Well, if you really want to pick it out with a hall device, you need a magnet to activate the hall-effect. Take a look at www.allegromicro.com They have some interesting gear tooth sensors, as well as some good basic information about hall sensors. But the real problem you'll have is the resolution you want. If you really need 1 degree accuracy, you'll need a sprocket with 360 teeth (probably 720 depending on how precise you really need) That's a pretty big sprocket. How is the shaft driven? If it's gear reduced you could sense it farther up the geartrain and then calculate it based on the gear ratio. Good Luck -Denny ----- Original Message ----- From: "Phil" To: Sent: Friday, September 12, 2003 12:33 AM Subject: [EE]:Shaft position indicator > Hello All, > > I have a need to know the position of a shaft, within one degree accuracy, > that rotates at a speed of one revolution in two minutes. The shaft can only > make one turn. > > I have been experimenting with a Hall Effect device (UGN 3503U) trying to > count the teeth on the sprocket that turns the shaft. Although promising, I > only get a one millivolt difference between the tooth and the gap and the > Hall Effect device has to almost tough the sprocket. To make matters worse, > there is a lot of grease in the area. > > While searching for inspiration I came across a linear pot that uses a Hall > Effect device and so contacted the distributer. Unfortunately, they didn't > respond. > > Does anyone know of any information that will show me how to construct such a > linear pot? > > I could use a photo optic device to count the sprocket teeth and if I don't > get any further with the Hall Effect device that's what I'll do. However a > direct read out device such as a very precise linear pot would make the job > so much easier. > > -- > Regards, > Phil. > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body