5D40.50 - Neon Bulb Trigger - Avalanche Trigger

Code Number:
5D40.50
Demo Title:
Neon Bulb Trigger - Avalanche Trigger
Condition:
Excellent
Principle:
Switch Trigger
Area of Study:
Circuits
Equipment:
0 - 150 Volt Power Supply, Neon Bulbs (Wheat and Bulb Style), and Green or UV Laser Pointer.
Procedure:

Plug the neon bulb into the power supply and turn the voltage up until the bulb comes on and note that voltage.  Turn the voltage down until the bulb is completely off.  Turn the voltage back up until it is about 5 to 10 volts below the voltage that will turn the bulb on.  You can now trigger the bulb to turn on by shining a laser onto the filament on the inside of the bulb.

For the large neon bulb you should be able to turn the voltage up to about 75 volts and then turn the bulb on by shining a green laser pointer onto the filament.  For the UV laser pointer the voltage needed to trigger the bulb is about 70 volts.  Note that once this bulb is triggered you will need to turn the voltage down to about 60 volts to turn off the bulb.

For the small "wheat" style neon bulbs the voltage needed to trigger it with the green laser pointer will be about 62 volts.  For the UV laser pointer the voltage needed to trigger this bulb will be about 55 volts.  Note that once this bulb is triggered you will need to turn the voltage down to about 50 volts to turn off the bulb.

 

References:
  • H. Richard Crane, "How Things Work: Touch-Panels in Elevators, and Idiosyncrasies of Gas Tubes", TPT, Vol. 21, #6, Sept. 1983, p. 402, also A Potpourri of Physics Teaching Ideas - Electricity and Magnetism, p. 157.
  • Jesus Gonzalez-Laprea, L. J. Borrero-Gonzalez, "Photoelectric Effect Measurements on a Conventional Neon Bulb", AJP, Vol. 89, #10, Oct. 2021, p. 969.
  • Cliff Bettis and Sam Sampere, Tap-L conversations, Feb. 20, 2020.

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