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From: Rich Webb
Subject: Re: Please help with PIC processor circuit.
Organization: Line Eater Memorial Fund
References: <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org> <email@example.com>
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Date: Wed, 09 Oct 2002 00:20:52 GMT
NNTP-Posting-Date: Tue, 08 Oct 2002 20:20:52 EDT
On 8 Oct 2002 08:56:12 -0700, firstname.lastname@example.org (LuuneeToon) wrote:
>Rich Webb wrote in message news:...
>> On 4 Oct 2002 21:36:10 -0700, email@example.com (LuuneeToon) wrote:
>> >It needs to be able to, using a photoelectric sensor, calculate wheel
>> >RPM. I will be using a C compiler for floating point math.
>> Is this for the control circuit to a 250 tph ball mill or for a
>> breadboarded homework project? If it's homework, the concept is to learn
>> by doing. Have you tried something that isn't quite working and need
>> some additional insight or just looking for a cookie cutter solution?
>Not sure what a 250 tph ball mill is. Probably something not related
>to my question. This isn't a breadboarded homework project for school.
It's a 250 ton per hour rock crusher. Needs a bit more robustness and
reliability than, say, a home-made anemometer. ;-)
>It's my own personal project, doing it on my free/spare time. However,
>I havn't been able to get anywhere. That's why I've posted this asking
>for help. If this circuit is relatively simple and someone can send it
>to me or post it up, or if you know of a website that will really help
>me get started, please post or e-mail me at LuuneeToon@yahoo.com
The most straightforward way may be to have the sensor triggered by a
patch of contrasting brightness on the rotating shaft. When it goes high
(or low) capture the counts in a free-running clock. WRT using
interrupts versus polling, each has advantages and disadvantages. You
may want to try them both. The number of counts between pulses is
linearly related to rotation rate.
How you get the pulse depends on what kind of photoelectric sensor you
have. Could be as simple as biasing it and wiring it to the input of a
TTL buffer. Probably better to use a simple op amp voltage comparator
Rich Webb Norfolk, VA
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