On Sun, 10 May 2009, Horace Heffner wrote: > On May 9, 2009, at 12:45 PM, Kyle Mcallister wrote: > All it takes is a bolt (core) wrapped with a small sense coil and a > larger energizing coil. You hook the sensor coil to a transistor > gate and the the power coil to emitter and battery. As a magnet
I finally heard the secret history of this device when I was working at Boston science museum. Its original inventor was at the U. of Mass. The coils/transistor motor is used all over the place in those animated swinging pendulum paperweight toys. It's also an easy way to build a brushless motor with a spinning magnet. The inventor, the infamous engineer Harry E. Stockman, never made a cent off it. I guess it didn't get popular until his 1961 patent ran out. His original design was a "Dipping Bird" toy with a glass of water. But the glass was empty, and had coils wrapped around the rim, with a magnet in the bird's beak. Here's the original article from 1961 (also text below.) Secret of the Dunking Duck American Journal of Physics -- June 1961 -- Volume 29, Issue 6, pp. 374-375 Am. J. Phys. / Volume 29 / Issue 6 / LETTERS TO THE EDITOR Dunking Duck without Liquid (just a teaser article, gives only hints) American Journal of Physics -- May 1961 -- Volume 29, Issue 5, pp. 335-336 Am. J. Phys. / Volume 29 / Issue 5 / LETTERS TO THE EDITOR Here's the PDF file, but you have to be subscribed to the service: http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=AJPIAS000029000006000374000002&idtype=cvips&prog=normal LETTERS TO THE EDITOR vol29 #6 Secret of the Dunking Duck "In the description of a dunking duck without liquid, it was stated that the creature did not need a glass of water, but now, when the day of reckoning is here, it must be admitted that the duck needs a glass, or some kind of "water hole," although it does not contain any water(1). Around the edge of the cavity into which the duck sinks his magnetic beak, is mounted a tiny inductor with many thousands of turns of fine wire. the inductor has a tap, which provides the common-emitter connection of a switching transistor; see Fig. 1 (2)(3) The bottom part L1 of the inductor is connected to the base electrode b, and the upper part L2 is connected through the battery E to the collector c. The transistor and the small flashlight cell used as battery are hidden in the molded base upon which the duck gracefully stands. Owing to the large value of the mutual inductance M, the system oscillates at ultrasonic frequency, so that a direct collector current of several mA results, although only 1.5v is available as driving voltage. The ultrasonic oscillation is then damped out then the ducks body rests comfortably in nearly horizontal position, and this is done by means of the damping resistor R. If now the duck is tipped over in drinking position, the value of M suddenly increases, so that beta-A of the oscillatory system exceeds 1. Oscillations thus commence, with a short rise-time collector current pulse as a result, which violently drives the duck's beak all the way down. The emf in the inductor L1 then ceases, the collector current pulse vanishes, and the duck proceeds to raise its beak at a rate determined by the natural frequency of the mechanical oscillatory system, which frequency may be as low as 1cps. Since the mechanical oscillation represents the signal, the ultrasonic oscillation represents a superregenerative action, which on an oscilloscope closely resembles that from the conventional tube or transistor superregenerative detector. Fig 1 diagram http://amasci.com/graphics/dbird.gif "The components are not critical, and the duck dunks merrily away for several months, even on a small flashlight cell. As far as the ancient history of this duck is concerned, its originator cannot quite overcome the suspicion that it migrated from the land of the Scots; for once it is through with its last "dunk," it leaves the battery so thoroughly emptied of electricity that it might just as well have been short-circuited. This high utilization ability of the device may be largely attributed to the superregenrative action, since the current "spikes" in the collector circuit represent a fairly low value of average current. HARRY E. STOCKMAN Lowell Technological Institute (1)H. E. Stockman, Am J Phys 29, 335 (1961) (2)Patent App Jan 19, 1961 USPTO Washington 25 DC (3) Made by SER Co., Waltham Mass (((((((((((((((((( ( ( ( ( (O) ) ) ) ) ))))))))))))))))))) William J. Beaty SCIENCE HOBBYIST website billb at amasci com http://amasci.com EE/programmer/sci-exhibits amateur science, hobby projects, sci fair Seattle, WA 206-762-3818 unusual phenomena, tesla coils, weird sci
