Subject:
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Re: Lego RC Set Questions - Overloading
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Newsgroups:
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lugnet.technic
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Date:
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Mon, 14 Jun 2004 22:27:51 GMT
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Viewed:
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2272 times
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In lugnet.technic, David Koudys wrote:
> In lugnet.technic, Avi Parvin wrote:
> > In lugnet.technic, Elroy Davis wrote:
> > > In lugnet.technic, Avi Parvin wrote:
> > > > I’ve just received my first Lego RC set, 8366.
> > > >
> > > > I have a few questions:
> > > >
> > > > 1. The remote control has two small pedals, what are there for?
> > > > 2. The battery/receiver unit has a gray power connector, what is it for?
> > > > 3. Is it possible to connect the standard mini-motor to the battery/receiver
> > > > unit without causing harm to any of them?
> > > >
> > > > Thanks in advance,
> > > >
> > > > Avi Parvin
> > >
> > >
> > > If I remember correctly (haven't had my RC out for a few months), 1 & 2 go
> > > together. That is, the two small pedals control any output that is connected to
> > > the gray power connector. As for attaching mini-motors, I have done that
> > > without having any issues.
> > >
> > > -Elroy
> >
> > Thanks Elroy.
> >
> > Here is another one:
> >
> > How many RC motors can be connected to the battery/control unit without harming
> > it? I was thinking about using 4 of them. Is there any sort of current limiter
> > in the unit?
> >
> > Avi Parvin
>
> I don't believe that would be a good thing--connecting more than two motors to
> the output. During one of rtlToronto's events, one of the competitors had 4
> motors connected. If I recall correctly, at the end of the competition, there
> was a melted hole in the RC unit, and one of the directional controls wasn't
> working anymore.
>
> http://peach.mie.utoronto.ca/events/lego/lego-022203-index.html
>
> Pics of the competition
>
> Talk to Wayne about the melted LEGO
>
> Dave K
Talking of overdriving Lego electrical components, I once used a 9V pole
reverser switch to connect 4 12V train motors on a robot to a 12V 6A power
supply. The robot used the wheels from the Big Cat Truck and was so powerful
that it would run along a bed, on a crumpled duvet, and climb a pillow that was
in the vertical position for someone to lean back on when sitting up on the bed.
Unfortunately, after a few runs, the pole reverser switch had melted internally
and the switch would no longer change position.
This is a more extreme example of overloading, but if a 12V motor takes 0.67A at
12V at full power, that's 2.67A through the switch. If an RC motor is rated at
7.2W at 9V, that's 1.6A for two motors and 3.2A for four.
Looks like the motor drive transistors in the RC unit are limited to about 2A,
but that's cos they were built for 2 motors!
If you need more power, consider an electronic speed controller from other RC
racing cars. I saw one that used 6 MOSFETs in parallel, such was the drive
current to the motor. You'll need a good heatsink though! If you know how, you
can modify a 7.2V one for 9V, but bear in mind that it would be designed to
operate with 7.2V NiCd packs, so you're probably best to stick with the lower
voltage. Some aircraft ones use 8.4V though, but they are often
uni-directional.
Do you have a no non-Lego rule in the robot competition?
Mark
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Message has 1 Reply:
 | | Re: Lego RC Set Questions - Overloading
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| (...) Standard RC car speed controllers are made to take from just a few amps to some as high as 500+ voltage wise they go from 6v to 24v I'm sure there is allot more but thats what I've seen. The speed controller in my Traxxas Emaxx for example is (...) (20 years ago, 14-Jun-04, to lugnet.technic)
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Message is in Reply To:
| | Re: Lego RC Set Questions
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| (...) I don't believe that would be a good thing--connecting more than two motors to the output. During one of rtlToronto's events, one of the competitors had 4 motors connected. If I recall correctly, at the end of the competition, there was a (...) (20 years ago, 14-Jun-04, to lugnet.technic)
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