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Old 01-26-2010, 03:10 PM   #12 (permalink)
dcb
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I know the controller doesn't put speed out there, that doesn't mean it should be ignored just because it isn't conveniently on the rs232 port.

but gps is expensive overkill, and not reliable in many situations (relies on radio signals, valleys, buildings, tunnels, etc.) when a wheel sensor probably already exists and can be read with a tiny bit of hardware and will work far more reliably.

And yes it will need calibrating, but you are going to add $50 to the pricetag for info that the vehicle already has otherwise.

I would suggest that you ask the controller folks to incorporate a speed signal onto the rs232 line, or make a simple proxy device that adds that info, i.e.
Code:
software -requestinfo-> speedmonitor -requestinfo-> cougar

cougar -response-> speedmonitor (adds current velocity to rs232 stream) -response+-> software
then compute distance based on last query, or have it somehow report actual distance.
Anyway, I wouldn't add gps expense and flakiness just for speed (the things take like 30 seconds to boot up?), it is simple and cheap and reliable to use what the car already has. And it is a critical piece of information when measuring vehicle efficiency.
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