Subject:
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Re: First Trains
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Newsgroups:
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lugnet.trains
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Date:
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Sat, 10 Feb 2001 16:03:22 GMT
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Viewed:
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1415 times
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> > Rich Thompson
>
> I've just checked my (UK) power adaptor, and it's rated at 10V. Being a
> fairly small box, I presume it's not too smooth. The output will be DC, but
> still have the ripples in it from the mains AC. Unfortunately I don't have
> an oscilloscope to put across it's output, but the LEGO train controller
> obviously has a capacitor in it to smooth the supply - check how the LED
> stays on for a while after you unplug it. Now this 10V could be peak, in
> which case it would smooth out to less than that, or it could be RMS (Root
> Mean Squared), which is the average voltage when completely smoothed. So,
> it may not be ideal for powering your RCX anyway. Digital circuits like
> this don't always need the exact voltage to run, but a smooth power supply
> is best. Rechargeable batteries are a lower voltage than regular ones, but
> still operate most equipment. A slightly higher voltage will probably just
> make it run a little warmer.
Actually, from what has been posted over in .robotics, it is not going to harm
the RCX to use the track power, except if you have 2 or 3 of the outputs loaded
down. The prefered input to the RCX is AC, because it contains internal
diodes, which if fed DC only one side of them will be used (vice both sets if
fed AC). However, for relatively low power draws (like shortish trains), then
DC should be fine. Otherwise, you are into the cut and splice feeder wires,
both internal and external to the motor. (one of the things I would like to
see is a motor with 2 connections, and a switch. That way, DCC could be
accomadated by a battery box (or smaller) DCC chip that mounts external to the
motor, and things like this would be possible with only minor cutting&splicing)
The limits are, IIRC, about 650mA draw from a RCX without overheating. This is
something like 3 train motors. Therefore, you should not have any problem with
running the train using the RCX as the power supply.
The RCX outputs do have overload protection built into them, so that should
aleviate some of your concerns. BUT! Don't blame me though, if you do manage
to burn something out
James
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Message is in Reply To:
 | | Re: First Trains
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| (...) You're forgetting something important - as the load on the motor increases (e.g. pulling more weight), the current it draws will increase { Power (W) = Voltage (V) x Current (A) }. You only regulate the voltage with the controller, not the (...) (24 years ago, 10-Feb-01, to lugnet.trains)
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