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I think you misuderstood what Larry said (or I misunderstood what you
said). I think Larry was saying that you should use the wall wart from
the train speed regulator, which is what Lego recommends. Also, I dont
see how you could burn out the diodes in the rectifier.* All the
discrete diodes in the RCX are 1N4002s, which can transmit at least 1
amp. However thay could have used a monolithic rectifier, but I dont
think Lego would produce anything that would fail like that.
*If youve done it, and youre sure thats what happened, then I stand
corrected.
Ross Crawford wrote:
> In lugnet.technic, Larry Pieniazek writes:
>
> > The wall wart from a speed reg can also power an RCX that has the power
> > connector
>
>
> You can do this but it's not recommended. As the RCX 1.0 has a bridge
> rectifier on the power input, it's recommended you use a 10v AC supply, to
> avoid buring out the diodes.
>
> ROSCO
>
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In lugnet.technic, Trevyn Watson writes:
> I think you misuderstood what Larry said (or I misunderstood what you
> said). I think Larry was saying that you should use the wall wart from
> the train speed regulator, which is what Lego recommends.
Yes. That is what I meant. I even believe sincerely that it's what I said. :-)
I am not sure who exactly within LEGO first recommended it but if you dig
hard enough in lugnet.robotics I believe you will find just such a
recommendation.... that you should use the wall wart from the speed reg (not
the speed reg itself) to power your RCX if you so desired.
If you put DC through a bridge you get 100% duty on one side and 0% duty on
the other, possibly resulting in asymmetric heating, contrast with AC which
gives 50-50 duty. Maybe that's what ROSCO was referring to.
However I would like to point out that the wall wart in my hand (from a 4558
I have handy) (which is stamped "Made In China for the LEGO Group", (sans
any (r) symbol, shame on them, but I digress)) takes in 120V AC & .12 A and
puts out 11 Volts AC & 7VA.
Do wall warts issued for 220 regions put out DC instead? If so that would
tend to be just as likely to burn out the bridge rectifier in the speed
controller if it is expecting AC, would it not? It may be a bit more rugged
than the one in the RCX though.
(and in fact hearsay at the time of the 1.5 introduction was that this was
precisely why it was omitted, that they had too many field returns of the
1.0 RCX with burned out bridge rectifiers... not that it was a cost savings
in manufacturing driven change)
++Lar
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In lugnet.technic, Larry Pieniazek writes:
> In lugnet.technic, Trevyn Watson writes:
> > I think you misuderstood what Larry said (or I misunderstood what you
> > said). I think Larry was saying that you should use the wall wart from
> > the train speed regulator, which is what Lego recommends.
>
> Yes. That is what I meant. I even believe sincerely that it's what I said. :-)
>
> I am not sure who exactly within LEGO first recommended it but if you dig
> hard enough in lugnet.robotics I believe you will find just such a
> recommendation.... that you should use the wall wart from the speed reg (not
> the speed reg itself) to power your RCX if you so desired.
>
> If you put DC through a bridge you get 100% duty on one side and 0% duty on
> the other, possibly resulting in asymmetric heating, contrast with AC which
> gives 50-50 duty. Maybe that's what ROSCO was referring to.
>
> However I would like to point out that the wall wart in my hand (from a 4558
> I have handy) (which is stamped "Made In China for the LEGO Group", (sans
> any (r) symbol, shame on them, but I digress)) takes in 120V AC & .12 A and
> puts out 11 Volts AC & 7VA.
>
> Do wall warts issued for 220 regions put out DC instead? If so that would
> tend to be just as likely to burn out the bridge rectifier in the speed
> controller if it is expecting AC, would it not? It may be a bit more rugged
> than the one in the RCX though.
>
> (and in fact hearsay at the time of the 1.5 introduction was that this was
> precisely why it was omitted, that they had too many field returns of the
> 1.0 RCX with burned out bridge rectifiers... not that it was a cost savings
> in manufacturing driven change)
I'd be a little surprised at a bridge rectifier which couldn't accept DC. Many
electronic appliances have them these days so that it doesn't really matter
what kind of wall wart you use, so long as the voltage is in the right range.
The wall wart can supply AC or DC, and it doesn't matter what the polarity of
the DC is.
Frank
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The current is going through two silicon diodes though, with attendant
.5 volt drop through each so consider if that will be a problem in this
application. Likely its not.
In lugnet.technic, Larry Pieniazek writes:
> In lugnet.technic, Trevyn Watson writes:
> > I think you misuderstood what Larry said (or I misunderstood what you
> > said). I think Larry was saying that you should use the wall wart from
> > the train speed regulator, which is what Lego recommends.
>
> Yes. That is what I meant. I even believe sincerely that it's what I said. :-)
>
> I am not sure who exactly within LEGO first recommended it but if you dig
> hard enough in lugnet.robotics I believe you will find just such a
> recommendation.... that you should use the wall wart from the speed reg (not
> the speed reg itself) to power your RCX if you so desired.
>
> If you put DC through a bridge you get 100% duty on one side and 0% duty on
> the other, possibly resulting in asymmetric heating, contrast with AC which
> gives 50-50 duty. Maybe that's what ROSCO was referring to.
> )
>
> ++Lar
Tom Napolitano tomnap@bersama.net
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In lugnet.technic, Larry Pieniazek writes:
>
> However I would like to point out that the wall wart in my hand (from a 4558
> I have handy) (which is stamped "Made In China for the LEGO Group", (sans
> any (r) symbol, shame on them, but I digress)) takes in 120V AC & .12 A and
> puts out 11 Volts AC & 7VA.
>
> Do wall warts issued for 220 regions put out DC instead? If so that would
> tend to be just as likely to burn out the bridge rectifier in the speed
> controller if it is expecting AC, would it not? It may be a bit more rugged
> than the one in the RCX though.
Ooops! Silly me!
Yes, the Australian (240v) train reg adapter is also 10v AC, so fine to use
with RCX.
ROSCO
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In lugnet.technic, Frank Filz writes:
> > (and in fact hearsay at the time of the 1.5 introduction was that this was
> > precisely why it was omitted, that they had too many field returns of the
> > 1.0 RCX with burned out bridge rectifiers... not that it was a cost savings
> > in manufacturing driven change)
>
> I'd be a little surprised at a bridge rectifier which couldn't accept DC. Many
> electronic appliances have them these days so that it doesn't really matter
> what kind of wall wart you use, so long as the voltage is in the right range.
> The wall wart can supply AC or DC, and it doesn't matter what the polarity of
> the DC is.
The main problem comes from the heat generated. This isn't a problem, unless
you're driving motors fairly constantly with your RCX, but can eventually
cause the diodes to break down.
Of course, when one half of the rectifier goes, you can always reverse the
supply polarity & use the other half, until it goes too!
ROSCO
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