> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of Marechiare
> Sent: 17 August 2009 18:26
> To: Microcontroller discussion list - Public.
> Subject: Re: [PIC] Bicycle Speedometer Project
> 
> > I've pretty much only seen reed switch type sensors, they
> > work so well I don't see the reason to go with another solution.
> 
> Tha's absolutely unacceptable reasoning for an Engineer. If something
> had been good for some time, it does not mean it would be good
> forever.

On the contrary I suggest that is perfectly sound reasoning for a good
professional engineer; you don't change a proven solution without a very
good reason.

Cost, performance and durability are good reasons.  Wanting to 'play'
with a newer/alternative technology is usually not, at least not in a
commercial sense.  Obviously the OP's project is a one-off with no
commercial considerations so he is free to choose whatever system he
would like.

My parents bought me a Raleigh "Sensor" bike after I passed my O levels
exams some 22 years ago.  It was one of the first bikes to come with a
(rather large) computer and it used a reed switch to sense speed.  I
still have the bike, and the computer still works.  Since then many
different companies have made bike computers that use reed switches.  If
no unacceptable shortcomings have appeared in the last 22 years I think
it's safe to suggest that it's a reasonably robust solution.  

Regards

Mike

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