Driver to drive?

[Joerg]

Hi Chris,

Protecting the rails is pretty easy. For example, a big old FET
driven by a reference such as the TLV431 (that one costs under a
quarter a pop). Set the resistor divider to wherever you want the
rails to top off. Just remember that prolonged exposure would cause a
FET to start glowing pretty quickly unless cooled. If you want the
fuse to blow under that condition you can fire a crowbar circuit
instead of holding things down with FETs.

Zener, TVS, MOV are not really to my liking in a situation where the
voltage differential between normal operation and catastrophe is
around a volt or so.


That's my feeling as well. I hadn't considered the FET approach. I
have used crowbars at times. On one buffer, I have 200mA SMD fuses so
if the overload into the output is continuous instead of just ESD, it
will blow to preotect the rest of the system.

The FET approach is more like a shunt regulator. In mission critical
designs you probably want both, the FET solution to handle brief
overages and a crowbar in case things do not turn back to normal within
a reasonable time. Meaning before plumes of smoke come out ;-)

Regards, Joerg

http://www.analogconsultants.com

 

[John Popelish]

Andrew wrote:

Mark,

First of all, thanks for bearing with me!

Secondly, the motor definitely is too hot. The housing of the motor
reached 225 degrees F after 3 hours of operation at 50% duty cycle.
This 225F is roughly 107C, which translates to roughly 203C in the
rotor, where the maximum rating for the motor is 155C.

The 3 hour test run consisted of 15 seconds drawing roughly 3 amps, 15
seconds drawing roughly 1 amp. This continued with roughly a 1 second
pause in between each cycle. The test setup was an arm with a 15lb.
weight on the end. All torque specs for this setup were calculated,
and the torque necessary to lift the arm is well below the maximum
continuous rating for this motor.

The motor is a high quallity brushed DC motor designed for continuous
use at 6A, 24V, max. The specs can be found here:

http://www.maxonmotorusa.com/files/catalog/2004/pdf/04_082_e.pdf

It the red column, 148867 motor.

From reading around at many sites, it seems that the inductance of this
motor is very low, and to use it with a PWM signal, the inductance
needs to be increase (by a DC choke). Maxon (the motor company) sells
some chokes, and indicates that they are necessary to be used with the
motor driver that they also sell and recommend for this motor.

I believe that with the driver that I am currently using, I need this
choke. With the inductance I currently have (no choke, just the
motor's 80uH), I am generating 9.71W due to the current ripple (via the
formula I posted earlier, assuming it is correcct). Dissipating this
9.71W raises temperature at the rotor (above the ambient) by roughly
123C more than ideal (ideal being no loss, 0W generated due to current
ripple). This temperature rise, coupled with the temperature rise that
is associated with the current flow through the windings (roughly 54C
for the application) brought the temperature well above the maximum
(brought it to over 202C assuming 25C ambient, where maximum rating is
155C).

Raising the inductance by 470uH (with a DC choke), raises total
inductance to 550uH, which changes the power generated by the current
ripple to 0.21W, reduced by a factor of over 46x! The new temperature
rise is roughly 2.6C, this is down from 123C! The new total
temperature rise of the rotor is 56.6C, making the rotor roughly 81C,
which is much more reasonable).

Hopefully my calculations are correct, and adding this DC motor choke
to increasea inductance will decrease the current ripple power loss and
in turn decrease the heat generated in the motor. I will let you know
how it goes.

It sounds lke you may benefit, significantly by adding an inductance
considerable lower than 470 uHy. Did you see my post suggesting a
type of low cost choke?

--
John Popelish

 

[Joop]

mike <spamme0@netscape.net> wrote:

Can you use a fet in place of the diode and run the gate off 12V?
mike

Yep, that is what I did for a PalmVx power unit. The Palm has a 4.2V
Li-Ion that I charged using an LM317L at 4.15V.

Behind this was an BS170. Source and drain were swapped compared to
normal use of the mosfet to prevent a discharge current due to the
internal diode.
I did not measured the leakage though. There might be better small
fets to choose from (pointers anyone?). From what I read in datasheets
of bigger fets, this goes up with lower Vds...

All in all it worked fine with a minimal amount of components. Size
15*5mm, small enough to be build into the clip-on GPS unit it was used
for.

One other thing is to limit the maximum charge current. I did that
simply by putting a resistor in series with the 12V input of the
LM317L.

Joop

 

[Rich The Philosophizer]

On Wed, 19 Jan 2005 15:17:03 +0000, Kryten wrote:

"Nicholas O. Lindan" <see@sig.com> wrote in message
news:yGuHd.549$cZ1.105@newsread2.news.atl.earthlink.net...
On Wed, 19 Jan 2005 02:44:40 GMT, "Kryten"
kryten_droid_obfusticator@ntlworld.com> wrote:

Try your own experiment: gently mist your nostrils with Perrier

How does that help?

In your case, it won't. You're beyond help. You have made up your mind,
and chosen the path of eternal death.

Good Luck!
Rich

 

[richard mullens]

Kryten wrote:

"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:m86tu0t26glpkdm49gsdn5i4siur5jnh79@4ax.com...


That would only delay the influence of the male engineer's most
effective form of birth control.


I'm a male engineer.

That is extremely effective birth control on its own.

It drastically reduces the proportion of women you meet, and the chances of
attracting one, let alone dating one.


Now if we could _please_ get back on topic, finding a job, because it makes
more difference to my life than anything else.

Looking further afield now.

Leicester and Peterborough look reasonably located. North of here but not
too north.

Anybody got any positive/negative opinions of these towns?

My Lonely Planet guide to Britain has Leicester in it but not Peterborough.

Has the latter got absolutely nothing of interest there?

There's a large cathedral and very fast trains to London - but not much else in my opinion.

 

[keith]

On Wed, 19 Jan 2005 08:25:51 -0600, Rhyanon wrote:

Backpedal away, dipshit -- you lose and you know it. HAH.

Lose to a top-poseur? Not possible.

You know that you're really a bottom. Why fight it?

--
Keith

 

[Kryten]

"John Larkin" <jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote in
message news:u90uu0t5meqb4v47vp3nu7uugf7tjh6akg@4ax.com...

Well, get out there and mingle.

As they say, there's no romance without finance.

No point shopping with a thin wallet!

There's a certain type of woman who likes engineers,
and there is a good supply of them.

I hadn't noticed, unless you mean 'homely' women.



> And they turn out to be an excellent lot.

 

[John Woodgate]

I read in sci.electronics.design that Jim Thompson
<thegreatone@example.com> wrote (in <81fou0h58a1sn7bngr7furemljvuug11h2@
4ax.com&gt about 'Cambridge (UK) engineer seeking job and home in
Cambridge', on Mon, 17 Jan 2005:

On Mon, 17 Jan 2005 22:04:06 +0000, John Woodgate <jmw@jmwa.demon.contra
spam.yuk> wrote:

I read in sci.electronics.design that Jim Thompson
thegreatone@example.com> wrote (in <gubou09td5nmr87226o3ji70dn649pr6dj@
4ax.com&gt about 'Cambridge (UK) engineer seeking job and home in
Cambridge', on Mon, 17 Jan 2005:
And the quality of life ?

Pretty good: that's why it's not cheap.

The OP opined that he got shabby quarters for Ł70/week. Is that "pretty
good" quality of life?

There's bound to be a range. Other aspects of 'life' in Cambridge UK are
good, even if your accommodation is not so good.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Winfield Hill]

John Larkin wrote...

The only use women have for engineers is to marry them.

Poppycock.

My wife relies on me for mechanical, cartographic and analytical
abilities. I rely on her for her creativity, intelligence, and
a remarkable discipline. And for an amazing ability to see what
I forgot, or need, and supply it. And most important, she helps
me to be a human, to love and to appreciate others. In turn, she
relies on my love for her, and for my watching out for her needs.
Speaking of which, I'm off. :&gt


--
Thanks,
- Win

 

[Kryten]

"Winfield Hill" <hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote in
message news:csna4001h07@drn.newsguy.com...

My wife

Sounds a splendid complementary component indeed.

If a similar quality alternative ever becomes available
then I will request a sample.

I will even pay shipping costs

K.

 

[John Larkin]

On 19 Jan 2005 19:55:44 -0800, Winfield Hill
<hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

John Larkin wrote...

The only use women have for engineers is to marry them.

Poppycock.

My wife relies on me for mechanical, cartographic and analytical
abilities. I rely on her for her creativity, intelligence, and
a remarkable discipline. And for an amazing ability to see what
I forgot, or need, and supply it. And most important, she helps
me to be a human, to love and to appreciate others. In turn, she
relies on my love for her, and for my watching out for her needs.
Speaking of which, I'm off. :&gt

Well, all that is why she married you.

John

 

[John Larkin]

On Thu, 20 Jan 2005 04:02:13 GMT, "Kryten"
<kryten_droid_obfusticator@ntlworld.com> wrote:

"John Larkin" <jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote in
message news:u90uu0t5meqb4v47vp3nu7uugf7tjh6akg@4ax.com...

Well, get out there and mingle.

As they say, there's no romance without finance.

Some women invest!

No point shopping with a thin wallet!

There's a certain type of woman who likes engineers,
and there is a good supply of them.

I hadn't noticed, unless you mean 'homely' women.

Generally not cheerleader, drop-dead gorgeous types (who are usually
more trouble than fun in the long term) but smart, interesting women,
and usually quite presentable. The wives and gf's of my engineering
buddies have always been an excellent lot.

John

 

[Kevin Aylward]

Kryten wrote:

"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:m86tu0t26glpkdm49gsdn5i4siur5jnh79@4ax.com...

That would only delay the influence of the male engineer's most
effective form of birth control.

I'm a male engineer.

That is extremely effective birth control on its own.

It drastically reduces the proportion of women you meet, and the
chances of attracting one, let alone dating one.


Now if we could _please_ get back on topic, finding a job, because it
makes more difference to my life than anything else.

Looking further afield now.

Leicester and Peterborough look reasonably located. North of here but
not too north.

Anybody got any positive/negative opinions of these towns?

My Lonely Planet guide to Britain has Leicester in it but not
Peterborough.

I lived in Peterborough for two years, just under a year ago. I quite
liked the place. Its good if you can live within walking distance of the
town as I did. Quite a few pubs with live bands in town.


Kevin Aylward
salesEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Aunty Kreist]

<uvcceet@juno.com> wrote in message
news:41ef49f3$2$woehfu$mr2ice@news.aros.net...

In <358ri3F4c2s3dU1@individual.net>, on 01/19/05
at 11:49 PM, "Aunty Kreist" <Aunty_Kreist@satanickittens.net> said:
---
Abortion _is_ murder.

That is opinion, not fact.

It's the taking of a life which, had it not
been intentionally interfered with, would have died of other causes.
---

Proof? I expect you to give cites.

Hey there. Take a look at the subject line of this thread for the answer
to your need for proof.

The only reason old scotty there got the death penalty was because he
killed his unborn son, aka, the fetus (as referred to by the other
murderers)

If killing an unborn child is not murder, how come scotty boy is gonna die
for doing it?

Um....because he also killed the human the fetus was attached to.

But, you raise a good point...when does a fetus become a human life?

 

[Kevin Aylward]

Aunty Kreist wrote:

I can't see the original post, but what the hell...

"John Fields" <jfields@austininstruments.com> wrote in message
news:9g1uu0hq4ct1nhms5be4s4mf8e95ib7gq9@4ax.com...
On Fri, 17 Dec 2004 01:37:02 GMT, "Pip" <Aetyr@nc.rr.com> wrote:

Hunh. I don't care if he lives or dies. He is guilty. Then again
lots of guilty people go free, and then, lots of innocent people go
to the chair. The only way you can cure that is to abolish the
death penalty. I oppose the death penalty because of its varying
application from state to state and judge to judge.

---
If you oppose the death penalty it shouldn't be be because of the way
it's capriciously enforced by man, it should be because a life which
you didn't create shouldn't be yours to take.

Ahmmm. Someone who unjustifiable takes a life should have his life
taken, imo. This is because life is *so* precious, it should never be
taken without good reason. Good reasons are to prevent or punish someone
from taking a life unjustifiable. The *only* reason I am against the
death penalty is because one must have absolute proof that the person
executed is guilty. Killing an innocent person is not an option in this
type of situation imo.

So, I absolutely believe that cold blooded killers should be executed in
principle, but must not be, due the lack of absolute proof of guilt.

---

Why John, how very white of you to inform Pip what her reasons and
emotions should be.


The law declaring the fetus a legal person disturbs me a great deal.

---
It shouldn't. From the moment of conception, when the two foreign
strands of DNA wrap around each other and form something that was
never there before, given time and lack of hate, a new human will
join us.

Complete nonsense. We only need you be concerned about a "life" after it
has first become *conscious*. Before something becomes conscious it is
no more then a carrot. What *makes* a life, that needs consideration for
its *own* sake, is a brain. Period.

---

Sure it isn't a malignant tumor? And still being so considerate,
telling people what should and shouldn't disturb them. That's quite
an ego you have there! I'm sure people will be polite, and not laugh
at you *too* loudly.


Its just one step to declaring abortion murder.

---
Abortion _is_ murder.

That is opinion, not fact.

I suppose this depends on the definition of "murder". Is it a legal one,
or one what we personally consider is murder. For me, certainly before
about 3 months there are simply no significant neuron connections in a
brain to make a conscious mind, so until that time, the foetus is no
more than a carrot.

Kevin Aylward
salesEXTRACT@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.

 

[Paul Burke]

Kevin Aylward wrote:

Someone who unjustifiable takes a life should have his life
taken, imo.
So, I absolutely believe that cold blooded killers should be executed in
principle, but must not be, due the lack of absolute proof of guilt.

Everybody who supports the death penalty should be shot.

Paul Burke

 

[Marco Dieckhoff]

On 2005-01-20, Parse Tree <account@domain.extension> wrote:

Aunty Kreist wrote:

Um....because he also killed the human the fetus was attached to.
But, you raise a good point...when does a fetus become a human life?

It doesn't. It's a parasite until it leaves the host.

Ah, "host". That's where comp.os.linux.networking comes in play, hm?

OK, I kill child processes every day on my host, hoping they don't
become zombies. And I don't feel guilty about that.


Sorry, but I can't see any reason why comp.os.linux.networking is
in the list of newsgroups to this topic.

Can anyone enlighten me? Otherwise please take care not to post
this thread to comp.os.linux.networking anymore. Thanks.

--
Marco Dieckhoff

 

[Rich The Philosophizer]

On Wed, 19 Jan 2005 19:55:44 -0800, Winfield Hill wrote:

John Larkin wrote...

The only use women have for engineers is to marry them.

Poppycock.

My wife relies on me for mechanical, cartographic and analytical
abilities. I rely on her for her creativity, intelligence, and
a remarkable discipline. And for an amazing ability to see what
I forgot, or need, and supply it. And most important, she helps
me to be a human, to love and to appreciate others. In turn, she
relies on my love for her, and for my watching out for her needs.
Speaking of which, I'm off. :&gt

Yikes! Hey, Win, are you God?

;^j
Rich

 

[Reg Edwards]

Proof? I expect you to give cites.

======================

How can cites provide proofs?

They are merely yet more opinions, no more reliable than the person who
didn't quote one.

Often more unreliable because of being taken out of context or misquoted.

Either you accept a statement or you dont accept it.

 

[Ian Stirling]

Chris Graham <chrisgr@shaw.ca> wrote:

I'm designing a product that includes a number of interchangable boards that
give various capabilities, each with its own small microcontroller and
sensors/actuators. Any modules in a system would be connected to a more
powerful main board (basically the reference design of a PDA). It must be
easy for the user to open the box and plug in new modules, or plug them into
sites on the outside, and also for third parties to provide modules that
also plug in.

Unfortunately, AIUI, there are no really cheap solutions to providing a
USB host, you pretty much need a fairly powerfull micro in order to talk
to the USB controller chip.
USB peripherals can be $0.99 and below.