[Fergy]

Okay, sorry, didn't have the stamina initially to look.... yeah, the AC line has been used before - in my last house, it was used for intercom units - we could talk or call from several points in the house - cool but not particularly secure. This was done by overlaying a signal on the AC that could only be detected by decoding units - it was out of phase from the standard AC and very low-level so it didn't affect standard AC devices. Still, for a system as complex as digital slot cars (worse actually than an internet connection because of the real-time urgency), and problems from external and internal noise sources, it just isn't as ideal as a complete DC system that is totally isolated from the mains voltage.

...and I don't want to know about UK electric sheep...

 

[Xlot]

I'm glad the thread is now in much more capable hands
Just two notes :

- I gleaned that the legal frequency limit to avoid EMI is 10 kHz - this comes from a Finn, Julius Wilkko a.k.a. lordjw, who as a matter of fact would be a very nice addition to SF's talent pool

- as for the maximum number of cars compatible with little response delay under DCC, I'm a great believer in the bumblebee theory (I suppose you know it) : since Davic runs well with 15 cars, I'm not worrying

Beppe

 

[Tropi]

Yes, Julius would be very welcome here - the more talent the better (especially better for the untalented like me)
He just seemed to disappear from SCI in mid-Nov-03.
I have messaged him via the EZBoard system and hope that he eventually takes a visit here.

 

[slotsutra]

Hi guys,
Fergy and the others do a very good job explaining digital slot tracks in a few lines.
But it seems you are not aware of some very fine sources on the internet about the subject:
At the university of Queensland some students wrote a thesis about digital slot racing end of 2003. It is all there for download as pdf files.
For example:
http://innovexpo.itee.uq.edu.au/2003/exhib...4106/thesis.pdf

There are more of them if you go to the following page :

http://innovexpo.itee.uq.edu.au/2003/exhib...byresearch.html

in order to find the documents on this long page do a search on the page (CTRL-F in IE) and look for 'slot car' or 'digital'. it will take you to the links that point to the pdf's.

The documents are +/-60 pages each but you do not have to read everything.

Happy reading.

 

[lordjw]

Hi Xlot, others

I finally registered myself to this forum. Nice to see people still discussing about DCC. If Scalextric system is cheap enough it can be that nobody bothers to build DCC though. It will be very interesting to try n' reverse engineer Scalex digital, but my first impression is that people who have designed the system really mean business. It may contain ASIC chips with heavy signal processing.

Julius

PS.
Xlot, our first RF link works in lab. It will hopefully be installed to a slotcar shortly.

 

[Xlot]

GREAT to hear from you again Julius !!

Look, we need to talk about a number of issues, which I beleve will lead to the much desired open source/ NMRA environment (you listening, Thomas ?)

The starting point is that Scalextric have adopted the LED emissor principle for lane changing. It's totally immaterial whether they saw my proposal or if they thought of it concurrently, what matters is that I believe the concept is not patenteable, and they have proved that it works - so this can be adopted universally
(OK, my only doubt is that there may be an even simpler method - Tropi was hinting darkly at ball-less, wireless optical mouse technology)

The next point is signal coding - it's not as essential, personally I'd be happy to live with a Scalextric monopoly - still, it would be nice if people could make aftermarket decoder chips
Here, I'm absolutely out of my depth - since you already mentioned it, could you elaborate? Oh, and are you saying that Scalextric's might not be DCC as we know it ?

Another point is lap counting : until now, nobody has been able to tell me how SCX and Scalextric make it work - any clue ?

Finally, how do you see your RF link alternative in this context ?

Ciao
Beppe

 

[Tropi]

Julius
MANY thanks for joining us here and we look forward, with enjoyment, to yours, Beppe's and other electro-boffins' continued attempts to educate the rest of us !

 

[lordjw]

Hi, Xlot, Tropi

So... you want to build independent digital system based on DCC? I think one alternative would be reverse-engineer Scalex system

(if possible), find out its command structure and see if it's viable to copy it. But as I mentioned, if you look at http://www.generics.co.uk/ - you can see that people who have designed Scalextric digital are experienced professionals. It may not be DCC type, may be more complicated voltage superimposed/modulated signal.

As I've said before at Slotcarillustrated forum: If digital prices are kept reasonable and the system is fully compatible with existing track/cars , there will be no need for reverse engineering or independent system. BUT... as always I'm interested to develope something new that would be beneficial to hobby.

RF link is too complicated for normal hobbyist to build. Naturally easy to install as ready made module. Also cost/car is higher than DCC.

LEDs at the bottom of a car are nice for lane change and lap counting. You can for example tell each car its individual LED frequency. Track sees LED flashing very rapidly and can determine which car went by according to frequency the LED just sent. Simple and efficient. We're talking about 1KHz frequencies.

Well, I'll have to catch up with you guys and this evening I'll read through most of the technical threads so that I can avoid repeating same things over and over.

Regards

Julius

 

[Xlot]

Julius,

fascinating reading about Generics (although they could have chosen a better name !) - one does feel the might of Scalex's power - but not to worry

OK, so we can live with a Scalex monopoly for the electronics package, at least for the time being - I do not believe price will be an issue, remember slot racers are not the target - toy buyers are, witness the reasonable price of SCX's Digital set
In this respect we are fortunate in being a minority, not like model trains, where DCC cost is significant

But the main implication is that LC operation is independent of the DCC control unit - this means that any track manufacturer can get into the business with a minimum investment, just by developing its own LC track piece - and since track manufacturers also make cars ....

So, come 2005 I can see a lot of clubs converting their 6 laner to a (much longer) 2 laner, with plenty of track left - too bad that corner marshalling effectively limits layouts and the number of curves you can have

Beppe

 

[Xlot]

Come to think of it, Julius, there's got to be another way for the lap counter : Scalex has no second LED, and SCX no LED at all !!

 

[lordjw]

Hi!

Thanks for slotsutra for interesting links.

Unfortunately university student teams were unable to produce working digital slotcar system. Not even one digitally controlled car if I did my reading right. They were able to construct individual parts of the system, but unable to compile all the elements into one working device. It was interesting to read how different teams approached the same problem though. Mainly it was lack of experience on hardware (schematic and PCB) design that caused these projects to fail. I guess they had also very limited time schedule for each project.

University world rule n 1 is: Publish or perish. Here the students were able to practice their technical documentation and writing. Usually this is the main reason for these projects.

I enjoyed reading, brings back memories when I studyed 10years ago. Wish I had known then all the stuff that I know now.

Julius

PS.
Beppe, surely the same LED can be used for LC and Counter/timer. Car LED sends car-identification signal to track LC and timer. It's the same signal for both. Can SCX system have IR LED on car windscreen? This way it could send data to control tower and activate LC and timer. I should see one system, then I could tell.

 

[slotsutra]

Lordjw,
Correct me if I am wrong but I thought these Australian students had the speed control technique working but not the lane switching part..
I also recall one of them having made a printed circuit board and publishing the programming code of the microcontroller.
they were even building this for HO cars !! not 1/32 scale.
Anyway there is a good part written about the possible methods to send commands to a pwm (pulse width modulation) controlled slotcar.