Model RC Servo motor
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Posts: 46,084
Anyone out there have experience with using a stamp to drive a model RC
servo motor?
The unit I am wanting to controll has a 3 wire connector and inside is a
microcontroller and a pot.
I want to be able to incrementally position the motor over a narrow range of
about 40 degrees of rotation.
servo motor?
The unit I am wanting to controll has a 3 wire connector and inside is a
microcontroller and a pot.
I want to be able to incrementally position the motor over a narrow range of
about 40 degrees of rotation.
Comments
servo motor?
The unit I am wanting to controll has a 3 wire connector and inside is a
microcontroller and a pot.
I want to be able to incrementally position the motor over a narrow range of
about 40 degrees of rotation.
RC servos (at least the ones I am familiar with) require a pulse every
so often to give it position data. The PULSOUT command will do this
easily. Usually a 1.5mS pulse will "center" the servo. Narrower pulses
make the shaft move one way and wider pulses make the shaft move the
other way. You need to resend the pulse about every 20mS or so.
Otherwise, the servo will not "hold" its position and will be easy to
move because of gravity, etc.
Of course, while the Stamp is generating PULSOUT commands, it can't do
other things. That's why we make the PAK-VIII which can generate 8
pulses at once and keeps generating them until you command it to stop.
This chip does lots of things, but one thing it can do very well is
drive servos. Have a look at
http://www.al-williams.com/awce/servo_bot.htm for an example. The main
page for the PAK-VIII is at http://www.al-williams.com/awce/pak8.htm.
So depending on what you want to do, the Stamp may work fine. Otherwise,
look at the PAK. You can find a write up on servos in lots of places. My
book "Microcontroller Projects with Basic Stamps" or the Parallax
Robotics course.
Many people modify servos for continuous rotation so they get get a
pretty good geared motor without having to mess with the drive
circuitry. You can read a lot about servos at
http://www.rdrop.com/~marvin/explore/servhack.htm and
http://www.brookshiresoftware.com/how_servos_work.htm.
Al Williams
AWC
* Easy RS-232 Prototyping
http://www.al-williams.com/awce/rs1.htm
>
Original Message
> From: FalconWireless Tech Support - KF4HAZ
> [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=OuHt02NzVDs3yVVi0uAlgZPVeVW040SJTvWbBi_w8RbMLoq_O8p-uDvDj2znm93hJx-GoswuzDyZebm1azW51VyyL5o]techsupport@f...[/url
> Sent: Friday, January 04, 2002 4:59 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Model RC Servo motor
>
>
> Anyone out there have experience with using a stamp to drive
> a model RC servo motor? The unit I am wanting to controll has
> a 3 wire connector and inside is a microcontroller and a pot.
> I want to be able to incrementally position the motor over a
> narrow range of about 40 degrees of rotation.
>
>
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>
MC/V2 digital Multiplex servo ( www.multiplexrc.com ). They allow you to
send one pulse, and the digital control with failsafe eliminates the need
for mainenance pulses by holding to the last good position.
If you want to use a cheap one, send it a 1-2ms pulse every 20ms or so. If
you don't maintain it, it will lose it's holding ability--which may or may
not be important to your application.
Cliff
Original Message
From: "FalconWireless Tech Support - KF4HAZ"
<techsupport@f...>
To: <basicstamps@yahoogroups.com>
Sent: Friday, January 04, 2002 3:02 PM
Subject: [noparse][[/noparse]basicstamps] Model RC Servo motor
Anyone out there have experience with using a stamp to drive a model RC
servo motor?
The unit I am wanting to controll has a 3 wire connector and inside is a
microcontroller and a pot.
I want to be able to incrementally position the motor over a narrow range of
about 40 degrees of rotation.
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
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/
> I've got a stamp driving an RC servo in an automation application. I used
a
> MC/V2 digital Multiplex servo ( www.multiplexrc.com ). They allow you to
> send one pulse, and the digital control with failsafe eliminates the need
> for mainenance pulses by holding to the last good position.
>
> If you want to use a cheap one, send it a 1-2ms pulse every 20ms or so. If
> you don't maintain it, it will lose it's holding ability--which may or may
> not be important to your application.
Cliff makes a good point. The failsafe mode of digital servos in general may
make more sense for certain applications where you don't want to "tend" them
regularly. I know that JR makes digital servos also and I believe Futaba
does as well. At least in the US where I live it's more likely a hobby shop
would have JR or Futaba servos in stock.
Tim
From what I remember, JR Futaba & Hitec digital servos don't have failsafe.
You'll want to verify this before purchasing one, as they cost about $80 and
more. I went with Multiplex because at the time, they were the only ones who
had failsafe. Hitec may have it by now, because I've heard they have a
"servo programmer" also.
Cliff
Original Message
From: "Tim McDonough" <tim@m...>
To: <basicstamps@yahoogroups.com>
Sent: Saturday, January 05, 2002 4:59 AM
Subject: Re: [noparse][[/noparse]basicstamps] Model RC Servo motor
Cliff Griffin wrote...
> I've got a stamp driving an RC servo in an automation application. I used
a
> MC/V2 digital Multiplex servo ( www.multiplexrc.com ). They allow you to
> send one pulse, and the digital control with failsafe eliminates the need
> for mainenance pulses by holding to the last good position.
>
> If you want to use a cheap one, send it a 1-2ms pulse every 20ms or so. If
> you don't maintain it, it will lose it's holding ability--which may or may
> not be important to your application.
Cliff makes a good point. The failsafe mode of digital servos in general may
make more sense for certain applications where you don't want to "tend" them
regularly. I know that JR makes digital servos also and I believe Futaba
does as well. At least in the US where I live it's more likely a hobby shop
would have JR or Futaba servos in stock.
Tim
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
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pulse, on one or more inputs, let it pick it up with Pulsein, then use
that stamp to maintain that pulse with Pulseout to your Servo(s) on
another output. Using this method, you could control as 1/2 as many
servo's as you have inputs / outputs on the stamp.
regards,
Leroy
Cliff Griffin wrote:
>
> My closest Hobby People carries Multiplex in stock.
> >From what I remember, JR Futaba & Hitec digital servos don't have failsafe.
> You'll want to verify this before purchasing one, as they cost about $80 and
> more. I went with Multiplex because at the time, they were the only ones who
> had failsafe. Hitec may have it by now, because I've heard they have a
> "servo programmer" also.
>
> Cliff
>
>
Original Message
> From: "Tim McDonough" <tim@m...>
> To: <basicstamps@yahoogroups.com>
> Sent: Saturday, January 05, 2002 4:59 AM
> Subject: Re: [noparse][[/noparse]basicstamps] Model RC Servo motor
>
> Cliff Griffin wrote...
> > I've got a stamp driving an RC servo in an automation application. I used
> a
> > MC/V2 digital Multiplex servo ( www.multiplexrc.com ). They allow you to
> > send one pulse, and the digital control with failsafe eliminates the need
> > for mainenance pulses by holding to the last good position.
> >
> > If you want to use a cheap one, send it a 1-2ms pulse every 20ms or so. If
> > you don't maintain it, it will lose it's holding ability--which may or may
> > not be important to your application.
>
> Cliff makes a good point. The failsafe mode of digital servos in general may
> make more sense for certain applications where you don't want to "tend" them
> regularly. I know that JR makes digital servos also and I believe Futaba
> does as well. At least in the US where I live it's more likely a hobby shop
> would have JR or Futaba servos in stock.
>
> Tim
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
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>
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>
>
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Application Cookbook (Gilliland) the
author presents a BS2 circuit in which the stamp delegates the production of a
servo driving pulse stream to a 555
timer. This is one example of a type of system presented in several books, but
in this particular circuit, the
pulse width from the 555 is set with a DS-1804 digital pot. The pot wiper in
turn is set by the BS2. In other
words, the stamp can "set it and forget it," and go off to do other things.
Because it is a 555, the cost seems to
be sort of minimal. Best, Michael
Leroy Hall wrote:
> You could use a separate Stamp as your servo controller. Send it a
> pulse, on one or more inputs, let it pick it up with Pulsein, then use
> that stamp to maintain that pulse with Pulseout to your Servo(s) on
> another output. Using this method, you could control as 1/2 as many
> servo's as you have inputs / outputs on the stamp.
>
> regards,
>
> Leroy
>
> Cliff Griffin wrote:
> >
> > My closest Hobby People carries Multiplex in stock.
> > >From what I remember, JR Futaba & Hitec digital servos don't have failsafe.
> > You'll want to verify this before purchasing one, as they cost about $80 and
> > more. I went with Multiplex because at the time, they were the only ones who
> > had failsafe. Hitec may have it by now, because I've heard they have a
> > "servo programmer" also.
> >
> > Cliff
> >
> >
Original Message
> > From: "Tim McDonough" <tim@m...>
> > To: <basicstamps@yahoogroups.com>
> > Sent: Saturday, January 05, 2002 4:59 AM
> > Subject: Re: [noparse][[/noparse]basicstamps] Model RC Servo motor
> >
> > Cliff Griffin wrote...
> > > I've got a stamp driving an RC servo in an automation application. I used
> > a
> > > MC/V2 digital Multiplex servo ( www.multiplexrc.com ). They allow you to
> > > send one pulse, and the digital control with failsafe eliminates the need
> > > for mainenance pulses by holding to the last good position.
> > >
> > > If you want to use a cheap one, send it a 1-2ms pulse every 20ms or so. If
> > > you don't maintain it, it will lose it's holding ability--which may or may
> > > not be important to your application.
> >
> > Cliff makes a good point. The failsafe mode of digital servos in general may
> > make more sense for certain applications where you don't want to "tend" them
> > regularly. I know that JR makes digital servos also and I believe Futaba
> > does as well. At least in the US where I live it's more likely a hobby shop
> > would have JR or Futaba servos in stock.
> >
> > Tim
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > 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/
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > 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/
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
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>
>
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In my application updating and failsafe are not a concern, if anything
malfunctions the controller can be turned off and the servo arm can be
manually positioned to a fixed "limp in mode" compromise position.
As for updating, the program will be a simple loop reading a couple of
inputs and driving the servo, and occasionally switching 2 solenoids.
There is however a bit of concern about setting the min and max rotation,
there is a mechanical limit and the servo shouldn't be driven all the way
against either stop, I assume I can program these limits into the stamp.
One final question, pin-outs, I assume one pin is +5v one is GND and one is
pulse-in? which ones?
Class "What's a Microcontroller" lesson #3 & 4. It tells you what pulses are
expected, the pinouts of a servo and all that good stuff. You can download and
print it out from the Parallax web site at
http://www.parallaxinc.com/html_files/downloads/downloads_sic.htm
Hank
Original Message
From: "FalconWireless Tech Support - KF4HAZ" <techsupport@f...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, January 07, 2002 12:14 PM
Subject: Re: [noparse][[/noparse]basicstamps] Model RC Servo Motor
> Thanks for the input.
> In my application updating and failsafe are not a concern, if anything
> malfunctions the controller can be turned off and the servo arm can be
> manually positioned to a fixed "limp in mode" compromise position.
> As for updating, the program will be a simple loop reading a couple of
> inputs and driving the servo, and occasionally switching 2 solenoids.
> There is however a bit of concern about setting the min and max rotation,
> there is a mechanical limit and the servo shouldn't be driven all the way
> against either stop, I assume I can program these limits into the stamp.
> One final question, pin-outs, I assume one pin is +5v one is GND and one is
> pulse-in? which ones?
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
of the message will be ignored.
>
>
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>
is
> pulse-in? which ones?
>
Normally, gnd is black or brown; red is +5 volts; and white or yellow is
pulse.
Ray McArthur