Bicycle Speed- Event Timers
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Posts: 46,084
A few weeks ago I asked for help on timing the revolutions of a
bicycle wheel using a BS2. Someone suggested the timer chips offer by
Peter Anderson (http://www.phanderson.com/) and I have since given
them a try and found that they worked very well. They are 8pin
PIC12C508's programmed to work as event or reaction timers. One type
has a 10usec resolution with a max time of 655msec and the other(the
one I used) has a 1msec resolution with a 65 sec max. The only
external circuitry is a ceramic resonator.
They work as follows. When pin 4 is momentarily taken low the timing
begins and when pin 5 is brought high the timing stops and the time
is send out on pin 6.
At first glance I thought they wouldn't work in my application
because I was measuring time for 4 revolutions of the wheel and using
the BS2 to count revolutions so I couldn't have the BS2 waiting with
a SERIN instruction as might normally be done. The solution proved
to be simple as had the BS2, after detecting the 4th revolution,
bring pin 5 of the timer high through a RC network(10K,0.1uF) which
gave a delay of less than 1 msec. This was less than the
resolution I needed but long enough for the BS2 to put the SERIN in
place to receive the output from the timer.
At $3.50 a chip they certainly a bargain. I bought his evaluation
kit ($16)which included both timers, 2 resonators, MAX232, a logic
probe(very handy) and misc parts. I like the fact that Prof. Anderson
presents his material in an experimental format which makes it more
of an educational experience rather than something you just plug in
and use.
bicycle wheel using a BS2. Someone suggested the timer chips offer by
Peter Anderson (http://www.phanderson.com/) and I have since given
them a try and found that they worked very well. They are 8pin
PIC12C508's programmed to work as event or reaction timers. One type
has a 10usec resolution with a max time of 655msec and the other(the
one I used) has a 1msec resolution with a 65 sec max. The only
external circuitry is a ceramic resonator.
They work as follows. When pin 4 is momentarily taken low the timing
begins and when pin 5 is brought high the timing stops and the time
is send out on pin 6.
At first glance I thought they wouldn't work in my application
because I was measuring time for 4 revolutions of the wheel and using
the BS2 to count revolutions so I couldn't have the BS2 waiting with
a SERIN instruction as might normally be done. The solution proved
to be simple as had the BS2, after detecting the 4th revolution,
bring pin 5 of the timer high through a RC network(10K,0.1uF) which
gave a delay of less than 1 msec. This was less than the
resolution I needed but long enough for the BS2 to put the SERIN in
place to receive the output from the timer.
At $3.50 a chip they certainly a bargain. I bought his evaluation
kit ($16)which included both timers, 2 resonators, MAX232, a logic
probe(very handy) and misc parts. I like the fact that Prof. Anderson
presents his material in an experimental format which makes it more
of an educational experience rather than something you just plug in
and use.