How does this work? A metallic toothed wheel with an inductive pickup next to it? Does the pickup need a magnet on one side (I think the hall effect devices work this way), or is the coil used as a variable inductor in a resonant circuit? It seems to me that by attaching small (1/4" dia x 1/8" thick) magnets equidistant around the rim, the balance effect would be minimized... Is there a reason other than this that cars have switched to a VR system? Thanks, Andy ----- Original Message ----- From: "Milosz Kardasinski" To: "Microcontroller discussion list - Public." Sent: Tuesday, October 19, 2004 1:13 PM Subject: Re: [PIC] Traction Control / Wheelspeed sensing > > >These sensors are inductive? So basically there is a metal > > >gear, and the sensor senses each tooth? > > > > > > > Yes, they are inductive and therefore a PITA to interface to, as the > > amplitude increases with wheel speed and the waveform changes polarity when > > the tooth moves away from the sensor. Your interface circuit has to be able > > to deal with all this to reliably detect the crossing point. IC's > > specifically for this application exist of course, but the hall-effect > > sensor refered to in another post looks like a much nicer solution. > > A VR sensor is the preferred method...all OEM's stopped using hall > effect stuff in the early 90's. Attaching magnets to stuff might pose > a problems with respect to balance and other aspects of the mechanical > system. > > I've been working with VSS sensors on automobiles lately and have > realized that they are robust little sensors. The LM1815 is a very > nice IC to use and solves all your noise and signal issues. > _______________________________________________ > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist _______________________________________________ http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist