Also - If I had a strobe light on my bicycle (to stop people from running
into me) that "just happened" to match the required pattern, then .....
Richard
> -----Original Message-----
> From: Craig Lee [mailto:clee@ATTCANADA.NET]
> Sent: Tuesday, August 03, 1999 9:47 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: Traffic Lights (Was Car LED lighting etc ...)
>
>
> Hmm.... I wonder if the sensors will respond to invisible or nearly
> invisible light....
>
> I was in a cab once where the cab driver looked both ways carefully,
> then flicked his lights on and off at a certain rate.  To my surprise,
> it worked!!
>
> Probably something you wouldn't want to get caught at, but what you
> can't see...
>
> Craig
>
> > -----Original Message-----
> > From: pic microcontroller discussion list
> > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Matthew Fries
> > Sent: August 2, 1999 2:54 PM
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: Re: Traffic Lights (Was Car LED lighting etc ...)
> >
> >
> > > A method that I have seen used here in the US is a system that
> > extends the
> > > green to emergency vehicles by keying off a white strobe
> mounted on the
> > > front of the vehicle.  The strobe frequency is specific
> (and unknown to
> > > me).  You can spot these intersections that are suchly
> equipped- the
> > > optical sensor is mounted in a horizontal tube pointed
> along the traffic
> > > flow, attached to the same support that the light is connected
> > to.  I used
> > > to see these all over the Washington, DC area, but since
> I have moved to
> > > Austin, TX, I have not noticed any.
> >
> > There are 2 strobe lights atop the ambulance, and they
> flash 2 times each
> > in the course of 1 second. The pulse looks something like this:
> >
> >     __    __       __    __
> > ___|  |__|  |_____|  |__|  |___
> >
> >    Left Left     Right  Right
> >
> > I cannot be sure of the duty cycle, but I would bet that
> the receiver is
> > not that accurate.
> >
> > Maybe it just counts the pulses in 5 seconds.
> >
>