Accelerometer | ADC | ADXL | Adxl20 | AVR | BasicStamp | BX-35 | BX28 | BX35 | COM3 | Compiler | Downloader | EEPROM | Electromagnet | GetADC | GP2D1 | GPS | I2C | IDE | Keypad | LCD | LCD+ | MIDI | Motors | Multitasking | Netmedia | Networking | PCB | PID | PlaySound | PWM | Relays | RTC | Servo | ShiftOut | SitePlayer | SPI | Stack | Timer | USB

I am setting up a BX-24 on a breadboard. I am powering pin 21 with
the breadboard's built-in +5V supply. I have the PC Com port on
pins 1-3, a Scott Edwards serial lCD as COM3 on pin 5, and an analog
input from the rectified output of a mic preamp on pin 13.

I worked with this debugging, etc for a couple of days and all was
fine. Yesterday AM when I turned on the power, every character
position of the lCD showed a black rectangle, and after a few
seconds I saw smoke from the back of the LCD.

The bottom line was that the BX-24 was toast but the LCD survived.
After finding no obvious problems I replaced the BX-24 and all was
fine. I thought possibly the problem was that my preamp stayed
powered up even when the BX-24 was shut down, so maybe I had a
problem applying voltage to a pin of a bx-24 that was unpowered?

No additional problems yesterday. Today, powered on in AM and same
situation, black characters on LCD. I immediately powered off, but
AGAIN the BX-24 was toasted. I am now on my third (and last!) BX-24
and would like to avoid losing this one if possible.

I am suspecting a problem with the +5V line at turn-on, (though why
it has only happened twice, and both times first thing in the
morning I can't imagine) so,
I am now coming off of the +15V breadboard supply through a 6V
regulator to pin 24, with pin 21 left unconnected. I noticed
(belatedly) that peter Anderson strongly recommends this method of
powering the BX-24 as opposed to putting +5v on pin 21.

Somehow my +5 must have been too high, I can think of no other
explanation for the smoke from the LCD.

However, if anyone has additional suggestions re protection of a bx-
24 I wouyld be happy to hear them.

-jim-

-jim-




(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Jim
You almost certainly have a power supply problem, or an earth
missing. About the only way to kill a BX24 is over voltage, or pulling
more than the rated current from a pin or the 5v regulated output pin.
How are you powering the LCD board?
I would unplug the bx24 and then power everything up, and check voltages
on the LCD power supply pin, the bx24 power supply pin, the earth pin
for the BX24, the preampearth pin, and the LCD erath pin. (All three
earths should be 0v).
Make sure the preamp pin is not supplying more than +5 to the BX24 input
you are using.
If that all looks OK, power off put in the BX24, power up and check all
the voltages again. NO pin on the BX24 should see more than 5v apart
from pin 24
neil

jstjohnz wrote:

> I am setting up a BX-24 on a breadboard. I am powering pin 21 with
> the breadboard's built-in +5V supply. I have the PC Com port on
> pins 1-3, a Scott Edwards serial lCD as COM3 on pin 5, and an analog
> input from the rectified output of a mic preamp on pin 13.
>
> I worked with this debugging, etc for a couple of days and all was
> fine. Yesterday AM when I turned on the power, every character
> position of the lCD showed a black rectangle, and after a few
> seconds I saw smoke from the back of the LCD.
>
> The bottom line was that the BX-24 was toast but the LCD survived.
> After finding no obvious problems I replaced the BX-24 and all was
> fine. I thought possibly the problem was that my preamp stayed
> powered up even when the BX-24 was shut down, so maybe I had a
> problem applying voltage to a pin of a bx-24 that was unpowered?
>
> No additional problems yesterday. Today, powered on in AM and same
> situation, black characters on LCD. I immediately powered off, but
> AGAIN the BX-24 was toasted. I am now on my third (and last!) BX-24
> and would like to avoid losing this one if possible.
>
> I am suspecting a problem with the +5V line at turn-on, (though why
> it has only happened twice, and both times first thing in the
> morning I can't imagine) so,
> I am now coming off of the +15V breadboard supply through a 6V
> regulator to pin 24, with pin 21 left unconnected. I noticed
> (belatedly) that peter Anderson strongly recommends this method of
> powering the BX-24 as opposed to putting +5v on pin 21.
>
> Somehow my +5 must have been too high, I can think of no other
> explanation for the smoke from the LCD.
>
> However, if anyone has additional suggestions re protection of a bx-
> 24 I wouyld be happy to hear them.
>
> -jim-
>
> -jim- >
> ------------------------------------------------------------------------
> *>.





(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Sorry to hear about your problems. I queried Peter Anderson about his
recommendation about using pin 24 versus pin 21, as I wanted to use
pin 21 with my own external 5V supply. He said "go ahead" and offered
no objections.

For the BS2 the recommendation is to use an external supply and not
rely on the internal regulator, so I didn't understand why the
recommendation for the BX24 would be different.

I've been running a couple of BX24's on pin 21 for awhile now with no
problems (knock on wood).

I wouldn't try your 3rd BX24 without sitting over top of it with DMM
in hand to monitor everything.

Harry Stoner

--- In basicx@basi..., "jstjohnz" <jim@j...> wrote:
> I am setting up a BX-24 on a breadboard. I am powering pin 21 with
> the breadboard's built-in +5V supply. I have the PC Com port on
> pins 1-3, a Scott Edwards serial lCD as COM3 on pin 5, and an analog
> input from the rectified output of a mic preamp on pin 13.
>
> I worked with this debugging, etc for a couple of days and all was
> fine. Yesterday AM when I turned on the power, every character
> position of the lCD showed a black rectangle, and after a few
> seconds I saw smoke from the back of the LCD.
>
> The bottom line was that the BX-24 was toast but the LCD survived.
> After finding no obvious problems I replaced the BX-24 and all was
> fine. I thought possibly the problem was that my preamp stayed
> powered up even when the BX-24 was shut down, so maybe I had a
> problem applying voltage to a pin of a bx-24 that was unpowered?
>
> No additional problems yesterday. Today, powered on in AM and same
> situation, black characters on LCD. I immediately powered off, but
> AGAIN the BX-24 was toasted. I am now on my third (and last!) BX-24
> and would like to avoid losing this one if possible.
>
> I am suspecting a problem with the +5V line at turn-on, (though why
> it has only happened twice, and both times first thing in the
> morning I can't imagine) so,
> I am now coming off of the +15V breadboard supply through a 6V
> regulator to pin 24, with pin 21 left unconnected. I noticed
> (belatedly) that peter Anderson strongly recommends this method of
> powering the BX-24 as opposed to putting +5v on pin 21.
>
> Somehow my +5 must have been too high, I can think of no other
> explanation for the smoke from the LCD.
>
> However, if anyone has additional suggestions re protection of a bx-
> 24 I wouyld be happy to hear them.
>
> -jim-
>
> -jim-




(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

BX24 POWER SUPPLY
Pin 24 is the input of the on-board 5v regulator. Pin 21 is the output
of this regulator.
It is perfectly acceptable to either: A) Supply 5.5 - 15v DC to pin
24 OR B) supply 5v to pin 21.
However, in my opinion it is slightly safer to use method A because if
you use method B) you must have an external 5v regulator otherwise you
run the risk of damaging the BX24 or the internal regulator. I say
again: In the interests of safety an external 5v regulator MUST be used
if you use method B.
If you are using method A), do not power other devices from pin 21
because if you exceed the current ratings of the onboard regulator you
are liable to damage the on-chip regulator. Even worse, if you manage
to poke more than +5 into pin21, you will kill the bx24.

My preferred method, which I use in ALL cases, no exceptions, is to
power pin 24 from an external 12volt regulator. I also include an
external 5v regulator on all my boards and use that for the peripheral
devices, 5v supply, so I never run the risk of damaging the BX24 on-chip
regulator, or the BX24 itself. An external regulator is cheaper than a
new BX24!!
neil harrybstoner wrote:

> Sorry to hear about your problems. I queried Peter Anderson about his
> recommendation about using pin 24 versus pin 21, as I wanted to use
> pin 21 with my own external 5V supply. He said "go ahead" and offered
> no objections.
>
> For the BS2 the recommendation is to use an external supply and not
> rely on the internal regulator, so I didn't understand why the
> recommendation for the BX24 would be different.
>
> I've been running a couple of BX24's on pin 21 for awhile now with no
> problems (knock on wood).
>
> I wouldn't try your 3rd BX24 without sitting over top of it with DMM
> in hand to monitor everything.
>
> Harry Stoner
>
> --- In basicx@basi..., "jstjohnz" <jim@j...> wrote:
> > I am setting up a BX-24 on a breadboard. I am powering pin 21 with
> > the breadboard's built-in +5V supply. I have the PC Com port on
> > pins 1-3, a Scott Edwards serial lCD as COM3 on pin 5, and an analog
> > input from the rectified output of a mic preamp on pin 13.
> >
> > I worked with this debugging, etc for a couple of days and all was
> > fine. Yesterday AM when I turned on the power, every character
> > position of the lCD showed a black rectangle, and after a few
> > seconds I saw smoke from the back of the LCD.
> >
> > The bottom line was that the BX-24 was toast but the LCD survived.
> > After finding no obvious problems I replaced the BX-24 and all was
> > fine. I thought possibly the problem was that my preamp stayed
> > powered up even when the BX-24 was shut down, so maybe I had a
> > problem applying voltage to a pin of a bx-24 that was unpowered?
> >
> > No additional problems yesterday. Today, powered on in AM and same
> > situation, black characters on LCD. I immediately powered off, but
> > AGAIN the BX-24 was toasted. I am now on my third (and last!) BX-24
> > and would like to avoid losing this one if possible.
> >
> > I am suspecting a problem with the +5V line at turn-on, (though why
> > it has only happened twice, and both times first thing in the
> > morning I can't imagine) so,
> > I am now coming off of the +15V breadboard supply through a 6V
> > regulator to pin 24, with pin 21 left unconnected. I noticed
> > (belatedly) that peter Anderson strongly recommends this method of
> > powering the BX-24 as opposed to putting +5v on pin 21.
> >
> > Somehow my +5 must have been too high, I can think of no other
> > explanation for the smoke from the LCD.
> >
> > However, if anyone has additional suggestions re protection of a bx-
> > 24 I wouyld be happy to hear them.
> >
> > -jim-
> >
> > -jim- >
> ------------------------------------------------------------------------
> *>.





(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

hi... just chiming in... i use a deep cycle 12v on pin 24 and it works
great.. i've also used a 9v and AAAs strapped together... the internal
reg works great so unless you ONLY have a 5v supply use the pin 24
method as it is much safer

Neil Jepsen wrote:

> BX24 POWER SUPPLY
> Pin 24 is the input of the on-board 5v regulator. Pin 21 is the output
> of this regulator.
> It is perfectly acceptable to either: A) Supply 5.5 - 15v DC to pin
> 24 OR B) supply 5v to pin 21.
> However, in my opinion it is slightly safer to use method A because if
> you use method B) you must have an external 5v regulator otherwise you
> run the risk of damaging the BX24 or the internal regulator. I say
> again: In the interests of safety an external 5v regulator MUST be used
> if you use method B.
> If you are using method A), do not power other devices from pin 21
> because if you exceed the current ratings of the onboard regulator you
> are liable to damage the on-chip regulator. Even worse, if you manage
> to poke more than +5 into pin21, you will kill the bx24.
>
> My preferred method, which I use in ALL cases, no exceptions, is to
> power pin 24 from an external 12volt regulator. I also include an
> external 5v regulator on all my boards and use that for the peripheral
> devices, 5v supply, so I never run the risk of damaging the BX24 on-chip
> regulator, or the BX24 itself. An external regulator is cheaper than a
> new BX24!!
> neil > harrybstoner wrote:
>
> > Sorry to hear about your problems. I queried Peter Anderson about his
> > recommendation about using pin 24 versus pin 21, as I wanted to use
> > pin 21 with my own external 5V supply. He said "go ahead" and offered
> > no objections.
> >
> > For the BS2 the recommendation is to use an external supply and not
> > rely on the internal regulator, so I didn't understand why the
> > recommendation for the BX24 would be different.
> >
> > I've been running a couple of BX24's on pin 21 for awhile now with no
> > problems (knock on wood).
> >
> > I wouldn't try your 3rd BX24 without sitting over top of it with DMM
> > in hand to monitor everything.
> >
> > Harry Stoner
> >
> > --- In basicx@basi..., "jstjohnz" <jim@j...> wrote:
> > > I am setting up a BX-24 on a breadboard. I am powering pin 21 with
> > > the breadboard's built-in +5V supply. I have the PC Com port on
> > > pins 1-3, a Scott Edwards serial lCD as COM3 on pin 5, and an analog
> > > input from the rectified output of a mic preamp on pin 13.
> > >
> > > I worked with this debugging, etc for a couple of days and all was
> > > fine. Yesterday AM when I turned on the power, every character
> > > position of the lCD showed a black rectangle, and after a few
> > > seconds I saw smoke from the back of the LCD.
> > >
> > > The bottom line was that the BX-24 was toast but the LCD survived.
> > > After finding no obvious problems I replaced the BX-24 and all was
> > > fine. I thought possibly the problem was that my preamp stayed
> > > powered up even when the BX-24 was shut down, so maybe I had a
> > > problem applying voltage to a pin of a bx-24 that was unpowered?
> > >
> > > No additional problems yesterday. Today, powered on in AM and same
> > > situation, black characters on LCD. I immediately powered off, but
> > > AGAIN the BX-24 was toasted. I am now on my third (and last!) BX-24
> > > and would like to avoid losing this one if possible.
> > >
> > > I am suspecting a problem with the +5V line at turn-on, (though why
> > > it has only happened twice, and both times first thing in the
> > > morning I can't imagine) so,
> > > I am now coming off of the +15V breadboard supply through a 6V
> > > regulator to pin 24, with pin 21 left unconnected. I noticed
> > > (belatedly) that peter Anderson strongly recommends this method of
> > > powering the BX-24 as opposed to putting +5v on pin 21.
> > >
> > > Somehow my +5 must have been too high, I can think of no other
> > > explanation for the smoke from the LCD.
> > >
> > > However, if anyone has additional suggestions re protection of a bx-
> > > 24 I wouyld be happy to hear them.
> > >
> > > -jim-
> > >
> > > -jim-
> >
> >
> >
> > ------------------------------------------------------------------------
> > *>.
> >
> > *>. >------------------------------------------------------------------------
>
>No virus found in this incoming message.
>Checked by AVG Anti-Virus.
>Version: 7.0.308 / Virus Database: 266.11.5 - Release Date: 5/4/2005





(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

At present I am working with a breadboard that has a built-in +5V
supply. Also I have some external 5v logic to power as well. I think
there must be something squirrely with that supply but it is
apparently intermittent as I have never seen anything wrong on the scope.

Right now I am using a 6-volt regulator off of the +15v supply to
power pin 24, and have no connection to pin 21. I am still using the
breadboard's +5 supply to power the other logic chips and the lcd panel.

In my final design I will go with separate +5 and +6 regulators but
right now it is a bit unnerving to wonder if I am going to smoke the
BX-24 when I flip on the switch.

-jim-

--- In basicx@basi..., Carol <carolkysela@y...> wrote:
> hi... just chiming in... i use a deep cycle 12v on pin 24 and it works
> great.. i've also used a 9v and AAAs strapped together... the internal
> reg works great so unless you ONLY have a 5v supply use the pin 24
> method as it is much safer



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Yes, those linear regs do put out some significant heat as soon as
you start drawing any worthwhile power from them. In an enclosed
PLASTIC box, this might get to be a problem for my project.

I have always supplied the BX-24 from the same 5v supply that runs
(ruins?) the rest of the system. So far I have never had a
problem. BUT, I have no other power sources coming in that might be
able to be wired wrong by me and then smoke important pieces.

I have no trouble with this technique.

I certainly would have no qualm using a 6v regulator to feed the on-
board 5v regulator of the bx-24. It is just that I have tight
space, and I do not want to have to use more space for the power
supply in the box.

Currently I am using a 1.5A LDO 5v regulator. I have a meduim size
finned heat sink on it and it gets warm if I run the LCD display
back light at full bright. I will eventually have another LCD and
I have been considering putting 2 regs in parallel.

I am not sure that it will work properly that way since the slightly
higher voltage variance regulator will supply everything until its
internal resistance drop causes the voltage to sag into the other
reg's range. I just do not know if this is a real issue or not.

-Tony

--- In basicx@basi..., "tombhandley" <gr13tbs@c...> wrote:
> Neil, you bring up some good points. I'd just like to add that
Linear
> regulators are not very efficient and the higher the input vs
output
> voltage, the more energy you waiste though small in this case. Old
> classic regulators typically have a drop-out voltage of around
2.5V.
> Newer Low Dropout regulators have a drop-out voltage in the mV
range.
> Note, this depends on the current. Instead of 12V I'd recommend as
> low a voltage as possible given the regulator's drop-out voltage
and
> current requirements.
>
> - Tom
>
> --- In basicx@basi..., Neil Jepsen <njepsen@i...> wrote:
> > BX24 POWER SUPPLY
> > Pin 24 is the input of the on-board 5v regulator. Pin 21 is the
> output
> > of this regulator.
> > It is perfectly acceptable to either: A) Supply 5.5 - 15v DC
to
> pin
> > 24 OR B) supply 5v to pin 21.
> > However, in my opinion it is slightly safer to use method A
because
> if
> > you use method B) you must have an external 5v regulator
otherwise
> you
> > run the risk of damaging the BX24 or the internal regulator. I
say
> > again: In the interests of safety an external 5v regulator MUST
be
> used
> > if you use method B.
> > If you are using method A), do not power other devices from pin
21
> > because if you exceed the current ratings of the onboard
regulator
> you
> > are liable to damage the on-chip regulator. Even worse, if you
> manage
> > to poke more than +5 into pin21, you will kill the bx24.
> >
> > My preferred method, which I use in ALL cases, no exceptions, is
to
> > power pin 24 from an external 12volt regulator. I also include
an
> > external 5v regulator on all my boards and use that for the
> peripheral
> > devices, 5v supply, so I never run the risk of damaging the BX24
on-
> chip
> > regulator, or the BX24 itself. An external regulator is cheaper
> than a
> > new BX24!!
> > neil




(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Neil, you bring up some good points. I'd just like to add that Linear
regulators are not very efficient and the higher the input vs output
voltage, the more energy you waiste though small in this case. Old
classic regulators typically have a drop-out voltage of around 2.5V.
Newer Low Dropout regulators have a drop-out voltage in the mV range.
Note, this depends on the current. Instead of 12V I'd recommend as
low a voltage as possible given the regulator's drop-out voltage and
current requirements.

- Tom

--- In basicx@basi..., Neil Jepsen <njepsen@i...> wrote:
> BX24 POWER SUPPLY
> Pin 24 is the input of the on-board 5v regulator. Pin 21 is the
output
> of this regulator.
> It is perfectly acceptable to either: A) Supply 5.5 - 15v DC to
pin
> 24 OR B) supply 5v to pin 21.
> However, in my opinion it is slightly safer to use method A because
if
> you use method B) you must have an external 5v regulator otherwise
you
> run the risk of damaging the BX24 or the internal regulator. I say
> again: In the interests of safety an external 5v regulator MUST be
used
> if you use method B.
> If you are using method A), do not power other devices from pin 21
> because if you exceed the current ratings of the onboard regulator
you
> are liable to damage the on-chip regulator. Even worse, if you
manage
> to poke more than +5 into pin21, you will kill the bx24.
>
> My preferred method, which I use in ALL cases, no exceptions, is to
> power pin 24 from an external 12volt regulator. I also include an
> external 5v regulator on all my boards and use that for the
peripheral
> devices, 5v supply, so I never run the risk of damaging the BX24 on-
chip
> regulator, or the BX24 itself. An external regulator is cheaper
than a
> new BX24!!
> neil





(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

I'm PWM'ing a DC motor with Timer2, so it's 8-bit PWM, which I'm running
at 450Hz. 30:1 gearing brings the output shaft to 1RPS when the motor
is at 1800RPM. I'd like the 1RPS to be as accurate and stable as
possible.

Currently, the motor approaches 1800RPM but, due to the relatively large
PWM steps, hunts about the target speed slightly as code alternately
accelerates and decelerates the motor with a Hall feedback loop. The
long-term average speed is correct.

Has anyone achieved an extra bit of virtual PWM by dithering its LSB?
The Hall feedback, for example, generates an interrupt at 30Hz. The
service routine calcs the interval and nudges the speed accordingly but,
if the interval change is small, no PWM change will occur if the
calculated PWM is well between 8-bit steps; that can be a relatively
stable state resulting in a slightly fast or slow speed that stays close
but is slightly and persistently wrong.

If I, however, add one-half a PWM bit of noise to the calculated speed
float value - at a faster rate than the feedback update - I figure the
average PWM will be more correct, resulting in less hunting about the
target speed. Any chance? Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Tom, I'm sure this will be stupid questions but for the dither are
using bipolar (ie: Add or Subtract)?. Have you considered PID? I ask
this as I'm dealing with this on my robot with two NuBotics
WheelWatcher WW02 encoders but I have not got that far yet. Your
dither idea is interesting. My initial approach was simple
measurement with a dead-band but I want to go with PID.

Thanks,

- Tom

--- In basicx@basi..., "Tom Becker" <gtbecker@r...> wrote:
> I'm PWM'ing a DC motor with Timer2, so it's 8-bit PWM, which I'm
running
> at 450Hz. 30:1 gearing brings the output shaft to 1RPS when the
motor
> is at 1800RPM. I'd like the 1RPS to be as accurate and stable as
> possible.
>
> Currently, the motor approaches 1800RPM but, due to the relatively
large
> PWM steps, hunts about the target speed slightly as code alternately
> accelerates and decelerates the motor with a Hall feedback loop.
The
> long-term average speed is correct.
>
> Has anyone achieved an extra bit of virtual PWM by dithering its
LSB?
> The Hall feedback, for example, generates an interrupt at 30Hz. The
> service routine calcs the interval and nudges the speed accordingly
but,
> if the interval change is small, no PWM change will occur if the
> calculated PWM is well between 8-bit steps; that can be a relatively
> stable state resulting in a slightly fast or slow speed that stays
close
> but is slightly and persistently wrong.
>
> If I, however, add one-half a PWM bit of noise to the calculated
speed
> float value - at a faster rate than the feedback update - I figure
the
> average PWM will be more correct, resulting in less hunting about
the
> target speed. Any chance? > Tom >
> Tom Becker
> --... ...--
> GTBecker@R... www.RighTime.com
> The RighTime Clock Company, Inc., Cape Coral, Florida USA
> +1239 540 5700




(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

> ... Have you considered PID?

Yup, but I haven't dug into that, yet. I suppose the I term would solve
it. Maybe worth a try. Thanks. Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

The darn thing about PID is it's incredibly hard to model in
software. You have to play with it in the 'real world' to pin down the
constants. Once you have done that, you can get really good results.

- Tom

--- In basicx@basi..., "Tom Becker" <gtbecker@r...> wrote:
> > ... Have you considered PID?
>
> Yup, but I haven't dug into that, yet. I suppose the I term would
solve
> it. Maybe worth a try. Thanks. > Tom >
> Tom Becker
> --... ...--
> GTBecker@R... www.RighTime.com
> The RighTime Clock Company, Inc., Cape Coral, Florida USA
> +1239 540 5700




(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Here's an extension of PWM dithering, with feedback, a sigma-delta
modulator. This method uses PWM output feedback to force the average to
the desired value, despite the available output resolution.

Perhaps the logical extreme of this notion is used in consumer audio
gear, a dithered _one-bit_ DAC that reproduces 16-bit signals. I should
be able to squeeze more from Timer 2's eight bits, I think.

DAC and PWM folks: this is worth taking a look at.

http://www.embedded.com/showArticle.jhtml?articleID=22101730 Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

http://www.embedded.com/showArticle.jhtml?articleID=162600189

"Spares and Tools"

"OK, so we do have a spare VW engine in the basement, though it's in
pieces. And yes, there is a leftover transmission there as well. Gentle
wife nudges me about the extra boat transmission in the living room.
Somehow I just don't see that anymore as it's buried under a couple
hundred feet of spare rope..."
Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Tom, I just checked that web site below and found it very helpfull.
Just exactly what are you trying to do?

- Tom

--- In basicx@basi..., "Tom Becker" <gtbecker@r...> wrote:
> Here's an extension of PWM dithering, with feedback, a sigma-delta
> modulator. This method uses PWM output feedback to force the
average to
> the desired value, despite the available output resolution.
>
> Perhaps the logical extreme of this notion is used in consumer audio
> gear, a dithered _one-bit_ DAC that reproduces 16-bit signals. I
should
> be able to squeeze more from Timer 2's eight bits, I think.
>
> DAC and PWM folks: this is worth taking a look at.
>
> http://www.embedded.com/showArticle.jhtml?articleID=22101730 > Tom >
> Tom Becker
> --... ...--
> GTBecker@R... www.RighTime.com
> The RighTime Clock Company, Inc., Cape Coral, Florida USA
> +1239 540 5700




(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Tom, ROLF!!!

I had a couple of VWs in the late 60's and early 70s. It's not the
spare engine, it's the valve clearance ;-) That's the main reason
those engines blew.

- Tom

--- In basicx@basi..., "Tom Becker" <gtbecker@r...> wrote:
> http://www.embedded.com/showArticle.jhtml?articleID=162600189
>
> "Spares and Tools"
>
> "OK, so we do have a spare VW engine in the basement, though it's in
> pieces. And yes, there is a leftover transmission there as well.
Gentle
> wife nudges me about the extra boat transmission in the living room.
> Somehow I just don't see that anymore as it's buried under a couple
> hundred feet of spare rope..." >
> Tom >
> Tom Becker
> --... ...--
> GTBecker@R... www.RighTime.com
> The RighTime Clock Company, Inc., Cape Coral, Florida USA
> +1239 540 5700




(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

> ... Just exactly what are you trying to do?

Part of the current project requires a precisely rotating low-mass
instrument platform. It ain't easy, I find. Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Jim;

I feel you pain about getting expensive. I'm going on a hunch here,
but try this. Disconnect the Preamp from the BX-24 completely, set your
DMM to measure AC, and connect it between the ground from the Preamp and
the ground of your BX-24 and PC setup. Now try reversing the AC Power
plugs on everything and anything that's plugged in, and see of any
combination makes the DMM read 120VAC or so. You're not defeating a three
prong, or polarized two prong (with a fat prong) AC power cord, are you? Good Luck!
Ken_S.

At 10:29 PM 5/4/2005, you wrote:
>I am setting up a BX-24 on a breadboard. I am powering pin 21 with
>the breadboard's built-in +5V supply. I have the PC Com port on
>pins 1-3, a Scott Edwards serial lCD as COM3 on pin 5, and an analog
>input from the rectified output of a mic preamp on pin 13.
>
>I worked with this debugging, etc for a couple of days and all was
>fine. Yesterday AM when I turned on the power, every character
>position of the lCD showed a black rectangle, and after a few
>seconds I saw smoke from the back of the LCD.
>
>The bottom line was that the BX-24 was toast but the LCD survived.
>After finding no obvious problems I replaced the BX-24 and all was
>fine. I thought possibly the problem was that my preamp stayed
>powered up even when the BX-24 was shut down, so maybe I had a
>problem applying voltage to a pin of a bx-24 that was unpowered?
>
>No additional problems yesterday. Today, powered on in AM and same
>situation, black characters on LCD. I immediately powered off, but
>AGAIN the BX-24 was toasted. I am now on my third (and last!) BX-24
>and would like to avoid losing this one if possible.
>
>I am suspecting a problem with the +5V line at turn-on, (though why
>it has only happened twice, and both times first thing in the
>morning I can't imagine) so,
>I am now coming off of the +15V breadboard supply through a 6V
>regulator to pin 24, with pin 21 left unconnected. I noticed
>(belatedly) that peter Anderson strongly recommends this method of
>powering the BX-24 as opposed to putting +5v on pin 21.
>
>Somehow my +5 must have been too high, I can think of no other
>explanation for the smoke from the LCD.
>
>However, if anyone has additional suggestions re protection of a bx-
>24 I wouyld be happy to hear them.
>
>-jim-
>
>-jim- >Yahoo! Groups Links




(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

I've corrected incorrectly used critical terms "rate" and "duty cycle"
in a few places below.

Two follow-ups:

PWM feedback is easy; the average duty cycle can be read on an analog
pin if an integrating capacitor on the analog input is charged through a
resistor from the PWM output. This forms a low-pass filter; it's values
should yield a RC time constant that is significantly longer than the
PWM rate period. If code then uses that analog input for feedback, the
effective dithered PWM resolution can be limited by the analog input
resolution - not by the PWM output resolution - which can be less.

I found, though, that no single PWM duty cycle is ever correct for an
entire rotation of my platform; integrated feedback shows that the
platform rotation rate varies roughly as a +/-1% sine (i.e., the rate is
fast on one side of rotation and slow on the other side), not good
enough for my requirements, and that changes somewhat with attitude and
temperature. Since the motor is geared 30:1 and I take a Hall tach from
the motor shaft, code has 30 (or 60) opportunities to correct PWM during
one output shaft rotation. I'm using a 30-bin FRAM buffer to maintain
30 independent period integrators and corresponding PWM duty cycles, one
for each 12 degrees of output shaft rotation, in a single multiplexed
closed loop. That has reduced the rotation irregularity, after some
tuning, to below 0.1% peak once it stabilizes in a few seconds from a
dead start.

That's superb for this simple system and I am a happy guy watching the
tach magnet stand absolutely still under a 30Hz strobe. Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700

Yahoo! Groups Links





(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

I said:
> ... I'm using a 30-bin FRAM buffer to maintain 30 independent period
integrators and corresponding PWM duty cycles...

Well, a few days later I am a wiser man. While the initial results
looked good, simply moving the apparatus wreaked havoc. That led to
trying to logically couple adjacent bins, essentially smoothing the lot
of them, but still I had what amounted to a train of locomotives, all
trying to drive the train.

Today, I gained insight. I realized that I am trying to change
something that naturally wants to do something else. I see now that it
is foolish to force anything exotic upon physics, but to, instead, just
accurately measure it and use that measurement in later data
manipulation to apply a correction mathematically, in lieu of correcting
physically. Much smarter.

This is an extension, I think, of the decision we make all the time: is
this function best implemented in hardware or software? In this case,
forcing physical reality to behave - making something rotate better - is
much more difficult than correcting the record of its behavior. The 30
FRAM bins still measure periods but don't feed back to the drive; they
provide, instead, the values I need to fix data later.

FWIW. Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )