Hi Robert... It is unlike me to send mail messages with no added content.... , and I have seen cases in the past where it has happened, and I thought 'fool, who replies to a mail, but adds nothing to it?'... Well, I guess I would be one of those, but it is for a technical reason, and, I believe it is your mailer's fault... ;-) really! Wihtout starting yet another e-mail system war, at a time when we have been recently chastised for it... I would like to point out, that in your previous message, you replied to Mark *below* his signature line.... and you (/your mail client) did not quote his signature line... As a consequence... everything *after* the unquoted signature line (the two dashes followed by a space ) was truncated from the message... including my reply (which was not really contributing anything anyway....). As a consequence... the e-mail went to piclist without any added content ... even though I had added content... because the signature (and my comment) got stripped somewhere. Hence, I am now top-posting to ensure I avoid that. Although not formalized in the RFC for email, other usenet and netiquette RFC's stipulate that the three characters '-' '-' and ' ' (i.e. 2 dashes and a space) on a line by themselves delimit the body of an e-mail from the signature. Just something to be aware of... Also, having just been a victim o this, I will now endeavor to think less poorly of people who reply to messages without adding any content.... Thanks Rolf Rolf wrote: > Robert Bullock wrote: > >> -----Original Message----- >> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of >> Mark Rages >> Sent: Sunday, August 16, 2009 12:09 PM >> To: Microcontroller discussion list - Public. >> Subject: Re: [PIC] Bicycle Speedometer Project >> >> On Sun, Aug 16, 2009 at 9:44 AM, Robert Bullock wrote: >> >> >>> I would not rule out the use of a Hall Effect sensor quite so quickly. >>> >>> >> >> >>> ... >>> >>> >> >> >>> Researching more, I see that Infineon has one that looks perfect for your >>> application. >>> It is very low power, (typically 4 uA averaged supply current ) and is >>> designed for >>> Battery operation from 2.4 to 5.5 volts. >>> >>> Infineon TLE4913 >>> >>> Digikey TLE4913INCT-ND $0.92 qty 1 >>> >>> >>> >> As I mentioned in my message, "low-power" sensors are actually duty >> cycled. This one is on for 50 us, then off for 200 ms. It is not >> suitable for measuring the period of a bicycle wheel: the spoke magnet >> could easily pass by in the 200 ms that the sensor is off. Even if >> you find one with a fast enough sampling frequency, it will still >> quantize the period to that frequency. So short-term speed resolution >> will suck compared to a reed switch. These hall sensors are made to >> notice your cell phone or laptop being open, not to actually measure a >> period. >> >> The humble reed switch is best for this application. I'm not sure why >> everyone is looking for something else. >> >> Regards, >> Mark >> markrages@gmail >> >> > > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist