Subject:
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Re: RCX Output
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 15 Dec 1999 22:43:04 GMT
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Viewed:
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606 times
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F'amos ... multiple networked RCX's would get pretty expensive. You
might want to consider a BASIC Stamp from Parallax or a BasicX device
from NetMedia.
http://www.parallaxinc.com/
http://basicx.com/
That is if you can tolerate a train system that isn't 100% pure LEGO.
Have fun,
- Nick -
"Avery, Amos E." wrote:
>
> Thanks for the much-needed input. My goal was/is to eventually build a
> fun, interactive multiple train layout with seemingly random events
> triggered by multiple networked RCX's. It looks like I may be designing
> a machine that manually turns the train rheostat to achieve my goal. The
> holidays could be interesting.
> F'amos
>
> -----Original Message-----
> From: Nick Taylor [mailto:ntaylor@iname.com]
> Sent: Wednesday, December 15, 1999 11:05 AM
> To: lego-robotics@crynwr.com
> Cc: Joel Shafer
> Subject: Re: RCX Output
>
> Hello Joel,
>
> Attempting to drive an RC servo directly from the RCX is NOT a good
> idea! The servo is a three wire device; +4.8V to +6.0V for power
> (usually the red wire), an approximately 40Hz pulse train of 1.0 to
> 2.0ms pulses at 0V and +5V logic levels (white or yellow wire), and
> ground (black wire). The pulse train does NOT power the servo motor,
> it only tells the chip in the servo where to go ... the red wire
> supplies power to drive the motor until an internal pot is turned
> to the point where the position of the servo equals the position
> commanded by the pulse width on the white wire.
>
> The RCX delivers a two wire output which changes polarity when a
> command is sent to reverse the motor ... and the servo's logic chip
> would not be very happy.
>
> I'm sure that you could build external circuitry to let the RCX
> control a servo, but I'll leave that exercise to the reader.
>
> Play well,
> - Nick -
>
> Joel Shafer wrote:
> >
> > So if you need a 1, 1.5 & 2ms pulse for controlling a servo and you said
> > the low setting in NQC = a 1ms pulse, are there other matching motor speed
> > settings to get a 1.5 or 2ms pulse?
> >
> > At 05:14 PM 12/15/99 +0000, you wrote:
> > > Hi F'Amos,
> > > I just now put a scope on the motor output ran an NQC motor test
> > > program. At OUT_FULL the motor output is about +7V DC. At OUT_LOW
> > > the motor output is a pulse train of 1ms 7V pulses at about 125Hz.
> > > The low level depends on the motor load ... almost 7V with no motor
> > > connected and approaching 0V with a stalled motor. NQC provides
> > > seven motor speeds ... and by increasing the duty cycle of the pulse
> > > train the average DC level to the motor is changed.
> > >
> > > RC servos are also controlled by varying the pulse width. For most
> > > servos a 1.5ms pulse tells the servo to go to the center position.
> > > Increasing the PW toward 2.0ms turns the servo CW and decreasing
> > > toward 1.0ms turns the servo CCW. The exact pulse width determines
> > > the exact stopping position. Servos that are modified for use as
> > > motors can never find a null position so they continue to turn
> > > seeking the nonexistent null. Unless the PW sent to the servo is
> > > very close to the null PW, the servo will turn at full speed. If
> > > the null PW is 1500us, then a 1550us PW will result in a slower
> > > speed.
> > >
> > > Hope this helps,
> > > - Nick -
> > >
> > > "Avery, Amos E." wrote:
> > > >
> > > > --- Nick Taylor <ntaylor@iname.com> wrote:
> > > > > If I'n not mistaken, the RCX output is pulse width
> > > > > modulated to control motor speed, while the train controller
> > > > > varies the DC voltage.
> > > >
> > > > Can anyone confirm the output characteristics of the RCX?
> > > > It is my understanding that PWM is used to control RC servos
> > > > and not to power them. Has anyone put a scope on the RCX's
> > > > outputs to see what they look like? If the info is available,
> > > > I'd be interested to know the exact output specs (eg. 0-9v 200ma).
> > > > F'amos
> >
> > Joel Shafer joel@connect.net
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Message has 1 Reply:
 | | Re: RCX Output
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| The Rcx uses 3 H-Bridge chips whose spec sheet is at: (URL) relevant specs are: * Small package (SOIC16) * Current limitation Low power consumption * Over temperature protection * Direct microcontroller compatible This IC drives directly small DC (...) (25 years ago, 16-Dec-99, to lugnet.robotics)
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Message is in Reply To:
| | RE: RCX Output
|
| Thanks for the much-needed input. My goal was/is to eventually build a fun, interactive multiple train layout with seemingly random events triggered by multiple networked RCX's. It looks like I may be designing a machine that manually turns the (...) (25 years ago, 15-Dec-99, to lugnet.robotics)
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