Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!accelerator.eng.ohio-state.edu!phao.eng.ohio-state.edu!abali From: abali@phao.eng.ohio-state.edu (Bulent Abali) Newsgroups: sci.electronics Subject: Re: Hobby laser show system Message-ID: <1185@accelerator.eng.ohio-state.edu> Date: 6 Dec 88 21:28:38 GMT References: <2110@puff.cs.wisc.edu> Sender: news@accelerator.eng.ohio-state.edu Reply-To: abali@phao.eng.ohio-state.edu (Bulent Abali) Distribution: na Organization: Ohio State Univ, College of Engineering Lines: 43 In article <2110@puff.cs.wisc.edu> boettche@gumby.cs.wisc.edu (Michael Boettcher) writes: >A bar magnet, or another electro-magnet is mounted on a pivot, with a >mirror on the opposite end. The polarity of the magnet end within the >fields of the four outer magnets would be the same. The inner magnet, >connector, and mirror would all be very low mass, for low inertia. >Michael Boettcher boettche@gumby.cs.wisc.edu Mechanical control of the mirror as described above can be difficult. Following is what I would try: reflected beam . ---------- . / (mirror) I . / Laser . . . beam . . . . . ..x I / ---------- / Mirror is rotating freely at very high speed, around a shaft centered at x. Any speed above 1800 rpm (30 revolutions/sec) should be adequate. We can track the position of the mirror by an optocoupler and a circular grid attached to the shaft. Laser is off most of the time. Whenever mirror comes to the desired angle, we pulse the laser on. Since mirror is revolving at very high speed, the pulsed beam appears continously on to the eye. Advantage of this method: All electronical; position of the mirror is not controlled mechanically. Mirror can rotate at any speed and no calibration is necessary. Disadvantages: 1)Angle of the beam can be changed only in a 2-D plane. 2) Can you turn the laser on-off in the desired interval? -=- Bulent Abali Ohio State Univ., Dept.of Electrical Eng. 2015 Neil Av. Columbus, Ohio 43210 abali@baloo.eng.ohio-state.edu