Bridge rectifier and polarity 'oops'

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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.

Re: Bridge rectifier and polarity 'oops'
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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.

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

Dave.

Re: Bridge rectifier and polarity 'oops'



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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


Re: Bridge rectifier and polarity 'oops'

"Wayne Kerr"

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 **  Will miracles never cease ......


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

  Toooot,   toooot  ...............




.......   phil




Re: Bridge rectifier and polarity 'oops'


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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.



Re: Bridge rectifier and polarity 'oops'



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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


Re: Bridge rectifier and polarity 'oops'
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the bridge should be rated for the stall current, when the motor is
running at full speed there will be less drop.

Bye.
   Jasen

Re: Bridge rectifier and polarity 'oops'
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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.


Re: Bridge rectifier and polarity 'oops'



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Uh ?

How did you understand his 'question' ?

Graham



Re: Bridge rectifier and polarity 'oops'
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I didnt really, just made guesses :)

Re: Bridge rectifier and polarity 'oops'



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LOL !

Graham



Re: Bridge rectifier and polarity 'oops'

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

Re: Bridge rectifier and polarity 'oops'



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Sadly doesn't surprise me.

I was helping out my nephew with an op-amp problem a little while back. He
finally got the gain equation right with some prompting but then told me he
needed a calculator. I said "use the one on your PC" but he said he needed an
'expression evaluator calculator' ! For something like A = B + ((C+D)/(E-F)) !

I got the answer accurate to 1 decimal place in my head FFS. <sigh>

Now go to Asia and see if they can answer it !

Graham



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LOL !

Graham


Re: Bridge rectifier and polarity 'oops'



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Guffaw ! What the heck DO they actually do for those 3 years ?

Graham


Update and clarification: Re: Bridge rectifier and polarity 'oops'
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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.

Re: Update and clarification: Re: Bridge rectifier and polarity 'oops'
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Absolutely,

If the voltage on the tracks changes that may cause brightness changes
in the LED, that depends on how your loco is controlled.

Bye.
   Jasen

Re: Update and clarification: Re: Bridge rectifier and polarity'oops'



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And you don't need effing LTSpice to tell you that !

Graham


Re: Update and clarification: Re: Bridge rectifier and polarity 'oops'
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If you want to do something fancy then go with DCC:
http://en.wikipedia.org/wiki/Digital_Command_Control
Just buy the modules and controllers you need.

Dave.

Re: Update and clarification: Re: Bridge rectifier and polarity 'oops'
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If my layout was bigger, then DCC is definitely the path I would take.

There was an article in RailBrick e-zine discussing DCC and Lego trains,
plus there is several sites dedicated to or have information about DCC
and similar controls.

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