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In lugnet.market.buy-sell-trade, Ondrew Hartigan wrote:
> > > > A stock Lego train controller uses an input of .7 amps and while this is
> > > > adequate for most, some have desired more power for there larger longer trains.
> > > > I have recently figured out how to both up the amperage to somewhere closer to
> > > > 1.2amps while also keeping the controller cool so that it does not over heat.
> > > >
> > > > Is this something that you would be interested in for around $65 a controller?
> > > >
> > > >
> > > > thank you for your input,
> > > > ondrew
> > >
> > > As someone who has built some heavy locomotives I would be interested. What are
> > > the main advantages of uping the amps?
> > >
> > > Cale
> >
> > Hi Ondrew,
> >
> > More power sounds nice, but I'd be even more interested in a controller than can
> > run high-load trains all day (such as at a show) without running hot. It sounds
> > like you're advertising this benefit as well, so I might be interested.
> >
> > -Jordan
>
> One of the big modifications I do is install a fan pointed directly at the
> source of the heat but the neat thing is the speed of that fan adjusts to the
> power setting of the controller while always spinning the correct way. I am also
> going to be doing a few other small things but I do not want to give it all
> away.
>
> This fan should more than solve the over heating issue. The other big benefit of
> higher Amps is you can run 4-6+ motors off one controller without issue. Now
> granted I have some testing still to do but all looks good at this point.
> OnDrew
>
> p.s. yes, the fan is fairly quiet.
The main component that is limiting current in a standard train controller is
the transformer (wall wart). The supplied transformer form LEGO has varied
between 500ma to 850ma .5Amp and .85Amp respectively. That's continuous duty.
You can pull a bit more for short periods of time.
The next problem is the diodes that are used to convert the AC output of the
transformer to DC, and the voltage regulator. The diodes supplied are rated at
1Amp average current. With an AC supply these should be fine up to 1.5 Amps as
they are off more then half the time. The regulator chip (lm317) is rated at 1.5
Amps. But the heat sink is most likely insufficient for that if you are running
continuously.
The amount of power (heat) the IC needs to dissipate depends on the (voltage in)
- (voltage out) x the amperes used, plus a small extra bit to run the chip. So
assuming a constant load (tain motors are not a constant load, but close enough
for this example), the controller chip burns about the same amount excess power
no matter what speed you run the trains at. So it's better to run the fan
continuously near peak voltage.
BTW a LEGO train motor under heavy load can run over to .4 amps!
My test have shown that you can run a unmodified LEGO train controller with
about a 1 amp load for hours on end at room temperature. And about 1.4 amps if
you add a larger heat sink or a fan to the setup. Both of these assume that you
have a transformer that can supply this much current as well.
Most of the controllers I own, and the ones for our club have been modified. I
replaced the LM317 chip with a LM350(3 amp version), adding a larger heat sink,
and replaced the diodes with 3 amp versions. I also increased the filter cap to
around 4700uf.
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
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Message has 3 Replies:
 | | 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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