Bridge rectifier and polarity 'oops'

[Wayne.]

I plugged into LTSpice the schematic for a bridge rectifier to test if
it could negotiate the change in DC polarity - which it did.

How much wear will the bridge endure before failing?

Along the train tracks, as it is now it is still in development, I have
segments that have reduced voltage and different polarity depending on
the function of the segment.

At this stage, I am only testing over a 3m section of track.

 

[Phil Allison]

"Wayne Kerr"

I plugged into LTSpice the schematic for a bridge rectifier to test if it
could negotiate the change in DC polarity - which it did.

** Will miracles never cease ......

How much wear will the bridge endure before failing?

** We might well ask - how much can a Koala bear ????

Toooot, toooot ...............




........ phil

 

[Cosmic Ray]

"Wayne." <abuse@hotmail.com> wrote in message
news:48f333ef$0$10588$5a62ac22@per-qv1-newsreader-01.iinet.net.au...

I plugged into LTSpice the schematic for a bridge rectifier to test if it
could negotiate the change in DC polarity - which it did.

How much wear will the bridge endure before failing?

Along the train tracks, as it is now it is still in development, I have
segments that have reduced voltage and different polarity depending on the
function of the segment.

At this stage, I am only testing over a 3m section of track.

If you are talking about a small model train set........

You need to know how much current the train(s) draw - I'd guess a small toy
train would draw < 2A, probably 300mA+ when running. Try something like a
W04 bridge. Be aware that a bridge will lose arount 2 x 0.7V. Your trains
may not run at full speed with the bridge in circuit.

 

[David L. Jones]

On Oct 13, 9:40 pm, "Wayne." <ab...@hotmail.com> wrote:

I plugged into LTSpice the schematic for a bridge rectifier to test if
it could negotiate the change in DC polarity - which it did.

How much wear will the bridge endure before failing?

That depends on a lot of factors, all of which you have not told us.
Generally, in a properly designed system with suitable margins, they
won't (or shouldn't) fail.

Along the train tracks, as it is now it is still in development, I have
segments that have reduced voltage and different polarity depending on
the function of the segment.

At this stage, I am only testing over a 3m section of track.

Your post really doesn't make any sense.
What are you trying to do here?

Dave.

 

[kreed]

On Oct 13, 9:40 pm, "Wayne." <ab...@hotmail.com> wrote:

I plugged into LTSpice the schematic for a bridge rectifier to test if
it could negotiate the change in DC polarity - which it did.

How much wear will the bridge endure before failing?

Along the train tracks, as it is now it is still in development, I have
segments that have reduced voltage and different polarity depending on
the function of the segment.

At this stage, I am only testing over a 3m section of track.

Well, if the change in polarity is happening across the AC or ~
terminals, and the voltage current ratings are followed, and the
frequency isnt high (you need a fast recovery type if so) the thing
shouldnt wear out for a long long time - possibly decades even.

 

[Eeyore]

"Wayne." wrote:

I plugged into LTSpice the schematic for a bridge rectifier to test if
it could negotiate the change in DC polarity

What is that supposed to mean ?

You're a student ? It's time you got back to doing bench work instead of
fucking about with wanky simulations that give you no feel for REAL
engineering.

Sorry, but it's true. Current graduates are almost worse than useless. In
fact I've seen (and rescued) an example where a new graduate nearly
completely wrote off a major project for a major UK plc. I understood the
main problem in under 30 seconds. Bet you never did electronics as a hobby
either. That's where the competent designers come from.

Graham

 

[Eeyore]

"David L. Jones" wrote:

Your post really doesn't make any sense.

That's modern education for you ! We're producing a generation of clowns,
idiots and know-nothings. And many are functionally quite illiterate and
innumerate too.

Graham

 

[Eeyore]

Cosmic Ray wrote:

Be aware that a bridge will lose arount 2 x 0.7V.

MORON ! 0.7V is a small signal current Vf for typical silcon diodes.

Power bridges are more in the region of 1V per diode at rated If.

Sigh !

Graham

 

[Eeyore]

kreed wrote:

Well, if the change in polarity is happening across the AC or ~
terminals, and the voltage current ratings are followed, and the
frequency isnt high (you need a fast recovery type if so) the thing
shouldnt wear out for a long long time - possibly decades even.

Uh ?

How did you understand his 'question' ?

Graham

 

[Jasen Betts]

On 2008-10-14, Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

Cosmic Ray wrote:

Be aware that a bridge will lose arount 2 x 0.7V.

MORON ! 0.7V is a small signal current Vf for typical silcon diodes.

the bridge should be rated for the stall current, when the motor is
running at full speed there will be less drop.

Bye.
Jasen

 

[Ross Vumbaca]

Hi,

Eeyore wrote:

Sorry, but it's true. Current graduates are almost worse than useless. In
fact I've seen (and rescued) an example where a new graduate nearly
completely wrote off a major project for a major UK plc. I understood the
main problem in under 30 seconds. Bet you never did electronics as a hobby
either. That's where the competent designers come from.

They gave a new graduate so much responsibility that he could write off
a major project? Sounds like the 'major UK plc' was a bit naive too.

Regards,

Ross..

 

[David L. Jones]

On Oct 14, 8:05 pm, Ross Vumbaca <ros...@au.com.optushome> wrote:

Hi,

Eeyore wrote:
Sorry, but it's true. Current graduates are almost worse than useless. In
fact I've seen (and rescued) an example where a new graduate nearly
completely wrote off a major project for a major UK plc. I understood the
main problem in under 30 seconds. Bet you never did electronics as a hobby
either. That's where the competent designers come from.

They gave a new graduate so much responsibility that he could write off
a major project?

It's possible, and you don't need much responsibility at all. I worked
on a project once that was worth around $10M that could be ruined if
you blew the one and only high end PCB prototype. All it would have
taken was one curious and/or careless grad to poke around and screw
something up.

Dave.

 

[Phil Allison]

"David L. Jones"

I've interviewed grads who couldn't tell me what the beta of a
transistor was.

** Old hat - everything is MOS these days.

Might as well ask them what the "mu factor " of a valve is.

One recent grad I interviewed (2 years industry experience) was
supposedly a "microcontroller specialist" but he couldn't name two
brands of micros.

** You mean there is ANOTHER brand besides PIC ??

He also bought in his thesis documentation so I
asked him a question from it. You guessed it, he couldn't even tell me
what a particular part of the circuit did, even when it was described
in his own text underneath it.

** Most students "outsource" their theses, these days.

Many will even "sub contract " sitting for exams.

Good business sense - really.

Simple questions sort out the morons quick smart.

** To be fair, even a supposedly "simple question " must not suffer from
ambiguity in the way it is presented - plus YOU must know all the possible
correct replies to it.

I also like to give them a loaded board and say "tell me anything you
can about it"

** ..... errr, its all covered in SMD, sir.



...... Phil

 

Sorry, but it's true. Current graduates are almost worse than useless. In
fact I've seen (and rescued) an example where a new graduate nearly
completely wrote off a major project for a major UK plc. I understood the
main problem in under 30 seconds. Bet you never did electronics as a hobby
either. That's where the competent designers come from.

Graham

Had a graduate recently apply for a job who could not calculate a
circuit with 1 zener, 1 battery and 1 resistor!

 

[David L. Jones]

On Oct 15, 12:11 pm, geoffjunks...@gmail.com wrote:

Sorry, but it's true. Current graduates are almost worse than useless. In
fact I've seen (and rescued) an example where a new graduate nearly
completely wrote off a major project for a major UK plc. I understood the
main problem in under 30 seconds. Bet you never did electronics as a hobby
either. That's where the competent designers come from.

Graham

Had a graduate recently apply for a job who could not calculate a
circuit with 1 zener, 1 battery and 1 resistor!

I've interviewed grads who couldn't tell me what the beta of a
transistor was.

One recent grad I interviewed (2 years industry experience) was
supposedly a "microcontroller specialist" but he couldn't name two
brands of micros. He also bought in his thesis documentation so I
asked him a question from it. You guessed it, he couldn't even tell me
what a particular part of the circuit did, even when it was described
in his own text underneath it.

Simple questions sort out the morons quick smart.
I also like to give them a loaded board and say "tell me anything you
can about it"

Dave.

 

[David L. Jones]

On Oct 15, 1:13 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:

"David L. Jones"

I've interviewed grads who couldn't tell me what the beta of a
transistor was.

** Old hat - everything is MOS these days.

I would have settled for that!

Might as well ask them what the "mu factor " of a valve is.

One recent grad I interviewed (2 years industry experience) was
supposedly a "microcontroller specialist" but he couldn't name two
brands of micros.

** You mean there is ANOTHER brand besides PIC ??

Apparently.
He hadn't even heard of PIC.

He also bought in his thesis documentation so I
asked him a question from it. You guessed it, he couldn't even tell me
what a particular part of the circuit did, even when it was described
in his own text underneath it.

** Most students "outsource" their theses, these days.

Many will even "sub contract " sitting for exams.

Good business sense - really.

Yep, they'll be able to climb that corporate ladder in no time.
Straight to the big-bickies for them.

Simple questions sort out the morons quick smart.

** To be fair, even a supposedly "simple question " must not suffer from
ambiguity in the way it is presented - plus YOU must know all the possible
correct replies to it.

I try to pick questions where an exact answer isn't required, or there
are many answers.
And I'm always happy to restate the question in different ways if they
don't understand, but never let the little buggers off the hook.
The idea is to find out if they have some general knowledge, or are
completely clueless. It's always easy to spot which after a few
minutes.

Phone and video conference interviews are harder.

I also like to give them a loaded board and say "tell me anything you
can about it"

** ..... errr, its all covered in SMD, sir.

"What *type* of SMD packages son?"
With some of the grads I've interviewed, I would have been impressed
if they knew what SMD was.

Dave.

 

[kreed]

On Oct 14, 10:01 am, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
wrote:

kreed wrote:
Well, if the change in polarity is happening across the AC or ~
terminals, and the voltage current ratings are followed, and the
frequency isnt high (you need a fast recovery type if so)  the thing
shouldnt wear out for a long long time - possibly decades even.

Uh ?

How did you understand his 'question' ?

Graham

I didnt really, just made guesses

 

[Eeyore]

kreed wrote:

Eeyore <rabbitsfriendsandrelati...@hotmail.com> wrote:
kreed wrote:
Well, if the change in polarity is happening across the AC or ~
terminals, and the voltage current ratings are followed, and the
frequency isnt high (you need a fast recovery type if so) the thing
shouldnt wear out for a long long time - possibly decades even.

Uh ?

How did you understand his 'question' ?

Graham

I didnt really, just made guesses

LOL !

Graham

 

[MisterE]

I've interviewed grads who couldn't tell me what the beta of a
transistor was.

One recent grad I interviewed (2 years industry experience) was
supposedly a "microcontroller specialist" but he couldn't name two
brands of micros. He also bought in his thesis documentation so I
asked him a question from it. You guessed it, he couldn't even tell me
what a particular part of the circuit did, even when it was described
in his own text underneath it.

Simple questions sort out the morons quick smart.
I also like to give them a loaded board and say "tell me anything you
can about it"

I graduated a few years back now. Electronic engeering needed an OP of 15 to
get in, so many useless people went in and dropped out. Austrlaian uni's
have a pass at 50%. Which means you can get a degree and only learn 1/2 the
stuff you really should know. Its not like america where anything below
about 80% is a fail. I graduated with about 90ish percent, the average was
56 (considering 50 in is the minimum pass you can see how low most were -
something like 90% of people from 50 to 55). Was pretty easy to get $80k job
after a year or so but all the graduate jobs started at $35-45k because the
skill level was so poor. Many people I know from my course now work at
jaycar or dicksmith shops. One is now an electricians apprentice. Others I
know work for $15/hour usually to companies that have won military
contracts.

Personally I blame the univerities, not so much the students (though many
are lazy). You simply are not taught most things anymore about circuit
design. A 4 year electronics degree probably only has 1 year of work that is
specialiased to electronics, the rest is general science, physics, and
mostly computer programming. You would be surprised how many couldn't tell
you what the beta of a transistor is, but how many could tell you have to
the pipeline in a pentium works. Its all about digital electronic circuit
design these days.

 

[Wayne.]

Wayne. wrote:

I plugged into LTSpice the schematic for a bridge rectifier to test if
it could negotiate the change in DC polarity - which it did.

How much wear will the bridge endure before failing?

Along the train tracks, as it is now it is still in development, I have
segments that have reduced voltage and different polarity depending on
the function of the segment.

At this stage, I am only testing over a 3m section of track.

I read through an article using a 6v dolphin battery and an LED. To
overcome the polarity in the dark, the author used a bridge rectifier.

What I am wondering, can this be relied upon when the train tracks
change polarity through a turn-out loop?

Oh, and no I am not a student. Just someone who want to do something
fancy with a train set that I am resurrecting after 20 years of sitting
idol.