5F30.60 - Relaxation Oscillators - Neon Bulb, Doorbell, and Strobe Lights

Code Number:
5F30.60
Demo Title:
Relaxation Oscillators - Neon Bulb, Doorbell, and Strobe Lights
Condition:
Excellent
Principle:
Relaxation Oscillators
Area of Study:
Electricity and Magnetism

Disclaimer

Equipment:
Neon Bulb Relaxation Oscillator Circuit, Variable Strobe Light Kits.
Procedure:

Video Credit: Jonathan M. Sullivan-Wood.

Connect the DC voltage source and turn up to the voltage indicated.  The neon bulb should flash with a rate of 2 to 5 seconds.  Changing the size of the resistor will change the time of oscillation.

The variable rate strobe units are the same as the neon circuit in that a capacitor charges and at some threshold voltage the strobe bulb triggers.  The capacitor voltage then falls and starts to recharge to the threshold voltage again.  The potentiometer control varies the resistor value and thus changes the charging time.  

A simple homopolar motor is made by attaching a magnet to the negative end of a AA battery and dropping the spiral copper spring over the battery.  Place a small dimple in the positive pole of the magnet to keep the spring centered while it rotates.  Observe the rotating coil closely and you will see it jump up and break contact repeatedly due to the slight contractions of the spring like coil when it is energized.

We have a variety of relaxation oscillators available.  Look at these webpages:

3A95.10 - Relaxation Oscillators

6-00.00 - Stroboscope (we have small variable frequency strobe lights available).

2B60.30 - Tantalus Cups

3D32.15 - Stadium Horn

4C30.25 - Geyser

4C31.30 - Drinking Bird

4C31.37 - Franklin's Pulse Glass Engine

5A40.70 - Kelvin Water Dropper

5F30.60 - Relaxation Oscillators - Neon Bulb, Doorbell, and Strobe Lights

10A06.10 - Relaxation Oscillators

13A10.10 - Perpetual Motion

References:
  • Stanisław Bednarek, "Amazing Vibrations Within the Homopolar Motor", TPT, Jan. 2018, Vol. 54, #1, Jan. 2018, p. 47.
  • George M. Caplan, "Simple DC Power Supply", TPT, Vol. 46, #1, Jan. 2008, p. 57.
  • Paul Chagnon, "Animated Displays V: Relaxation Oscillators", TPT, Vol. 32, # 7, p. 432- 436, Oct. 1994.
  • Richard Crane, "What Does the Drinking Bird Know About Jet Lag?", TPT, Vol. 27, #6, Sept. 1989, p. 470.
  • Earl M. Sawyer, "The Perpetual Light", TPT, Vol. 10, #7, Oct. 1972, p. 362.
  • Zenon Gubanski, "Capacitance by Relaxation Oscillations", TPT, Vol. 9, #2, Feb. 1971, p. 105 & TPT, Vol. 41, #2, Feb. 2003, p. 123.
  • Paul J. Ring, "Lecture Demonstration of the Validity of the Rules for Finding Equivalent Resistance and Capacitance", AJP, Vol. 46, #7, July 1978, p. 762.
  • James H. Vignos, "Comment on: 'Relaxation Oscillators: Electrical and Water'", AJP, Vol. 40, #2, Feb. 1972, p. 360.
  • Leonard Finegold, "Relaxation Oscillators: Electrical and Water", AJP, Vol. 39, #5, May 1971, p. 575.
  • D. Rae Carpenter Jr. and Richard B. Minnix, "E-240. Relaxation Oscillator", DICK and RAE Physics Demo Notebook, 1993.
  • D. Rae Carpenter Jr. and Richard B. Minnix, "E-400. Relaxation Oscillator w/Scope", DICK and RAE Physics Demo Notebook, 1993.
  • E-4f: "A Flashing Neon Light", Wallace A. Hilton, Physics Demonstration Experiments, p. 73.
  • Robert L. Wild, "150: RC Circuit-Relaxation Oscillator", Low-Cost Physics Demonstrations, p. 88.
  • "The Neon-Tube Relaxation Oscillator", The Physics Instructional Resource Association (PIRA) Newsletter, Vol. 3, #3, May 1988, p. 2.
  • Forrest M. Mims, "The Neon Glow Lamp", Experimenter's Corner, Dec. 1976, p. 111.




Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.