Subject:
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Re: rcx power circuit
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 6 Dec 2001 23:17:53 GMT
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Viewed:
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1708 times
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"Tilman Sporkert (webMethods)" wrote:
>
> Thanks for all the information. Just a few comments...
>
> > - rcx 1.0 (with power plug) • ...
> > * the external power source is rectified with a bridge
> > rectifier (4 diodes), filtered with 6 caps of 330uF each
> > and then stabilized with a voltage regulator ic. • ...
> > even attach an ac source (which i tested) and even
> > more than 12v (which i didn't test, don't sue me!).
>
> I have not verified this myself, but from discussions a long time ago I
> remember that the power for the motors is not run through the voltage
> regulator. Which means that you need to be careful with the input voltage. A
> 9.6V AC power adapter, like the one shipped with the train sets, is a good
> choice.
>
> > * the positive pole of the battery input is protected with
> > a diode against batteries put in the wrong way.
>
> No, it's part of the "mixing" circuit of the two power supplies. The
> external power goes through a diode, too. It's part of the rectifier. So
> whichever power supply has the higher voltage will supply power to the RCX.
> The other power supply is protected from this higher voltage by the diode -
> it blocks the reverse current. That's very important for the batteries -
> otherwise connecting an external power supply with a sufficiently high
> voltage would act as an unregulated charger for the batteries. Things would
> get really hot and ugly really quick.
>
> A few things to remember (somewhat simplified):
> - A diode usually drops voltage by 0.7 Volts. So if the batteries deliver
> 9V, you will only have 8.3V after the diode. A rectifier drops voltage by
> 1.4V, because the current has to go through 2 diodes.
> - If you run a AC through a rectifier and smooth it with a capacitor, the
> voltage will increase by a factor of 1.41 (square root of 2), minus the 1.4V
> drop of the rectifier of course. Or in other words, connecting a 12V DC
> power supply becomes 10.6V DC for the RCX (even though it's DC, it still is
> run through the rectifier), but connecting a 12V AC power supply would
> supply it with 15.5V DC - too much.
The 12 volt AC Train transformers work just fine. I've used one for
weeks at a time. Also, I believe Dacta sells the Train Transformer as
the RCX power pack.
Dean
--
Dean Husby
LUGNET Member #320
TFM's LEGO Workshop - http://www.akasa.bc.ca/tfm
The Vancouver LEGO Club - http://www.akasa.bc.ca/vlc/
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Message is in Reply To:
 | | RE: rcx power circuit
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| Thanks for all the information. Just a few comments... (...) ... (...) ... (...) I have not verified this myself, but from discussions a long time ago I remember that the power for the motors is not run through the voltage regulator. Which means (...) (25 years ago, 6-Dec-01, to lugnet.robotics)
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