The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: "Phil Allison"
Subject: Re: Detecting moment when a fast moving object passes over a line
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Sun, 24 Nov 2002 13:04:27 +1100
NNTP-Posting-Date: Sun, 24 Nov 2002 12:54:07 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"Richard Sim" wrote in message
> "Phil Allison" wrote in message
> > ** Nonsense - every club I know of has one or shares one with
> I'm from Australia too, and I know for a fact that a lot of small clubs
> there do NOT have an automatic lap counting system - a good number just
> a box that you push a button on that corresponds to which car passed the
> start/finish line.
** Funny your X trace suggests Canada ???
** How small is small ?? I live in Sydney, car clubs here have 100
I've been racing for about 13 years, so I know how things
> are organized in Australia quite well, so please don't try to say
> otherwise - the clubs in your area may very well have this kind of system,
> but that doesn't mean that they all do. My club used to borrow a system
> ORRCA for big races.
** You mean Dave Smith ??
> The story is much the same here in Canada (where I moved recently), and
> about everywhere else - the demand for a cheap alternative to the
> systems is quite large.
** The demand for such things is universal - and dopey.
> I may not have an electronics engineering degree, but neither do a lot of
> hobbiests, and that doesn't mean I know nothing of electronics. I did say
> that I'm a beginner, which I am, but not as much of a beginner as you have
> taken it to mean.
** To design a worthwhile RC car transponder system requires an
experienced design engineer or two plus a software writer - I was being
> > ** You have explained nothing. You mention Hall effect and then
> > how does your transponder output a signal to the receiver ? Is it a
> radio> > frequency signal ? If so what is the frequency ? Modulation ?
> I stated the manufacturer and models of the RF modules that I'll be using
> the origional post - the ES series that I'll be using operate on 916 MHz
> (FM), and the LC series that I'm prototyping with operate on 433MHz (AM).
** I have re- read your OP several times and think I have worked out
most of the ambiguities.
You require lap counting and maybe timing - is that right ??
You intend to use a common frequency for all cars and a single receiver -
You intend to gate the tranponder on as it crosses the line for a busrt of
code - right ?
Your question is about the best way to do the gating - right ?
The gating must be very brief so two cars cannot both gate at the
same time ( maybe 1 mS) and not possible by another means than line
crossing. Forget a static magnetid field - the cars are carrying one
around with them.
You MUST consider costs here. The system you may build will be far
from cheap in components alone and maybe not work 100% reliably and *that*
will make it worthless. You could possibly buy a second hand commercial
system for no more money.
The trandponders must be very sturdy or they will get broken -
most surface mount stuff is too fragile unless you encapsulate the lot. You
need to make at least 20 transponders - two sets of 10.
The gating business is a non-trivial problem. A loop around and
under the track carrying a AC signal at say 100 kHz is one idea then the
transponder had to have a receiver for that and a cct to power up the
transmitter which must have no delay in sending the code.
Anything relying on magnetic strips under the track or similar is
not on - the transponders will see another car as the same thing.
All the commercial jobs I know of avoid this idea like the plague -
it is just too complex. They have the transponders permanently on and pick
them up with a loop antenna, recording the exact time at the moment of max
One I partly reverse engineered had simple oscillators at spaced
20 kHz apart at frequencies from 170 to 260 kHz in each transponder. A
multi turn loop ( ribbon wire) picked op the signal and fed it to a pre-amp
and then a set of matching filters and detectors so it could be identified.
The only trap was a simultaneous passing of two cars - the
software sometimes failed to detect one of them.
Such a system is technically simple, low cost, rugged and much
easier to clone than your proposed one.
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup