Vehicle Speed Threshold Trigger

Electronics Computer Programming Q&A
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Joined: Thu Nov 12, 2009 9:39 am

Vehicle Speed Threshold Trigger

Post by MJR » Thu Nov 12, 2009 9:46 am

To assist with parking, I'm installing front- & side-view cameras on my truck. The vehicle is already equipped with a rear-view camera (with display & associated electronics), and I also have a video switcher to select desired view. As viewing any video while driving may be dangerous though, my goal is to disable camera outputs at, say, 5 mph.

I'd like to use a PIC to monitor vehicle speed and output a signal when speed threshold is met. The truck's PCM currently provides a 5V square-wave pulse signal, which appears to be close to the actual vehicle speed (mph)--eg. 12Hz = 10 mph. Any help utilizing a PIC to achieve the above goal would be greatly appreciated.

Many thanks!

Posts: 582
Joined: Tue May 09, 2006 12:44 am

Re: Vehicle Speed Threshold Trigger

Post by SETEC_Astronomy » Thu Nov 12, 2009 11:44 am

In the PIC run a timed loop of sufficient speed, within that loop count the number of tranisitions. A little math later you've got a finished project. It may be helpful to Google "PIC frequency counter".

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