Thanks for all your suggestions. A few more details would probably help.
I have a G sensor with serial input. I can read this quite easily. This
gives me x and y acceleration of the vehicle which can then be integrated to
give speed and distance (approximately). I have a working program which
does all this.
I want some way to read the rpm at the same time. A serial port is out, as
this is already in use for the g sensor and my laptop has only one port.
Currently I am thinking of a inductive pickup on the spark plug. This has
the advantage that it is easy to attach (If you have ever seen under the
bonnet of a WRX, you will understand why this is important). There are a
few shareware programs on the net which use a inductive pickup wired to a
mic plug to generate a wave file. This is then analysed to produce a rough
hosepower graph.
My intention is to be able to track vehicle performance: go for a blast on a
flat bit of road and let physics tell me the vehicle horsepower. I want to
be able to transfer the set-up easily from one vehicle to another (I have a
car I want to play with, my flatmate has several racing motorbikes :-) ).
Measuring this requires a loop reading time, accellration and rpm. Little
or no display is required during data acquisition and any serious processing
can be left until afterwards.
As an aside, my flatmate wants to build a bike dyno. That is more straight
forward as you can use a hall sensor on the dyno drum (requiring less in the
way of electronics) and use a desktop computer. Hopefully anything I can
use for my project will be readily portable to his.
The result of this discussion appear to be that it will be difficult to
impossible to do all this in software. I can either continue without rpm
info (estinmating rpm from speed, a bit of a dodgy propisition) or build
hardware. However my electronic skills are limited, so anything complicated
will require assistance. I am willing to pay for this, but as this is a toy
project, the budget is limited.
If anyone is willing to give me a hand, or has some bright ideas, please let
me know.
Sean
--------------------------------------------
Sean Cross
IT Manager
CRM Group Ltd
PO Box 91-603
126 Vincent St
Auckland
Ph (9) 309 5959
Fax (9) 309 5939
Mob (25) 270 3466
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