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[DPRG] Speedometer

Subject: [DPRG] Speedometer
From: Triffid Hunter triffid_hunter at funkmunch.net
Date: Mon Jul 10 00:42:27 CDT 2006

A hall effect sensor should give you a great signal from a magnet, and is much 
easier to interface to a uC than an inductive pickup.

You could even put the magnet above the sensor, and allow the flux conducted 
by the spokes to give you your reading for even higher precision.

If you used something like a gumstix, you'd have enough ram to record the time 
of every pulse from your sensor, allowing you to build graphs of speed and/or 
acceleration vs time.

Balter Wiggin wrote:
> First off, i finished my line follower, and it works beautifully. I just 
> need to wait for my new motors to come in so i can replace the ones i 
> have now.
> 
> My next project will be slightly more advanced, and i require some 
> comprehensive help (meaning not spending hours on google looking for the 
> infinitescimal scrap of information that i need). What i am planning is 
> a combination RPM counter by means of a magnetic encoder, and a 
> speedometer, probably fashioned through some modification of a 
> tachometer. The purpose of this is to successfully measure the distance 
> and average speed of a bicycle piloted around White Rock Lake. I know i 
> will require either a microprocessor or a microcontroller for this 
> project, which is why im pursuing it in the first place. I'd prefer a 
> microprocessor as they are slightly harder to manipulate, but have far 
> more options. Also, i have created things like this many times on an 
> MCU, and id like to do something different.
> 
> By my calculations, the distance around the lake in question is about 
> 30,000 wheel rotations of a 26" wheel, which is a short integer. At 
> least i know that i dont need a terribly big EEPROM. But the main area 
> where i need help is the display and the setup of the MPU.
> 
> My question for today is:
> How would i begin to utilize a microprocessor? I know i would need a 
> stable power supply, a clock, and an EEPROM, but how would i put them 
> together? Which MPU is the best for beginners in the field? For that 
> particular processor, would i need a serial or parallel EEPROM?
> 
> All input is much appreciated, and i thank you for giving the time to 
> read that mess. Happy roboting!
> 
> -Walter

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