Subject:
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Re: Any interest in high amp. Train controllers?
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Newsgroups:
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lugnet.trains
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Date:
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Wed, 5 Mar 2008 02:51:47 GMT
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Viewed:
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14790 times
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In lugnet.trains, Steven Barile wrote:
> I was poking around looking at LM317 specs and can't seem to find the Max Vin.
> What's the max Vin we can plug into the controller... I see old laptop "wall
> warts" and inline "bricks" getting tossed all the time here at work. If this
> alone helps the controllers provide a more constant Vout I'd love to reclaim
> some of these power supplies and use them to juice the controllers!
>
> SteveB
>
>
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> > I also picked up some laptop style power blocks that are rated at 12v 3+ amps.
> > This allows the controller to run at over 2 amps continuously. We have several
> > trains in the club that have 3 or more motors. There's also a 5 amp version of
> > the LM350. I've built on controller with this, and am adding PWM to this as
> > well.
> >
> > Mat Clayson
The LM317 is made by a bunch of different manufacturers, so there's some
variation. But the original maximum suggested input is 35V or 32V between input
and output. But as I mentioned before, the difference between input voltage and
output voltage gets dissipated as heat. Also the the ripple capacitor in some
LEGO controllers are rated as low as 25v. And standard safe practice is to use
at least 50% above expected peak voltage. 100% above is better when using a
rectified AC power supply.
With an AC supply, after rectification the the DC peak can be about 40% above
the rated AC RMS value. The capacitor can reduce this some, but not much with no
load.
An ideal supply would be a regulated 12 to 13 volts DC. As it would have the
least waste heat, and wouldn't stress the cap. But with DC you are now running
all for the current trough 2 series diodes, instead of switching back and forth
between 2 pair. Diodes are rated at their average current, and some of those
used in the LEGO controller are only rated at 1 amp.
Mat Clayson
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Message is in Reply To:
 | | Re: Any interest in high amp. Train controllers?
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| I was poking around looking at LM317 specs and can't seem to find the Max Vin. What's the max Vin we can plug into the controller... I see old laptop "wall warts" and inline "bricks" getting tossed all the time here at work. If this alone helps the (...) (16 years ago, 4-Mar-08, to lugnet.trains)
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