Retro "Rayotron" Night Light (Part 1)

Introduction

In December of 1956, Atomic Laboratories advertised the Rayotron as the "First Low-Cost Electrostatic Generator and Particle Accelerator” for science teachers and hobbyists [1]. The Rayotron was a supersized, rubber belt-charged, Van de Graaff (VdG) generator capable of hurling 500,000 volt sparks from its metal terminal. VdGs are electro-mechanical examples of shuffling rubber-soled shoes across a carpet and then touching a grounded metal object. Although the spectacular lightning display produced by this impressive machinery could shock an unsuspecting person off their feet, the microamp discharge was not a risk to a healthy person according to the manufacturer.

The negatively charged terminal of the Rayotron repelled negative electrons down the length of a sealed glass tube under a hard vacuum to a target located at the base. The collision of this energized particle beam with the target enabled users to conduct various physics experiments (and also exposed unprotected persons in close proximity to dangerous X-ray showers [1]). Eventually, Atomic Laboratories discontinued production due to safety issues.

I designed this night light as a tribute to a forgotten piece of mid-century, educational technology. Unlike the original unit, this semi-scale model doesn't emit hazardous radiation and won't ruin your day by leaving you with a ghostly green afterglow :>). The Rayotron's particle beam of the is modeled with a miniature cold cathode light (CCL).

I. Basic Operation

I replaced the noisy belt and motorized roller mechanism used in the original unit with a quiet, negative ion generator marketed for home use. A power supply provides low voltage DC for the ionizer; which drives the CCL. The lamp was axially mounted in a plastic cylinder that supported a discharge globe. The CCL and support structure were attached to the top panel of the console.

II. Instrument Panel Assembly

The console's instrument panel was the one of the few components that changed in appearance during the Rayotron 's production run. Images and descriptions from various sources documenting these modifications guided panel design; photos show early and later Rayotron models. I used a mid-century, 50 microamp meter to display ionizer output as well as a vintage control knob and toggle switches in combination with indicator lights. The meter and control knob were salvaged from discarded consumer electronics.

(Fun Fact: A product safety label on the unit's base warned of X-ray emission during operation. As an added precaution, the manufacturer suggested enclosing the Rayotron in a bunker constructed of concrete pipe to protect operator and bystanders from radiation poisoning [2] !)

III. Cardboard Console Assembly

The console was "MacGyvered" by re-purposing cardboard taken from a stack of 3-ring binders bought at a local yard sale. The instrument panel and plastic support column topped by the terminal were mounted on the console. An earlier version used faux metal trim on the panel for a splash of color, which made the project appear too contemporary IMHO; so decided on a retro, shabby chic look to give the impression of age.

Physical dimensions are not critical, so scale the project as needed. By the end of this instructable, you will have an inexpensive source of high voltage DC (HVDC) for simple, electrostatic demos as well as a rad night light without the problems of lethal radiation poisoning ruining your day (bad pun, but I couldn't resist :>). Lastly, use common sense with the ionizer. Avoid surprises -- disconnect power before working on HV wiring.

I reduced construction costs by recycling used or discarded items when possible. Some components can be improvised. For example, an 8 oz soft drink can makes an inexpensive discharge terminal.

(Fun Fact: The mid-century model featured a spherical discharge terminal. A more ominous terminal resembling a rising mushroom cloud appeared in an updated model from the 1960s [1, 2].

Required electronic components are identified in each step. Miscellaneous items needed for construction are: cardboard sheets from 3-ring binders; circuit boards; clear & blue tape; connecting/ mounting hardware; cyano-acrylate (CA) glue; insulated project wire; pencil; pinch clips; protractor; ruler; sandpaper; scissors (or commercial paper cutter); spray paints; and Elmer's X-treme School Glue as well as various hand tools; an electric drill with assorted bits and a soldering pencil.

I found a vintage Radio Shack Micronta room ionizer at a rummage sale for $1.50. The ionizer was missing the original power supply, so I hacked a DC source from a portable B&W TV (remember those?).

I opened the case and swapped out the original 12 VDC @ 1 amp transformer with another transformer because of its rusted condition. Caution: if you do this, be sure the components are rated for the new transformer or you will cook the rectifier circuit! I mounted the new transformer and original rectifier on a circuit board and soldered the components together. I placed this assembly aside for later instillation when console construction was complete.

No worries if you don't want to do a time consuming rebuild. A much better work-around is to use a commercial power supply. I found a 12 VDC, 4 amp adapter at a garage sale that belonged to a laptop computer and used it with the ionizer without a problem (see Step 14).

Most of the effort for this project was spent designing, fabricating and finishing the cardboard console. Skip the following steps to save time and just use an ordinary shoe box. For the true DIY warriors out there: get busy building!

Peel the plastic covering from binders to obtain cardboard for instrument and other console panels. Layout meter, control knob, two switches and two signal lights on a cardboard strip of suitable length, width and double thickness. I placed switches and lights in a rectangular arrangement. Cut or drill appropriate sized holes to mount each component. I spread a thin layer of glue around and inside each hole and then sanded with fine paper, which helped maintain sidewall shape when glue hardened.

An early version of project incorporated an advertising brochure for the Discover Platinum Card to give panel a faux metal finish. I trimmed the brochure and then drilled/cut out mounting holes. I left an approximately 5 mm border to create a contrast effect when panel was spray painted in a light color. A dial plate was added to cover most of the logo. (Eventually, I spray painted entire instrument panel and discarded the brochure because it was easily dinged.) Place panel and components aside until later.

(Fun Fact: Original operation manuals are in the permanent collection of the National Institutes of Health Museum Library in Bethesda, MD [3].)

Determine size of the console given dimensions of your instrument panel. Allow sufficient room for mounting power supply and ionizer. Also, consider desired height of your support column and diameter of discharge globe; scale console accordingly.

I drew an outline for each panel on cardboard and then cut them out. Side panels have a 23 degree, downward slant from the horizontal axis, to enhance visibility of meter, control knob and signal light cluster. I cut a small kick panel of double thickness to insert at the enclosure's front end for additional support of instrument panel. (I opted to use double thickness for all panels except top panel for a better quality enclosure.)

After panels are cut, place them on a flat surface; check whether edges and corners are even. Glue side, kick, back and bottom panels together for double thickness. Clip in place. Sand uneven edges on a flat surface with med/fine paper. Temporarily assemble panels using pinch clips and 2.5 cm corner braces to mock-up console. Position instrument panel on console. Verify square corners and flush edges. As shown in one photo, I used blue tape to hold console together -- BIG MISTAKE! Don't do this! The edges almost never aligned properly and the entire console always collapsed when the instrument panel was put in place. Glue all panels together except top and instrument panels. Secure with clips and braces until glue dries.

• Construction Tip #1: Use a commercial-grade paper cutter available at FedEx or Staples for clean, neat edges! (Also, paint the console at this point to avoid removing the hardware later to finish the project.)

Even edges with a sanding block and med/fine paper if needed. For added structural integrity, drill a hole at the midpoint of side and back panels to accommodate #8-32 x 1/2 inch round head machine screws with flat washers and braces that will secure bottom panel; also, drill a hole at the bottom corners of each of these panels to accommodate a brace. Coat hole sidewall with glue by inserting and turning a pencil tip several times before glue hardens; lightly sand around hole until smooth. (BTW, I thought the screws and braces attached to kick panel were a visual distraction, so I removed them and filled in holes before painting. Hand torque all hardware because it must be removed before painting.)

Locate your instrument panel. Attach hinges to inside, lower left and right corners with #8-32 x 1/2 inch machine screws and flat washers. Place and align panel on console. Screw hinges to inside of kick panel. Instrument panel should rest evenly against slant of each side panel. Hand torque hinge screws; sand panel edges until flush with side panels. Caution: instrument panel is not designed to move more than several degrees because of console's configuration! Access to the inside of console is through top panel; see next step.

• Construction Tip #2: Drill over size holes in upper corners of kick panel to allow for slight hinge adjustments.

Note: This step requires concentration and frequent rest breaks!

Cut notches on upper left and right corners of back panel to accommodate hinges; position them so they are level with height of back and side panels. Mark, drill and prep screw holes. Mount suitable hinges on outside of back panel. Confirm top panel's front edge is flush with upper edge of instrument panel when closed. Be careful when sanding either horizontal or slanted edges of one or both side panels as needed to ensure smooth fit between top and instrument panels. Too much sanding will lead to gaps between panels! Secure top panel firmly with rubber bands so panel remains in position. Remove instrument panel to access hinges. Reach into console and mark screw holes for top panel.

• Construction Tip #3: Bevel inside edge of instrument panel with med sandpaper to improve fit with top panel.

I used two coffee stir sticks between each hinge and the top panel as spacers to reduce binding during opening and closing. The sticks were cut to size, glued, stacked together and clipped to the underside of panel before drilling holes. Afterwards, I glued a piece of scrap plywood to the underside of the panel to provide additional support for mounting beam tube assembly in a later step.

Smear glue along front edge of top panel and upper edge of instrument panel; rub glue into cardboard to strengthen edges and corners of panels. Allow panels to dry; then sand all edges and corners with fine paper.

ID midpoint on front edge of top panel. Center and mount a magnetic catch with two #4-40 round head machine screws, flat and locking washers. A piece of scrap wood screwed to exterior of top panel served as a convenient handle for opening console. ID midpoint on upper edge of instrument panel. Center and mount strike plate using machine screws. Remember to drill oversize mounting holes and prep with glue. Catch and plate will require adjustments for proper fit. Confirm alignment of top panel; then install hinge mounting screws and washers.

I used four scrap wood pieces from an art supply store as feet; each piece had a pre-drilled 3/16" hole. I painted each piece before gluing a wood dowel into each one. I drilled a 3/16" hole in each corner of bottom panel. Dowels held feet in place temporarily. BTW, don't glue pieces until console is painted.

Initially, I cut off the bottoms from two discarded medicine vials and blue-taped them end-to-end to make a support column. The column was secured by bolting a vial cap to console lid as shown. Bummer... the dark plastic dimmed the internal lighting and the tape was visually distracting.

Here's a work-around: buy a clear acrylic tube from scrap bin of a hardware or plastics supply store. I found a heavy plastic tube with same outside diameter as entry hole of a hollow aluminum sphere (8 cm diameter; bought at a Teslathon event). BTW, if you don't have a discharge sphere, use a metal world globe from the dollar store or even an aluminum soft drink can. Cut out an entry hole for your support column with metal snips. BTW, save vial cap used to secure column to console lid.

Cut eight blanks from a single cardboard sheet equal to outside diameter of tube. I drilled center holes in each blank to accommodate a 6 cm, #6-32 machine screw; placed blanks on screw; clamped them with a lock washer and retaining nut, then chucked them in an electric drill. I ground blanks with course, then medium sandpaper until entire assembly slid easily through tube.

Remove completed blanks from machine screw. You will need two, 1/4 inch nylon screw insulators (P/N: B-IN-14S/4; Small Parts). Ream center hole to accommodate insulator diameter. Make two centering rings by gluing, then stacking four rings together. Clamp rings until glue dries. I used a 1-1/2 x 1/4 inch bolt and two, 3-cm metal flat washers as a clamps. Save these parts because they will be reused. Decide whether you want to paint retaining rings. Insert an insulator into each ring stack.

Prep two caps obtained from toothpaste tubes by drilling a 1/4 inch hole through the tops to make retaining cones for the CCLs. Paint cones if desired. Locate a rubber grommet that fits into well of cap. Hole should have sufficient diameter to accept your lamp (P/N: 239610; Jameco). Use vial cap from earlier step for column base. Place a flat washer inside of vial cap as an anchor, then place a retaining ring on washer. Secure vial cap, washer and ring to console lid with bolt used to clamp rings. Temporarily place a cone over bolt head and insulator lip. Secure assembly to lid with nut. Upper cone assembly is nearly identical to the lower cone; however, don't bolt parts together. Hold pieces together with blue tape until ready to glue.

Position column on vial cap. Drop lamp into column and confirm that it slips into grommet hole of lower cone and physically touches bolt head. Insert upper assembly (grommet facing down) into column. Lamp should pass through grommet hole but not protrude beyond surface of ring. Cut support column to proper length or use more washers as spacers to raise lamp. When you have obtained correct height, glue and then clamp remaining flat washer to top of upper retaining ring assembly. Remove lamp.

• Construction Tip #4: Increase illumination by removing rubber grommets and insert a second lamp directly into cone retainers.

The discharge terminal rests on a support ring. Construct one from scrap plastic sheet. Make optional electron beam focusing rings by cutting segments of a plastic straw and slipping them over the lamp (remove them, as I did, if they cause too much light reduction when lamp is tested).

Use a metal bolt to secure vial cap (from Step 9) to console lid. Insert beam tube assembly in cap. I inserted the meter, control knob, toggles and signal lights.in the appropriate holes of instrument panel to get a sense of how project would look.

Bolt the your modified power supply and ionizer to base of console. Hard wire these two assemblies along with meter, toggles, indicator lights and fuse. BTW, the power control knob in the center of the instrument panel is for decoration; it is non-functional -- this issue gets remedied in the upcoming Rayotron Renovation.

If you are using a commercial power source (highly recommended!), use velcro strips to secure the unit to console's base, then hard wire ionizer and instrument panel.

If you didn't paint the console in Step 5: remove connecting hardware, separate instrument panel from console as well as handle from top panel. I used these colors to finish the project:

Main Console Panels - Gloss Almond

Lid and Instrument Panels - Metallic Silver

Lid Handle - Copper

I mounted a telescoping TV antenna on the top panel with a pinch clip. The antenna, when wired to the ionizer's ground return, served as discharge electrode.

Power up the project, then extend antenna as needed until you can draw continuous 1 mm discharges from the terminal. Adjust spark gap with a non-conducting object, such as a plastic pen, until CCL provides a continuous glow. The meter should display 15 - 20 microamps. Your Rayotron Night Light project is now complete!

1. Baez AV. The Rayotron (a High-Voltage Generator and X-Ray Source). American J Physics. 1957;25:499-501. Accessed from: https://aapt.scitation.org/doi/10.1119/1.1934537.

2. Miller E. Report of Tests for X-Ray Emission from a Rayotron Electrostatic Generator and Particle Accelerator. Rocksville, MD: US Dept Health, Education & Welfare. 1970. Accessed from: https://www.osti.gov/biblio/4083666.

3. Rayotron Operation Manual. Atomic Laboratories, LLC. 1956. Accessed from: https://history.nih.gov/museum/manualsa.html.