also saves the stamp from
having to do the counting, and the associated overhead.
> I plan to use the stamp as an arm "server": it polls sensors (and the PAK
> VII) and sends that data to a PC. The PC then sends speed and direction
> commands. The control algorithms can then be carried out on the PC.
Sounds like fun. Keep us updated!
-dave
Passion must be present. Everything else can be learned.
WCCR chief engineer, Professional student, geek at large, and I'm 6'4
dave paton http://homepage.mac.com/dpaton dave at ieee dot org
My last message applies to the L293. I just looked at the data for the
SN754410NE, and it DOES show clamp diodes built into the IC. Also, they do
not have the recommendation to use them. What I don't understand is that
they still used external clamps in their example circuit.
Ray McArthur
Original Message
From: rjmca <rjmca@w...>
To: <basicstamps@egroups.com>
Sent: Thursday, April 06, 2000 10:32 PM
Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> Joe:
> The TI datasheet states that external clamp diodes should be used with
> inductive loads. The equivalent circuit they show does not have clamp
> diodes. This is probably what caused your smoke. You need 4 diodes. At
> each motor terminal, connect two diodes: one to the bridge positive
supply,
> the other to bridge gnd or negative. All diodes should "point" up toward
> plus supply.
>
> Ray McArthur
>
>
Original Message
> From: Joseph Driscoll <driscoll85@h...>
> To: <basicstamps@egroups.com>
> Sent: Thursday, April 06, 2000 8:50 PM
> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> > Hi,
> >
> > Thanks for the reply. Yes, please send me your program -- that would
help
> a
> > lot. When you say "you must be sure that the inductance of the motor is
> high
> > enough so that the current continues to flow during the off time", I'm
not
> > sure I understand that part. With the SN754410NE and the L293D, when the
> > enable pin is low, the outputs are at a high impedance state. Is that a
> > problem? It seems like the back emf produced during that "off" time
needs
> to
> > go somewhere. Maybe this is the problem?
> >
> > Thanks,
> > Joe Driscoll
>
>
>
>
>
diodes. the L293D does -- you have to make sure which one you have.
Regards,
Al Williams
AWC
* 8 Channels of PWM with the PAK-V at
http://www.al-williams.com/awce/pak5.htm
>
> Joe:
> My last message applies to the L293. I just looked at the data for the
> SN754410NE, and it DOES show clamp diodes built into the IC.
> Also, they do
> not have the recommendation to use them. What I don't understand is that
> they still used external clamps in their example circuit.
>
I have the L293D and the SN754410NE, both of which have built-in diode
protection at the outputs. The current draw from the motor I'm using is
around 0.5A (which is close to max on the L293D, so that's why I use the
SN754410NE). And still, poof: the chip blew up during PWM operation (not at
startup). I have a schematic in GIF format if anyone is interested.
Joe Driscoll
Original Message
From: Al Williams <alw@a...>
To: <basicstamps@egroups.com>
Sent: Thursday, April 06, 2000 10:21 PM
Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
> I'm not an expert on motor drivers, but I think the L293 does NOT have
> diodes. the L293D does -- you have to make sure which one you have.
>
> Regards,
>
> Al Williams
> AWC
> * 8 Channels of PWM with the PAK-V at
> http://www.al-williams.com/awce/pak5.htm
>
> >
> > Joe:
> > My last message applies to the L293. I just looked at the data for the
> > SN754410NE, and it DOES show clamp diodes built into the IC.
> > Also, they do
> > not have the recommendation to use them. What I don't understand is
that
> > they still used external clamps in their example circuit.
> >
>
>
>
>
>
Ray McArthur
Original Message
From: Al Williams <alw@a...>
To: <basicstamps@egroups.com>
Sent: Thursday, April 06, 2000 11:21 PM
Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
> I'm not an expert on motor drivers, but I think the L293 does NOT have
> diodes. the L293D does -- you have to make sure which one you have.
>
> Regards,
>
> Al Williams
> AWC
> * 8 Channels of PWM with the PAK-V at
> http://www.al-williams.com/awce/pak5.htm
>
> >
> > Joe:
> > My last message applies to the L293. I just looked at the data for the
> > SN754410NE, and it DOES show clamp diodes built into the IC.
> > Also, they do
> > not have the recommendation to use them. What I don't understand is
that
> > they still used external clamps in their example circuit.
> >
>
>
>
>
You may send me a schematic off-list if you want. No guarantees, but I can
try. Question: what is the PWM frequency?
Ray McArthur
Original Message
From: Joseph Driscoll <driscoll85@h...>
To: <basicstamps@egroups.com>
Sent: Thursday, April 06, 2000 11:53 PM
Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> Hi,
>
> I have the L293D and the SN754410NE, both of which have built-in diode
> protection at the outputs. The current draw from the motor I'm using is
> around 0.5A (which is close to max on the L293D, so that's why I use the
> SN754410NE). And still, poof: the chip blew up during PWM operation (not
at
> startup). I have a schematic in GIF format if anyone is interested.
>
> Joe Driscoll
>
>
>
Original Message
> From: Al Williams <alw@a...>
> To: <basicstamps@egroups.com>
> Sent: Thursday, April 06, 2000 10:21 PM
> Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> > I'm not an expert on motor drivers, but I think the L293 does NOT have
> > diodes. the L293D does -- you have to make sure which one you have.
> >
> > Regards,
> >
> > Al Williams
> > AWC
> > * 8 Channels of PWM with the PAK-V at
> > http://www.al-williams.com/awce/pak5.htm
> >
> > >
> > > Joe:
> > > My last message applies to the L293. I just looked at the data for
the
> > > SN754410NE, and it DOES show clamp diodes built into the IC.
> > > Also, they do
> > > not have the recommendation to use them. What I don't understand is
> that
> > > they still used external clamps in their example circuit.
> > >
> >
> >
> >
> >
> >
>
>
>
originator of the thread. I know we covered this off line already. Whoops.
Regards,
Al Williams
AWC
*Solderless Stamp Prototyping: http://www.al-williams.com/awce
>
Original Message
> From: Joseph Driscoll [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=PxENTq7vd_PsjAG31F35qo7Sn1vR611Cpd0UG4npeQkQmtS3GzHQ0TrgeSGqjpZR2xAWbm24sAP1F7Du4K47Q88]driscoll85@h...[/url
> Sent: Thursday, April 06, 2000 10:54 PM
> To: basicstamps@egroups.com
> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> Hi,
>
> I have the L293D and the SN754410NE, both of which have built-in diode
> protection at the outputs. The current draw from the motor I'm using is
> around 0.5A (which is close to max on the L293D, so that's why I use the
> SN754410NE). And still, poof: the chip blew up during PWM
> operation (not at
> startup). I have a schematic in GIF format if anyone is interested.
>
> Joe Driscoll
>
>
>
Original Message
> From: Al Williams <alw@a...>
> To: <basicstamps@egroups.com>
> Sent: Thursday, April 06, 2000 10:21 PM
> Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> > I'm not an expert on motor drivers, but I think the L293 does NOT have
> > diodes. the L293D does -- you have to make sure which one you have.
> >
> > Regards,
> >
> > Al Williams
> > AWC
> > * 8 Channels of PWM with the PAK-V at
> > http://www.al-williams.com/awce/pak5.htm
> >
> > >
> > > Joe:
> > > My last message applies to the L293. I just looked at the
> data for the
> > > SN754410NE, and it DOES show clamp diodes built into the IC.
> > > Also, they do
> > > not have the recommendation to use them. What I don't understand is
> that
> > > they still used external clamps in their example circuit.
> > >
> >
> >
> >
> >
> >
>
>
>Hi,
>
>The GIF is on its way to you off list. I have a question for everyone: what
>happens if you switch the enable pin of the motor driver chip too fast?
>Maybe the frequency of the PWM signal is too high? Would too fast a
>switching time fry the driver chip?
Hi Joe -
Sure could !
There is generally a frequency (aka repetition) maximum in the data sheet.
Sorry - I don't have a data sheet handy.
It should be under the AC characteristics - even though this is a DC device.
Regards,
Bruce
>
>Thanks,
>Joe Driscoll
>
>
>
Original Message
>From: rjmca <rjmca@w...>
>To: <basicstamps@egroups.com>
>Sent: Friday, April 07, 2000 12:10 AM
>Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
>> Joe:
>>
>> You may send me a schematic off-list if you want. No guarantees, but I
>can
>> try. Question: what is the PWM frequency?
>>
>> Ray McArthur
>>
>>
Original Message
>> From: Joseph Driscoll <driscoll85@h...>
>> To: <basicstamps@egroups.com>
>> Sent: Thursday, April 06, 2000 11:53 PM
>> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>>
>>
>> > Hi,
>> >
>> > I have the L293D and the SN754410NE, both of which have built-in diode
>> > protection at the outputs. The current draw from the motor I'm using is
>> > around 0.5A (which is close to max on the L293D, so that's why I use the
>> > SN754410NE). And still, poof: the chip blew up during PWM operation (not
>> at
>> > startup). I have a schematic in GIF format if anyone is interested.
>> >
>> > Joe Driscoll
>> >
>> >
>> >
Original Message
>> > From: Al Williams <alw@a...>
>> > To: <basicstamps@egroups.com>
>> > Sent: Thursday, April 06, 2000 10:21 PM
>> > Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
>> >
>> >
>> > > I'm not an expert on motor drivers, but I think the L293 does NOT have
>> > > diodes. the L293D does -- you have to make sure which one you have.
>> > >
>> > > Regards,
>> > >
>> > > Al Williams
>> > > AWC
>> > > * 8 Channels of PWM with the PAK-V at
>> > > http://www.al-williams.com/awce/pak5.htm
>> > >
>> > > >
>> > > > Joe:
>> > > > My last message applies to the L293. I just looked at the data for
>> the
>> > > > SN754410NE, and it DOES show clamp diodes built into the IC.
>> > > > Also, they do
>> > > > not have the recommendation to use them. What I don't understand is
>> > that
>> > > > they still used external clamps in their example circuit.
>> > > >
>> > >
>> > >
>> > >
>> > >
>> > >
>> >
>> >
>> >
>>
>>
>>
>>
>>
>
>
>
>
>Hi,
>
>The GIF is on its way to you off list. I have a question for everyone: what
>happens if you switch the enable pin of the motor driver chip too fast?
>Maybe the frequency of the PWM signal is too high? Would too fast a
>switching time fry the driver chip?
>
>Thanks,
>Joe Driscoll
>
Joe -
Just one more comment -
The PWM signal should be going to the POWER LEADS, *NOT* the ENABLE lines.
At least that's what I've generally seen, YMMV depending on the particular
chip.
egards,
Bruce
>
>
Original Message
>From: rjmca <rjmca@w...>
>To: <basicstamps@egroups.com>
>Sent: Friday, April 07, 2000 12:10 AM
>Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
>> Joe:
>>
>> You may send me a schematic off-list if you want. No guarantees, but I
>can
>> try. Question: what is the PWM frequency?
>>
>> Ray McArthur
>>
>>
Original Message
>> From: Joseph Driscoll <driscoll85@h...>
>> To: <basicstamps@egroups.com>
>> Sent: Thursday, April 06, 2000 11:53 PM
>> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>>
>>
>> > Hi,
>> >
>> > I have the L293D and the SN754410NE, both of which have built-in diode
>> > protection at the outputs. The current draw from the motor I'm using is
>> > around 0.5A (which is close to max on the L293D, so that's why I use the
>> > SN754410NE). And still, poof: the chip blew up during PWM operation (not
>> at
>> > startup). I have a schematic in GIF format if anyone is interested.
>> >
>> > Joe Driscoll
>> >
>> >
>> >
Original Message
>> > From: Al Williams <alw@a...>
>> > To: <basicstamps@egroups.com>
>> > Sent: Thursday, April 06, 2000 10:21 PM
>> > Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
>> >
>> >
>> > > I'm not an expert on motor drivers, but I think the L293 does NOT have
>> > > diodes. the L293D does -- you have to make sure which one you have.
>> > >
>> > > Regards,
>> > >
>> > > Al Williams
>> > > AWC
>> > > * 8 Channels of PWM with the PAK-V at
>> > > http://www.al-williams.com/awce/pak5.htm
>> > >
>> > > >
>> > > > Joe:
>> > > > My last message applies to the L293. I just looked at the data for
>> the
>> > > > SN754410NE, and it DOES show clamp diodes built into the IC.
>> > > > Also, they do
>> > > > not have the recommendation to use them. What I don't understand is
>> > that
>> > > > they still used external clamps in their example circuit.
>> > > >
>> > >
>> > >
>> > >
>> > >
>> > >
>> >
>> >
>> >
>>
>>
>>
>>
>>
>
>
>
>
The GIF is on its way to you off list. I have a question for everyone: what
happens if you switch the enable pin of the motor driver chip too fast?
Maybe the frequency of the PWM signal is too high? Would too fast a
switching time fry the driver chip?
Thanks,
Joe Driscoll
Original Message
From: rjmca <rjmca@w...>
To: <basicstamps@egroups.com>
Sent: Friday, April 07, 2000 12:10 AM
Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> Joe:
>
> You may send me a schematic off-list if you want. No guarantees, but I
can
> try. Question: what is the PWM frequency?
>
> Ray McArthur
>
>
Original Message
> From: Joseph Driscoll <driscoll85@h...>
> To: <basicstamps@egroups.com>
> Sent: Thursday, April 06, 2000 11:53 PM
> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> > Hi,
> >
> > I have the L293D and the SN754410NE, both of which have built-in diode
> > protection at the outputs. The current draw from the motor I'm using is
> > around 0.5A (which is close to max on the L293D, so that's why I use the
> > SN754410NE). And still, poof: the chip blew up during PWM operation (not
> at
> > startup). I have a schematic in GIF format if anyone is interested.
> >
> > Joe Driscoll
> >
> >
> >
Original Message
> > From: Al Williams <alw@a...>
> > To: <basicstamps@egroups.com>
> > Sent: Thursday, April 06, 2000 10:21 PM
> > Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
> >
> >
> > > I'm not an expert on motor drivers, but I think the L293 does NOT have
> > > diodes. the L293D does -- you have to make sure which one you have.
> > >
> > > Regards,
> > >
> > > Al Williams
> > > AWC
> > > * 8 Channels of PWM with the PAK-V at
> > > http://www.al-williams.com/awce/pak5.htm
> > >
> > > >
> > > > Joe:
> > > > My last message applies to the L293. I just looked at the data for
> the
> > > > SN754410NE, and it DOES show clamp diodes built into the IC.
> > > > Also, they do
> > > > not have the recommendation to use them. What I don't understand is
> > that
> > > > they still used external clamps in their example circuit.
> > > >
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
>
>
>
>
>
I'm looking at the SN754410NE datasheet, and they have some timing diagrams
using a "test circuit" that had a pulse high-time of 10 uS. But I can't tell
if that is a minimum by looking at the page. On another page, where min,
max, and typical values are given, the rise time, fall time, and pulse
duration values are blank. I'm using the PAK Va from AWC for PWM. It has two
modes of operation, equal area mode and proportional PWM mode. Its data
sheet says that when using equal area mode, the time period is about 512 uS,
and proportional PWM mode uses a 2 uS time base. Sound like equal mode is
slower, and therefore safer in my application? What driver chips have others
used with the PAK Va? How were things connected?
Thanks,
Joe Driscoll
Original Message
From: Bruce Bates <bvbates@u...>
To: <basicstamps@egroups.com>
Sent: Friday, April 07, 2000 9:13 AM
Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> At 09:22 AM 4/7/00 -0500, Joseph Driscoll promulgated:
> >Hi,
> >
> >The GIF is on its way to you off list. I have a question for everyone:
what
> >happens if you switch the enable pin of the motor driver chip too fast?
> >Maybe the frequency of the PWM signal is too high? Would too fast a
> >switching time fry the driver chip?
>
> Hi Joe -
>
> Sure could !
>
> There is generally a frequency (aka repetition) maximum in the data sheet.
>
> Sorry - I don't have a data sheet handy.
>
> It should be under the AC characteristics - even though this is a DC
device.
>
> Regards,
>
> Bruce
>
> >
> >Thanks,
> >Joe Driscoll
> >
> >
> >
Original Message
> >From: rjmca <rjmca@w...>
> >To: <basicstamps@egroups.com>
> >Sent: Friday, April 07, 2000 12:10 AM
> >Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> >
> >
> >> Joe:
> >>
> >> You may send me a schematic off-list if you want. No guarantees, but I
> >can
> >> try. Question: what is the PWM frequency?
> >>
> >> Ray McArthur
> >>
> >>
Original Message
> >> From: Joseph Driscoll <driscoll85@h...>
> >> To: <basicstamps@egroups.com>
> >> Sent: Thursday, April 06, 2000 11:53 PM
> >> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> >>
> >>
> >> > Hi,
> >> >
> >> > I have the L293D and the SN754410NE, both of which have built-in
diode
> >> > protection at the outputs. The current draw from the motor I'm using
is
> >> > around 0.5A (which is close to max on the L293D, so that's why I use
the
> >> > SN754410NE). And still, poof: the chip blew up during PWM operation
(not
> >> at
> >> > startup). I have a schematic in GIF format if anyone is interested.
> >> >
> >> > Joe Driscoll
> >> >
> >> >
> >> >
Original Message
> >> > From: Al Williams <alw@a...>
> >> > To: <basicstamps@egroups.com>
> >> > Sent: Thursday, April 06, 2000 10:21 PM
> >> > Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
> >> >
> >> >
> >> > > I'm not an expert on motor drivers, but I think the L293 does NOT
have
> >> > > diodes. the L293D does -- you have to make sure which one you have.
> >> > >
> >> > > Regards,
> >> > >
> >> > > Al Williams
> >> > > AWC
> >> > > * 8 Channels of PWM with the PAK-V at
> >> > > http://www.al-williams.com/awce/pak5.htm
> >> > >
> >> > > >
> >> > > > Joe:
> >> > > > My last message applies to the L293. I just looked at the data
for
> >> the
> >> > > > SN754410NE, and it DOES show clamp diodes built into the IC.
> >> > > > Also, they do
> >> > > > not have the recommendation to use them. What I don't understand
is
> >> > that
> >> > > > they still used external clamps in their example circuit.
> >> > > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> >
> >> >
> >> >
> >>
> >>
> >>
> >>
> >>
> >
> >
> >
> >
>
>
>
>
the driver channel inputs? I've heard of the latter, but I've seen many
cases of pulsing the enable lines (but maybe they were using a slower PWM
frequency). Why is pulsing the enable lines bad? Is it because when the
enable is low, the outputs are at high-Z?
Joe
Original Message
From: Bruce Bates <bvbates@u...>
To: <basicstamps@egroups.com>
Sent: Friday, April 07, 2000 9:15 AM
Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> Joe -
>
> Just one more comment -
>
> The PWM signal should be going to the POWER LEADS, *NOT* the ENABLE lines.
> At least that's what I've generally seen, YMMV depending on the particular
> chip.
>
> egards,
>
> Bruce
>
> >
> >
Original Message
> >From: rjmca <rjmca@w...>
> >To: <basicstamps@egroups.com>
> >Sent: Friday, April 07, 2000 12:10 AM
> >Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> >
> >
> >> Joe:
> >>
> >> You may send me a schematic off-list if you want. No guarantees, but I
> >can
> >> try. Question: what is the PWM frequency?
> >>
> >> Ray McArthur
> >>
> >>
Original Message
> >> From: Joseph Driscoll <driscoll85@h...>
> >> To: <basicstamps@egroups.com>
> >> Sent: Thursday, April 06, 2000 11:53 PM
> >> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> >>
> >>
> >> > Hi,
> >> >
> >> > I have the L293D and the SN754410NE, both of which have built-in
diode
> >> > protection at the outputs. The current draw from the motor I'm using
is
> >> > around 0.5A (which is close to max on the L293D, so that's why I use
the
> >> > SN754410NE). And still, poof: the chip blew up during PWM operation
(not
> >> at
> >> > startup). I have a schematic in GIF format if anyone is interested.
> >> >
> >> > Joe Driscoll
> >> >
> >> >
> >> >
Original Message
> >> > From: Al Williams <alw@a...>
> >> > To: <basicstamps@egroups.com>
> >> > Sent: Thursday, April 06, 2000 10:21 PM
> >> > Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
> >> >
> >> >
> >> > > I'm not an expert on motor drivers, but I think the L293 does NOT
have
> >> > > diodes. the L293D does -- you have to make sure which one you have.
> >> > >
> >> > > Regards,
> >> > >
> >> > > Al Williams
> >> > > AWC
> >> > > * 8 Channels of PWM with the PAK-V at
> >> > > http://www.al-williams.com/awce/pak5.htm
> >> > >
> >> > > >
> >> > > > Joe:
> >> > > > My last message applies to the L293. I just looked at the data
for
> >> the
> >> > > > SN754410NE, and it DOES show clamp diodes built into the IC.
> >> > > > Also, they do
> >> > > > not have the recommendation to use them. What I don't understand
is
> >> > that
> >> > > > they still used external clamps in their example circuit.
> >> > > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> >
> >> >
> >> >
> >>
> >>
> >>
> >>
> >>
> >
> >
> >
> >
>
>
>
>
1) The PAK-V and the PAK-Va are identical except the old PAK-V required a
shunt resistor across its timing element. The PAK-Va does not. There are no
more PAK-Vs, just the PAK-Va, but we have several volume customers who would
be upset if we just changed how the chip works and didn't give it a new
name. However, informally, we just call them PAK-V.
2) In either mode, the time base is 2uS. Here's how it works.
Proportional mode (like the Stamp) figures the least amount of work
required. At 50%, for example, there is a 2uS on time and a 2uS off time.
For 33% there is a 2uS on time and 4uS off time. The proportion of the
pulses is correct, but the total frequency varies depending on the duty
cycle. So 50% is 250kHz and 33% is 166.7kHz. This mode charges a capacitor
as fast as possible for a given duty cycle.
Equal Area mode always uses 256 time periods (512uS or 1.95kHz). 50% is
256uS on and 256uS off. 1/256 is 2uS on and 510uS off. This mode is often
used in controlling LEDs. Makes for a nice scope display too.
The mode is set for the whole chip. So all 8 PWM outputs are in one mode or
the other.
I know from your previous e-mails that the Stamp's PWM is not driving your
motors any better than the PAK-V. I wonder if you try driving the supply pin
if that will make a difference?
Regards,
Al Williams
AWC
* Expand your Stamp I/O with a PAK-III or IV:
http://www.al-williams.com/awce/pak3.htm
>
Original Message
> From: Joseph Driscoll [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=EPcTaQR2fLlHk8jpF-e73hTe-nQ9RaY-e4XCVcppGi8M_fq-LLZGhyyl2WUGbbB_bCnVMA31mmpxxcjX]driscoll85@h...[/url
> Sent: Friday, April 07, 2000 9:45 AM
> To: basicstamps@egroups.com
> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> Hi,
>
> I'm looking at the SN754410NE datasheet, and they have some
> timing diagrams
> using a "test circuit" that had a pulse high-time of 10 uS. But I
> can't tell
> if that is a minimum by looking at the page. On another page, where min,
> max, and typical values are given, the rise time, fall time, and pulse
> duration values are blank. I'm using the PAK Va from AWC for PWM.
> It has two
> modes of operation, equal area mode and proportional PWM mode. Its data
> sheet says that when using equal area mode, the time period is
> about 512 uS,
> and proportional PWM mode uses a 2 uS time base. Sound like equal mode is
> slower, and therefore safer in my application? What driver chips
> have others
> used with the PAK Va? How were things connected?
>
> Thanks,
> Joe Driscoll
>
>
>
Original Message
> From: Bruce Bates <bvbates@u...>
> To: <basicstamps@egroups.com>
> Sent: Friday, April 07, 2000 9:13 AM
> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> > At 09:22 AM 4/7/00 -0500, Joseph Driscoll promulgated:
> > >Hi,
> > >
> > >The GIF is on its way to you off list. I have a question for everyone:
> what
> > >happens if you switch the enable pin of the motor driver chip too fast?
> > >Maybe the frequency of the PWM signal is too high? Would too fast a
> > >switching time fry the driver chip?
> >
> > Hi Joe -
> >
> > Sure could !
> >
> > There is generally a frequency (aka repetition) maximum in the
> data sheet.
> >
> > Sorry - I don't have a data sheet handy.
> >
> > It should be under the AC characteristics - even though this is a DC
> device.
> >
> > Regards,
> >
> > Bruce
> >
> > >
> > >Thanks,
> > >Joe Driscoll
> > >
> > >
> > >
Original Message
> > >From: rjmca <rjmca@w...>
> > >To: <basicstamps@egroups.com>
> > >Sent: Friday, April 07, 2000 12:10 AM
> > >Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> > >
> > >
> > >> Joe:
> > >>
> > >> You may send me a schematic off-list if you want. No
> guarantees, but I
> > >can
> > >> try. Question: what is the PWM frequency?
> > >>
> > >> Ray McArthur
> > >>
> > >>
Original Message
> > >> From: Joseph Driscoll <driscoll85@h...>
> > >> To: <basicstamps@egroups.com>
> > >> Sent: Thursday, April 06, 2000 11:53 PM
> > >> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> > >>
> > >>
> > >> > Hi,
> > >> >
> > >> > I have the L293D and the SN754410NE, both of which have built-in
> diode
> > >> > protection at the outputs. The current draw from the motor
> I'm using
> is
> > >> > around 0.5A (which is close to max on the L293D, so that's
> why I use
> the
> > >> > SN754410NE). And still, poof: the chip blew up during PWM operation
> (not
> > >> at
> > >> > startup). I have a schematic in GIF format if anyone is interested.
> > >> >
> > >> > Joe Driscoll
> > >> >
> > >> >
> > >> >
Original Message
> > >> > From: Al Williams <alw@a...>
> > >> > To: <basicstamps@egroups.com>
> > >> > Sent: Thursday, April 06, 2000 10:21 PM
> > >> > Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
> > >> >
> > >> >
> > >> > > I'm not an expert on motor drivers, but I think the L293 does NOT
> have
> > >> > > diodes. the L293D does -- you have to make sure which
> one you have.
> > >> > >
> > >> > > Regards,
> > >> > >
> > >> > > Al Williams
> > >> > > AWC
> > >> > > * 8 Channels of PWM with the PAK-V at
> > >> > > http://www.al-williams.com/awce/pak5.htm
> > >> > >
> > >> > > >
> > >> > > > Joe:
> > >> > > > My last message applies to the L293. I just looked at the data
> for
> > >> the
> > >> > > > SN754410NE, and it DOES show clamp diodes built into the IC.
> > >> > > > Also, they do
> > >> > > > not have the recommendation to use them. What I don't
> understand
> is
> > >> > that
> > >> > > > they still used external clamps in their example circuit.
> > >> > > >
> > >> > >
> > >> > >
> > >> > >
> > >> > >
> > >> > >
> > >> >
> > >> >
> > >> >
> > >>
> > >>
> > >>
> > >>
> > >>
> > >
> > >
> > >
> > >
> >
> >
> >
> >
>
>
to the supply pos and neg. all 4 diodes go arrow up toward the rail. They are
not ON except during back emf.
They need to be rated at 2 x the rail max volts and at least equal to max amps.
To: <basicstamps@egroups.com>
Date sent: Thu, 6 Apr 2000 19:50:42 -0500
From: "Joseph Driscoll" <driscoll85@h...>
Send reply to: basicstamps@egroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> Hi,
>
> Thanks for the reply. Yes, please send me your program -- that would help a
> lot. When you say "you must be sure that the inductance of the motor is high
> enough so that the current continues to flow during the off time", I'm not
> sure I understand that part. With the SN754410NE and the L293D, when the
> enable pin is low, the outputs are at a high impedance state. Is that a
> problem? It seems like the back emf produced during that "off" time needs to
> go somewhere. Maybe this is the problem?
>
> Thanks,
> Joe Driscoll
>
>
>
Original Message
> From: Ronald Doctors <rdoctors@h...>
> To: <basicstamps@egroups.com>
> Sent: Thursday, April 06, 2000 6:32 PM
> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> > HI,
> >
> > Don't know about the SN754410NE chip but the MC33030 chip is very easy to
> use
> > with a STAMP2 . I am using them with an x-Y control system and it is
> fairly simple.
> > I found that the STAMP needs expansion for both analog signal and digital
> data handling.
> > If you want I can email my prgm ( not yet fully debugged ) and it will
> give you some idea of the complexity.
> > The noises are the PWM causing the windings to vibrate. If you are using
> a PWM to control speed
> > you must be sure that the inductance of the motor is high enough so that
> the current continues to flow during the off
> > time. Try the chip in a simple config before using it in a STAMP control
> system to make sure you have that part working smoothly.
> >
> > Also you need diodes to make sure that the stored energy in the inductance
> has somewhere to go.. In the case of full H bridge that means 4 diodes
> > for each motor. Usually they are built in to the control chip.
> >
> > ( PLEASE NO MORE DIODE RELAY STUFF!!! [noparse]:)[/noparse])
> > To: <basicstamps@egroups.com>
> > Date sent: Thu, 6 Apr 2000 17:51:40 -0500
> > From: "Joseph Driscoll" <driscoll85@h...>
> > Send reply to: basicstamps@egroups.com
> > Subject: [noparse][[/noparse]basicstamps] Stamps and motor control
> >
> > > Hello,
> > >
> > > I have an old Hero 2000 robot arm, which was sold by Heathkit. The same
> arm
> > > was sold separately from the robot as an "arm trainer". Not counting the
> > > gripper, the arm is moved by four identical, 12V gearmotors. One for
> > > shoulder, one for elbow, and two for wrist (the wrist is a differential
> > > mechanism).
> > >
> > > I have been trying to create an interface so that I can control the arm
> with
> > > my PC. I am using the Basic Stamp II for PC interfacing. To drive the
> > > motors, I am using SN754410NE motor driver chips. For PWM speed control,
> I'm
> > > using the PAK Va from AWC.
> > >
> > > Here's the problem: I'm a bit new at motors, and I'm having some
> troubles.
> > > At low PWM duty cycles, the motor makes a high pitched sound and won't
> move.
> > > At slightly higher speeds, the tone is still there but the motor starts
> to
> > > move. What is this tone?
> > >
> > > Also, I was under the impression that the SN754410NE had built-in diodes
> for
> > > backEMF protection. One of the chips exploded (sparks, little divot out
> of
> > > the top of the IC) today, leading me to believe that something was
> wrong.
> > >
> > > Does anyone have experience working with the Hero 2000 arm? What I'd
> really
> > > love is a circuit to build that lets the PC or Stamp (or other
> > > microcontroller) drive the arm's motors. I can handle control
> algorithms,
> > > etc. I'm just having trouble with the hardware interfacing. I'd like to
> see
> > > someone's
> > > circuit to see where I'm going wrong.
> > >
> > > Thanks,
> > > Joe Driscoll
> > >
> > >
> > >
> > >
> >
> >
> > ron... the motor man...
> > Ronald Doctors
> > http://www.members.home.net/rdoctors
> >
> >
> >
> >
>
>
>
ron... the motor man...
Ronald Doctors
http://www.members.home.net/rdoctors
I have to study your circuit & info, but a general answer about frequency is
yes, it can make smoke if it's too high. PWM is used to minimize power
dissipation in the control transistors, because the transistors are switched
"on" or "off". Power dissipated is Vce x Ic. When the transistor is "on",
Vce is low, so power is small. When the switch is "off", power is low
because current is zero. However, during switching "on" to "off" or vice
versa, power dissipation can be quite high (especially with an inductive
load). If switching frequency is low enough, these intervals of high power
dissipation occur a small percentage of total time, so the average power is
small. Another problem is that diodes have a "recovery time", which means
that they momentarily are like a "short" when going from conduction to
non-conduction. This causes current spikes in the switching transistors
which becomes more important as frequency rises.
The question of what is "too high" a frequency depends on the speed of the
transistors & diodes used. Off hand I don't know. Maybe we will have an
idea after studying your stuff. I wonder if Ron Doctors has experience with
this?
Ray McArthur.
Original Message
From: Joseph Driscoll <driscoll85@h...>
To: <basicstamps@egroups.com>
Sent: Friday, April 07, 2000 10:22 AM
Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> Hi,
>
> The GIF is on its way to you off list. I have a question for everyone:
what
> happens if you switch the enable pin of the motor driver chip too fast?
> Maybe the frequency of the PWM signal is too high? Would too fast a
> switching time fry the driver chip?
>
> Thanks,
> Joe Driscoll
>
>
>
Original Message
> From: rjmca <rjmca@w...>
> To: <basicstamps@egroups.com>
> Sent: Friday, April 07, 2000 12:10 AM
> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> > Joe:
> >
> > You may send me a schematic off-list if you want. No guarantees, but I
> can
> > try. Question: what is the PWM frequency?
> >
> > Ray McArthur
> >
> >
Original Message
> > From: Joseph Driscoll <driscoll85@h...>
> > To: <basicstamps@egroups.com>
> > Sent: Thursday, April 06, 2000 11:53 PM
> > Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> >
> >
> > > Hi,
> > >
> > > I have the L293D and the SN754410NE, both of which have built-in diode
> > > protection at the outputs. The current draw from the motor I'm using
is
> > > around 0.5A (which is close to max on the L293D, so that's why I use
the
> > > SN754410NE). And still, poof: the chip blew up during PWM operation
(not
> > at
> > > startup). I have a schematic in GIF format if anyone is interested.
> > >
> > > Joe Driscoll
> > >
> > >
> > >
Original Message
> > > From: Al Williams <alw@a...>
> > > To: <basicstamps@egroups.com>
> > > Sent: Thursday, April 06, 2000 10:21 PM
> > > Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
> > >
> > >
> > > > I'm not an expert on motor drivers, but I think the L293 does NOT
have
> > > > diodes. the L293D does -- you have to make sure which one you have.
> > > >
> > > > Regards,
> > > >
> > > > Al Williams
> > > > AWC
> > > > * 8 Channels of PWM with the PAK-V at
> > > > http://www.al-williams.com/awce/pak5.htm
The data for the SN754410 calls out 400-900ns enable/disable time. This
means that if you are applying PWM to the enable line in proportional mode,
the frequency is way too high. Al Williams states that this mode outputs in
the range of 200kHz. But Al also points out that equal area mode is ~ 2kHz,
which is much more reasonable for your chips. Could you operate in this
lower frequency mode?
Ray McArthur
Original Message
From: Joseph Driscoll <driscoll85@h...>
To: <basicstamps@egroups.com>
Sent: Friday, April 07, 2000 10:22 AM
Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> Hi,
>
> The GIF is on its way to you off list. I have a question for everyone:
what
> happens if you switch the enable pin of the motor driver chip too fast?
> Maybe the frequency of the PWM signal is too high? Would too fast a
> switching time fry the driver chip?
>
> Thanks,
> Joe Driscoll
cycle -- 4uS per cycle or 250kHz. So I think that is OK.
Regards,
Al Williams
AWC
* Microcontroller Projects with Basic Stamps:
www.al-williams.com/awce/sbook.htm
>
Original Message
> From: rjmca [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ADECN2VpSCzZk-QMXGKncAgrpvCwYEuZifuRdFWK8nPb9MpcMsSTpmWzbKt5VOiKjmHmt-7ImpSf]rjmca@w...[/url
> Sent: Saturday, April 08, 2000 8:26 PM
> To: basicstamps@egroups.com
> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> Joe:
>
> The data for the SN754410 calls out 400-900ns enable/disable time. This
> means that if you are applying PWM to the enable line in
> proportional mode,
> the frequency is way too high. Al Williams states that this mode
> outputs in
> the range of 200kHz. But Al also points out that equal area mode
> is ~ 2kHz,
> which is much more reasonable for your chips. Could you operate in this
> lower frequency mode?
>
> Ray McArthur
>
>
Original Message
> From: Joseph Driscoll <driscoll85@h...>
> To: <basicstamps@egroups.com>
> Sent: Friday, April 07, 2000 10:22 AM
> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> > Hi,
> >
> > The GIF is on its way to you off list. I have a question for everyone:
> what
> > happens if you switch the enable pin of the motor driver chip too fast?
> > Maybe the frequency of the PWM signal is too high? Would too fast a
> > switching time fry the driver chip?
> >
> > Thanks,
> > Joe Driscoll
>
>
>
>
I am afraid that the switching losses will be very high when the time spent
transitioning from hi to lo and back is an appreciable part of the total
duty cycle. Is there a problem running at the lower frequency? If you have
a chance, read my message of 4/7 at 5:30PM and see if you agree with it.
Thanks,
Ray McArthur
Original Message
From: Al Williams <alw@a...>
To: <basicstamps@egroups.com>
Sent: Saturday, April 08, 2000 10:55 PM
Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
> Well, 900nS on and 900nS off is 1.8uS. The PAK works at 2uS per half
> cycle -- 4uS per cycle or 250kHz. So I think that is OK.
>
> Regards,
>
> Al Williams
> AWC
> * Microcontroller Projects with Basic Stamps:
> www.al-williams.com/awce/sbook.htm
>
>
> >
Original Message
> > From: rjmca [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=T_TNx--ywac1zdd1INVKdayt8-CMaYxVQ9wAfGzeEZkxiGt1xknCDVHH5Cq3LnQAI0Rm1n0rr3Fw]rjmca@w...[/url
> > Sent: Saturday, April 08, 2000 8:26 PM
> > To: basicstamps@egroups.com
> > Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> >
> >
> > Joe:
> >
> > The data for the SN754410 calls out 400-900ns enable/disable time. This
> > means that if you are applying PWM to the enable line in
> > proportional mode,
> > the frequency is way too high. Al Williams states that this mode
> > outputs in
> > the range of 200kHz. But Al also points out that equal area mode
> > is ~ 2kHz,
> > which is much more reasonable for your chips. Could you operate in this
> > lower frequency mode?
> >
> > Ray McArthur
> >
> >
Original Message
> > From: Joseph Driscoll <driscoll85@h...>
> > To: <basicstamps@egroups.com>
> > Sent: Friday, April 07, 2000 10:22 AM
> > Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> >
> >
> > > Hi,
> > >
> > > The GIF is on its way to you off list. I have a question for everyone:
> > what
> > > happens if you switch the enable pin of the motor driver chip too
fast?
> > > Maybe the frequency of the PWM signal is too high? Would too fast a
> > > switching time fry the driver chip?
> > >
> > > Thanks,
> > > Joe Driscoll
> >
> >
> >
> >
>
>
>
>
your baud rate by the same factor. This also reduces current consumption to
the chip. So a 25Mhz resonator (or crystal) will cut your baud rate in half
and set the time base to 4uS.
Regards,
Al Williams
AWC
* Solderless Stamp prototyping at http://www.al-williams.com/awce
>
Original Message
> From: rjmca [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=E1MvJwF7-3meP_okLo2fuy27sy2c2e65DgLVAadGLbKm5hjcH3B54S0TSTi2O8qWcVSkBAqhXHC2FA]rjmca@w...[/url
> Sent: Sunday, April 09, 2000 12:09 AM
> To: basicstamps@egroups.com
> Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> Al:
> I am afraid that the switching losses will be very high when the
> time spent
> transitioning from hi to lo and back is an appreciable part of the total
> duty cycle. Is there a problem running at the lower frequency?
> If you have
> a chance, read my message of 4/7 at 5:30PM and see if you agree with it.
>
> Thanks,
> Ray McArthur
>
>
Original Message
> From: Al Williams <alw@a...>
> To: <basicstamps@egroups.com>
> Sent: Saturday, April 08, 2000 10:55 PM
> Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
>
>
> > Well, 900nS on and 900nS off is 1.8uS. The PAK works at 2uS per half
> > cycle -- 4uS per cycle or 250kHz. So I think that is OK.
> >
> > Regards,
> >
> > Al Williams
> > AWC
> > * Microcontroller Projects with Basic Stamps:
> > www.al-williams.com/awce/sbook.htm
> >
> >
> > >
Original Message
> > > From: rjmca [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=E1MvJwF7-3meP_okLo2fuy27sy2c2e65DgLVAadGLbKm5hjcH3B54S0TSTi2O8qWcVSkBAqhXHC2FA]rjmca@w...[/url
> > > Sent: Saturday, April 08, 2000 8:26 PM
> > > To: basicstamps@egroups.com
> > > Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> > >
> > >
> > > Joe:
> > >
> > > The data for the SN754410 calls out 400-900ns enable/disable
> time. This
> > > means that if you are applying PWM to the enable line in
> > > proportional mode,
> > > the frequency is way too high. Al Williams states that this mode
> > > outputs in
> > > the range of 200kHz. But Al also points out that equal area mode
> > > is ~ 2kHz,
> > > which is much more reasonable for your chips. Could you
> operate in this
> > > lower frequency mode?
> > >
> > > Ray McArthur
> > >
> > >
Original Message
> > > From: Joseph Driscoll <driscoll85@h...>
> > > To: <basicstamps@egroups.com>
> > > Sent: Friday, April 07, 2000 10:22 AM
> > > Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> > >
> > >
> > > > Hi,
> > > >
> > > > The GIF is on its way to you off list. I have a question
> for everyone:
> > > what
> > > > happens if you switch the enable pin of the motor driver chip too
> fast?
> > > > Maybe the frequency of the PWM signal is too high? Would too fast a
> > > > switching time fry the driver chip?
> > > >
> > > > Thanks,
> > > > Joe Driscoll
> > >
> > >
> > >
> > >
> >
> >
> >
> >
>
>
>
I'll try things in equal area mode and see what happens. I'll be away from
the arm for a week or so, but I'll let you know when I've tried things.
Thanks,
Joe Driscoll
>From: "Al Williams" <alw@a...>
>Reply-To: basicstamps@egroups.com
>To: <basicstamps@egroups.com>
>Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
>Date: Sun, 9 Apr 2000 00:37:47 -0500
>
>That's true too. Actually, you can scale back the clock element and reduce
>your baud rate by the same factor. This also reduces current consumption to
>the chip. So a 25Mhz resonator (or crystal) will cut your baud rate in half
>and set the time base to 4uS.
>
>Regards,
>
>Al Williams
>AWC
>* Solderless Stamp prototyping at http://www.al-williams.com/awce
>
>
> >
Original Message
> > From: rjmca [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=s5GumWWCPH2R8A8RWbxD1GJF2ze-xvrDOa1_YXdYNF9QA0ihwHXTE8x5LWa-N02mmuq5JQDi7hwJ2l3w]rjmca@w...[/url
> > Sent: Sunday, April 09, 2000 12:09 AM
> > To: basicstamps@egroups.com
> > Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> >
> >
> > Al:
> > I am afraid that the switching losses will be very high when the
> > time spent
> > transitioning from hi to lo and back is an appreciable part of the total
> > duty cycle. Is there a problem running at the lower frequency?
> > If you have
> > a chance, read my message of 4/7 at 5:30PM and see if you agree with
>it.
> >
> > Thanks,
> > Ray McArthur
> >
> >
Original Message
> > From: Al Williams <alw@a...>
> > To: <basicstamps@egroups.com>
> > Sent: Saturday, April 08, 2000 10:55 PM
> > Subject: RE: [noparse][[/noparse]basicstamps] Stamps and motor control
> >
> >
> > > Well, 900nS on and 900nS off is 1.8uS. The PAK works at 2uS per half
> > > cycle -- 4uS per cycle or 250kHz. So I think that is OK.
> > >
> > > Regards,
> > >
> > > Al Williams
> > > AWC
> > > * Microcontroller Projects with Basic Stamps:
> > > www.al-williams.com/awce/sbook.htm
> > >
> > >
> > > >
Original Message
> > > > From: rjmca [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=s5GumWWCPH2R8A8RWbxD1GJF2ze-xvrDOa1_YXdYNF9QA0ihwHXTE8x5LWa-N02mmuq5JQDi7hwJ2l3w]rjmca@w...[/url
> > > > Sent: Saturday, April 08, 2000 8:26 PM
> > > > To: basicstamps@egroups.com
> > > > Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> > > >
> > > >
> > > > Joe:
> > > >
> > > > The data for the SN754410 calls out 400-900ns enable/disable
> > time. This
> > > > means that if you are applying PWM to the enable line in
> > > > proportional mode,
> > > > the frequency is way too high. Al Williams states that this mode
> > > > outputs in
> > > > the range of 200kHz. But Al also points out that equal area mode
> > > > is ~ 2kHz,
> > > > which is much more reasonable for your chips. Could you
> > operate in this
> > > > lower frequency mode?
> > > >
> > > > Ray McArthur
> > > >
> > > >
Original Message
> > > > From: Joseph Driscoll <driscoll85@h...>
> > > > To: <basicstamps@egroups.com>
> > > > Sent: Friday, April 07, 2000 10:22 AM
> > > > Subject: Re: [noparse][[/noparse]basicstamps] Stamps and motor control
> > > >
> > > >
> > > > > Hi,
> > > > >
> > > > > The GIF is on its way to you off list. I have a question
> > for everyone:
> > > > what
> > > > > happens if you switch the enable pin of the motor driver chip too
> > fast?
> > > > > Maybe the frequency of the PWM signal is too high? Would too fast
>a
> > > > > switching time fry the driver chip?
> > > > >
> > > > > Thanks,
> > > > > Joe Driscoll
> > > >
> > > >
> > > >
> > > >
> > >
> > >
> > >
> > >
> >
> >
> >
>
>
>
>
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