Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!oliveb!tymix!antares!pnelson
From: pnelson@antares.UUCP (Phil Nelson)
Newsgroups: sci.electronics
Subject: Re: Car Detectors for Traffic Lights
Summary: How can I trigger them from my bicycle?
Message-ID: <456@antares.UUCP>
Date: 28 May 89 19:52:37 GMT
References: <18811@cup.portal.com> <3185@kitty.UUCP>
Reply-To: pnelson@antares.UUCP (Phil Nelson)
Organization: Tymnet QSATS, San Jose CA
Lines: 42

In article <3185@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes:
>In article <18811@cup.portal.com>, mmm@cup.portal.com (Mark Robert Thorson) writes:
>> Does anybody know how the car detectors for traffic lights work?  Are
>> they tuned circuits?  If so, what frequency?


>> More importantly, can they be activated from a distance?
>
>	On the assumption that a magnetic disturbance detector is involved,
>the answer is most likely no.  If memory serves me correctly, the Eagle
>Signal unit that I have uses a coincidence circuit which requires detected
>signals to be in-phase with the excitation oscillator, thereby minimizing
>the probability of external interference.
>
>	I won't even begin to ponder why you pose this question. :-)
>

 I have a related question, can they be activated without the metal mass?
The question has probably been asked before, it must be a common problem
for urban bicyclists; how do you get the left-turn light to change? I
havn't seen any solution though, is everyone waiting for George to do it?

 So, what kind of transmitter do I need to trip these things? Could it be
carried on a bicycle? The phase problem seems easy enough, simply build a
receiver-transmitter combination that retransmits in phase with received
signals. I wonder how much power I need though, if I have to pack 20lbs of
electronics and a 10' diameter antenna on my bike, it won't be worth it.
Also if I have to have a separate system for each style of detector things
could get complicated. Anyone tried anything like this?

 There might even be some money in it, if the price of helmets is any
indication. I can't believe I just paid $75. for 7 oz. of Styrofoam.


><>  Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp.
><>  UUCP {allegra|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry

-- 
Phil Nelson at (but not speaking for)                  OnTyme:NSC.P/Nelson
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