> Is there a ready made way to capture the period of every rotation

When you say "capture" do you mean store ?

If you stored results once / sec that's 246 samples - rpm, current and
voltage - for the 82 seconds. Any 18F PIC will have a block of 256
RAM, enough for storage and a few variables

rpm could be recorded as usec or multiples for the rev/sec. If you
took the 10,000 rpm figure of 166.666Hz, that's 6000usec. Similarly
9,990rpm would be 6006usec. Way down at 1rps it would obviously
be 1,000,000us

1,000,000 would require 5 bytes to store, and 2 bytes for 6,000

So you might decide to use 2 bytes for rpm storage and use a factor
when the storage would exceed 2 bytes. This is at 915 rpm

1000000/65536 =3D 15.26rps =3D 915.5rpm

As for current and voltage, they could also be stored as 2 bytes each.
Voltage change is unlikely to cover 5V, so if this was a 12V motor
you might assume that there was a 9V base value and measure from
9V to 14V.

Joe


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