Crosstalk Driving Servos?
Archiver
Posts: 46,084
I'm having what I think are some crosstalk/isolation problems. This is
probably something simple, but I can't see it...
I've breadboarded my circuit with a BS2. It's driving servos from outputs
0, 1, and 2, LED's on outputs 4, 5, and 7, and a trigger for a separate
speech board on output 6 (triggered low). The breadboard and speech board
share grounds, but not power.
After I trigger the speech board to start talking, if I then move a servo
the sound will turn to static.
It also seems that I can't move the servos as fast as I want. A friend is
using the same servos and uses a PAUSE 10 after each movement. The best I
can do is PAUSE 25 or weird things start to happen. The servo will stop
before finishing it's set of movements.
And if I try to run two servos at the same time they'll both start fine and
then one of them will go into the weeds.
I tried using a 1uF cap between power and ground where the servos connect to
the breadboard. That didn't help.
I've disconnected the servos altogether, and just tried triggering the sound
chip. It's fine. If I tell the stamp2 to start moving a servo while the
speech is still going though, I still get static (this is without any servos
connected to the board). So it's not the servo, it's something in the
breadboard. Do I need a cap between power and ground at the stamp?
Thanks!
Bob Pony
probably something simple, but I can't see it...
I've breadboarded my circuit with a BS2. It's driving servos from outputs
0, 1, and 2, LED's on outputs 4, 5, and 7, and a trigger for a separate
speech board on output 6 (triggered low). The breadboard and speech board
share grounds, but not power.
After I trigger the speech board to start talking, if I then move a servo
the sound will turn to static.
It also seems that I can't move the servos as fast as I want. A friend is
using the same servos and uses a PAUSE 10 after each movement. The best I
can do is PAUSE 25 or weird things start to happen. The servo will stop
before finishing it's set of movements.
And if I try to run two servos at the same time they'll both start fine and
then one of them will go into the weeds.
I tried using a 1uF cap between power and ground where the servos connect to
the breadboard. That didn't help.
I've disconnected the servos altogether, and just tried triggering the sound
chip. It's fine. If I tell the stamp2 to start moving a servo while the
speech is still going though, I still get static (this is without any servos
connected to the board). So it's not the servo, it's something in the
breadboard. Do I need a cap between power and ground at the stamp?
Thanks!
Bob Pony
Comments
Two standard sanity checks:
1. Are you using separate regulation for the servos and or the speech board?
I'd recommend separate regulation for both, with plenty of decoupling
capacitors.
2. How is your grounding between modules- is it short but fat enough enough
to carry the current for the servos?
regards,
Tony Wells
Original Message
From: "Poniatowski Bob" <bobpony@m...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, March 10, 2002 5:00 PM
Subject: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
> I'm having what I think are some crosstalk/isolation problems. This is
> probably something simple, but I can't see it...
>
> I've breadboarded my circuit with a BS2. It's driving servos from outputs
> 0, 1, and 2, LED's on outputs 4, 5, and 7, and a trigger for a separate
> speech board on output 6 (triggered low). The breadboard and speech board
> share grounds, but not power.
>
> After I trigger the speech board to start talking, if I then move a servo
> the sound will turn to static.
>
> It also seems that I can't move the servos as fast as I want. A friend is
> using the same servos and uses a PAUSE 10 after each movement. The best I
> can do is PAUSE 25 or weird things start to happen. The servo will stop
> before finishing it's set of movements.
>
> And if I try to run two servos at the same time they'll both start fine
and
> then one of them will go into the weeds.
>
> I tried using a 1uF cap between power and ground where the servos connect
to
> the breadboard. That didn't help.
>
> I've disconnected the servos altogether, and just tried triggering the
sound
> chip. It's fine. If I tell the stamp2 to start moving a servo while the
> speech is still going though, I still get static (this is without any
servos
> connected to the board). So it's not the servo, it's something in the
> breadboard. Do I need a cap between power and ground at the stamp?
>
> Thanks!
> Bob Pony
>
>
>
> 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/
>
>
>
The speech board is the guts of one of those recordable greeting cards.
It's got it's own battery, so the power for it is separate (I'm running from
the battery).
I'm using an alligator clip lead to connect the ground of the speech board
to the stamp breadboard. So it's not short and fat, but then the servos
aren't running from the speech board. They're connected directly to the
power/ground bus of the breadboard.
Bob
Original Message
From: <tony.wells@a...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, March 10, 2002 10:36 AM
Subject: Re: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
> Hi Bob,
>
> Two standard sanity checks:
>
> 1. Are you using separate regulation for the servos and or the speech
board?
> I'd recommend separate regulation for both, with plenty of decoupling
> capacitors.
>
> 2. How is your grounding between modules- is it short but fat enough
enough
> to carry the current for the servos?
>
> regards,
>
> Tony Wells
>
>
Original Message
> From: "Poniatowski Bob" <bobpony@m...>
> To: <basicstamps@yahoogroups.com>
> Sent: Sunday, March 10, 2002 5:00 PM
> Subject: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
>
>
> > I'm having what I think are some crosstalk/isolation problems. This is
> > probably something simple, but I can't see it...
> >
> > I've breadboarded my circuit with a BS2. It's driving servos from
outputs
> > 0, 1, and 2, LED's on outputs 4, 5, and 7, and a trigger for a separate
> > speech board on output 6 (triggered low). The breadboard and speech
board
> > share grounds, but not power.
> >
> > After I trigger the speech board to start talking, if I then move a
servo
> > the sound will turn to static.
> >
> > It also seems that I can't move the servos as fast as I want. A friend
is
> > using the same servos and uses a PAUSE 10 after each movement. The best
I
> > can do is PAUSE 25 or weird things start to happen. The servo will stop
> > before finishing it's set of movements.
> >
> > And if I try to run two servos at the same time they'll both start fine
> and
> > then one of them will go into the weeds.
> >
> > I tried using a 1uF cap between power and ground where the servos
connect
> to
> > the breadboard. That didn't help.
> >
> > I've disconnected the servos altogether, and just tried triggering the
> sound
> > chip. It's fine. If I tell the stamp2 to start moving a servo while
the
> > speech is still going though, I still get static (this is without any
> servos
> > connected to the board). So it's not the servo, it's something in the
> > breadboard. Do I need a cap between power and ground at the stamp?
> >
> > Thanks!
> > Bob Pony
> >
> >
> >
> > 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/
>
>
A crocodile clip might *just* be too high a resistance. Short lengths of
ordinary power cord wire is probably the sort of cable for a good low
resistance ground. How are the units powered?
T
Original Message
From: "Poniatowski Bob" <bobpony@m...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, March 10, 2002 7:29 PM
Subject: Re: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
> Thanks Tony.
>
> The speech board is the guts of one of those recordable greeting cards.
> It's got it's own battery, so the power for it is separate (I'm running
from
> the battery).
>
> I'm using an alligator clip lead to connect the ground of the speech board
> to the stamp breadboard. So it's not short and fat, but then the servos
> aren't running from the speech board. They're connected directly to the
> power/ground bus of the breadboard.
>
> Bob
>
Original Message
> From: <tony.wells@a...>
> To: <basicstamps@yahoogroups.com>
> Sent: Sunday, March 10, 2002 10:36 AM
> Subject: Re: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
>
>
> > Hi Bob,
> >
> > Two standard sanity checks:
> >
> > 1. Are you using separate regulation for the servos and or the speech
> board?
> > I'd recommend separate regulation for both, with plenty of decoupling
> > capacitors.
> >
> > 2. How is your grounding between modules- is it short but fat enough
> enough
> > to carry the current for the servos?
> >
> > regards,
> >
> > Tony Wells
> >
> >
Original Message
> > From: "Poniatowski Bob" <bobpony@m...>
> > To: <basicstamps@yahoogroups.com>
> > Sent: Sunday, March 10, 2002 5:00 PM
> > Subject: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
> >
> >
> > > I'm having what I think are some crosstalk/isolation problems. This
is
> > > probably something simple, but I can't see it...
> > >
> > > I've breadboarded my circuit with a BS2. It's driving servos from
> outputs
> > > 0, 1, and 2, LED's on outputs 4, 5, and 7, and a trigger for a separat
e
> > > speech board on output 6 (triggered low). The breadboard and speech
> board
> > > share grounds, but not power.
> > >
> > > After I trigger the speech board to start talking, if I then move a
> servo
> > > the sound will turn to static.
> > >
> > > It also seems that I can't move the servos as fast as I want. A
friend
> is
> > > using the same servos and uses a PAUSE 10 after each movement. The
best
> I
> > > can do is PAUSE 25 or weird things start to happen. The servo will
stop
> > > before finishing it's set of movements.
> > >
> > > And if I try to run two servos at the same time they'll both start
fine
> > and
> > > then one of them will go into the weeds.
> > >
> > > I tried using a 1uF cap between power and ground where the servos
> connect
> > to
> > > the breadboard. That didn't help.
> > >
> > > I've disconnected the servos altogether, and just tried triggering the
> > sound
> > > chip. It's fine. If I tell the stamp2 to start moving a servo while
> the
> > > speech is still going though, I still get static (this is without any
> > servos
> > > connected to the board). So it's not the servo, it's something in the
> > > breadboard. Do I need a cap between power and ground at the stamp?
> > >
> > > Thanks!
> > > Bob Pony
> > >
> > >
> > >
> > > 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 of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
for failing where the wire is crimped into the metal clip -- cut, strip and
solder to fix.
Original Message
> A crocodile clip might *just* be too high a resistance. Short lengths of
> ordinary power cord wire is probably the sort of cable for a good low
> resistance ground. How are the units powered?
> > The speech board is the guts of one of those recordable greeting cards.
> > It's got it's own battery, so the power for it is separate (I'm running
> from
> > the battery).
> >
> > I'm using an alligator clip lead to connect the ground of the speech
board
> > to the stamp breadboard. So it's not short and fat, but then the servos
> > aren't running from the speech board. They're connected directly to the
> > power/ground bus of the breadboard.
I'm not sure the ground to the sound card is the issue though, because the
servos seem to interfere with each other as well, even with the sound card
completely removed. I'm running three servos now, and I've had to add a bit
more pause time after moving each one of them so that they don't all go
crazy.
They all still go crazy when I first power everything up. I have to
disconnect the control lead from the breadboard for two of the three servos
(any two), and then plug them back in, before the three servos will calm
down. Otherwise they get the jitters...all three sit there and jitter back
and forth just a tiny bit. I tried putting a pause into my program right up
front, figuring maybe they just needed a bit of time to settle before I
centered them and started the program. They still start jittering right
away, but the weird thing is that the speed of the jitter is related to the
length of this first pause statement. If I make that first pause statement
longer, the servos jitter becomes slower. But they're still uncontrollable
until I briefly disconnect two of them. Once I've done that everything
works fine.
I did realize that earlier when they occasionally went off into the weeds it
was when one of them was always near their maximum rotation. I backed this
off a bit (by 25) and haven't had them go out of control since.
But in order to make them work without stomping on eachother I've had to
make them soooooo sloooooowwwwww. And take the sound trigger out! This
can't be right. I'm missing something obvious.
Everything is built on a Jameco JE25 breadboard, part of the kit I bought
from Peter Anderson (good kit by the way). The power for the breadboard is
from a 9V, 250mA wall transformer feeding a 7805 regulator to produce 5V.
Is it possible that the 250mA is enough to run the servos in steady state,
but the inrush when they turn on is pulling everything low and causing a
reset to happen over and over and over? The 250mA wall wort was the only
one sitting around here. Peter's kit normally ships with a 1A wall wort,
mine was missing in the shipment.
This is my first time experimenting with stamps, it's been years since I
built breadboarded anything. So my rust is probably showing. This has got
to be something dead simple I'm doing wrong. I just can't see it yet. [noparse];)[/noparse]
Thanks again,
Bob
Original Message
From: <tony.wells@a...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, March 10, 2002 3:01 PM
Subject: Re: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
> Hi Bob,
>
> A crocodile clip might *just* be too high a resistance. Short lengths of
> ordinary power cord wire is probably the sort of cable for a good low
> resistance ground. How are the units powered?
>
> T
>
Original Message
> From: "Poniatowski Bob" <bobpony@m...>
> To: <basicstamps@yahoogroups.com>
> Sent: Sunday, March 10, 2002 7:29 PM
> Subject: Re: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
>
>
> > Thanks Tony.
> >
> > The speech board is the guts of one of those recordable greeting cards.
> > It's got it's own battery, so the power for it is separate (I'm running
> from
> > the battery).
> >
> > I'm using an alligator clip lead to connect the ground of the speech
board
> > to the stamp breadboard. So it's not short and fat, but then the servos
> > aren't running from the speech board. They're connected directly to the
> > power/ground bus of the breadboard.
> >
> > Bob
> >
Original Message
> > From: <tony.wells@a...>
> > To: <basicstamps@yahoogroups.com>
> > Sent: Sunday, March 10, 2002 10:36 AM
> > Subject: Re: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
> >
> >
> > > Hi Bob,
> > >
> > > Two standard sanity checks:
> > >
> > > 1. Are you using separate regulation for the servos and or the speech
> > board?
> > > I'd recommend separate regulation for both, with plenty of decoupling
> > > capacitors.
> > >
> > > 2. How is your grounding between modules- is it short but fat enough
> > enough
> > > to carry the current for the servos?
> > >
> > > regards,
> > >
> > > Tony Wells
> > >
> > >
Original Message
> > > From: "Poniatowski Bob" <bobpony@m...>
> > > To: <basicstamps@yahoogroups.com>
> > > Sent: Sunday, March 10, 2002 5:00 PM
> > > Subject: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
> > >
> > >
> > > > I'm having what I think are some crosstalk/isolation problems. This
> is
> > > > probably something simple, but I can't see it...
> > > >
> > > > I've breadboarded my circuit with a BS2. It's driving servos from
> > outputs
> > > > 0, 1, and 2, LED's on outputs 4, 5, and 7, and a trigger for a
separat
> e
> > > > speech board on output 6 (triggered low). The breadboard and speech
> > board
> > > > share grounds, but not power.
> > > >
> > > > After I trigger the speech board to start talking, if I then move a
> > servo
> > > > the sound will turn to static.
> > > >
> > > > It also seems that I can't move the servos as fast as I want. A
> friend
> > is
> > > > using the same servos and uses a PAUSE 10 after each movement. The
> best
> > I
> > > > can do is PAUSE 25 or weird things start to happen. The servo will
> stop
> > > > before finishing it's set of movements.
> > > >
> > > > And if I try to run two servos at the same time they'll both start
> fine
> > > and
> > > > then one of them will go into the weeds.
> > > >
> > > > I tried using a 1uF cap between power and ground where the servos
> > connect
> > > to
> > > > the breadboard. That didn't help.
> > > >
> > > > I've disconnected the servos altogether, and just tried triggering
the
> > > sound
> > > > chip. It's fine. If I tell the stamp2 to start moving a servo
while
> > the
> > > > speech is still going though, I still get static (this is without
any
> > > servos
> > > > connected to the board). So it's not the servo, it's something in
the
> > > > breadboard. Do I need a cap between power and ground at the stamp?
> > > >
> > > > Thanks!
> > > > Bob Pony
> > > >
> > > >
> > > >
> > > > 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 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/
>
>
move a servo to far too fast. At least that seems to be part of the
problem.
In the last email (sorry for the diatribe this is becoming, I appreciate the
help) I thought that maybe having all three servos start up at once was
pulling the power supply low and resetting the stamp.
So I put a couple of 22uF caps between power and ground at the stamp. When
I powered the board up, all three servos still jitter, but only for a couple
of seconds. Then they center up as they're supposed to and act fine. My
theory is that the couple of seconds is the time it takes for the caps to
get enough charge to keep the stamp powered even when the three servos pull
the power supply low. Once that inrush is past, everything moves along
normally.
Now I've got another part of the routine where I'm only moving a single
servo. But it moves much faster than when I'm moving all three at once. I
tried that part of the program and it also seems to be causing a reset.
It'll stick (usually after a very quick and large movement/swing of the
single servo) and then all three servos will jitter for a moment. Then the
program appears to start from the top.
So I'm thinking I've got too weak a supply for running three servos (the
servos are Hitech 300's). The wall wort is 9V, 250mA. It's regulated
through a 7805.
Just sending all of this out in hopes that it makes sense to someone.
Thanks,
Bob
Original Message
From: Poniatowski Bob <bobpony@m...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, March 10, 2002 7:13 PM
Subject: Re: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
> Thanks, I'll try a short bit of wire instead of the alligator lead wire.
>
> I'm not sure the ground to the sound card is the issue though, because the
> servos seem to interfere with each other as well, even with the sound card
> completely removed. I'm running three servos now, and I've had to add a
bit
> more pause time after moving each one of them so that they don't all go
> crazy.
>
> They all still go crazy when I first power everything up. I have to
> disconnect the control lead from the breadboard for two of the three
servos
> (any two), and then plug them back in, before the three servos will calm
> down. Otherwise they get the jitters...all three sit there and jitter
back
> and forth just a tiny bit. I tried putting a pause into my program right
up
> front, figuring maybe they just needed a bit of time to settle before I
> centered them and started the program. They still start jittering right
> away, but the weird thing is that the speed of the jitter is related to
the
> length of this first pause statement. If I make that first pause
statement
> longer, the servos jitter becomes slower. But they're still
uncontrollable
> until I briefly disconnect two of them. Once I've done that everything
> works fine.
>
> I did realize that earlier when they occasionally went off into the weeds
it
> was when one of them was always near their maximum rotation. I backed
this
> off a bit (by 25) and haven't had them go out of control since.
>
> But in order to make them work without stomping on eachother I've had to
> make them soooooo sloooooowwwwww. And take the sound trigger out! This
> can't be right. I'm missing something obvious.
>
> Everything is built on a Jameco JE25 breadboard, part of the kit I bought
> from Peter Anderson (good kit by the way). The power for the breadboard
is
> from a 9V, 250mA wall transformer feeding a 7805 regulator to produce 5V.
> Is it possible that the 250mA is enough to run the servos in steady state,
> but the inrush when they turn on is pulling everything low and causing a
> reset to happen over and over and over? The 250mA wall wort was the only
> one sitting around here. Peter's kit normally ships with a 1A wall wort,
> mine was missing in the shipment.
>
> This is my first time experimenting with stamps, it's been years since I
> built breadboarded anything. So my rust is probably showing. This has
got
> to be something dead simple I'm doing wrong. I just can't see it yet. [noparse];)[/noparse]
>
> Thanks again,
> Bob
>
>
Original Message
> From: <tony.wells@a...>
> To: <basicstamps@yahoogroups.com>
> Sent: Sunday, March 10, 2002 3:01 PM
> Subject: Re: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
>
>
> > Hi Bob,
> >
> > A crocodile clip might *just* be too high a resistance. Short lengths of
> > ordinary power cord wire is probably the sort of cable for a good low
> > resistance ground. How are the units powered?
> >
> > T
> >
Original Message
> > From: "Poniatowski Bob" <bobpony@m...>
> > To: <basicstamps@yahoogroups.com>
> > Sent: Sunday, March 10, 2002 7:29 PM
> > Subject: Re: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
> >
> >
> > > Thanks Tony.
> > >
> > > The speech board is the guts of one of those recordable greeting
cards.
> > > It's got it's own battery, so the power for it is separate (I'm
running
> > from
> > > the battery).
> > >
> > > I'm using an alligator clip lead to connect the ground of the speech
> board
> > > to the stamp breadboard. So it's not short and fat, but then the
servos
> > > aren't running from the speech board. They're connected directly to
the
> > > power/ground bus of the breadboard.
> > >
> > > Bob
> > >
Original Message
> > > From: <tony.wells@a...>
> > > To: <basicstamps@yahoogroups.com>
> > > Sent: Sunday, March 10, 2002 10:36 AM
> > > Subject: Re: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
> > >
> > >
> > > > Hi Bob,
> > > >
> > > > Two standard sanity checks:
> > > >
> > > > 1. Are you using separate regulation for the servos and or the
speech
> > > board?
> > > > I'd recommend separate regulation for both, with plenty of
decoupling
> > > > capacitors.
> > > >
> > > > 2. How is your grounding between modules- is it short but fat enough
> > > enough
> > > > to carry the current for the servos?
> > > >
> > > > regards,
> > > >
> > > > Tony Wells
> > > >
> > > >
Original Message
> > > > From: "Poniatowski Bob" <bobpony@m...>
> > > > To: <basicstamps@yahoogroups.com>
> > > > Sent: Sunday, March 10, 2002 5:00 PM
> > > > Subject: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
> > > >
> > > >
> > > > > I'm having what I think are some crosstalk/isolation problems.
This
> > is
> > > > > probably something simple, but I can't see it...
> > > > >
> > > > > I've breadboarded my circuit with a BS2. It's driving servos from
> > > outputs
> > > > > 0, 1, and 2, LED's on outputs 4, 5, and 7, and a trigger for a
> separat
> > e
> > > > > speech board on output 6 (triggered low). The breadboard and
speech
> > > board
> > > > > share grounds, but not power.
> > > > >
> > > > > After I trigger the speech board to start talking, if I then move
a
> > > servo
> > > > > the sound will turn to static.
> > > > >
> > > > > It also seems that I can't move the servos as fast as I want. A
> > friend
> > > is
> > > > > using the same servos and uses a PAUSE 10 after each movement.
The
> > best
> > > I
> > > > > can do is PAUSE 25 or weird things start to happen. The servo
will
> > stop
> > > > > before finishing it's set of movements.
> > > > >
> > > > > And if I try to run two servos at the same time they'll both start
> > fine
> > > > and
> > > > > then one of them will go into the weeds.
> > > > >
> > > > > I tried using a 1uF cap between power and ground where the servos
> > > connect
> > > > to
> > > > > the breadboard. That didn't help.
> > > > >
> > > > > I've disconnected the servos altogether, and just tried triggering
> the
> > > > sound
> > > > > chip. It's fine. If I tell the stamp2 to start moving a servo
> while
> > > the
> > > > > speech is still going though, I still get static (this is without
> any
> > > > servos
> > > > > connected to the board). So it's not the servo, it's something in
> the
> > > > > breadboard. Do I need a cap between power and ground at the
stamp?
> > > > >
> > > > > Thanks!
> > > > > Bob Pony
> > > > >
> > > > >
> > > > >
> > > > > 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 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 of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
> servos are Hitech 300's). The wall wort is 9V, 250mA. It's regulated
> through a 7805.
>
Bob, you're right, the wimpy supply is probably the problem. I have
measured current into 300-size servos at well over 1 amp when moving fast,
or hauling a heavy load.
Ray McArthur
solution?
--- In basicstamps@y..., "Poniatowski Bob" <bobpony@m...> wrote:
> I'm having what I think are some crosstalk/isolation problems.
This is
> probably something simple, but I can't see it...
>
> I've breadboarded my circuit with a BS2. It's driving servos from
outputs
> 0, 1, and 2, LED's on outputs 4, 5, and 7, and a trigger for a
separate
> speech board on output 6 (triggered low). The breadboard and
speech board
> share grounds, but not power.
>
> After I trigger the speech board to start talking, if I then move a
servo
> the sound will turn to static.
>
> It also seems that I can't move the servos as fast as I want. A
friend is
> using the same servos and uses a PAUSE 10 after each movement. The
best I
> can do is PAUSE 25 or weird things start to happen. The servo will
stop
> before finishing it's set of movements.
>
> And if I try to run two servos at the same time they'll both start
fine and
> then one of them will go into the weeds.
>
> I tried using a 1uF cap between power and ground where the servos
connect to
> the breadboard. That didn't help.
>
> I've disconnected the servos altogether, and just tried triggering
the sound
> chip. It's fine. If I tell the stamp2 to start moving a servo
while the
> speech is still going though, I still get static (this is without
any servos
> connected to the board). So it's not the servo, it's something in
the
> breadboard. Do I need a cap between power and ground at the stamp?
>
> Thanks!
> Bob Pony
board.
The servos can pull in a lot of current, along with browbouts, surges, RFI
and EMI noise interference.
I use a 4 AA cell battery pack for the servos, with the regular 9 volt
battery for the Stamp board. If your using Nicad's or NMH rechargeables, you
should hook up a 5th AA battery cell for the servos. Rechargeable batteries
are nice as they can provide a lot of current to prevent brownouts and
surges, whereas the dry cells don't do as well. Only the ground wire is
common to everything.
I also put in .01 bypass caps to cut down on the RFI that is generated. I
also run 1000ufd (works good) or 2200 mfd (works better) electrolytic caps
to minimize the brownout current surge problems you can get when the servos
kick in. The size of the caps depends on the sensitivity of the circuits.
The other thing is overall wire length for the different signal/data I/O
wires and such, you need to keep these as short as possible, so that they
don't act as antennas and pick up additional interference.
The servos can draw between 1 to 2 amperes of current when they stall or
stall when they slam into the stops. Under load the servos can suck up
current close to stall amounts. Sometimes when they jitter, they draw a lot
of current too. Sometimes one servo starts to run, causing another servo to
starve and flake out, setting of a cascade where all the servos flake out in
turn. Then the brownout condition causes the MCU or servo controller to
flake out.
On the Stamp boards, be careful, the VIN line provides "unregulated: voltage
to the servos, whereas the Stamp itself has a onboard 5 volt regulator.
Plugging in a 9 volt AC adapter can provide over 12 volts at low loads to
the servos. The problem is the I/O port line from the Stamp to the Servo
signal wire. Some servos can present higher than 5 volts to the Stamp, and
you could lose a I/O port pin, it it burns it out. Even the 6 volt AC
adapters can provide 7-10 volts to the servos and Stamp. A 12 volt AC
adapter may be feeding over 15 volts to the board.
I'd suggest putting in a 6 volt voltage regulator on the Stamp board, if
possible, and then run the output from the regulator to everything like
normal.
Original Message
From: mysemicon2000 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=J8JSVoNqiqOovoB8_ay7h-Y_DjYtKMemNDDF1w80D7Jd0m45GXT9FgcygvsuNLwLWmz2BksT-nFRz8aCFLKKxRHO0Xvc]semiconductor@p...[/url
Sent: Monday, March 11, 2002 3:54 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: Crosstalk Driving Servos?
I realized this also in my Parallax BOE Robot, any suggestions for a
solution?
--- In basicstamps@y..., "Poniatowski Bob" <bobpony@m...> wrote:
> I'm having what I think are some crosstalk/isolation problems.
This is
> probably something simple, but I can't see it...
>
> I've breadboarded my circuit with a BS2. It's driving servos from
outputs
> 0, 1, and 2, LED's on outputs 4, 5, and 7, and a trigger for a
separate
> speech board on output 6 (triggered low). The breadboard and
speech board
> share grounds, but not power.
>
> After I trigger the speech board to start talking, if I then move a
servo
> the sound will turn to static.
>
> It also seems that I can't move the servos as fast as I want. A
friend is
> using the same servos and uses a PAUSE 10 after each movement. The
best I
> can do is PAUSE 25 or weird things start to happen. The servo will
stop
> before finishing it's set of movements.
>
> And if I try to run two servos at the same time they'll both start
fine and
> then one of them will go into the weeds.
>
> I tried using a 1uF cap between power and ground where the servos
connect to
> the breadboard. That didn't help.
>
> I've disconnected the servos altogether, and just tried triggering
the sound
> chip. It's fine. If I tell the stamp2 to start moving a servo
while the
> speech is still going though, I still get static (this is without
any servos
> connected to the board). So it's not the servo, it's something in
the
> breadboard. Do I need a cap between power and ground at the stamp?
>
> Thanks!
> Bob Pony
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/
The problem was that the supply was just too weak for the three servos and
the stamp. I dug out a power supply from an old PC and used that to drive
everything. All three servos work great now, even at full speed.
But...the servos are still stomping on the signals in my sound card. I've
got a board that once was the guts of a recordable greeting card, and I'm
using one of the stamp outputs to trigger that to play while the servos are
running. As soon as the servo starts moving the sound turns to garbage.
Actually, I've seen this happen even when the servos aren't connected to the
breadboard. So it's something to do with the stamp driving one pin (where
it thinks there's a servo) and that signal interfering with the pin that
triggers the sound card.
I've tried a very short lead from the stamp output to the sound board, as
well as a very short ground between the two. Still have static whenever the
stamp tries to move a servo.
The sound card from the greeting card is triggered with a low, so I thought
maybe I needed a pullup resistor on the stamp output (to keep the trigger
from floating around when it's not being driven). Wrong, that didn't help
either.
I guess I haven't tried a very fat, very short ground between the greeting
card board and the breadboard with the stamp/servos. That's next I guess.
Any other ideas?
Thanks,
Bob
Original Message
From: Ray McArthur <rjmca@u...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, March 10, 2002 10:36 PM
Subject: Re: [noparse][[/noparse]basicstamps] Crosstalk Driving Servos?
> > So I'm thinking I've got too weak a supply for running three servos (the
> > servos are Hitech 300's). The wall wort is 9V, 250mA. It's regulated
> > through a 7805.
> >
> Bob, you're right, the wimpy supply is probably the problem. I have
> measured current into 300-size servos at well over 1 amp when moving fast,
> or hauling a heavy load.
>
> Ray McArthur
>
>
> 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/
>
>