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In lugnet.trains, Ralph Hempel wrote:
> I'm guessing that there is a cheap DCC module that we can use
> for things like sensors. If not, all that is really needed
> (I think) is a DCC decoder that can use the ACK pulse to
> indicate that something is here or not. Smarter sensors
> would be able to sense direction too.
>
> With a minimum of 30 msgs/sec and a maximum of about 75-100
> the polling of 16 sensors would be no slower than once every
> .5 seconds or so.
>
> The nice thing about this would be very little wiring. Just
> power the sensor off the track...
The basic DCC ack is defined as an increase of load on
the track of at least 60ma for 6ms +/- 1ms. Normally
this happens on a quiet track where all you have powered
is the decoder being programmed at the time. However, if you
have a bunch or trains on the track, all moving at various
speeds (all using pulse width modulation), the load is going
to be bouncing all over the place and it seems like it would
be difficult to pull the ack signal out of all that noise.
Special headlight effects, like available on the Digitrax
DZ143, could inadvertantly create load patterns that aren't
discernable from an ack.
However, there might be other ways, like introducing a
load the varies at a specific frequency and duration (chosen
to not conflict with the type of load you see from a mobile
decoder). You could use a bandpass filter to pick that
signal out of all the noise.
> Is there another way we can get lots of sensor inputs to
> an RCX, or are we better off just buying a "real"" DCC
> controller that can be driven from a PC???
Well, you can control LDCC from either a PC or even another
RCX (running NQC or BrickOS) using the LDCC IR Protocol.
Look at the bottom of this message for a decription of the
protocol:
http://news.lugnet.com/robotics/rcx/java/?n=269
The zip file for LDCC 1.05 has sample programs for
NQC and BrickOS illustrating the use of the protocol.
Thomas Waadeland has a cool page describing a small
automated layout using a second RCX (running NQC) to
check sensors and control the train using this
protocol (look under Train Control 3):
http://folk.uio.no/thomasw/robotics/creations.html
As Chris mentions, if you want to do automation using
a PC, you can use a Control Lab (or two) to get a lot
of sensor input into the PC and then issue LDCCIRP
commands from the IR tower to the RCX running LDCC.
Sorry if LDCCIRP is old news to you, but in reading
your messages it wasn't clear to me if that was the
case or not.
Cheers,
Mark
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Message has 2 Replies:
 | | Re: Trains, DCC, and pbForth
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| (...) So if I understand this correctly, my idea of inserting some kind of optoisolator or other power driver between the RCX and the track would interfere with LDCC receiving the ACK signal. Or could the sensor 1 input still be (safely) connected (...) (21 years ago, 21-Nov-03, to lugnet.trains, lugnet.robotics.rcx.pbforth)
| | | RE: Trains, DCC, and pbForth
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| (...) DOH! Of course. In the fire alarm business, we have a three state voltage out to the sensors. Usually the Vout is 24V and the device can respond when the voltage falls to 5 V. The devices have a power supply that is basically a big cap and a (...) (21 years ago, 21-Nov-03, to lugnet.trains, lugnet.robotics.rcx.pbforth)
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Message is in Reply To:
| | RE: Trains, DCC, and pbForth
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| (...) Dave, don't take ALL the fun out of driving your trains :-) How about being able to focus on just one train that you control, but automate things so the OTHER trains don't hit yours? Your description was great, except that it involves MANY (...) (21 years ago, 21-Nov-03, to lugnet.trains, lugnet.robotics.rcx.pbforth)
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