Subject:
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Re: Use RCX motor output to switch devices
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 30 Aug 2002 03:54:46 GMT
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Viewed:
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732 times
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Here's a circuit you might try (please forgive the crudeness,
it's hand drawn):
http://home.surewest.net/markril/Lego/switch.gif
The transistor is easy to find (Radio Shack in the U.S. carries it).
The resistor is such a low value because the current being
switched is relatively high and it's important to keep the transistor
in saturation to avoid it overheating. Also, the RCX can output as
little as 6V when batteries are low so this ensures sufficient
base drive. The diode is there to protect the transistor when
the motor output on the RCX is switched to the wrong polarity.
A 1N914 will work fine (also available at Radio Shack).
I tried this circuit with a load of 120ma (didn't have the
resistors to do 280ma) and it works fine. The load got hot,
the transistor did not. ;-)
This all assumes a non-inductive load. If the load is inductive,
then you'll need to add some additional protection diode(s).
Also, don't try to hook up more than one switched device
to the RCX in this fashion. Otherwise, bad things can happen!
At that point, going the optoisolator route would be best.
Mark
"Da Byte" <dabyte@hotmail.com> wrote in message
news:H1GxyK.5yJ@lugnet.com...
> Hi all!
> The quest continues: I have now (with the help of the posters at
> circuitsonline.net) designed a circuit that should do the trick (clicking
> the link below should reveal a schematic representation of the circuitry).
>
> "http://home.tiscali.nl/~hito/schakeling.gif">
>
> Although I wonder if I'll need an additional diode in the RCX, resistance,
> transistor-circuit. Can anyone help me with designing a universal switch • for
> th RCX?
>
>
> Thanks in advance.
> R. Roodselaar
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Message has 1 Reply:
 | | Re: Use RCX motor output to switch devices
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| Oh yeah, I forgot to add my usual disclaimer for things of this nature: Do it at your own risk. If things aren't connected up quite right, you could fry your RCX. To be safe try the circuit first by connecting it to a 9v battery box (try both (...) (22 years ago, 30-Aug-02, to lugnet.robotics)
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Message is in Reply To:
| | Use RCX motor output to switch devices
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| Hi all! The quest continues: I have now (with the help of the posters at circuitsonline.net) designed a circuit that should do the trick (clicking the link below should reveal a schematic representation of the circuitry). "(URL) Although I wonder if (...) (22 years ago, 26-Aug-02, to lugnet.robotics)
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